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450 Sentences With "germ cells"

How to use germ cells in a sentence? Find typical usage patterns (collocations)/phrases/context for "germ cells" and check conjugation/comparative form for "germ cells". Mastering all the usages of "germ cells" from sentence examples published by news publications.

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"The potential to use gene editing in germ cells or embryos is very real," she says.
Her family says that multiple hospitals confirmed Burns' rare cancer, a combination of carcinoma and mixed germ cells.
These develop from the germ cells of the testes, which are cells that eventually develop into mature sperm.
In December 2017, Surani announced a crucial milestone concerning the eight-week cycle, after which germ cells begin the process of transforming into gametes.
Early during an embryo's development, the germ cells — which are basically the cellular grandparents or great grandparents of sperm — travel to the nascent gonads.
But the manipulation of genomes in their native context, particularly in embryonic cells or germ cells, opens the door to a vastly more powerful technology.
Germ-plasm is composed of our germ cells, which are involved in sexual reproduction and contain the genes that are passed down from previous generations.
That means someone needs to work out exactly which of the chemicals in testes and ovaries tell primordial germ cells whether to become eggs or sperm.
Researchers from Nanjing Medical University created functional primordial germ cells—cells that get passed down to the next generation—from the embryonic stem cells (ESCs) of mice.
These germ cells then divide to form stem cells that can produce more of themselves, and more of the cells that, through a series of divisions, make sperm.
"Genetic changes that promote cancer can be inherited from our parents if the changes are present in germ cells, which are the reproductive cells of the body (eggs and sperm)," the National Cancer Institute says.
And they will need to show that this technique is applicable to humans, which won't be easy; the gene expression profile of human germ cells is similar to those of mice, but different in important ways.
But baby mice do not a human make, and Saitou and another scientist, Azim Surani, are each working directly with human cells, trying to understand the differences between how mice and human iPSCs become primordial germ cells.
As he had discovered in his experiments creating sperm, judicious application of a molecule called bone morphogenetic protein 4 turns pluripotent cells into primordial germ cells—the type of stem cell ancestral to both sperm and eggs.
Maybe in the future with genetic modification, you can alter a man's germ cells that produce his sperm — but for now, if those are impacted adversely, a man will have a lowered sperm count his whole life.
In October, she had gone to a doctor complaining of stomach pains and fatigue, but what officials thought were simple ovarian cysts, turned out to be the rare, terminal cancer – a combination of carcinoma and mixed germ cells.
In the winter of 226, a team of embryologists in Cambridge, England, and at the Weizmann Institute in Israel developed a system to make primordial germ cells—the precursors of sperm and eggs—out of human embryonic stem cells.
Once scientists and regulators are confident they have minimized the potential risks of IVG, we could easily make heritable changes to germ cells like eggs, sperm, or early-stage embryos, and with those changes, we'd be altering the germ line, our shared human inheritance.
To use it as a gene drive, all that is required is to include in the payload the genes for the CRISPR-Cas9 system itself, and to ensure that some copies get inserted into an organism's germ cells—those that develop into sperm or eggs.
The experiment showed that meiosis, the special process of cell division and genetic rearrangement required to form germ cells (sperm and eggs), can be achieved in the lab by treating stem cells with a cocktail of chemicals and hormones in the presence of testicular tissue.
In 2014, as a consequence of Yamanaka's work, a Stanford researcher named Renee Reijo Pera cut skin from infertile men's forearms, reprogrammed the skin cells to become iPSCs, and transplanted them into the testicles of mice to create human germ cells, the primitive precursors to eggs and sperm.
"Earlier this month, Bartha Knoppers, a health-policy expert at McGill University, presented a consensus statement from Ravitsky and others at an annual meeting of stem cell and regenerative-medicine researchers arguing that "basic and pre-clinical research on human germ cells and embryos in the earliest stages of development should be allowed.
For germline modification, we have at least three compelling cases: 1) mitochondrial diseases; 2) families in which post-natal remedies are inadequate and both parents are fully afflicted (20 percent of the world's marriages involve close relatives); and 3) scenarios in which treating (and possibly pre-screening) single germ cells is safer than treating millions of somatic cells, since each cell adds to the collective risk of developing cancer.
Germ cells migrate from near the allantois and colonize the primordial gonads. In the female, the germ cells colonise the cortex and become oogonia. In the male, the germ cells colonise the seminiferous cords of the medulla, becoming spermatogonia.
Main article: Primordial germ cell migration Primordial germ cells, germ cells that still have to reach the gonads (also known as PGCs, precursor germ cells or gonocytes) divide repeatedly on their migratory route through the gut and into the developing gonads.
Fibronectin maps here also a polarized network together with other molecules. The somatic cells on the path of germ cells provide them attractive, repulsive, and survival signals. But germ cells also send signals to each other. In reptiles and birds, germ cells use another path.
These potential renewable germ cells were identified as positive for these essential oocyte markers. The discovery of these active germ cells and oogonia in the adult female could be very useful in the advancement of fertility research and treatment of infertility. Germ cells have been extracted, isolated and grown successfully in vitro. These germ cells have been used to restore fertility in mice by promoting follicle generation and upkeep in previously infertile mice.
Germ cells share some features with cancers. The motile and penetrating features and colonization of primitive germ cells resemble the migration of cancer cells from primary tumor to metastasis. Also, during spermatogenesis, germ cells exhibit characteristics similar to cancer cells. These phenomena led to the hypothesis that the activation of CT antigens in normal stomatic tissues related to tumorigenesis.
Spermatogonia and oogonia are classified as sexually differentiated germ cells.
Gonocytes are long-lived precursor germ cells responsible for the production of spermatogonial stem cells (SSCs). Gonocytes relate to both fetal and neonatal germ cells from the point at which they enter the testis primordial until they reach the base membrane at the seminiferous cords and differentiate. At the time of gasturalation, certain cells are set aside for later gamete development. These cells are called post migratory germ cells (PGCs).
An example of this is the modern cultivated species of wheat, Triticum aestivum L., a hexaploid species whose somatic cells contain six copies of every chromatid. The frequency of spontaneous mutations is significantly lower in advanced male germ cells than in somatic cell types from the same individual. Female germ cells also show a mutation frequency that is lower than that in corresponding somatic cells and similar to that in male germ cells. These findings appear to reflect employment of more effective mechanisms to limit the initial occurrence of spontaneous mutations in germ cells than in somatic cells.
Some investigators suggest that this distribution arises as a consequence of abnormal migration of germ cells during embryogenesis. Others hypothesize a widespread distribution of germ cells to multiple sites during normal embryogenesis, with these cells conveying genetic information or providing regulatory functions at somatic sites.
Very few studies used gonocytes to also refer to the female germ cells in the ovarium primordium. The specification of gonocytes to be confined to male germ cells occurred after foundational differences between the mechanisms of male and female fetal germ cells were uncovered. Some scientists prefer the terms “prospermatogonia” and “prespermatogonia” for their functional clarity. Later studies found that the process from primordial germ cell to spermatogonial development is gradual, without clear gene expression markers to distinguish the precursor cells.
The end-products of the germ cell cycle are the egg or sperm. Under special conditions in vitro germ cells can acquire properties similar to those of embryonic stem cells (ES). The underlying mechanism of that change is still unknown. These changed cells are then called embryonic germ cells (EG).
This occurs shortly before and during the arrival of the primordial germ cells (PGCs) to the paired gonadal ridges.
Instead, germ cells can arise from somatic cells in the adult, such as the floral meristem of flowering plants.
The piwi-piRNA pathway also appears to protect the genome. First observed in Drosophila, mutant piwi-piRNA pathways led to a direct increase in dsDNA breaks in ovarian germ cells. The role of the piwi-piRNA pathway in transposon silencing may be responsible for the reduction in dsDNA breaks in germ cells.
As the ovaries differentiate, ingrowths called cortical cords develop. This is where the primordial germ cells collect. During the 6th to 8th week of female (XX) embryonic development, the primordial germ cells grow and begin to differentiate into oogonia. Oogonia proliferate via mitosis during the 9th to 22nd week of embryonic development.
The lineage of germ cells is called germ line. Germ cell specification begins during cleavage in many animals or in the epiblast during gastrulation in birds and mammals. After transport, involving passive movements and active migration, germ cells arrive at the developing gonads. In humans, sexual differentiation starts approximately 6 weeks after conception.
First phase of proliferation occurs during cyst establishment promoting also migration of germ cells into it. second one is to enlarge the cyst and produce a space for priliferating germ cells. Commonly accepted fact that Sertol cells are terminally differentiated in amniota was recently changed. After xenogeneic transplantation Sertoli cells were able to proliferate.
The effect is one-way: germ cells produce somatic cells, and more germ cells; the germ cells are not affected by anything the somatic cells learn or any ability the body acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. This is referred to as the Weismann barrier.Germ-Plasm, a theory of heredity (1893) This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck and implied by Charles Darwin's pangenesis theory of inheritance.
Gonocytes are the precursors of spermatogonia that differentiate in the testis from primordial germ cells around week 7 of embryonic development and exist up until the postnatal period, when they become spermatogonia. Despite some uses of the term to refer to the precursors of oogonia, it was generally restricted to male germ cells. Germ cells operate as vehicles of inheritance by transferring genetic and epigenetic information from one generation to the next. Male fertility is cetered around continual spermatogonia which is dependent upon a high stem cell population.
Germ cells are specified early in development and can only differentiate into gametes. The segregation of germ cells is often determined by the species, with some undergoing preformation, where the germ cells are determined by maternally inherited factors before or immediately after fertilisation, and others undergoing epigenesis, where the germ cell lineage is determined from signalling from surrounding tissues. Preformation was initially perceived as more common than epigenesis, as it appears in many model organisms like the common fruit fly, roundworms and some amphibians. Epigenesis has since been shown to be the more common mechanism.
Recent research, however, has identified that renewable oogonia may be present in the lining of the female ovaries of humans, primates and mice. It is thought that these germ cells might be necessary for the upkeep of the reproductive follicles and oocyte development, well into adulthood. It has also been discovered that some stem cells may migrate from the bone marrow to the ovaries as a source of extra-genial germ cells. These mitotically active germ cells found in mammalian adults were identified by tracking several markers that were common in oocytes.
In mammals, a few cells of the early embryo are induced by signals of neighboring cells to become primordial germ cells. Mammalian eggs are somewhat symmetrical and after the first divisions of the fertilized egg, the produced cells are all totipotent. This means that they can differentiate in any cell type in the body and thus germ cells. Specification of primordial germ cells in the laboratory mouse is initiated by high levels of bone morphogenetic protein (BMP) signaling, which activates expression of the transcription factors Blimp-1/Prdm1 and Prdm14.
In the gonads, the germ cells undergo either spermatogenesis or oogenesis depending on whether the sex is male or female respectively.
The mutations can be inherited, or can arise from mutations early in embryogenesis, or in one of the parent's germ cells.
In Drosophila, geranylgeranyl pyrophosphate is synthesised by HMG-CoA encoded by the Columbus gene. Geranylgeranyl pyrophosphate is utilised as a chemoattractant for migrating germ cells that have traversed the midgut epithelia. The attractant signal is produced at the gonadal precursors, directing the germ cells to these sites, where they will differentiate into ova (eggs) and spermatozoa (sperm).
Anthozoans are either gonochoristic or hermaphrodites. Germ cells originate in the endoderm and are eventually moved to the gastrodermis where they will differentiate. Once the germ cells have matured they are released through the coelentron into the sea, as a result reproduction is external. In this process many gametes are produced to increase likelihood of fertilization.
Vasa expression is restricted to tissue specific cells. Until recently it was thought that Vasa protein can only be found in gametes and is undetectable in somatic cells. Within germ cells, Vasa is expressed in the cytoplasm. During embryogenesis, Vasa is expressed in migratory primordial germ cells (PGCs) at the gonadal ridge in both males and females.
In vertebrate development, the location where primordial germ cells are specified and the subsequent migratory paths that they take differs among species.
The insertion and subsequent expression of hobo-like sequences results in the loss of germ cells in the gonads of developing flies.
Primordial Germ Cell Migration Primordial germ cell (PGC) migration is the process of distribution of primordial germ cells throughout the embryo during embryogenesis.
Testicular germ cell tumors, that occur primarily in young adults, are the consequent of preinvasive cells called carcinoma in situ (CIS). The development of CIS is due to fetal germ cells, such as gonocytes, arrested in quiescence and unable to properly differentiate. This leads to malignant transformation of the germ cells until it becomes an overt germ cell cancer after puberty.
This specificity allows Vasa to be used as a highly specific marker for germ cells. In a patient with Sertoli cell syndrome, no Vasa signal was detected from testicular biopsy. However, recent studies show that Vasa functions in other cells as well. A study on Macrostomum lignano found Vasa expression in multipotent neoblast stem cells in addition to germ cells.
Oogenesis and ovulation. In "Book 1: Germ cells and fertilization" (C. R. Austin and R. V. Short, Eds.), pp. 17-45. Cambridge University Press, Cambridge.
The only adult tissue Rex1 has been identified in are the testicles. Using in situ hybridization it was determined that the spermatocytes in the more inner layers of the testicles are expressing Rex1. Thus, the male germ cells undergoing meiosis are the specific cells in the testicles that express Rex1. It has not been observed, however, that Rex1 is expressed in the female germ cells.
Sex specification of the germ cells requires the repression of pluripotency and relies on the communication between the somatic cells of the gonads and germ cells Reitzel et al., 2015. The mechanisms for male and female differentiation are markedly different, since a population of sperm producing spermatogonia are retained throughout development and into adult life Reitzel et al., 2015, unlike oogonia which only produce oocyte in utero.
Some of Extavour's research during this period showed that bone morphogenetic proteins (BMPs) can help to induce primordial germ cells (PGCs) in the early stages of embryo development in a cricket. Extavour and her colleagues were able to specify that two BMPs, BMP8b and BMP4, help induce PGCs in this insect. This is significant because it was the first demonstration of a specific signaling pathway operating in the induction of embryonic germ cells in an Invertebrate.Derivation of male germ cells from induced pluripotent stem cells by inducers: A review From 2010-2015 Extavour directed a national research collaborative called EDEN, which stands for Evo-Devo-Eco (evolutionary-developmental-ecological) Network.
The abnormal development of gonocytes leads to fertility-related diseases. They are also identified as prespermatogonia, prospermatogonia and primitive germ cells, although gonocyte is most common.
It may serve a function in cell cycle control of both somatic cells and germ cells in addition to its putative role in spermatogenesis and sperm function.
In mouse primordial germ cells, genome-wide reprogramming leading to totipotency involves erasure of epigenetic imprints. Reprogramming is facilitated by active DNA demethylation involving the DNA base excision repair enzymatic pathway. This pathway entails erasure of CpG methylation (5mC) in primordial germ cells via the initial conversion of 5mC to 5-hydroxymethylcytosine (5hmC), a reaction driven by high levels of the ten-eleven dioxygenase enzymes TET-1 and TET-2.
The Cul4a gene is required for normal spermatogenesis and meiosis in male germ cells of mice. Cul4a−/− males produce abnormal sperm and are infertile. While both CUL4A and CUL4B are expressed in male gametes, CUL4A is highly expressed in pachytenes and diplotenes. It is at these stages that CUL4A-deficient male germ cells exhibit high levels of apoptosis, improper DNA repair and accumulation of the CRL4 substrate Cdt1.
This is the stage when chromosomes are fully synapsed, and Holliday junctions are formed and then resolved into recombinants. FANCA mutant males exhibit an increased frequency of mispaired meiotic chromosomes, implying a role for FANCA in meiotic recombination. Also apoptosis is increased in the mutant germ cells. The Fanconi anemia DNA repair pathway appears to play a key role in meiotic recombination and the maintenance of reproductive germ cells.
In the blastocyst of the mammalian embryo, primordial germ cells arise from proximal epiblasts under the influence of extra-embryonic signals. These germ cells then travel, via amoeboid movement, to the genital ridge and eventually into the undifferentiated gonads of the fetus. During the 4th or 5th week of development, the gonads begin to differentiate. In the absence of the Y chromosome, the gonads will differentiate into ovaries.
A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development.
Retinoic acid (RA) is an important factor that causes differentiation of primordial germ cells. In males, the mesonephros releases retinoic acid. RA then goes to the gonad causing an enzyme called CYP26B1 to be released by sertoli cells. CYP26B1 metabolizes RA, and because sertoli cells surround primordial germ cells (PGCs), PGCs never come into contact with RA, which results in a lack of proliferation of PGCs and no meiotic entry.
As the meiosis I only completes with ovulation, human germ cells exist in this stage from the first weeks of development until puberty. The completion of meiosis leads to: # XaM AND XaP haploid germ cells (eggs). The X activation cycle has been best studied in mice, but there are multiple studies in humans. As most of the evidence is coming from mice, the above scheme represents the events in mice.
Another study showed that culture of human embryonic stem cells in mitotically inactivated porcine ovarian fibroblasts (POF) causes differentiation into germ cells, as evidenced by gene expression analysis.
After splitting into two populations, the germ cells continue migrating laterally and in parallel until they reach the gonads. Columbus proteins, chemoattractants, stimulate the migration in the gonadal mesoderm.
In Drosophila, vasa expression is seen in germ cells, specifically the germline stem cells (GSC's) of female ovaries and in the early stages of spermatogensis in the male testis.
Genome- wide reprogramming in mouse primordial germ cells involves epigenetic imprint erasure leading to totipotency. Reprogramming is facilitated by active DNA demethylation, a process that entails the DNA base excision repair pathway. This pathway is employed in the erasure of CpG methylation (5mC) in primordial germ cells. The erasure of 5mC occurs via its conversion to 5-hydroxymethylcytosine (5hmC) driven by high levels of the ten-eleven dioxygenase enzymes TET1 and TET2.
Testicular tissue-derived seipin is essential for male fertility by modulating testicular phospholipid homeostasis. The lack of seipin in germ cells results in complete male infertility and teratozoospermia. Spermatids devoid of seipin in germ cells are morphologically abnormal with large ectopic lipid droplets and aggregate in dysfunctional clusters. Elevated levels of phosphatidic acid accompanied with an altered ratio of polyunsaturated to monounsaturated and saturated fatty acids show impaired phospholipid homeostasis during spermiogenesis .
Then demethylation of the PGCs takes place in two waves. There is both passive and active, TET-dependent demethylation of the primordial germ cells. At day 9.5 the primordial germ cells begin to rapidly replicate going from about 200 PGCs at embryo day 9.5 to about 10,000 PGCs at day 12.5. During days 9.5 to 12.5 DNMT3a and DNMT3b are repressed and DNMT1 is present in the nucleus at a high level.
GCNIS is not palpable, and not visible on macroscopic examination of testicular tissue. Microscopic examination of affected testicular tissue most commonly shows germ cells with enlarged hyperchromatic nuclei with prominent nucleoli and clear cytoplasm. These cells are typically arranged along the basement membrane of the tubule, and mitotic figures are frequently seen. The sertoli cells are pushed toward the lumen by the neoplastic germ cells, and spermatogenesis is almost always absent in the affected tubules.
The remainder of the male reproductive system is derived from embryonic mesoderm, except for the germ cells, or spermatogonia, which descend from the primordial pole cells very early during embryogenesis.
Mottled sculpin reach sexual maturity at the age of two.Hann, H.W. 1927. The history of the germ cells of Cottus bairdi Girard. Journal of Morphology and Physiology 43:427-497 .
This gene is X-linked and is expressed in only male germ cells. Two alternatively spliced transcript variants encoding distinct isoforms have been found for this gene. [provided by RefSeq, Jul 2008].
A sporoplasm packet at the end of the style contains 64 germ cells surrounded by a cellular envelope. There are also three polar capsules, each of which contains a coiled polar filament.
The promoter region predicted by the Genomatix El Dorado algorithm spans from 10108742-10108009 bp. Promoters are associated with a wide variety of tissues including B-lymphocyes, germ cells, muscle, neurons & prostate.
During meiosis, diploid cells divide twice to produce haploid germ cells. During this process, recombination results in a reshuffling of the genetic material from homologous chromosomes so each gamete has a unique genome.
Using Immunohistochemistry of human testis, Ramasamy et al. (2015) found the presence of NPAS2 protein in both germ cells within the tubules of the testes and in the interstitial space of Leydig cells.
"Ultrastructure of male germ cells in the testes of abalone, Haliotis ovina Gmelin". Molluscan Research 23(2): 109–121. , PDF. and from Malaysia to Fiji, Tonga, southern Japan and Australia (Queensland, Western Australia).
Both EG and ES are pluripotent in vitro, but only ES has proven pluripotency in vivo. Recent studies have demonstrated that it is possible to give rise to primordial germ cells from ES.
A null mutation causes female sterility due to severe defects in oogenesis but males are fertile. Homozygous mutations for partial loss of function allows eggs to be fertilized but embryos lack germ cells.
Extavour received an Honors BSc at the University of Toronto. Her Ph.D. thesis was on germ cell selection in genetic mosaics and was published in 2001 in PNAS. In 2003 Extavour did a study at Cambridge University on the mechanisms of germ cell formation that showed animal germ cells were likely specified by inductive signals more often than previously thought. This went against the mainstream scientific view at the time that animal germ cells are usually specified by maternally inherited determinants.
Zebrafish PGCs are specified at four different locations within the early embryo via inheritance of germ plasm (a mixture of RNA and protein often associated with mitochondria). Germ cells from these four locations will then migrate dorsally after down-regulation of the rgs14a G-protein which regulates E-cadherin. Down-regulation will result in reduced cell-cell adhesion which allows the germ cells to separate and begin the migration process. Migration of the PGCs then continues towards the developing somites 1-3.
The testes begin as an immigration of primordial germ cells into testicular cords along the gonadal ridge in the abdomen of the early embryo. The interaction of several male genes organizes this developing gonad into a testis rather than an ovary by the second month of gestation. During the third to fifth months, the cells in the testes differentiate into testosterone-producing Leydig cells, and anti-Müllerian hormone-producing Sertoli cells. The germ cells in this environment become fetal spermatogonia.
An examination of Weismannism. The Open court publishing company in Chicago 1893 according to which inheritance (in a multicellular organism) only takes place by means of the germ cells—the gametes such as egg cells and sperm cells. Other cells of the body—somatic cells—do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life.
When she moved the somatic cell to a different place, germ cells started dividing in that new location. This was the first time a single cell with such an oversight function had been identified.
These tumors can be benign or malignant. On arrival at the gonad, primordial germ cells that do not properly differentiate may produce germ cell tumors of the ovary or testis in a mouse model.
Chicken primordial germ cells are initially specified in the area pellucida (a one-cell thick layer of epiblast lying above the sub-germinal space). Following the formation of the primitive streak, the germ cells are carried to the germinal crescent region. Unlike most model organisms where germ cell migration is predominantly via the gut epithelium, chicken PGCs migrate through the embryonic vascular epithelium. Once they have exited the capillary vessels, the final stage of migration is along the dorsal mesentery to the developing gonad.
There, she worked with molecular biologist David Hirsh who was studying the model organism Caenorhabditis elegans. Kimble then moved to the MRC Laboratory of Molecular Biology, where she spent four years as a postdoctoral fellow working with Sir John Sulston on the control of organogenesis. During the course of her work, Kimble found a special somatic cell at the tip of the gonad which tells nearby germ cells - reproductive cells - how to divide. When she destroyed the distal tip cell, germ cells stopped dividing.
Spermatogenesis is a complex process regulated by extracellular and intracellular factors as well as cellular interactions among interstitial cells of the testis, Sertoli cells, and germ cells. This gene is expressed in the testis in Sertoli cells but not germ cells. The protein encoded by this gene contains plant homeodomain (PHD) finger domains, also known as leukemia associated protein (LAP) domains, believed to be involved in transcriptional regulation. The protein, which localizes to the nucleus of transfected cells, has been implicated in the transcriptional regulation of spermatogenesis.
Koopman's early work with Anne McLaren spawned an interest in the regulation of the germ cells during fetal development—cells that later become sperm or oocytes. His group discovered that the vitamin A metabolite retinoic acid stimulates germ cells to enter meiosis, a critical step in the formation of gametes. They also demonstrated that the developmental signaling molecule Nodal and its receptor Cripto regulate male germ cell pluripotency in the fetal gonad, opening the way for new non-invasive diagnostics and targeted additional therapies for testicular cancers.
Stevens' post-doctoral year of work at the Carnegie Institution required fellowship support, and both Wilson and Morgan wrote recommendations on her behalf. She applied for funding for research on heredity related to Mendel's laws, specifically sex determination. After receiving the grant, she used germ cells of aphids to examine possible differences in chromosome sets between the two sexes. One paper, written in 1905,NM Stevens. (1905) “A Study of the Germ Cells of Aphis rosae and Aphis oenotherae.” Journal of Experimental Zoology 2 (3):313-334.
After female (XX) germ cells collect in the undifferentiated gonads, the up-regulation of Stra8 is required for germ cell differentiation into an oogonium and eventually enter meiosis. One major factor that contributes to the up-regulation of Stra8, is the initiation of the β-Catenin signaling pathway via RSPO1, which is also responsible for ovary differentiation. Since RSPO1 is produced in somatic cells, this protein acts on germ cells in a paracrine mode. Rspo1, however, is not the only factor in Stra8 regulation.
Dysfunctional development in germ cells plays a significant role in fertility- related diseases. The development of PGCs to gonocytes, and gonocyte differentiation to SSCs is critical for adult fertility and the defective growth often leads to infertility.
The tumor is caused when the germ cells in the ovaries begin divide uncontrollably and become malignant which are characterized with their less organized nuclei and unclearly defined border. Another potential etiology is the dysfunctioning of the tumor suppressor gene, TRC8/RNF139, or even karyotypic abnormalities after close molecular examination. OGCT has its roots in embryonic development where the primordial germ cells (PGCs) are isolated in early stages and have the ability to alter the genome as well as the transcriptome. OGCTs can be attributed to the internal mechanism of PGCs and their transforming characteristics.
When a DMRT1 gene is lost, the most common disease is chromosome 9p deletion, which causes abnormal testicular formation and feminization. The DMRT1 gene is critical for male sex determination; without this gene the default female characteristic takes over and male characteristic is slight or non-existent. When DMRT1 is knocked out in mice, the mice showed changes in both Sertoli and germ cells soon after formation of the gonadal ridge. The main defects associated with DMRT1 knockout were developmental arrest, excess proliferation of germ cells, and failure to undergo meiosis, mitosis, or migration.
Before the work of Beard, the use of enzymes to treat cancer had almost never been proposed; an exception is the advocation for using papaya enzymes by indigenous populations, an argument not scientifically developed. Beard, on the other hand, ultimately recommended the use of pancreatic enzymes to treat cancer from his extensive knowledge base of embryology. In 1902, Beard determined that cancer developed because of germ cells that lost direction to the gonads during the process of embryogenesis. These problematic germ cells ultimately developed into an "irresponsible trophoblast", as coined by Beard.
In between E7.5 and E12.5, these PGCs migrate towards the genital ridge, where they form the testicular cords, via the cytokine interactions of the CXCR4 and c-Kit membrane receptors and their ligands SDF1 and SCF respectively. During this migratory period, PGCs undergo epigenetic reprogramming through genome-wide DNA demethylation. Once resident in the genital ridge, these germ cells and surrounding supporting cells undergo sex determination driven by the expression of the SRY gene. It is only after these developmental steps that the germ cells present in the developed testicular cords are identified as gonocytes.
Page used the mouse as a model to study the genetics of meiotic initiation, showing that retinoic acid (RA) is the key factor which induces meiosis, as well as identifying several important genes crucial to the meiotic initiation pathway, including Stra8 and DAZL. Page further discovered that the differentiation germ cells into gametocytes (oocytes in females or spermatocytes in males) does not depend on meiotic initiation, as commonly thought, showing that germ cells deficient in Stra8, a gene that activates the meiotic pathway, are still capable of growth and differentiation.
There are two mechanisms to establish the germ cell lineage in the embryo. The first way is called preformistic and involves that the cells destined to become germ cells inherit the specific germ cell determinants present in the germ plasm (specific area of the cytoplasm) of the egg (ovum). The unfertilized egg of most animals is asymmetrical: different regions of the cytoplasm contain different amounts of mRNA and proteins. The second way is found in mammals, where germ cells are not specified by such determinants but by signals controlled by zygotic genes.
Gonadoblastomas can contain elements of both germ cells and gonadal stroma.Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2009) Robbins & Cotran Pathologic Basis of Disease (8th ed.). Saunders. Chapter 21. . Formerly, gonadoblastoma was sometimes regarded as a subset of dysgerminoma.
Oogonia are formed in large numbers by mitosis early in fetal development from primordial germ cells. In humans they start to develop between weeks 4 and 8 and are present in the fetus between weeks 5 and 30.
In the absence of the Sry gene, primordial germ cells differentiate into eggs. Removing genital ridges before they start to develop into testes or ovaries results in the development of a female, independent of the carried sex chromosome.
The cells that give rise to the gametes are often set aside during embryonic cleavage. During development, these cells will differentiate into primordial germ cells, migrate to the location of the gonad, and form the germline of the animal.
Whether in fact viable germ cells of both species may be, or have been, produced within the same individual is unknown. The term shoat is sometimes used for sheepgoat hybrids and chimeras, but that term more conventionally means a young piglet.
5th ed. London: Churchill Livingstone; 2003. p. 694-8. This includes tumour cells as well as hair follicles, bone marrow and other germ cells. For this reason, common chemotherapy side effects such as hair loss occur; sometimes this can be permanent.
The term Keimplasma (germ plasm) was first used by the German biologist August Weismann (1834–1914), and described in his 1892 book Das Keimplasma: eine Theorie der Vererbung (The Germ Plasm: a theory of inheritance). His theory states that multicellular organisms consist of germ cells that contain and transmit heritable information, and somatic cells which carry out ordinary bodily functions. In the germ plasm theory, inheritance in a multicellular organism only takes place by means of the germ cells: the gametes, such as egg cells and sperm cells. Other cells of the body do not function as agents of heredity.
The DAZ (Deleted in AZoospermia) gene family encodes potential RNA binding proteins that are expressed in prenatal and postnatal germ cells of males and females. The protein encoded by this gene is localized to the nucleus and cytoplasm of fetal germ cells and to the cytoplasm of developing oocytes. In the testis, this protein is localized to the nucleus of spermatogonia but relocates to the cytoplasm during meiosis where it persists in spermatids and spermatozoa. Transposition and amplification of this autosomal gene during primate evolution gave rise to the DAZ gene cluster on the Y chromosome.
Pluripotent stem cells are used in lieu of in vivo cells when researching germ cell development but is not without its issues. There is a limited amount of information on early germ cells, so it is difficult to ascertain if the resultant cells in the culture are the same as germ cells. Instead, research is based on inducing cells with the same or similar properties in order to study the underlying mechanisms of germ cell differentiation. Additionally, it is also difficult to compare with previous studies, especially since the majority have been done on mice, and there are different processes between species.
Germinomas are thought to originate from an error of development, when certain primordial germ cells fail to migrate properly. Germinomas lack histologic differentiation, whereas nongerminomatous germ-cell tumors display a variety of differentiation. Like other germ-cell tumors, germinomas can undergo malignant transformation.
Most MAGE-A genes are not expressed in healthy tissues except testicular, ovarian, and placental germ cells. They are expressed in tumor cells. MAGE-A11 in particular shows high expression in a small number of tumors, but low levels in all others.
After migration primordial germ cells will become oogonia in the forming gonad (ovary). The oogonia proliferate extensively by mitotic divisions, up to 5-7 million cells in humans. But then many of these oogonia die and about 50,000 remain. These cells differentiate into primary oocytes.
The barrier also protects the germ cells from blood-borne noxious agents, prevents antigenic products of germ cell maturation from entering the circulation and generating an autoimmune response, and may help establish an osmotic gradient that facilitates movement of fluid into the tubular lumen.
DNA methylation dynamic during mouse embryonic development After fertilization some cells of the newly formed embryo migrate to the germinal ridge and will eventually become the germ cells (sperm and oocytes) of the next generation. Due to the phenomenon of genomic imprinting, maternal and paternal genomes are differentially marked and must be properly reprogrammed every time they pass through the germline. Therefore, during the process of gametogenesis the primordial germ cells must have their original biparental DNA methylation patterns erased and re-established based on the sex of the transmitting parent. After fertilization, the paternal and maternal genomes are demethylated in order to erase their epigenetic signatures and acquire totipotency.
When the germ cells reach the gonads, they undergo proliferation via mitosis and at 13.5 days of rat development they begin to undergo meiosis in the ovary but arrested at the mitotic stage in the testes. In the ovary, after mitosis, the gametogonium undergo meiosis, which is initiated by intrinsic competence factor DazL and extrinsic retinoic acid, excreted by the mesonephros. Retinoic acid is the major factor in meiosis, upregulating genes including ‘‘Stra8’‘, ‘‘Dmc1’‘ and ‘‘Sycp3’‘, which all have a role in meiosis. The male germ cells are protected from external signalling, like retinoic acid from the mesonephros, by the Leydig and Sertoli cells.
Following the establishment of Mendel's laws, the gene- chromosome theory of heredity was confirmed by the work of August Weismann who identified chromosomes as the hereditary material. Also, in observing the halving of the chromosome number in germ cells he anticipated work to follow on the details of meiosis, the complex process of redistribution of hereditary material that occurs in the germ cells. In the 1920s and 1930s population genetics combined the theory of evolution with Mendelian genetics to produce the modern synthesis. By the mid-1960s the molecular basis of metabolism and reproduction was firmly established through the new discipline of molecular biology.
This protein is localized in germ cells of the testis at all stages of spermatogenesis and is localized to the acrosomal region of mature spermatozoa. Alternatively spliced variants that encode different protein isoforms have been described but the full-length sequences of only two have been determined.
Microscopically, they appear identical to seminomas and very close to embryonic primordial germ cells, having large, polyhedral, rounded clear cells. The nuclei are uniform and round or square with prominent nucleoli and the cytoplasm has high levels of glycogen. Inflammation is another prominent histologic feature of dysgerminomas.
Host- parasite interaction studies show the involvement of Bcl-2 proteins in parasite survival. Other studies with cells having high division index like cancer cells and mammalian germ cells provides insight into the various pathways that are triggered by stress and their functional relevance in cell survival.
This keeps spermatogenesis from starting too soon. In females, the mesonephros releases RA, which enters the gonad. RA stimulates Stra8, a critical gatekeeper of meiosis (1), and Rec8, causing primordial germ cells to enter meiosis. This causes the development of oocytes that arrest in meiosis I. 1\.
Since the egg contributes the organelles and has more space and opportunity for intracellular symbionts to be passed to subsequent generations, it is a very common method of vertical transmission. Intracellular symbionts can migrate from the bacteriocyte to the ovaries and become incorporated in germ cells.
This movement is coordinated by the expression of the chemo- attractant SDF1A (stromal derived factor 1a). The final migration towards the developing gonad occurs 13 hours-post-fertilisation after which point the germ cells coalesce with the somatic gonadal precursor cells. The entire process takes around 24 hours.
FANCB mutant mice are infertile and exhibit primordial germ cell defects during embryogenesis. The germ cells and testicular size are severely compromised in FANCB mutant mice. FANCB protein is essential for spermatogenesis and likely has a role in the activation of the Fanconi anemia DNA repair pathway during meiosis.
Spermatogenesis is the production of sperm cells in the testis. In mature testes primordial germ cells divide mitotically to form the spermatogonia, which in turn generate spermatocytes by mitosis. Then each spermatocyte gives rise to four spermatids through meiosis. Spermatids are now haploid and undergo differentiation into sperm cells.
Testis has two major functions: To produce sperm by meiotic division of germ cells within the seminiferous tubules, and to synthesize and secrete androgens that regulate the male reproductive functions. The site of production of androgens is the Leydig cells that are located in the interstitium between seminoferous tubules.
Nematocyte precursors migrate into feeding polyps and germ cells migrate into sexual polyps. Nerve cells are found in all parts of the colony. While Hydractinia do not have a bodily axis of symmetry, the polyps exhibit oral/aboral symmetry. In the planula stage, the Hydractinia exhibit anterior/posterior symmetry.
Spermatogenesis as the cells progress from spermatogium, to primary spermatocytes, to secondary spermatocytes, to spermatids and to Sperm. Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules.
Increasing the hormones FSH and LH in males will not increase the rate of spermatogenesis. However, with age, the rate of production will decrease, even when the amount of hormone that is secreted is constant; this is due to higher rates of degeneration of germ cells during meiotic prophase.
Mammalian spermatogenesis is representative for most animals. In human males, spermatogenesis begins at puberty in seminiferous tubules in the testicles and go on continuously. Spermatogonia are immature germ cells. They proliferate continuously by mitotic divisions around the outer edge of the seminiferous tubules, next to the basal lamina.
DMRT1, a gene that regulates development of Sertoli cells, was found to be expressed in female germ cells before meiosis, however no Sertoli cells were present in the fully-developed ovotestes. Additionally, the female germ cells only enter meiosis postnatally, a phenomenon that has not been found in any other eutherian mammal. Phylogenetic analyses have suggested that, like in lemuroids, this trait must have evolved in a common ancestor of the clade, and has been "turned off and on" in different Talpid lineages. Female European moles are highly territorial and will not allow males in to their territory outside of breeding season, the probable cause of this behavior being the high levels of testosterone secreted by the female ovotestes.
In 1892, the Austrian biologist August Weismann proposed that multicellular organisms consist of two separate types of cell: somatic cells, which carry out the body's ordinary functions, and germ cells, which transmit heritable information. He called the material that carried the information, now identified as DNA, the germ plasm, and individual components of it, now called genes, determinants which controlled the organism. Weismann argued that there is a one-way transfer of information from the germ cells to somatic cells, so that nothing acquired by the body during an organism's life can affect the germ plasm and the next generation. This effectively denied that Lamarckism (inheritance of acquired characteristics) was a possible mechanism of evolution.
When CSF 1 was added in culture with GDNF and FGF2 no further increase in proliferation was observed, however, the longer the germ cells remained in culture with CSF-1 the greater the SSC density observed when these germ cells were transplanted into host seminiferous tubules. This showed CSF 1 to be a specific renewal factor that tilts the SSCs towards renewal over differentiation, rather than affecting proliferation of SSCs and spermatogonia. GDNF, FGF 2 and CSF 1 have also been shown to influence self- renewal of stem cells in other mammalian tissues. Plzf (Promyelocytic leukaemia zinc finger) has also been implicated in regulating SSC self-renewal and is expressed by Asingle, Apaired and Aaligned spermatogonia.
It is theorized that oogonia either degenerate or differentiate into primary oocytes which enter oogenesis and are halted in prophase I of the first meiosis post partum. Therefore, it is believed that adult mammalian females lack a population of germ cells that can renew or regenerate, and instead have a large population of primary oocytes that are arrested in the first meiosis until puberty. At puberty, one primary oocyte will continue meiosis each menstrual cycle. Because there is an absence of regenerating germ cells and oogonia in the human, the number of primary oocytes dwindles after each menstrual cycle until menopause, when the female no longer has a population of primary oocytes.
The gonocyte population develops from the post migratory germ cells (PGCs) around embryonic day (ED) 15. At this point of development, PGCs become dormant and remain inactiveted until birth. Shortly after birth, the cell cycle continues and the production of postnatal spermatogonia commences. Gonocytes migrate to the basement membrane to proliferate.
Due to the localization of vasa, immunohistochemistry staining can be done with vasa antibodies. For example, vasa antibody staining is specific for germline stem cells in the D. melanogaster germarium. This protein is localized to the cytoplasm of fetal germ cells and to the cytoplasm of developing oocytes in the mammals.
Histopathology of testicular tissue showing immature germ cells and spermatagonia with decreased tubular diameter. Scattered groups of Leydig cells appearing immature. All forms of androgen insensitivity, including CAIS, are associated with infertility, though exceptions have been reported for both the mild and partial forms. CAIS is associated with a decreased bone mineral density.
Normal spermatogenesis, testis biopsy. High-power view of a seminiferous tubule with normal spermatogenesis. Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules.
This period consists of the primordial germ cells (PGC), the initial cells that commence germ cell development in the embryo, and the gonocytes, which after being differentiated from PGCs, undergo regulated proliferation, differentiation, migration and apoptosis to produce the SSCs. Gonocytes therefore correspond to the developmental stages between the PGCs and SSCs.
At this point the PGCs have about the same level of methylation as the somatic cells. The newly formed primordial germ cells (PGC) in the implanted embryo devolve from the somatic cells. At this point the PGCs have high levels of methylation. These cells migrate from the epiblast toward the gonadal ridge.
Allelic gene conversion occurs during meiosis when homologous recombination between heterozygotic sites results in a mismatch in base pairing. This mismatch is then recognized and corrected by the cellular machinery causing one of the alleles to be converted to the other. This can cause non-Mendelian segregation of alleles in germ cells.
In the Xenopus egg, the germ cell determinants are found in the most vegetal blastomeres. These presumptive PGCs are brought to the endoderm of the blastocoel by gastrulation. They are determined as germ cells when gastrulation is completed. Migration from the hindgut along the gut and across the dorsal mesentery then takes place.
Heilmann's comparative illustrations of the embryos and adults of several extant birds and reptiles In this section, Heilmann draws evidence from his observations of germ cells, impregnation, cell division, ontogeny and comparative embryology about the probable ancestry of birds. A fair amount of detail is devoted early in the section to comparative studies between the germ cells of many different species of extant bird and reptile (and several mammals), including some comments on the corkscrew locomotion observed in the spermatozoa cells of several bird and reptile species, but no mammals.Heilmann (1926) pp. 61–63. He then goes on to offer a similar comparison between the egg cells of birds and reptiles, and finds considerably more similarity there than either has to the egg cell of a mammal.
RNP granules are a highly diverse group of compartments. These include stress granules, processing bodies, and exosomes in somatic cells. Many RNP granules are cell type and/or species specific. For example, chromatoid bodies are found only in male germ cells, whereas transport granules have so far been found only in neurons and oocytes.
An up- regulation of egfl7 is observed in endothelial cells during vascular remodelling tissues, such as in reproductive organs during pregnancy, in regenerating endothelium following arterial injury, in atherosclerotic plaques, and in growing tumours. Expression of egfl7 has also been reported in primordial germ cells and in adult ovaries and testes and in neurons.
The developing salamander thus metabolizes the oxygen, producing carbon dioxide (which then the alga consumes). Photosynthetic algae are present within the somatic and possibly the germ cells of the salamander. When the eggs hatch depends on the water temperatures. Spotted Salamander (Ambystoma maculatum) Larva As larvae, they are usually light brown or greenish-yellow.
This protein localizes to the plasma membrane of germ cells in the testis and to the post-acrosomal plasma membrane of mature spermatozoa. Recombinant polypeptide binds GTP and exhibits GTPase activity. Thus, this protein may regulate GTP signal transduction pathways involved in spermatogenesis and fertilization. Two transcript variants of this gene encode the same protein.
An oocyte (, ), oöcyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell (PGC), which then undergoes mitosis, forming oogonia.
Treatment of male mice with melphalan, a bifunctional alkylating agent frequently employed in chemotherapy, induces DNA lesions during meiosis that may persist in an unrepaired state as germ cells progress through DNA repair-competent phases of spermatogenic development. Such unrepaired DNA damages in sperm cells, after fertilization, can lead to offspring with various abnormalities.
Although tissue-level expression is ubiquitous, C1orf112 is expressed highest in the testes, lymph nodes, brain marrow, and cerebellum, with samples from 97 individual in 27 different tissues. In-situ hybridization of the human transcriptome indicates expression is highest in the atrioventricular node, followed by the testis, testis germ cells, and testis interstitial tissue.
Germ- line mutations are the result of a change in the genetic structure of germ cells. These mutations are able to be transmitted to the offspring and give rise to a constitutional mutation. Constitutional mutations is a mutation that when present in one cell, is also present in all other cells associated with the organism.
Therefore, chimeric individuals exhibit a phenotype that is the result of more than one genotype, and potentially more than one father. Researchers first discovered chimerism in the bone marrow of marmosets in the 1960s. More recent work has shown that chimerism can occur in all cell lines, including germ cells. This allows for the possibility of horizontal inheritance.
Then demethylation of the PGCs takes place in two waves. At day 9.5 the primordial germ cells begin to rapidly replicate going from about 200 PGCs at embryo day 9.5 to about 10,000 PGCs at day 12.5. During days 9.5 to 12.5 DNMT3a and DNMT3b are repressed and DNMT1 is present in the nucleus at a high level.
Also, Primordial germ cells are first found in the wall of the yolk sac. After the 4th week of development, the growing embryonic disc becomes a great deal larger than the yolk sac and its presence usually dies out before birth. However, seldom will the yolk sac remain as deviation of the digestive tract named Meckel's diverticulum.
In mammals, epigenetic marks are erased during two phases of the life cycle. Firstly just after fertilization and secondly, in the developing primordial germ cells, the precursors to future gametes. During fertilization the male and female gametes join in different cell cycle states and with different configuration of the genome. The epigenetic marks of the male are rapidly diluted.
Oct-4 has been implicated in tumorigenesis of adult germ cells. Ectopic expression of the factor in adult mice has been found to cause the formation of dysplastic lesions of the skin and intestine. The intestinal dysplasia resulted from an increase in progenitor cell population and the upregulation of β-catenin transcription through the inhibition of cellular differentiation.
Rediae: The rediae are the second larval stage of the trematode life cycle, that develops from the miracidum and contains germ cells that develop into cercariae. The rediae are found in the second intermediate host, the snail. Rediae can range from 0.45 mm to 3 mm, and the larger rediae can contain up to 76 cercariae.
Similar germ plasm has been identified in Amphibians in the polar cytoplasm at the vegetal pole. This cytoplasm moves to the bottom of the blastocoel and eventually ends up as its own subset of endodermal cells. While specified to produce germ cells, the germ plasm does not irreversibly commit these cells to produce gametes and no other cell type.
In the mouse, primordial germ cells are from epiblast cells. This specification is accompanied by extensive epigenetic reprogramming that involves global DNA demethylation, chromatin reorganization and imprint erasure . This results in totipotency. The mammalian equivalent to the chick hypoblast is called the Anterior visceral endoderm (AVE) and creates an anterior region by secreting antagonists of Nodal.
In addition to this, the cells of the organism, at every stage of development, throw off such particles, which are conducted to the germ-cells and transmit to them those characters which the respective cells may have acquired during development. De Vries also coined the term 'pangene' which 20 years later was shortened by Wilhelm Johannsen to gene.
A chromatoid body is a dense structure in the cytoplasm of male germ cells. It is composed mainly of RNAs and RNA-binding proteins and is thus a type of RNP granule. Chromatoid body-like granules first appear in spermatocytes and condense into a single granule in round spermatids. The structure disappears again when spermatids start to elongate.
In Silkmoth germ cells, it was proposed that Vasa protein coordinates the Ping-Pong mechanism of Silkmoth Aub (Siwi) and Ago3. It is likely that the mechanism of Ping-Pong is primarily coordinated by Krimper but factors such as Kumo/Qin and Vasa, in addition to other factors have necessary functions in the Ping-Pong mechanism.
It interacts with the enhancer of polycomb protein and represses gene transcription. It is also thought to be involved in the differentiation of male germ cells. Fusion of the N-terminus of this protein with the truncated C-terminus of the RET gene product has been shown to result in production of the ret transforming protein.
There is also research being done on possible germ line regeneration in primates. Mitotically active human female germ cells could be very beneficial to a new method of embryonic stem cell development that involves a nuclear transfer into a zygote. Using these functional oogonia may help to create patient-specific stem cell lines using this method.
Mutations in Vasa homolog, Mvh, cause defects in spermatogenesis but females are fertile. Male sterility may be due to deficiencies in germ cell proliferation and differentiation (the mouse homolog of Droso.). Female fertility may be due to functional redundancy by other DEAD-box family members. Null mutation still allows primordial germ cells to form but have severe defects.
Innovative experimental methods such as Louis Pasteur's contributed to the young field of bacteriology in the late 19th century. Cell theory led zoologists to re-envision individual organisms as interdependent assemblages of individual cells. Scientists in the rising field of cytology, armed with increasingly powerful microscopes and new staining methods, soon found that even single cells were far more complex than the homogeneous fluid-filled chambers described by earlier microscopists. Much of the research on cell reproduction came together in August Weismann's theory of heredity: he identified the nucleus (in particular chromosomes) as the hereditary material, proposed the distinction between somatic cells and germ cells (arguing that chromosome number must be halved for germ cells, a precursor to the concept of meiosis), and adopted Hugo de Vries's theory of pangenes.
The Xi marks the inactive, Xa the active X chromosome. XP denotes the paternal, and XM to denotes the maternal X chromosome. When the egg (carrying XM), is fertilized by a sperm (carrying a Y or an XP) a diploid zygote forms. From zygote, through adult stage, to the next generation of eggs, the X chromosome undergoes the following changes: # XiP XiM zygote → undergoing zygotic genome activation, leading to: # XaP XaM → undergoing imprinted (paternal) X-inactivation, leading to: # XiP XaM → undergoing X-activation in the early blastocyst stage, leading to: # XaP XaM → undergoing random X-inactivation in the embryonic lineage (inner cell mass) in the blastocyst stage, leading to: # XiP XaM OR XaP XiM → undergoing X-reactivation in primordial germ cells before meiosis, leading to: # XaM XaP diploid germ cells in meiotic arrest.
Theoretically, these cells are not germ cells (the source of gametes); they transmit their mutations, to their cellular descendants (if they have any), but not to the organism's descendants. However, in sponges, non-differentiated somatic cells form the germ line and, in Cnidaria, differentiated somatic cells are the source of the germline. Mitotic cell division is only seen in diploid somatic cells.
Muscle tissues are derived from the mesodermal layer of embryonic germ cells in a process known as myogenesis. There are three types of muscle, skeletal or striated, cardiac, and smooth. Muscle action can be classified as being either voluntary or involuntary. Cardiac and smooth muscles contract without conscious thought and are termed involuntary, whereas the skeletal muscles contract upon command.
Studies in Dp2 gene-deficient (i.e. Dp2−/-) mice indicate that DP2 is essential for controlling cell cycle genes in fetal testes which contribute to the arrest of mitotic process and to the differentiate of germ cells. This control involves, at least in part, the DP2-dependent activation of the male germ cell marker Nanos2 and the inhibition of meiosis through repression of Stra8.
Some lines of iPSCs have the potentiality to differentiate into male germ cells and oocyte- like cells in an appropriate niche (by culturing in retinoic acid and porcine follicular fluid differentiation medium or seminiferous tubule transplantation). Moreover, iPSC transplantation make a contribution to repairing the testis of infertile mice, demonstrating the potentiality of gamete derivation from iPSCs in vivo and in vitro.
Cancer/testis (CT) antigens are a group of proteins united by their importance in development and in cancer immunotherapy. In general, expression of these proteins is restricted to male germ cells in the adult animal. However, in cancer these developmental antigens are often re-expressed and can serve as a locus of immune activation. Thus, they are often classified as tumor antigens.
Through directional migration - which requires multiple genes to work, one being the Columbus (clb) gene, which codes for Drosophila HMG CoA reductase - the germ cells move towards the somatic gonadal precursor cells and associate with them. These two associated cell types then migrate together anteriorly, until they coalesce into the embryonic gonad at the future site of the mature gonad.
Meiotic resumptio is visually manifested as “germinal vesicle breakdown” (GVBD), referring to the primary oocyte nucleus. GVBD is the process of nuclear envelope dissolution and chromosome condensation similar to mitotic prophase. In females, the process of folliculogenesis begins during fetal development. Folliculogenesis is the maturation of ovarian follicles. Primordial germ-cells (PGC’S) undergo meiosis leading to the formation of primordial follicles.
The NR4A1 gene is a transcription factor important in the development of cells that secrete the hormone insulin-like 3 (INSL3). In general, the NR4A gene family regulates cell growth and differentiation. In humans, INSL3 aids in the regulation of testicular descent during fetal development. In an adult INSL3 helps in keeping germ cells alive, in both males and females.
However, in general, dysgerminomas are bilateral 10–20% of the time. They are composed of cells that cannot differentiate further and develop directly from germ cells or from gonadoblastomas. Dysgerminomas contain syncytiotrophoblasts in approximately 5% of cases, and can therefore cause elevated hCG levels. On gross appearance, dysgerminomas are typically pink to tan-colored, have multiple lobes, and are solid.
Tcfap2c mutants exhibited an early loss of primordial germ cells. Tcfap2c is thought to repress somatic gene expression, including the mesodermal marker Hoxb1. So, Blimp1, Tcfap2c and Prdm14 together are able to activate and repress the transcription of all the necessary genes to regulate PGC specification. Mutation of Prdm14 results in the formation of PGCs that are lost by embryonic day 11.5.
As postmeiotic germ cells develop to mature sperm they progressively lose the ability to repair DNA damage that may then accumulate and be transmitted to the zygote and ultimately the embryo. In particular, the repair of DNA double-strand breaks by the non-homologous end joining pathway, although present in round spermatids, appears to be lost as they develop into elongated spermatids.
Oogenesis takes place during fetal life, in which primordial germ cells undergo mitosis until a few weeks prior to birth, forming oogonia. These then begin meiosis to form the oocyte within the primordial follicle. This follicle consists of the oocyte surrounded by flattened pregranulosa cells. Babies are born with 1-2 million primordial follicles, and by puberty have around 300,000.
Both male and female Ercc1-deficient mice are infertile. The DNA repair function of Ercc1 appears to be required in both male and female germ cells at all stages of their maturation. The testes of Ercc1-deficient mice have an increased level of 8-oxoguanine in their DNA, suggesting that Ercc1 may have a role in removing oxidative DNA damages.
Vaccines are injections of weak germ cells into the body that stimulate the body to produce antibodies specific to that germ. This ensures that the body will build an immunity, and that next time the germ is introduced, it will be more equipped to fight it off. Mosaic proteins of the germs can be designed in order to maximize antibody production and quality.
In terms of spermatogonia distribution, the structure of teleost testes have two types: in the most common, spermatogonia occur all along the seminiferous tubules, while in Atherinomorpha, they are confined to the distal portion of these structures. Fish can present cystic or semi-cystic spermatogenesis in relation to the release phase of germ cells in cysts to the lumen of the seminiferous tubules.
Deleted in azoospermia protein 3 is a protein that in humans is encoded by the DAZ3 gene. This gene is a member of the DAZ gene family and is a candidate for the human Y-chromosomal azoospermia factor (AZF). Its expression is restricted to premeiotic germ cells, particularly in spermatogonia. It encodes an RNA- binding protein that is important for spermatogenesis.
Mosaicism arises after the zygote has formed and a mutation occurs during development. The mutated cell line can be passed down to offspring if the germ- cells are affected. When an individual has inherited an abnormality it is usually present in all of their cells. However some mutations like DNA code change, epigenetic alterations and chromosomal abnormalities, can occur later in development.
In S phase, the chromosomes are replicated in order for the genetic content to be maintained. During G2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized. The M phase, can be either mitosis or meiosis depending on the type of cell. Germ cells, or gametes, undergo meiosis, while somatic cells will undergo mitosis.
Multicellular eukaryotes are made of two fundamental cell types. Germ cells produce gametes and are the only cells that can undergo meiosis as well as mitosis. These cells are sometimes said to be immortal because they are the link between generations. Somatic cells are all the other cells that form the building blocks of the body and they only divide by mitosis.
Deleted in azoospermia protein 2 is a protein that in humans is encoded by the DAZ2 gene. This gene is a member of the DAZ gene family and is a candidate for the human Y-chromosomal azoospermia factor (AZF). Its expression is restricted to premeiotic germ cells, particularly in spermatogonia. It encodes an RNA- binding protein that is important for spermatogenesis.
A somatic cell (from Ancient Greek σῶμα sôma, meaning "body"), or vegetal cell, is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell. In contrast, gametes are cells that fuse during sexual reproduction, germ cells are cells that give rise to gametes, and stem cells are cells that can divide through mitosis and differentiate into diverse specialized cell types. For example, in mammals, somatic cells make up all the internal organs, skin, bones, blood and connective tissue, while mammalian germ cells give rise to spermatozoa and ova which fuse during fertilization to produce a cell called a zygote, which divides and differentiates into the cells of an embryo. There are approximately 220 types of somatic cell in the human body.
Weismann worked on the embryology of sea urchin eggs, and in the course of this observed different kinds of cell division, namely equatorial division and reductional division, terms he coined (Äquatorialteilung and Reduktionsteilung respectively). His germ plasm theory states that multicellular organisms consist of germ cells containing heritable information, and somatic cells that carry out ordinary bodily functions. The germ cells are influenced neither by environmental influences nor by learning or morphological changes that happen during the lifetime of an organism, which information is lost after each generation. The concept as he proposed it was referred to as Weismannism in his day, for example in the book An examination of Weismannism by George Romanes This idea was illuminated and explained by the rediscovery of Gregor Mendel's work in the early years of the 20th century (see Mendelian inheritance).
Horizontal, or lateral, transmission describes the acquisition of a facultative symbiont from the environment or from a nearby host. The life cycle of the host includes both symbiotic and aposymbiotic phases. The aposymbiotic phase generally begins in the germ cells and during development the host organism acquires the symbiont and translocates it to a symbiont-housing organ. The host will release the symbiont before reproduction.
The study confirmed the presence of the chromosome translocation known as Robertsonian translocation (1;29), a widespread evolutionary marker common to all known tragelaphid species. An accidental mating between a male giant eland and a female kudu produced a male offspring, but it was azoospermic. Analysis showed that it completely lacked germ cells, which produce gametes. Still, the hybrid had a strong male scent and exhibited male behaviour.
In males, meiosis occurs during spermatogenesis in the seminiferous tubules of the testicles. Meiosis during spermatogenesis is specific to a type of cell called spermatocytes, which will later mature to become spermatozoa. Meiosis of primordial germ cells happens at the time of puberty, much later than in females. Tissues of the male testis suppress meiosis by degrading retinoic acid, proposed to be a stimulator of meiosis.
Researchers at Münster University developed in vitro culture conditions using a three-dimensional agar culture system which induces mouse testicular germ cells to reach the final stages of spermatogenesis, including spermatozoa generation. If reproduced in humans, this could potentially enable infertile men to father children with their own sperm. Researchers from Montana State University developed precursors of sperm from skin cells of infertile men. Sharpe et al.
The study confirmed the presence of the chromosome translocation known as Robertsonian translocation (1;29), a widespread evolutionary marker common to all known tragelaphid species. An accidental mating between a male giant eland and a female kudu produced a male offspring, but it was azoospermic. Analysis showed that it completely lacked germ cells, which produce gametes. Still, the hybrid had a strong male scent and exhibited male behaviour.
In essence, DNA methylation patterns differ between germ cells and somatic cells as well as between the human and chimpanzee sperm cells. Meaning, differences in promoter methylation could possible account for the phenotypic differences between humans and primates.Molaro A, Hodges E, Fang F, Song Q, McCombie WR, et al. Sperm methylation profiles reveal features of epigenetic inheritance and evolution in primates. Cell. 2011;146:1029–41.
Most gross genomic mutations in gamete germ cells probably result in inviable embryos; however, a number of human diseases are related to large-scale genomic abnormalities. Down syndrome, Turner Syndrome, and a number of other diseases result from nondisjunction of entire chromosomes. Cancer cells frequently have aneuploidy of chromosomes and chromosome arms, although a cause and effect relationship between aneuploidy and cancer has not been established.
The majority of DMRT1 protein is located in the testicular cord and Sertoli cells, with a small amount in the germ cells. This gene exhibits a gonad-specific and sexually dimorphic expression pattern, just like the related doublesex gene in fruit flies. Defective testicular development and XY feminization occur when this gene is hemizygous. Two copies of the DMRT1 gene are required for normal sexual development.
Kimble moved to the University of Wisconsin-Madison in 1983 where she took up an assistant professorship position. Discovery of the distal tip cell gave her the means of exploring the control of germline stem cells. She then began to examine the genetic and molecular mechanisms responsible for germline stem cells and the processes by which germ cells develop into sperm or egg cells.
Tyrosine phosphorylation mediates in signal transduction pathways during germ cell development and determines their association with the differentiation of a functional gamete. Until testicular germ cells differentiate into spermatozoa, cAMP-induced tyrosine phosphorylation is not detectable. Entry of these cells into the epididymis is accompanied by sudden activation of the tyrosine phosphorylation pathway, initially in the principal piece of the cell and subsequently in the midpiece.
Oogenesis is the formation of a cell who will produce one ovum and three polar bodies. Oogenesis begins in the female embryo with the production of oogonia from primordial germ cells. Like spermatogenesis, the primordial germ cell undergo mitotic division to form the cells that will later undergo meiosis, but will be halted at the prophase I stage. This is known as the primary oocyte.
Cleavage in most animals segregates cells containing germ plasm from other cells. The germ plasm effectively turns off gene expression to render the genome of the cell inert. Cells expressing germ plasm become primordial germ cells (PGCs) which will then give rise to the gametes. The germ line development in mammals, on the other hand, occurs by induction and not by an endogenous germ plasm.
For over 130 years, electrology has been in use in the United States. It is approved by the FDA. This technique permanently destroys germ cells responsible for hair growth by way of insertion of a fine probe in the hair follicle and the application of a current adjusted to each hair type and treatment area. Electrology is the only permanent hair removal method recognized by the FDA.
Albacore have asynchronous oocyte development, that is their immature egg cells do not develop at regular intervals. The creation of ova, known as oogenesis, begins with the rapid production of oogonia (undifferentiated germ cells that give rise to oocytes) by mitotic separations in the oogonial nests of female tuna. The resulting oocytes are cast en masse into the sea, where full development and later fertilization take place.
Viruses causing disease in humans often enter through the mouth, nose, genital tract, or through damaged areas of skin, so cells of the respiratory, gastrointestinal, skin and genital tissues are often the primary site of infection. Some viruses are capable of transmission to a mammalian fetus through infected germ cells at the time of fertilization, later in pregnancy via the placenta, and by infection at birth.
Gametogonium (plural gametogonia) are stem cells for gametes located within the gonads. They originate from primordial germ cells, which have migrated to the gonads. Male gametogonia which are located within the testes during development and adulthood are called spermatogonium (plural spermatogonia). Female gametogonia, known as oogonium (plural oogonia), are found within the ovaries of the developing foetus and were thought to be depleted at or after birth.
The developing male germ cells do not complete cytokinesis during spermatogenesis. Consequently, cytoplasmic bridges assure connection between the clones of differentiating daughter cells to form a syncytium. In this way the haploid cells are supplied with all the products of a complete diploid genome. Sperm that carry a Y chromosome, for example, is supplied with essential molecules that are encoded by genes on the X chromosome.
The ovaries are not part of the Mullerian system and arise from primordial germ cells, which develop at the gonadal ridge. The formation of the female reproductive tract via the Mullerian ducts has 3 distinct stages. An array of Mullerian anomalies can occur if any of these processes are arrested or impaired. The first stage of Mullerian duct development is organogenesis, where both Mullerian ducts are formed.
Not all cells carry out cell cycle withdrawal. In some cells, such as germ cells, stem cells and white blood cells, the withdrawal process do not occur. This is to ensure that these cells continue dividing for body growth or reproduction. Such phenomena is brought about by the presence of telomerase, which would catalyse the reaction of adding nucleotide sequences to the ends of telomeres.
Much of the research on cell reproduction came together in August Weismann's theory of heredity: he identified the nucleus (in particular chromosomes) as the hereditary material, proposed the distinction between somatic cells and germ cells (arguing that chromosome number must be halved for germ cells, a precursor to the concept of meiosis), and adopted Hugo de Vries's theory of pangenes. Weismannism was extremely influential, especially in the new field of experimental embryology.Sapp, Genesis, chapter 8; Coleman, Biology in the Nineteenth Century, chapter 3 By the mid-1850s the miasma theory of disease was largely superseded by the germ theory of disease, creating extensive interest in microorganisms and their interactions with other forms of life. By the 1880s, bacteriology was becoming a coherent discipline, especially through the work of Robert Koch, who introduced methods for growing pure cultures on agar gels containing specific nutrients in Petri dishes.
Germ plasm () is a biological concept developed in the 19th century by the German biologist August Weismann. It states that heritable information is transmitted only by germ cells in the gonads (ovaries and testes), not by somatic cells. The related idea that information cannot pass from somatic cells to the germ line, contrary to Lamarckism, is called the Weismann barrier. The theory to some extent anticipated the development of modern genetics.
The newly formed primordial germ cells (PGC) in the implanted embryo devolve from the somatic cells. At this point the PGCs have high levels of methylation. These cells migrate from the epiblast toward the gonadal ridge. As reviewed by Messerschmidt et al., the majority of PGCs are arrested in the G2 phase of the cell cycle, while they migrate toward the hindgut during embryo days 7.5 to 8.5.
The ejaculatory duct is derived from an invagination of the epidermal cells during development and, as a result, has a cuticular lining. The terminal portion of the ejaculatory duct may be sclerotized to form the intromittent organ, the aedeagus. The remainder of the male reproductive system is derived from embryonic mesoderm, except for the germ cells, or spermatogonia, which descend from the primordial pole cells very early during embryogenesis.
This gene encodes a member of the RING-B-box- coiled-coil (RBCC) family and encodes a protein with an N-terminal RING finger motif, a PRY domain and a C-terminal SPRY domain. The mouse ortholog of this gene is specifically expressed in germ cells at the round spermatid stages during spermatogenesis and, when overexpressed, induces apoptosis. Alternatively spliced transcript variants encoding distinct isoforms have been described.
This paved the way to assign the nucleus an important role in heredity. In 1873, August Weismann postulated the equivalence of the maternal and paternal germ cells for heredity. The function of the nucleus as carrier of genetic information became clear only later, after mitosis was discovered and the Mendelian rules were rediscovered at the beginning of the 20th century; the chromosome theory of heredity was therefore developed.
During foetal development, gonocytes develop from primordial germ cells and following this SSCs develop from gonocytes in the testis. SSCs are the early precursor for spermatozoa and are responsible for the continuation of spermatogenesis in adult mammals. The stem cells are capable of dividing into more SSCs which is vital for maintaining the stem cell pool. Alternatively, they go on to differentiate into spermatocytes, spermatids and finally spermatozoa.
Elizabeth Shull Russell (May 1, 1913 – May 28, 2001), also known as "Tibby" Russell, was an American biologist in the field of mammalian developmental genetics, spending most of her career at the Jackson Laboratory in Bar Harbor, Maine. Russell is most recognized for her ground breaking work in pigmentation, blood-forming cells, and germ cells. She also raised awareness of the benefits of genetically-defined laboratory animals in biomedical research.
A-kinase anchor protein 4 is a scaffold protein that in humans is encoded by the AKAP4 gene. It involves in the intracellular signalling of protein kinase -A. AKAP4 is called as cancer /testis antigen (CTA), it belongs to a class of tumour linked antigens categories by high expression in germ cells and cancer than normal tissues. AKAP4 is not normally expressed in mRNA and protein level in MM cell line.
Known clastogens include acridine yellow, benzene, ethylene oxide, arsenic, phosphine and mimosine. Exposure to clastogens increases frequency of abnormal germ cells in paternal males, contributing to developmental effects in the fetus upon fertilization. : _Illustrative sentence_ : "This leads to the conclusion that a chemical that fails to induce a significant response in an in vitro clastogenicity assay is unlikely to be clastogenic in vivo, in bone marrow assays."Rose, John. (1988).
Germ plasm has been studied in detail in Drosophila. The posterior pole of the embryo contains necessary materials for the fertility of the fly. This cytoplasm, pole plasm, contains specialized materials called polar granules and the pole cells are the precursors to primordial germ cells. Pole plasm is organized by and contains the proteins and mRNA of the posterior group genes (such as oskar, nanos gene, Tudor, vasa, and Valois).
Overall, the functional X chromosome usually comes from the mother. In most cases, Turner syndrome is a sporadic event, and for the parents of an individual with Turner syndrome the risk of recurrence is not increased for subsequent pregnancies. Rare exceptions may include the presence of a balanced translocation of the X chromosome in a parent, or where the mother has 45,X mosaicism restricted to her germ cells.
The capacity for selfing in these fishes has apparently persisted for at least several hundred thousand years. Meioses that lead to self-fertilization can reduce genetic fitness by causing inbreeding depression. However, self- fertilization does provide the benefit of “fertilization assurance” (reproductive assurance) at each generation. Meiosis can also provide the adaptive benefit of efficient recombinational repair of DNA damages during formation of germ cells at each generation.
This gene encodes a member of the SOX (SRY- related HMG-box) family of transcription factors involved in the regulation of embryonic development and in the determination of the cell fate. The encoded protein may act as a transcriptional regulator after forming a protein complex with other proteins. The protein may be involved in the differentiation of developing male germ cells. Alternative splicing results in multiple transcript variants.
The MSP has two main functions in the reproduction of the helminthes: i) as cytosolic component it is responsible for the crawling movement of the mature sperm (without flagellum), and ii) once released, it acts as hormone on the female germ cells, where it triggers oocyte maturation and stimulates the oviduct wall to contract to bring the oocytes into position for fertilization. MSP has first been identified in Caenorhabditis elegans.
He was mentioned in dispatches in 1945. After the second world war he went to Bristol to train in cardiology and in 1948 was appointed registrar at Bristol Royal Infirmary, noted for studies in rheumatic heart disease. From 1951 to 1957 he was lecturer in medicine at Bristol University. During this time he published research on vibration sense, patent ductus arteriosus, paroxysmal nodal tachycardia, and primordial germ cells.
Although the overall risk of cancer in Down syndrome is not changed, the risk of testicular cancer and certain blood cancers, including acute lymphoblastic leukemia (ALL) and acute megakaryoblastic leukemia (AMKL) is increased while the risk of other non- blood cancers is decreased. People with Down syndrome are believed to have an increased risk of developing cancers derived from germ cells whether these cancers are blood or non-blood related.
Calcium/calmodulin-dependent protein kinase type IV is an enzyme that in humans is encoded by the CAMK4 gene. The product of this gene belongs to the serine/threonine protein kinase family, and to the Ca2+/calmodulin-dependent protein kinase (CAMK) subfamily. This enzyme is a multifunctional serine/threonine protein kinase with limited tissue distribution, that has been implicated in transcriptional regulation in lymphocytes, neurons, and male germ cells.
True multicellular organisms contain cells that are specialized for different functions. This is, in fact, an essential feature of sexual reproduction as well, since the male and female gametes are specialized cells. Organisms that reproduce sexually must solve the problem of generating an entire organism from just the germ cells. Sexual reproduction and the ability of gametes to develop into an organism are the necessary antecedents to true multicellularity.
In the model organism Drosophila, pole cells passively move from the posterior end of the embryo to the posterior midgut because of the infolding of the blastoderm. Then they actively move through the gut into the mesoderm. Endodermal cells differentiate and together with Wunen proteins they induce the migration through the gut. Wunen proteins are chemorepellents that lead the germ cells away from the endoderm and into the mesoderm.
The germ cells split into two populations and move to the paired gonadal ridges. Migration starts with 3-4 cells that undergo three rounds of cell division so that about 30 PGCs arrive at the gonads. On the migratory path of the PGCs, the orientation of underlying cells and their secreted molecules such as fibronectin play an important role. Mammals have a migratory path comparable to that in Xenopus.
Success of germ cell proliferation and differentiation is also ensured by a balance between germ cell development and programmed cell death. Identification of «death triggering signals» and corresponding receptor proteins is important for the fertilization potential of males. Apoptosis in germ cells can be induced by variety of naturally occurring toxicant. Receptors belonging to the taste 2 family are specialized to detect bitter compounds including extremely toxic alkaloids.
Offspring that contain the oncogene and have every cell in their body affected (including germ cells and somatic cells) by it are referred to as oncomice. Oncomice are useful for carcinogenic studies as they are more susceptible to carcinogens.Harvard College [2002] 4 SCR 45 at para 121 Such mice can be given material suspected of being a carcinogen and if tumours develop, it is an indication that the material is carcinogenic.
Plants and basal animals such as sponges and corals do not have a germline; instead they generate gametes from pluripotent stem cells in adult somatic tissues. In flowering plants, for example, germ cells can arise from adult somatic cells in the floral meristem. Other animals without a designated germ line include tunicates and flatworms. This distinction is also blurred in organisms that can reproduce asexually, without production of gametes.
Epigenetic changes may be temporary or may remain through successive cell divisions for the remainder of the cell's life. Some epigenetic changes have been shown to be heritable, while others are reset in the germ cells. Epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells.
Spermatogenesis-associated protein 16 is a mammalian protein encoded by the SPATA16 gene. SPATA16, also known as NYD-SP12, is a developmental protein that aids in differentiation of germ cells for spermatogenesis and participates in acrosome formation for appropriate sperm-egg fusion. SPATA16 is located on chromosome 3 at position 26.31 (reverse strand) and is a member of the tetratricopeptide repeat-like superfamily, which facilitate interactions and assemblies between proteins and protein complexes.
Gametes are produced within the gonads through a process known as gametogenesis. This occurs when certain types of germ cells undergo meiosis to split the normal diploid number of chromosomes (n=46) into haploid cells containing only 23 chromosomes.Development of sex cells in Reproductive system, Body Guide. Adam. Anatomy of the testis In males, this process is known as spermatogenesis, and takes place only after puberty in the seminiferous tubules of the testes.
Coiled-coil domain-containing protein 181 (CCDC181) is a protein that in human is encoded by C1orf114, which is located at the Chromosome 1 at 1q24.2. The accession is Q5T1D7. Researches have recently revealed that CCDC 181 is a microtubule-binding protein that interacts with murine Hook1 in haploid male germ cells and localizes to the sperm tail and motile cilia. The disruption of Hook1 may lead to inappropriate function of spermatogenesis.
Within an organism, DNA methylation levels can also vary throughout development and by region. For example, in mouse primordial germ cells, a genome wide de-methylation even occurs; by implantation stage, methylation levels return to their previous somatic values. When DNA methylation occurs at promoter regions, the sites of transcription initiation, it has the effect of repressing gene expression. This is in contrast to unmethylated promoter regions which are associated with actively expressed genes.
In cell biology, Meiomitosis is an aberrant cellular division pathway that combines normal mitosis pathways with ectopically expressed meiotic machinery resulting in genomic instability. Meiotic pathways are normally restricted to germ cells. Meiotic proteins drive double stranded DNA breaks, chiasma formation, sister chromatid adhesion and rearrange the spindle apparatus. During meiosis, there are 2 sets of cell divisions, the second division is similar to mitosis in that sister chromatids are directly separated.
Gonadotropin and sex steroid levels fall to low levels (nearly undetectable by current clinical assays) for approximately another 8 to 10 years of childhood. Evidence is accumulating that the reproductive system is not totally inactive during the childhood years. Subtle increases in gonadotropin pulses occur, and ovarian follicles surrounding germ cells (future eggs) double in number. Normal puberty is initiated in the hypothalamus, with de-inhibition of the pulse generator in the arcuate nucleus.
Schöler's major research interests are the molecular biology of cells of the germline (pluripotent cells and germ cells), transcriptional regulation of genes in the mammalian germline, deciphering the molecular processes of reprogramming somatic cells after induction with transcription factors, nuclear transfer into oocytes, or fusion with pluripotent cells. Nearly 170 of Schöler's publications are listed in the Citation Index. These publications were cited over 12,000 times. His Hirsch- Index is 58 (status December 2013).
Culture of human embryonic stem cells in mitotically inactivated porcine ovarian fibroblasts (POF) causes differentiation into germ cells (precursor cells of oocytes and spermatozoa), as evidenced by gene expression analysis. Human embryonic stem cells have been stimulated to form Spermatozoon-like cells, yet still slightly damaged or malformed. It could potentially treat azoospermia. In 2012, oogonial stem cells were isolated from adult mouse and human ovaries and demonstrated to be capable of forming mature oocytes.
The tumor is uniform in appearance, consisting of large, round cells with vesicular nuclei and clear or finely granular cytoplasm that is eosinophilic. On gross examination, the external surface is smooth and bosselated (knobby), and the interior is soft, fleshy, and either cream-coloured, gray, pink, or tan. Microscopic examination typically reveals uniform cells that resemble primordial germ cells. Typically, the stroma contains lymphocytes, and about 20% of patients have sarcoid-like granulomas.
He spent years conducting experiments on the effects of alcohol on germ cells, embryos and offspring. Stockard tested the effects of alcohol intoxication on the offspring of pregnant guinea pigs. He discovered that repeated alcohol intoxication in the guinea pigs produced defects and malformations in their offspring that was passed down to two or more generations. His results were challenged by the biologist Raymond Pearl who performed the same experiments with chickens.
Ruth Lehmann is a developmental and cell biologist. She is the Director of the Whitehead Institute for Biomedical Research, succeeding David Page. She previously was affiliated with the New York University School of Medicine, where she was the Director of the Skirball Institute of Biomolecular Medicine, the Laura and Isaac Perlmutter Professor of Cell Biology, and the Chair of the Department of Cell Biology. Her research focuses on germ cells and embryogenesis.
The development of germ cells can be divided into two phases. The first phases involves the fetal and neonatal phases of germ cell development that lead to the formation of the SSCs. The second phase is spermatogenesis, which is a cycle of regulated mitosis, meiosis and differentiation (via spermiogenesis) leading to the production of mature spermatozoa, also known as sperm cells. Gonocytes are functionally present during the first phase of germ cell maturation and development.
Achondroplasia is a dominant genetic disorder caused by mutations in FGFR3 that make the resulting protein overactive. Individuals with these mutation have a head size that is larger than normal and are significantly shorter in height. Only a single copy of the mutated FGFR3 gene results in achondroplasia. It is generally caused by spontaneous mutations in germ cells; roughly 80 percent of the time, parents with children that have this disorder are normal size.
This undergoes a period of divisions to form a ball or sheet of similar cells called a blastula or blastoderm. These cell divisions are usually rapid with no growth so the daughter cells are half the size of the mother cell and the whole embryo stays about the same size. They are called cleavage divisions. Mouse epiblast primordial germ cells (see Figure: “The initial stages of human embryogenesis”) undergo extensive epigenetic reprogramming.
The 23rd pair of chromosomes are the sex chromosomes. Normal females have two X chromosomes, while normal males have one X chromosome and one Y chromosome. The characteristics of the chromosomes in a cell as they are seen under a light microscope are called the karyotype. Karyogram from a normal male human During meiosis, when germ cells divide to create sperm and egg (gametes), each half should have the same number of chromosomes.
Sexual reproduction in flowering plants involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in stamens, and is carried to the pistil, which has the ovary at its base where fertilization can take place. Within each pollen grain is a male gametophyte which consists of only three cells. In most flowering plants the female gametophyte within the ovule consists of only seven cells.
But the cell has an enzyme called telomerase, which carries out the task of adding repetitive nucleotide sequences to the ends of the DNA. Telomerase "replenishes" the telomere "cap." In most multicellular eukaryotic organisms, telomerase is active only in germ cells, some types of stem cells such as embryonic stem cells, and certain white blood cells. Telomerase can be reactivated and telomeres reset back to an embryonic state by somatic cell nuclear transfer.
Most anthozoans are unisexual but some stony corals are hermaphrodite. The germ cells originate in the endoderm and move to the gastrodermis where they differentiate. When mature, they are liberated into the coelenteron and thence to the open sea, with fertilisation being external. To make fertilisation more likely, corals emit vast numbers of gametes, and many species synchronise their release in relation to the time of day and the phase of the moon.
The blood–testis barrier is a physical barrier between the blood vessels and the seminiferous tubules of the animal testes. The name "blood-testis barrier" is misleading in that it is not a blood-organ barrier in a strict sense, but is formed between Sertoli cells of the seminiferous tubule and as such isolates the further developed stages of germ cells from the blood. A more correct term is the "Sertoli cell barrier" (SCB).
Hydra oligactis with two buds. Reproduction by budding is an exception the rule that somatic mutations can not be inherited. The definition of a somatic mutation as any mutation that cannot be passed down to offspring is useful in animals that have a dedicated germline to produce reproductive cells. However, it is of little value in understanding the inheritance of somatic mutation in multicellular organisms that do not designate germ cells in early development.
Initial development of external genital is independent of androgens before indifferent gonads differentiate into testes. It occurs by week eight of gestation, as directed by a number of genes. External genitalia develop from mesenchymal cells underlying coelomic epithelium lining urogenital ridges on posterior wall of abdomen. Primordial germ cells (PGCs), precursors of gametes, migrate from egg sac into urogenital ridges, the site of gonad development in early embryonic development, by week six.
A. thaliana is a predominantly self-pollinating plant with an outcrossing rate estimated at less than 0.3%. An analysis of the genome-wide pattern of linkage disequilibrium suggested that self-pollination evolved roughly a million years ago or more. Meioses that lead to self-pollination are unlikely to produce significant beneficial genetic variability. However, these meioses can provide the adaptive benefit of recombinational repair of DNA damages during formation of germ cells at each generation.
The immature spermatozoa or sperm are then sent to the epididymis, where they gain a tail, enabling motility. Each of the original diploid germ cells or primary spermatocytes forms four functional gametes which is each forever young. The production and survival of sperms require a temperature below the normal core body temperature. Since the scrotum, where the testes is present, is situated outside the body cavity, it provides a temperature about 3 °C below normal body temperature.
This factor is thought to be expressed in the peritubular cells in human testes. Fibroblast growth factor (FGF2) is another molecule crucial for the regulation of stem cell renewal and is expressed in Sertoli cells, Leydig cells, and germ cells. FGF2 signalling interacts with GDNF to enhance proliferation rate. Chemokine (C-X-C motif) ligand 12 (CXCL12) signaling via its receptor C-X-C chemokine receptor type 4 (CXCR4) is also involved in regulation of SSC fate decisions.
Ovarian germ cell tumors (OGCTs) are heterogeneous tumors that are derived from the primitive germ cells of the embryonic gonad, which accounts for about 2.6% of all ovarian malignancies. There are four main types of OGCTs, namely dysgerminomas, yolk sac tumor, teratoma, and choriocarcinoma. Dygerminomas are Malignant germ cell tumor of ovary and particularly prominent in patients diagnosed with gonadal dysgenesis. OGCTs are relatively difficult to detect and diagnose at an early stage because of the nonspecific histological characteristics.
Whole genome duplication or polyploidization can be either autopolyploidization or alloploidization. Autopolyploidization is the duplication of the same genome and allopolyploidization is the duplication of two closely related genomes or hybridized genomes from different species. Duplication occurs primarily through uneven crossing over events in meiosis of germ cells. (1,2) When two chromosomes misalign, crossing over - the exchange of gene alleles - results in one chromosome expanding or increasing in gene number and the other contracting or decreasing in gene number.
Zinc finger protein basonuclin-1 is a protein that in humans is encoded by the BNC1 gene. The protein encoded by this gene is a zinc finger protein present in the basal cell layer of the epidermis and in hair follicles. It is also found in abundance in the germ cells of testis and ovary. This protein is thought to play a regulatory role in keratinocyte proliferation and it may also be a regulator for rRNA transcription.
Cancer-germline genes are an important source of tumor-specific antigens. These genes are expressed in a significant fraction of tumors of many different histological types. They are not expressed in normal adult cells with the exception of male and female germline cells. But the expression of cancer-germline genes in germ cells is inconsequential because in the healthy state these cells are devoid of HLA class I molecules and therefore cannot present antigens to T cells.
Serine/threonine-protein kinase MAK is an enzyme that in humans is encoded by the MAK gene. The product of this gene is a serine/threonine protein kinase related to kinases involved in cell cycle regulation. It is expressed almost exclusively in the testis, primarily in germ cells. Studies of the mouse and rat homologs have localized the kinase to the chromosomes during meiosis in spermatogenesis, specifically to the synaptonemal complex that exists while homologous chromosomes are paired.
Heilmann (1926) pp. 64–65. Following an analysis of the germ cells, he moves onward through the developmental cycle by next examining the process of fertilization and subsequent cleavage of the zygote. He presents here several figures and illustrations of the cleavage of the blastoderm in reptiles and birds. He examines in detail the expression of evolutionary stages in the development of embryos, tracing from the process of cell division to the development of specific anatomical features.
These gain-of-function mutations have been identified as germline mutations, meaning variations in the lineage of germ cells. Most mutations identified were de novo, meaning originating in the symptomatic patient and not inherited from either parent. However, multiple cases of inheritance have also been identified. In 2 families, family members carrying a STAT3 mutation were asymptomatic or had a less severe phenotype, indicating that there are carriers of these mutations who display autosomal dominant inheritance with incomplete penetrance.
Human germline engineering is the process by which the genome of an individual is edited in such a way that the change is heritable. This is achieved through genetic alterations within the germ cells, or the reproductive cells, such as the egg and sperm. Human germline engineering is a type of genetic modification that directly manipulates the genome using molecular engineering techniques. Aside from germline engineering, genetic modification can be applied in another way, somatic genetic modification.
Thus, the function and quality of a differentiated sperm cell is dependent upon the capacity of its originating spermatogonial stem cell (SSC). Gonocytes represent the germ cells undergoing the successive, short-term and migratory stages of development. This occurs between the time they inhabit the forming gonads on the genital ridge to the time they migrate to the basement membrane of the seminiferous cords. Gonocyte development consists of several phases of cell proliferation, differentiation, migration and apoptosis.
An enzyme system is present in oocytes that ordinarily accurately repairs DNA double- strand breaks. This repair system is called "homologous recombinational repair", and it is especially effective during meiosis. Meiosis is the general process by which germ cells are formed in all sexual eukaryotes; it appears to be an adaptation for efficiently removing damages in germ line DNA. (See Meiosis.) Human primary oocytes are present at an intermediate stage of meiosis, termed prophase I (see Oogenesis).
Estradiol produces cell proliferation in both normal and malignant breast epithelial tissue. However, GPER knockout mice show no overt mammary phenotype, unlike ERα knockout mice, but similarly to ERβ knockout mice. This indicates that although GPER and ERβ play a modulatory role in breast development, ERα is the main receptor responsible for estrogen-mediated breast tissue growth. GPER is expressed in germ cells and has been found to be essential for male fertility, specifically, in spermatogenesis.
During meiosis, unstable repeats can undergo triplet expansion (see later section); in this case, the germ cells produced have a greater number of repeats than are found in the somatic tissues. The mechanism behind the expansion of the triplet repeats is not well understood. One hypothesis is that the increasing number of repeats influence the overall shape of the DNA, which can have an effect on its interaction with DNA polymerase and thus the expression of the gene.
All higher multicellular organisms contain cells specialised for different functions. Most distinct cell types arise from a single totipotent cell that differentiates into hundreds of different cell types during the course of development. Differentiation of cells is driven by different environmental cues (such as cell–cell interaction) and intrinsic differences (such as those caused by the uneven distribution of molecules during division). Multicellular organisms are composed of cells that fall into two fundamental types: germ cells and somatic cells.
Her cytology research primarily concerned bowfin (Amia calva) and the lateral cell lines of these bony fish. She also worked on the cytology of the germ cells of certain hydroids, and published papers describing her findings in the academic journal, Biological Bulletin. Beckwith's teaching career at Vassar College began when she was appointed an assistant professor in 1900. She was later named a full professor and was chair of the zoology department when she retired in 1940.
Anemonia sulcata has a symbiotic relationship with zooxanthellae, which inhabit the tissues and provide energy for the sea anemone. It is dioecious, with individuals becoming sexually mature when they weigh about and the basal disc measures about across. There are no gonads, and the germ cells develop inside the mesenteries and break through the epithelium to enter the body cavity and thence move into the water column. At this stage, the oocytes already contain symbiotic zooxanthellae.
An illustration of the inheritance pattern and phenotypic effects of an autosomal recessive gene. Autosomal genetic disorders can arise due to a number of causes, some of the most common being nondisjunction in parental germ cells or Mendelian inheritance of deleterious alleles from parents. Autosomal genetic disorders which exhibit Mendelian inheritance can be inherited either in an autosomal dominant or recessive fashion. These disorders manifest in and are passed on by either sex with equal frequency.
In the other variant or Comstockiella system, the somatic cells have the paternal genome untouched. A third variant found in Diaspididae involves the paternal genome being completely removed at an early stage making males haploid both in somatic and germ cells even though they are formed from diploids, ie from fertilized eggs. In addition to this there is also true haplodiploidy with females born from fertilized eggs and males from unfertilized eggs. This is seen in the genus Icerya.
JAMs play a critical role in the regulation of cell movement in multiple different cell types, such as epithelial, endothelial, leukocyte, and germ cells. JAM-1 regulates motility in epithelial cells by moderating expression of β1 integrin protein downstream of Rap1. JAM-1 has been shown to be able to cause cell adhesion, spreading and movement along β1 ligands like collagen IV and fibronectin. JAM-1 also acts to moderate migration of vitronectin in endothelial cells.
The newly formed primordial germ cells (PGC) in the implanted embryo devolve from the somatic cells at about day 7 of embryogenesis in the mouse. At this point the PGCs have high levels of methylation. These cells migrate from the epiblast toward the gonadal ridge. As reviewed by Messerschmidt et al., the majority of PGCs are arrested in the G2 phase of the cell cycle while they migrate toward the hindgut during embryo days 7.5 to 8.5.
The discovery that expression of only four transcription factors was necessary to induce pluripotency allowed future regenerative medicine research to be conducted considering minor manipulations. Loss of pluripotency is regulated by hypermethylation of some Sox2 and Oct4 binding sites in male germ cells and post-transcriptional suppression of Sox2 by miR134. Varying levels of Sox2 affect embryonic stem cells' fate of differentiation. Sox2 inhibits differentiation into the mesendoderm germ layer and promotes differentiation into neural ectoderm germ layer.
Although Stevens did not have a university position, she made a career for herself by conducting research at leading marine stations and laboratories. Her record of 38 publications includes several major contributions that further the emerging concepts of chromosomal heredity. By experimenting on germ cells, Stevens interpreted her data to conclude that chromosomes have a role in sex determination during development. As a result of her research, Stevens provided critical evidence for Mendelian and chromosomal theories of inheritance.
This gene is a member of the DAZ gene family and is a candidate for the human Y-chromosomal azoospermia factor (AZF). Its expression is restricted to pre-meiotic germ cells, particularly in spermatogonia. It encodes an RNA-binding protein that is important for spermatogenesis. Four copies of this gene are found on chromosome Y within palindromic duplications; one pair of genes is part of the P2 palindrome and the second pair is part of the P1 palindrome.
This gene encodes a histone H1 binding protein that is involved in transporting histones into the nucleus of dividing cells. The somatic form is expressed in all mitotic cells, is localized to the nucleus, and is coupled to the cell cycle. The testicular form is expressed in embryonic tissues, tumor cells, and the testis. In male germ cells, this protein is localized to the cytoplasm of primary spermatocytes, the nucleus of spermatids, and the periacrosomal region of mature spermatozoa.
Germ cell neoplasia in situ (GCNIS) represents the precursor lesion for many types of testicular germ cell tumors. As the name suggests, it represents a neoplastic process of germ cells that is confined to the spermatogonial niche. The term GCNIS was introduced with the 2016 edition of the WHO classification of urological tumours. GCNIS more accurate describes the lesion as it arises between the basement membrane and Sertoli cells (the cells that 'nurse' the developing germ cell).
Some of the benefits of targeting this signaling pathway include: • Many of the current DNA-targeting anticancer drugs carry the risk of giving rise to secondary tumors or additional primary cancers. • Preferentially killing rapidly replicating malignant cells via cytotoxic agents cause serious side effects by injuring normal cells, particularly hematopoietic cells, intestinal cells, hair follicle and germ cells. • Differentiated tumor cells in a state of quiescence are typically not affected by drugs can may account for tumor recurrence.
As eusocial animals, only the breeding pair within a colony is capable of reproduction. Non-reproductive individuals are not truly sterile, however, and become capable of reproduction if they establish a colony of their own. The reproductive systems of non-reproductive females are underdeveloped, with small, unvascularised uteri and tiny ovaries that contain undeveloped germ cells, but which are incapable of ovulation. Non-reproductive males have smaller testes than their reproductive counterparts and produce little, if any, viable sperm.
Gynandromorphs occasionally afford a powerful tool in genetic, developmental, and behavioral analyses. In Drosophila melanogaster, for instance, they provided evidence that male courtship behavior originates in the brain, that males can distinguish conspecific females from males by the scent or some other characteristic of the posterior, dorsal, integument of females, that the germ cells originate in the posterior-most region of the blastoderm, and that somatic components of the gonads originate in the mesodermal region of the fourth and fifth abdominal segment.
In germline gene therapy (GGT), germ cells (sperm or egg cells) are modified by the introduction of functional genes into their genomes. Modifying a germ cell causes all the organism's cells to contain the modified gene. The change is therefore heritable and passed on to later generations. Australia, Canada, Germany, Israel, Switzerland, and the Netherlands prohibit GGT for application in human beings, for technical and ethical reasons, including insufficient knowledge about possible risks to future generations and higher risks versus SCGT.
Common symptoms of OGCT are bloating, abdominal distention, ascites, and dyspareunia. OGCT is caused mainly due to the formation of malignant cancer cells in the primordial germ cells of the ovary. The exact pathogenesis of OGCTs is still unknown however, various genetic mutations and environmental factors have been identified. OGCTs are commonly found during pregnancy when an adnexal mass is found during a pelvic examination, ultrasound scans show a solid mass in ovary or blood serum test shows elevated alpha-fetoprotein levels.
Meiosis was initially discovered by Oscar Hertwig in 1876 as he examined the fusion of the gametes in sea urchin eggs. In 1890, August Weismann, concluded that two different rounds of meiosis are required and defined the difference between somatic cells and germ cells. Studies regarding meiotic arrest and resumption have been difficult to attain because within females, the oocyte is inaccessible. The majority of research was conducted by removing the follicles and artificially maintaining the oocyte in meiotic arrest.
Normal cells will display the normal protein antigen on their MHC molecules, whereas cancer cells will display the mutant version. Some viral proteins are implicated in forming cancer (oncogenesis), and some viral antigens are also cancer antigens. Cancer-testis antigens are antigens expressed primarily in the germ cells of the testes, but also in fetal ovaries and the trophoblast. Some cancer cells aberrantly express these proteins and therefore present these antigens, allowing attack by T-cells specific to these antigens.
Multipotent stem cells with a claimed equivalency to embryonic stem cells have been derived from spermatogonial progenitor cells found in the testicles of laboratory mice by scientists in Germany and the United States, and, a year later, researchers from Germany and the United Kingdom confirmed the same capability using cells from the testicles of humans. The extracted stem cells are known as human adult germline stem cells (GSCs) Multipotent stem cells have also been derived from germ cells found in human testicles.
During mammalian development, the gonads are at first capable of becoming either ovaries or testes. In humans, starting at about week 4, the gonadal rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, epithelial sex cords develop within the forming testes and incorporate the germ cells as they migrate into the gonads. In males, certain Y chromosome genes, particularly SRY, control development of the male phenotype, including conversion of the early bipotential gonad into testes.
During puberty, androgen, LH and follicle stimulating hormone (FSH) production increase and the sex cords hollow out, forming the seminiferous tubules, and the germ cells start to differentiate into sperm. Throughout adulthood, androgens and FSH cooperatively act on Sertoli cells in the testes to support sperm production. Exogenous androgen supplements can be used as a male contraceptive. Elevated androgen levels caused by use of androgen supplements can inhibit production of LH and block production of endogenous androgens by Leydig cells.
The remainder of the male reproductive system is derived from embryonic mesoderm, except for the germ cells, or spermatogonia, which descend from the primordial pole cells very early during embryogenesis. The aedeagus can be quite pronounced or de minimis. The base of the aedeagus may be the partially sclerotized phallotheca, also called the phallosoma or theca. In some species the phallotheca contains a space, called the endosoma (internal holding pouch), into which the tip end of the aedeagus may be withdrawn (retracted).
The cause of the condition is often unclear. There are cases where abnormalities in the FSH-receptor have been reported. Apparently either the germ cells do not form or interact with the gonadal ridge or undergo accelerated atresia so that at the end of childhood only a streak gonad is present, unable to induce pubertal changes. As girls' ovaries produce no important body changes before puberty, there is usually no suspicion of a defect of the reproductive system until puberty fails to occur.
DAZ is not absolutely required for spermatogenesis as some DAZ deleted men are still able to father children. DAZ pushes ESCs in to germ cells with molecular features of being spermatids. DAZL is expressed in humans from early progenitor germ cell migration, right up to spermatozoa differentiation. Since DAZL is located on an autosome, it has been shown to be important in germ cell development of both oocyte and spermatocytes (in spermatogenesis and oogenesis), albeit in different expression patterns for both.
Most oogonia have either degenerated or differentiated into primary oocytes by birth. Primary oocytes will undergo oogenesis in which they enter meiosis. However, primary oocytes are arrested in prophase 1 of the first meiosis and remain in that arrested stage until puberty begins in the female adult. This is in contrast to male primordial germ cells which are arrested in the spermatogonial stage at birth and do not enter into spermatogenesis and meiosis to produce primary spermatocytes until puberty in the adult male.
It is speculated that induction was the ancestral mechanism, and that the preformistic, or inheritance, mechanism of germ cell establishment arose from convergent evolution. There are several key differences between these two mechanisms that may provide reasoning for the evolution of germ plasm inheritance. One difference is that typically inheritance occurs almost immediately during development (around the blastoderm stage) while induction typically does not occur until gastrulation. As germ cells are quiescent and therefore not dividing, they are not susceptible to mutation.
Germ cell tumor is a rare cancer that can affect people at all ages. As of 2018, germ cell tumors account for 3% of all cancers in children and adolescents 0-19 years old. Germ cell tumors are generally located in the gonads but can also appear in the abdomen, pelvis, mediastinum, or brain. Germ cells migrating to the gonads may not reach that intended destination and a tumor can grow wherever they end up, but the exact cause is still unknown.
Inducing differentiation of certain cells to germ cells has many applications. One implication of induced differentiation is that it may allow for the eradication of male and female factor infertility. Furthermore, it would allow same-sex couples to have biological children if sperm could be produced from female cells or if eggs could be produced from male cells. Efforts to create sperm and eggs from skin and embryonic stem cells were pioneered by Hayashi and Saitou's research group at Kyoto University.
The term somatic is generally used in biology to refer to the cells of the body in contrast to the reproductive (germline) cells, which usually give rise to the egg or sperm. For example, in mammals, somatic cells make up all the internal organs, skin, bones, blood and connective tissue. There are approximately 220 types of somatic cells in the human body. In most animals, separation of germ cells from somatic cells (germline development) occurs during early stages of development.
The testes are covered by a tough membranous shell called the tunica albuginea. Within the testes are very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells (germ cells) that develop from puberty through old age into sperm cells (also known as spermatozoa or male gametes). The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis).
Krohn had previously argued that the Kalevala evolved from small "poetic germ cells" that merged to form a heroic epic. In Kalevala Questions he instead took the position that the poems were born as complete works, and had fragmented over time. Krohn argued that the poems were composed at the same time as the Scandinavian Viking Age, and were accounts of real historical events. This was in stark contrast to his previous view of the Kalevala as a work of Medieval origin that borrowed significantly from hagiography.
First, the protamines associated with male DNA are replaced with histones from the female's cytoplasm, most of which are acetylated due to either higher abundance of acetylated histones in the female's cytoplasm or through preferential binding of the male DNA to acetylated histones. Second, male DNA is systematically demethylated in many organisms, possibly through 5-hydroxymethylcytosine. However, some epigenetic marks, particularly maternal DNA methylation, can escape this reprogramming; leading to parental imprinting. In the primordial germ cells (PGC) there is a more extensive erasure of epigenetic information.
PGCs that are able to migrate the fastest and reach the gonad are more likely to colonise it and give rise to future gametes. The PGCs that go off route or don’t reach the gonad undergo programmed cell death (apoptosis). It is thought that every step after specification may function as a selective mechanism to ensure germ cells are of the highest quality. The selective mechanisms may also be important for removing PGCs with abnormal epigenetic marks and in doing so preserving the germline.
In panoistic ovaries, each egg-to-be produced by stem germ cells develops into an oocyte; there are no helper cells from the germ line. Production of eggs by panoistic ovaries tends to be slower than that by meroistic ovaries. Accessory glands or glandular parts of the oviducts produce a variety of substances for sperm maintenance, transport, and fertilization, as well as for protection of eggs. They can produce glue and protective substances for coating eggs or tough coverings for a batch of eggs called oothecae.
NIMA (never in mitosis gene a)-related kinase 1, also known as NEK1, is a human gene highly expressed in germ cells and thought to be involved in meiosis. It is also involved in the response to DNA damage from radiation; defects in this gene can be a cause of polycystic kidney disease. NEK1 is thought to be involved in amytrophic lateral sclerosis. The gene was discovered by researchers with Project MinE, with the ALS Association providing funding raised through the Ice Bucket Challenge.
Cryptorchidism, also known as undescended testis, is a common birth defect affecting male genital formation. Individuals diagnosed with cryptorchidism are often at risk of testicular cancer and infertility due to dysfunction in the development of the neonatal germ cells, in particular, the disruption of the differentiation of gonocytes into adult dark- spermatogonia. It is proposed that this dysfunction is a product of heat stress caused by the undescended testes remaining in the abdomen and unable to regulate its temperature which is often accomplished by the scrotum.
During the 1950s and 1960s Jost studied the mechanism of somatic sex differentiation; his research showed that male characteristics must be imposed on the fetus by the testicular hormones testosterone and AMH, and that in the absence or inactivity of these hormones, the fetus becomes phenotypically female. Jost also studied testicular differentiation, in collaboration with Solange Magre. He was the first to show that testicular organization is heralded by the development of pre-Sertoli cells, which progressively surround germ cells to form seminiferous tubules.
Primordial follicles are immature primary oocytes surrounded by a single layer of granulosa cells. An enzyme system is present in oocytes that normally accurately repairs DNA double-strand breaks. This repair system is referred to as homologous recombinational repair, and it is especially active during meiosis. Meiosis is the general process by which germ cells are formed in eukaryotes, and it appears to be an adaptation for efficiently removing damages in germ line DNA by homologous recombinational repair (see Origin and function of meiosis).
In panoistic ovaries, each egg-to-be produced by stem germ cells develops into an oocyte; there are no helper cells from the germ line. Production of eggs by panoistic ovaries tends to be slower than that by meroistic ovaries. Accessory glands or glandular parts of the oviducts produce a variety of substances for sperm maintenance, transport, and fertilization, as well as for protection of eggs. They can produce glue and protective substances for coating eggs or tough coverings for a batch of eggs called oothecae.
The three TET genes are expressed as different isoforms, including at least two isoforms of TET1, three of TET2 and three of TET3. Different isoforms of the TET genes are expressed in different cells and tissues. The full-length canonical TET1 isoform appears virtually restricted to early embryos, embryonic stem cells and primordial germ cells (PGCs). The dominant TET1 isoform in most somatic tissues, at least in the mouse, arises from alternative promoter usage which gives rise to a short transcript and a truncated protein designated TET1s.
This aids the recruitment of ribosomal units and hence the initiation of translation. This is an important function of DAZL as many mRNAs within germ cells have short pol(A)-tails and would therefore not be recruited for translation without the assistance of DAZL. DAZ and DAZL also interact with the translationally repressive RNA Binding Protein PUM2 from the Pumilio RBP family. PUM2 interacts with both the conserved RRM and DAZ regions to form a complex which can interact other mRNAs to regulate their translation.
In humans, 50% of infertility issues are caused by males, and of this, genetic deletions in the Y chromosome make up a lot of this majority, since only men have the Y chromosome. DAZ gene in present on Y chromosome and deletion of this gene has been directly shown as a main cause of infertility. This causes no sperm cell found in semen and it is termed Azoospermia. One DAZ homologue is expressed in nearly every stage of spermatogenesis, from Primordial Germ Cells (PGCs) to mature spermatozoa.
Penetration of the fish by these spores takes only a few seconds. Within five minutes, a sac of germ cells called a sporoplasm has entered the fish epidermis, and within a few hours, the sporoplasm splits into individual cells that will spread through the fish. Within the fish, both intracellular and extracellular stages reproduce in its cartilage by asexual endogeny, meaning new cells grow from within old cells. The final stage within the fish is the creation of the myxospore, which is formed by sporogony.
Later in the recombination process, Exo1 acts to facilitate the resolution of DHJs into COs, independently of its nuclease activities. In resolving DHJs, Exo 1 acts together with MLH1-MLH3 heterodimer (MutL gamma) and Sgs1 (ortholog of Bloom syndrome helicase) to define a joint molecule resolution pathway that produces the majority of crossovers. Male mice deficient for Exo1 are capable of normal progress through the pachynema stage of meiosis, but most germ cells fail to progress normally to metaphase I due to dynamic loss of chiasmata .
DNMT3b begins to be expressed in the blastocyst. Methylation begins to increase at 3.5 days after fertilization in the blastocyst, and a large wave of methylation then occurs on days 4.5 to 5.5 in the epiblast, going from 12% to 62% methylation, and reaching maximum level after implantation in the uterus. By day seven after fertilization, the newly formed primordial germ cells (PGC) in the implanted embryo segregate from the remaining somatic cells. At this point the PGCs have about the same level of methylation as the somatic cells.
At certain stages of the life cycle, germ cells produce gametes. Somatic cells make up the body of the organism and are not involved in gamete production. Cycling meiosis and fertilization events produces a series of transitions back and forth between alternating haploid and diploid states. The organism phase of the life cycle can occur either during the diploid state (diplontic life cycle), during the haploid state (haplontic life cycle), or both (haplodiplontic life cycle, in which there are two distinct organism phases, one during the haploid state and the other during the diploid state).
This is overcome at puberty when cells within seminiferous tubules called Sertoli cells start making their own retinoic acid. Sensitivity to retinoic acid is also adjusted by proteins called nanos and DAZL. Genetic loss-of-function studies on retinoic acid-generating enzymes have shown that retinoic acid is required postnatally to stimulate spermatogonia differentiation which results several days later in spermatocytes undergoing meiosis, however retinoic acid is not required during the time when meiosis initiates. In female mammals, meiosis begins immediately after primordial germ cells migrate to the ovary in the embryo.
Animation of the migration of spermatozoa from their origin as germ cells to their exit from the vas deferens. A.) Blood vessels; B.) Head of epididymis; C.) Efferent ductules; D.) Seminiferous tubules; E.) Parietal lamina of tunica vaginalis; F.) Visceral lamina of tunica vaginalis; G.) Cavity of tunica vaginalis; H.) Tunica albuginea; I.) Lobule of testis; J.) Tail of epididymis; K.) Body of epididymis; L.) Mediastinum; M.) Vas deferens. Testicle or testis (plural testes) is the male reproductive gland or gonad in all animals, including humans. It is homologous to the female ovary.
Rare cases of adult onset acute megakaryoblastic leukemia are associated with malignant mediastinal germ cell tumor. In these cases, the mediastinal germ cell tumor develops before or concomitantly with but not after acute megakaryoblastic leukemia. The three most common genetic aberrations in the bone marrow cells of these individuals (representing ~65% of all cases) are inversions in the long arm of chromosome 12, trisomy 8, and an extra X chromosome. In several of these cases, the genetic aberrations in the malignant megakaryoblasts were similar to those in the malignant mediastinal germ cells.
Loveland has published over 130 peer-reviewed manuscripts, and is an Associate Editor for Andrology. Her laboratory investigates the molecular and cellular mechanisms that underpin mammalian testis development and sperm production. The team's objective is to identify and characterize the molecular switches that regulate cell fate decisions in sperm precursor cells (germ cells) and in the somatic cells that support them. Specific research focus areas are : Signaling by activin/ TGFβ superfamily, Wnt and Hedgehog pathways, growth factor/hormone signaling cross- talk, and the contribution of regulated nuclear transport molecules to cellular development and stress responses.
Even within humans and other mortal species, there are cells with the potential for immortality: cancer cells which have lost the ability to die when maintained in a cell culture such as the HeLa cell line, and specific stem cells such as germ cells (producing ova and spermatozoa). In artificial cloning, adult cells can be rejuvenated to embryonic status and then used to grow a new tissue or animal without aging. Normal human cells however die after about 50 cell divisions in laboratory culture (the Hayflick Limit, discovered by Leonard Hayflick in 1961).
For pre-pubertal boys undergoing chemotherapy, or any other treatment which may be significantly gonadotoxic, options to preserve fertility include cryopreservation of testicular tissue (TT). This procedure is ideally done before the commencement of any treatments to avoid mutagenic effects of this on the germ cells being preserved. These procedures are still experimental and clear guidelines on the restoring of fertility after cryopreservation of TT have yet to be published. Testicular fragments are retrieved during surgery and immediately placed into a transport medium at 4 – 8 °C to reduce contamination.
Asexual reproduction in the first larval stage is ubiquitous. While the sexual formation of the digenean eggs and asexual reproduction in the first larval stage (miracidium) is widely reported, the developmental biology of the asexual stages remains a problem. Electron microscopic studies have shown that the light microscopically visible germ balls consist of mitotically dividing cells which give rise to embryos and to a line of new germ cells that become included in these embryonic stages. Since the absence of meiotic processes is not proven, the exact definition remains doubtful.
DMRT1 is a dose sensitive transcription factor protein that regulates Sertoli cells and germ cells. The DMRT1 gene is located at the end of the 9th chromosome. This gene is found in a cluster with two other members of the gene family, having in common a zinc finger-like DNA-binding motif (DM domain). The DM domain is an ancient, conserved component of the vertebrate sex-determining pathway that is also a key regulator of male development in flies and nematodes, and is found to be the key sex-determining factor in chickens.
The signaled by retinoic acid 8 (Stra8) gene is activated only upon stimulation by retinoic acid and expresses a cytoplasmic protein in the gonads of male and female vertebrates. This protein functions to initiate the transition between mitosis and meiosis, aiding in spermatogenesis and oogenesis. In females, its signaling begins 12.5 days after conception, is localized in the primordial germ cells of female ovaries, and ushers in the first stage of meiosis. Male expression begins postnatally and continues throughout life, matching the need of spermatogenesis compared to the limited window of oogenesis in females.
XRCC1 is involved in the efficient repair of DNA single-strand breaks formed by exposure to ionizing radiation and alkylating agents. This protein interacts with DNA ligase III, polymerase beta and poly (ADP-ribose) polymerase to participate in the base excision repair pathway. It may play a role in DNA processing during meiogenesis and recombination in germ cells. A rare microsatellite polymorphism in this gene is associated with cancer in patients of varying radiosensitivity. The XRCC1 protein does not have enzymatic activity, but acts as a scaffolding protein that interacts with multiple repair enzymes.
Germ cell tumors of the ovary develop from the ovarian germ cells. Germ cell tumor accounts for about 30% of ovarian tumors, but only 5% of ovarian cancers, because most germ-cell tumors are teratomas and most teratomas are benign. Malignant teratomas tend to occur in older women, when one of the germ layers in the tumor develops into a squamous cell carcinoma. Germ-cell tumors tend to occur in young women (20s–30s) and girls, making up 70% of the ovarian cancer seen in that age group.
Generally, idic(15) is not inherited; it is said to appear de novo, in one member of the family, by chance. In most cases, the abnormal chromosome is generated in the mother's germ cells: the oocytes. This finding is due to ascertainment bias; cases with maternally derived idic(15) usually have clinical findings and attract attention, but those with paternally derived idic(15) usually do not. Thus, diagnosed cases are usually patients where the duplicated material is derived from the mother's egg cell rather than the father's sperm cell.
Human sperm cells are particularly vulnerable to free radical attack and the generation of oxidative DNA damage. (see e.g. 8-Oxo-2'-deoxyguanosine) The postmeiotic phase of mouse spermatogenesis is very sensitive to environmental genotoxic agents, because as male germ cells form mature sperm they progressively lose the ability to repair DNA damage. Irradiation of male mice during late spermatogenesis can induce damage that persists for at least 7 days in the fertilizing sperm cells, and disruption of maternal DNA double-strand break repair pathways increases sperm cell-derived chromosomal aberrations.
In vitro spermatogenesis is the process of creating male gametes (spermatozoa) outside of the body in a culture system. The process could be useful for fertility preservation, infertility treatment and may further develop the understanding of spermatogenesis at the cellular and molecular level. Spermatogenesis is a highly complex process and artificially rebuilding it in vitro is challenging. These include creating a similar microenvironment to that of the testis as well as supporting endocrine and paracrine signalling, and ensuring survival of the somatic and germ cells from spermatogonial stem cells (SSCs) to mature spermatozoa.
It is the N-terminal and C-terminal regions of the large subunit that participate in interactions with the small subunit. These regions are separated by another domain whose sequence is always present in large subunits from various species but whose size varies and whose sequence is poorly conserved. A second gene encoding a large TFIIA subunit has been found in some higher eukaryotes. This gene, ALF/TFIIAtau (gene name GTF2A1LF) is expressed only in oocytes and spermatocytes, suggesting it has a TFIIA-like regulatory role for gene expression only in germ cells.
Zika can be transmitted from men and women to their sexual partners; most known cases involve transmission from symptomatic men to women. As of April 2016, sexual transmission of Zika has been documented in six countries – Argentina, Australia, France, Italy, New Zealand, and the United States – during the 2015 outbreak. ZIKV can persist in semen for several months, with viral RNA detected up to one year. The virus replicates in the human testis, where it infects several cell types including testicular macrophages, peritubular cells and germ cells, the spermatozoa precursors.
Enhanced telomerase activity can be an indicator of abnormal cells. Most normal tissues have inactivated or repressed telomerase activity, but it becomes activated in germ cells and most malignant tumors. Treatment of SPC-A1 cells with gambogic acid resulted in a significant decline in telomerase activity when treated for 48 or 72 hours (detecting 80.7% and 84.9% reduction in activity, respectively). When treated with gambogic acid for only 24 hours, the decrease was only 25.9% which led researchers to believe there are at least two mechanisms responsible for slowing cell growth.
In genetics, genotoxicity describes the property of chemical agents that damages the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, whereas not all genotoxic substances are mutagenic. The alteration can have direct or indirect effects on the DNA: the induction of mutations, mistimed event activation, and direct DNA damage leading to mutations. The permanent, heritable changes can affect either somatic cells of the organism or germ cells to be passed on to future generations.
Recombination frequency even exceeds the frame shift mutation frequency (slipped strand mispairing) of (average fast) Y-STRs, however many recombination products may lead to infertile germ cells and "daughter out". Recombination events (RecLOH) can be observed if YSTR databases are searched for twin alleles at 3 or more duplicated markers on the same palindrome (hairpin). E.g. DYS459, DYS464 and DYS724 (CDY) are located on the same palindrome P1. A high proportion of 9-9, 15-15-17-17, 36-36 combinations and similar twin allelic patterns will be found.
In plants, genetic changes in somatic lines can and do result in genetic changes in the germ lines, because the germ cells are produced by somatic cell lineages (vegetative meristems), which may be old enough (many years) to have accumulated multiple mutations since seed germination, some of them subject to natural selection. Likewise, basal animals such as sponges (Porifera) and corals (Anthozoa) contain multipotent stem cell lineages, that give rise to both somatic and reproductive cells. The Weismann barrier appears to be of a more recent evolutionary origin.
Gene therapy involves supplying a functional gene to cells lacking that function, with the aim of correcting a genetic disorder or acquired disease. Gene therapy can be broadly divided into two categories. The first is alteration of germ cells, that is, sperm or eggs, which results in a permanent genetic change for the whole organism and subsequent generations. This “germ line gene therapy” is considered by many to be unethical in human beings. The second type of gene therapy, “somatic cell gene therapy”, is analogous to an organ transplant.
The tubules are lined with a layer of cells (germ cells) that from puberty into old age, develop into sperm cells (also known as spermatozoa or male gametes). The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis). The sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions. However, most fish do not possess seminiferous tubules.
Cancer/testis antigen 1 also known as LAGE2 or LAGE2B is a protein that in humans is encoded by the CTAG1B gene. It is most often referenced by its alias NY-ESO-1. Cancer/Testis Antigen 1B is a protein belonging to the family of Cancer Testis Antigens (CTA) that are expressed in a variety of malignant tumours at the mRNA and protein levels, but also restricted to testicular germ cells in normal adult tissues. A clone of CTAG gene was originally identified by immunological methods in oesophageal carcinoma using patient serum.
Expression of DAZ proteins varies between species but is mainly expressed in Primordial Germ Cells (PGCs). One DAZ homologue is expressed in nearly every stage of spermatogenesis, from PGCs to mature spermatozoa. The conservation of DAZ family genes among various species ranging from unicellular organisms to humans indicates their important role in fertility. More precisely, DAZ is only present in higher primates, without any homologues being present in unicellular organisms whereas BOULE is found in species ranging from sea anemones to humans and DAZL is conserved among vertebrates.
FGF2 (Fibroblast growth factor −2), secreted by sertoli cells, has also been shown to influence the renewal of SSCs and undifferentiated spermatogonia in a similar manner to GDNF. Although sertoli cells appear to play a major role in renewal, it expresses receptors for testosterone that is secreted by Leydig cells whereas germ cells do not contain this receptor- thus alluding to an important role of Leydig cells upstream in mediating renewal. Leydig cells also produce CSF 1 (Colony stimulating factor −1) for which SSCs strongly express the receptor CSF1R.
The germ cell nuclear factor (GCNF), also known as RTR (retinoid receptor- related testis-associated receptor) or NR6A1 (nuclear receptor subfamily 6, group A, member 1), is a protein that in humans is encoded by the NR6A1 gene. GCNF is a member of the nuclear receptor family of intracellular transcription factors . In adults, GCNH is expressed mainly in the germ cells of gonads and is involved in the regulation of embryogenesis and germ cell differentiation. Its expression pattern suggests that it may be involved in neurogenesis and germ cell development.
The regulation and differentiation of germ cells into primary gametocytes ultimately depends on the sex of the embryo and the differentiation of the gonads. In female mice, the protein RSPO1 is responsible for the differentiation of female (XX) gonads into ovaries. RSPO1 activates the β-catenin signaling pathway by up-regulating Wnt4 which is an essential step in ovary differentiation. Research has shown that ovaries lacking Rspo1 or Wnt4 will exhibit sex reversal of the gonads, the formation of ovotestes and the differentiation of somatic sertoli cells, which aid in the development of sperm.
The gonads of FANCF mutant mice function abnormally, having compromised follicle development and spermatogenesis as has been observed in other Fanconi anemia mouse models and in Fanconi anemia patients. Histological examination of the testes from FANCF-deficient mice showed that the seminiferous tubules were devoid of germ cells. At 14 weeks of age, FANCF- deficient female mice were almost or completely devoid of primordial follicles. It was concluded that FANCF-deficient mice display a rapid depletion of primordial follicles at a young age resulting in advanced ovarian aging.
Efforts for human cells are less advanced due to the fact that the PGCs formed by these experiments are not always viable. In fact Hayashi and Saitou's method is only one third as effective as current in vitro fertilization methods, and the produced PGCs are not always functional. Furthermore, not only are the induced PGCs not as effective as naturally occurring PGCs, but they are also less effective at erasing their epigenetic markers when they differentiate from iPSCs or ESCs to PGCs. There are also other applications of induced differentiation of germ cells.
Extracellular signals are transduced into cells through mitogen-activated protein kinases. The structural organization of these kinases into specific signaling domains is facilitated by scaffolding proteins involved in closely tethering different kinases so that successive phosphorylation events can occur. The protein encoded by this gene is a scaffolding protein that brings together mitogen- activated protein kinases and their transcription factor targets for the activation of specific signaling pathways. This gene which is abundantly expressed in testicular haploid germ cells encodes a protein that is recognized by sperm-agglutinating antibodies and implicated in infertility.
The presence of the SCB allows Sertoli cells to control the adluminal environment in which germ cells (spermatocytes, spermatids and sperm) develop by influencing the chemical composition of the luminal fluid. The barrier also prevents passage of cytotoxic agents (bodies or substances that are toxic to cells) into the seminiferous tubules. The fluid in the lumen of seminiferous tubules is quite different from plasma; it contains very little protein and glucose but is rich in androgens, estrogens, potassium, inositol and Glutamic and Aspartic acid. This composition is maintained by blood–testis barrier.
Diagram of a human egg cell Ovum and sperm fusing together The process of fertilizing an ovum (Top to bottom) In all mammals the ovum is fertilized inside the female body. The human ova grow from primitive germ cells that are embedded in the substance of the ovaries. Each of them divides repeatedly to give secretions of the uterine glands, ultimately forming a blastocyst. The ovum is one of the largest cells in the human body, typically visible to the naked eye without the aid of a microscope or other magnification device.
In vertebrates, rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually forms the supporting axis of the body and is then called the spine or vertebral column. Rachis can also mean the central shaft of pennaceous feathers. In the gonad of the invertebrate nematode C. elegans, a rachis is the central cell-free core or axis of the gonadal arm of both adult males and hermaphrodites where the germ cells have achieved pachytene and are attached to the walls of the gonadal tube.
Plant genetic resources that are conserved by any of these methods are often referred to as germplasm, which is a shorthand term meaning "any genetic materials". The term originates from germ plasm, August Weismann's theory that heritable information is transmitted only by germ cells, and which has been superseded by modern insights on inheritance, including epigenetics and non- nuclear DNA. After the Second World War, efforts to conserve plant genetic resources came mainly from breeders’ organizations in the USA and Europe, which led to crop-specific collections primarily located in developed countries (e.g. IRRI, CIMMYT).
Mobile DNA (jumping gene) technology uses retrotransposons and transposons for the production of knockout rat models. This platform technology meets all of the criteria for a successful gene knockout approach in mammals by permitting random mutagenesis directly in the germ cells (sperm and oocytes) of mammalian model organisms, including rats. Using this technology, genes are disrupted completely and in a stable manner, are knocked out at a high frequency, and are randomly disrupted throughout the entire genome. The genomic location of mutations can be easily mapped, creating a library of knockout rats for later use.
During early embryonic development, cells from the dorsal endoderm of the yolk sac migrate along the hindgut to the gonadal ridge. These primordial germ cells (PGCs) multiply by mitosis and once they have reached the gonadal ridge they are called oogonia (diploid stem cells of the ovary). Once oogonia enter this area they attempt to associate with the other somatic cells, derived from both the peritoneum and mesonephros. Development proceeds and the oogonia become fully surrounded by a layer of connective tissue cells (pre-granulosa cells) in an irregular manner.
Susan Strome is a Distinguished Professor of Molecular, Cell, and Developmental Biology at the University of California Santa Cruz. Strome received a B.A. degree in Chemistry from University of New Mexico and a Ph.D. in Biochemistry from the University of Washington, as well as post-graduate work at the University of Colorado Boulder. Strome's work in developmental genetics investigates how germ cells are established and maintain identity, immortality, and potency from parent to offspring. Strome is a member of the American Academy of Arts and Sciences and the National Academy of Sciences.
Anatomy of the ovaryIn females, gametogenesis is known as oogenesis; this occurs in the ovarian follicles of the ovaries. This process does not produce mature ovum until puberty. In contrast with males, each of the original diploid germ cells or primary oocytes will form only one mature ovum, and three polar bodies which are not capable of fertilization. It has long been understood that in females, unlike males, all of the primary oocytes ever found in a female will be created prior to birth, and that the final stages of ova production will then not resume until puberty.
TET dioxygenase isoforms include at least two isoforms of TET1, one of TET2 and three isoforms of TET3. The full-length canonical TET1 isoform appears virtually restricted to early embryos, embryonic stem cells and primordial germ cells (PGCs). The dominant TET1 isoform in most somatic tissues, at least in the mouse, arises from alternative promoter usage which gives rise to a short transcript and a truncated protein designated TET1s. The isoforms of TET3 are the full length form TET3FL, a short form splice variant TET3s, and a form that occurs in oocytes and neurons designated TET3o.
An Extracranial Germ-Cell Tumor (EGCT) occurs in the abnormal growth of germ cells in the gonads (testes or ovaries) and the areas other than the brain via tissue, lymphatic system, or circulatory system. The tumor can be benign or malignant (cancerous) by its growth rate. According to the National Cancer Institute and St. Jude Children's Research Hospital, the chance of children who are under 15 years old having EGCTs is 3%, in comparison to adolescents, a possibility of 14% with aged 15 to 19 can have EGCTs. There is no obvious cut point in between children and adolescents.
The mouth and pharynx have both cilia and well-developed muscles. In other parts of the canal system, the gastrodermis is different on the sides nearest to and furthest from the organ that it supplies. The nearer side is composed of tall nutritive cells that store nutrients in vacuoles (internal compartments), germ cells that produce eggs or sperm, and photocytes that produce bioluminescence. The side furthest from the organ is covered with ciliated cells that circulate water through the canals, punctuated by ciliary rosettes, pores that are surrounded by double whorls of cilia and connect to the mesoglea.
The expression of CT antigens in various malignancies is heterogeneous and often correlates with tumor progression. CT antigens have been described in melanoma, liver cancer, lung cancer, bladder cancer, and pediatric tumors such as neuroblastoma. Gametogenesis offers an important role for many of these antigens in the differentiation, migration, and cell division of primordial germ cells, spermatagonia spermatocytes and spermatids. Because of their tumor-restricted expression and strong in vivo immunogenicity, CT antigens are identified as ideal targets for tumor specific immunotherapeutic approaches and prompted the development of several clinical trials of CT antigens-based vaccine therapy.
In molecular biology, apovitellenin-1 is a family of proteins found in birds. As part of the avian reproductive effort, large quantities of triglyceride- rich very-low-density lipoprotein (VLDL) particles are transported by receptor-mediated endocytosis into the female germ cells, apovitellenin-1 is a protein component of this VLDL. Although the oocytes are surrounded by a layer of granulosa cells harbouring high levels of active lipoprotein lipase, non- lipolysed VLDL is transported into the yolk. This is because the VLDL particles are protected from lipolysis by apovitellenin-1a, which acts as a potent dimeric lipoprotein lipase inhibitor.
The position of the nuclei along the embryonic axes determines the relative exposure of different amounts of Bicoid, Nanos, and other morphogens. Those nuclei with more Bicoid will activate genes that promote differentiation of cells into head and thorax structures. Nuclei exposed to more Nanos will activate genes responsible for differentiation of posterior regions, such as the abdomen and germ cells. The same principles hold true for the specification of the dorso- ventral axis – higher concentration of nuclear Dorsal protein on the ventral side of the egg specify the ventral fate, whereas absence thereof allows dorsal fates.
Primordial germ cells are among the first lineages that are established in development and they are the precursors for gametes. It is thought that the process of primordial germ cell migration itself has been conserved rather than the specific mechanisms within it, as chemoattraction and repulsion seem to have been borrowed from blood cells, neurones, and the mesoderm. For most organisms, PGC migration starts in the posterior (back end) of the embryo. This process is in most cases distinct from PGC proliferation, with the exception of mammals in which both processes occur at the same time.
There, the imprint is removed, leading to the downregulation of Xist and thus reactivation of the inactive X chromosome. Recent data suggests that Xist activity is regulated by an anti- sense transcript. The epiblast cells are then formed and they begin to be differentiated, and the Xist is upregulated from either of the two X chromosomes and at random in ICM, but the Xist is maintained in epiblast, an X is inactivated and the Xist allele is turned off in the active X chromosome. In maturing XX primordial germ cells, Xist is downregulated and X reactivation occurs once again.
Embryonal carcinomas, a rare tumor type usually found in mixed tumors, develop directly from germ cells but are not terminally differentiated; in rare cases they may develop in dysgenetic gonads. They can develop further into a variety of other neoplasms, including choriocarcinoma, yolk sac tumor, and teratoma. They occur in younger people, with an average age at diagnosis of 14, and secrete both alpha- fetoprotein (in 75% of cases) and hCG. Histologically, embryonal carcinoma appears similar to the embryonic disc, made up of epithelial, anaplastic cells in disorganized sheets, with gland-like spaces and papillary structures.
Her findings up to this point indicated that germ cells avoid differentiation into somatic cells through a combination of her previously studied regulatory mechanisms, each of which has the potential to silence transcription and control translation. Currently, Lehmann is studying piRNA production and the role it plays in preventing transposable element insertion and movement across the Drosophila genome. She discovered that biogenesis of piRNAs and activation of the piRNA pathway is directly dependent on a number of proteins and epigenetic interactions. These results indicate that piRNAs play a paramount role in maintaining genomic integrity while allowing for genetic variation to occur.
Co-culture allows for the interactions between cell populations to be observed and experimented on, which is seen as an advantage over the monoculture model. Isolated cell culture, specifically co-culture of testis tissue, has been a useful technique for examining the influences of specific factors such as hormones or different feeder cells on the progression of spermatogenesis in vitro. For example, factors such as temperature, feeder cell influence and the role of testosterone and follicle-stimulating hormone (FSH) have all been investigated using isolated cell culture techniques. Studies have concluded that different factors can influence the culture of germ cells e.g.
In mammalian embryogenesis, differentiation and segregation of cells composing the inner cell mass of the blastocyst yields two distinct layers—the epiblast ("primitive ectoderm") and the hypoblast ("primitive endoderm"). While the cuboidal hypoblast cells delaminate ventrally, away from the embryonic pole, to line the blastocoele, the remaining cells of the inner cell mass, situated between the hypoblast and the polar trophoblast, become the epiblast and comprise columnar cells. In the mouse, primordial germ cells are specified from epiblast cells. This specification is accompanied by extensive epigenetic reprogramming that involves global DNA demethylation, chromatin reorganization and imprint erasure leading to totipotency.
Lepidopteran chromosomes possess a localized kinetochore plate to which the spindle microtubules attach during cell division. The kinetochore plates are large and cover a significant portion of the chromosome length, ensuring that more radiation-induced breaks will not lead to the loss of chromosome fragments as is typical in species with monocentric chromosomes. In species with large kinetochore plates, the fragments may persist for a number of mitotic cell divisions, and can even be transmitted through germ cells to the next generation. The plates also reduce the risk of lethality caused by the formation of dicentric chromosomes, acentric fragments, and other unstable aberrations.
In the mouse, primordial germ cells (PGCs) arise in the posterior primitive streak of the embryo and start to migrate around 6.25 days after conception. PGCs start to migrate to the embryonic endoderm and then to the hindgut and finally towards the future genital ridges where the somatic gonadal precursors reside. This migration requires a series of attractant and repellent cues as well as a number of adhesion molecules such as E-cadherin and β1-Integrin to guide the migration of PGCs. Around 10 days post conception; the PGCs occupy the genital ridge where they begin to lose their motility and polarized shape.
Prior to their arrival at the gonads, PGCs express pluripotency factors, generate pluripotent cell lines in cell culture (known as EG cells,) and can produce multi-lineage tumors, known as teratomas. Similar findings in other vertebrates indicate that PGCs are not yet irreversibly committed to produce gametes, and no other cell type. On arrival at the gonads, human and mouse PGCs activate widely conserved germ cell-specific factors, and subsequently down-regulate the expression of pluripotency factors. This transition results in the determination of germ cells, a form of cell commitment that is no longer reversible.
Plant virus transmission from generation to generation occurs in about 20% of plant viruses. When viruses are transmitted by seeds, the seed is infected in the generative cells and the virus is maintained in the germ cells and sometimes, but less often, in the seed coat. When the growth and development of plants is delayed because of situations like unfavorable weather, there is an increase in the amount of virus infections in seeds. There does not seem to be a correlation between the location of the seed on the plant and its chances of being infected.
In adult-AMKL, mediastinal germ cell tumors that are associated with adult-AMKL are not seminomas (i.e. do not originate from the sperm cell line) and occur before or concomitantly with but not after the diagnosis AMKL is made. The three most common genetic aberrations in the bone marrow cells of these individuals (representing ~65% of all cases) were inversions in the p arm of chromosome 12, trisomy 8, and an extra X chromosome. In several of these cases, the genetic aberrations in the malignant platelet precursor cells were similar to those in the malignant mediastianal germ cells.
The duplication and transmission of genetic material from one generation of cells to the next is the basis for molecular inheritance and the link between the classical and molecular pictures of genes. Organisms inherit the characteristics of their parents because the cells of the offspring contain copies of the genes in their parents' cells. In asexually reproducing organisms, the offspring will be a genetic copy or clone of the parent organism. In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene.
Animals: From Mythology to Zoology "Plastitude" pangenes, granules, or germs, were supposed to be shed by the organs of the body and carried in the bloodstream to the reproductive organs where they accumulated in the germ cells or gametes. Their accumulation was thought to occur by some sort of a 'mutual affinity.' Each gemmule was said to be specifically related to a certain body part- as described, they did not contain information about the entire organism. The different types were assumed to be dispersed through the whole body, and capable of self- replication given 'proper nutriment'.
The isoforms of the TET enzymes include at least two isoforms of TET1, one of TET2 and three isoforms of TET3. The full-length canonical TET1 isoform appears virtually restricted to early embryos, embryonic stem cells and primordial germ cells (PGCs). The dominant TET1 isoform in most somatic tissues, at least in the mouse, arises from alternative promoter usage which gives rise to a short transcript and a truncated protein designated TET1s. The isoforms of TET3 are the full length form TET3FL, a short form splice variant TET3s, and a form that occurs in oocytes and neurons designated TET3o.
In these cases, expressed and silent alleles differ by their methylation status, and loss of DNA methylation results in loss of imprinting and re-expression of Xist in somatic cells. During embryonic development, few genes change their methylation status, at the important exception of many genes specifically expressed in the germline. DNA methylation appears absolutely required in differentiated cells, as knockout of any of the three competent DNA methyltransferase results in embryonic or post-partum lethality. By contrast, DNA methylation is dispensable in undifferentiated cell types, such as the inner cell mass of the blastocyst, primordial germ cells or embryonic stem cells.
Since DNA methylation appears to directly regulate only a limited number of genes, how precisely DNA methylation absence causes the death of differentiated cells remain an open question. Due to the phenomenon of genomic imprinting, maternal and paternal genomes are differentially marked and must be properly reprogrammed every time they pass through the germline. Therefore, during gametogenesis, primordial germ cells must have their original biparental DNA methylation patterns erased and re-established based on the sex of the transmitting parent. After fertilization, the paternal and maternal genomes are once again demethylated and remethylated (except for differentially methylated regions associated with imprinted genes).
When neonatal female mice were treated with coumestrol, similar reproductive irregularities occurred, and at 22 months old, atypical collagen distribution was observed in the uterine wall. When 2 day old male Wistar rats are injected with coumestrol daily, they exhibit a decrease in size in the lumens of their seminiferous tubules and germ cells go through increased rates of apoptosis. When bulls graze on pastures containing coumestrol, metaplasia occurs in the prostate and bulbourethral glands, and sperm maturation is suppressed. Female cows that consumed alfalfa experienced lower pregnancy rates and spontaneous abortions, as well as abnormal estrogen levels during pregnancy.
They degenerate in males of certain species, but the adjoining mesonephric ducts develop into male reproductive organs. The sex based differences in the contributions of the paramesonephric ducts to reproductive organs is based on the presence, and degree of presence, of Müllerian inhibiting factor. During the formation of the reproductive system, the paramesonephric ducts are formed just lateral to the mesonephric ducts in both female and male embryos 6 weeks after fertilization. During this time primordial germ cells migrate from the yolk sac to the gonadal ridge; a region of mesenchyme arising from, and running parallel with, the mesonephros.
In animals, the different types of change are male to female (protandry), female to male (protogyny), female to hermaphrodite (protogynous hermaphroditism), and male to hermaphrodite (protandrous hermaphroditism). Both protogynous and protandrous hermaphroditism allow the organism to switch between functional male and functional female. These various types of sequential hermaphroditism may indicate that there is no advantage based on the original sex of an individual organism. Those that change gonadal sex can have both female and male germ cells in the gonads or can change from one complete gonadal type to the other during their last life stage.
The term somatic is often used in biology to refer to the cells of the body in contrast to the reproductive (germline) cells, which usually give rise to the egg or sperm (or other gametes in other organisms). These somatic cells are diploid, containing two copies of each chromosome, whereas germ cells are haploid, as they only contain one copy of each chromosome (in preparation for fertilisation). Although under normal circumstances all somatic cells in an organism contain identical DNA, they develop a variety of tissue-specific characteristics. This process is called differentiation, through epigenetic and regulatory alterations.
The stages that infect fish, called triactinomyxon spores, are made of a single style that is about 150 micrometers (µm) long and three processes or "tails", each about 200 micrometers long. A sporoplasm packet at the end of the style contains 64 germ cells surrounded by a cellular envelope. There are also three polar capsules, each of which contains a coiled polar filament between 170 and 180 µm long. Polar filaments in both this stage and in the myxospore stage (see picture above) rapidly shoot into the body of the host, creating an opening through which the sporoplasm can enter.
In Drosophila melanogaster, the GSC niche resides in the anterior-most region of each ovariole, known as the germarium. The GSC niche consists of necessary somatic cells-terminal filament cells, cap cells, escort cells, and other stem cells which function to maintain the GSCs. The GSC niche holds on average 2–3 GSCs, which are directly attached to somatic cap cells and Escort stem cells, which send maintenance signals directly to the GSCs. GSCs are easily identified through histological staining against vasa protein (to identify germ cells) and 1B1 protein (to outline cell structures and a germline specific fusome structure).
The murine GSC niche in males, also called spermatogonial stem cell (SSC) niche, is located in the basal region of seminiferous tubules in the testes. The seminiferous epithelium is composed of sertoli cells that are in contact with the basement membrane of the tubules, which separates the sertoli cells from the interstitial tissue below. This interstitial tissue comprises Leydig cells, macrophages, mesenchymal cells, capillary networks, and nerves. During development, primordial germ cells migrate into the seminiferous tubules and downward towards the basement membrane whilst remaining attached to the sertoli cells where they will subsequently differentiate into SSCs, also referred to as Asingle spermatogonia.
The various SALL4-null mouse models mimic human mutations in the SALL4 gene, which were shown to cause developmental problems in patients with Okihiro/Duane-Radial-ray syndrome. These individuals frequently have family history of hand malformation and eye movement disorders. SALL4 expression is low to undetectable in most adult tissues with the exception of germ cells and human blood progenitor cells. However, SALL4 is re-activated and mis-regulated in various cancers such as acute myeloid leukemia (AML), B-cell acute lymphocytic leukemia (B-ALL), germ cell tumors, gastric cancer, breast cancer, hepatocellular carcinoma (HCC), lung cancer, and glioma.
Tachibana was educated in Japan, Austria, and the UK. She obtained her PhD working on the cell cycle and cancer formation in the group of Ron Laskey at Cambridge University, UK. She later joined the lab of Kim Nasmyth in Oxford, UK as a post-doc, where she did pioneering work on the role of the protein cohesin in female mouse germ cells. In November 2011 she joined IMBA as a group leader, where she investigates totipotency in mouse oocytes and zygotes as well as the role of maternal aging on egg cell health using mouse as a model system.
Cancer treatments can affect a person's fertility, with these changes being temporary or permanent. Whether fertility is affected depends on factors such as a person's baseline fertility, age at the time of treatment, the type of cancer and treatment(s), the amount (dose) of treatment, the duration of treatment, the amount of time that has passed since cancer treatment, and other personal health factors. Cancer treatments may harm reproductive organs and glands that control fertility. Chemotherapy (especially alkylating agents) can affect a female's ovaries, causing them to stop releasing eggs and estrogen, and can damage sperm and sperm-forming cells (germ cells) in young men.
In humans, starting at about week 4 the gonadal rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, sex cords develop within the forming testes. These are made up of early Sertoli cells that surround and nurture the germ cells that migrate into the gonads shortly before sex determination begins. In males, the sex-specific gene SRY that is found on the Y-chromosome initiates sex determination by downstream regulation of sex-determining factors, (such as GATA4, SOX9 and AMH), which leads to development of the male phenotype, including directing development of the early bipotential gonad down the male path of development.
Variable charge X-linked protein 1 is a protein that in humans is encoded by the VCX gene. This gene belongs to the VCX/Y gene family, which has multiple members on both X and Y chromosomes, and all are expressed exclusively in male germ cells. The X-linked members are clustered on chromosome Xp22 and Y-linked members are two identical copies of the gene within a palindromic region on Yq11. The family members share a high degree of sequence identity, with the exception that a 30-bp unit is tandemly repeated in X-linked members but occurs only once in Y-linked members.
The development of the CRISPR-Cas9 gene editing system as a cheap and fast way of directly modifying germ cells, effectively halving the amount of time needed to develop genetically modified mammals. A porcine model of hemophilia A. Mammals are the best models for human disease, making genetic engineered ones vital to the discovery and development of cures and treatments for many serious diseases. Knocking out genes responsible for human genetic disorders allows researchers to study the mechanism of the disease and to test possible cures. Genetically modified mice have been the most common mammals used in biomedical research, as they are cheap and easy to manipulate.
Cassandra Extavour is a Canadian geneticist, researcher of organismic and evolutionary biology, professor of molecular and cell biology at Harvard University, and a classical singer. Her research has focused on evolutionary and developmental genetics. She is known for demonstrating that germ cells engage in cell to cell competition before becoming a gamete, which indicates that natural selection can affect and change genetic material before adult sex reproduction takes place. She was also the Director of EDEN (the Evo-Devo-Eco Network), a National Science Foundation-funded research collaborative that encouraged scientists working on organisms other than the standard lab model organisms to share protocols and techniques.
In normal tissues, CT antigens are exclusively expressed in testis, making it no access to the immune system. Besides, the existence of blood-testis barrier and the lack of human leukocyte antigen (HLA) class I expression on the surface of germ cells prevent the immune system interacting with CT antigens proteins and recognizing it as invading structures. Thus, CT antigens can be regarded as essentially tumor-specific targets when they are expressed in cancers. Distinct CT antigens encode for different antigenic peptides presented to the immune system in association with various HLA class I or HLA class II allospecificities, eliciting both CTL and humoral immune responses.
Endogenous retrovirus sequences are the product of reverse transcription of retrovirus genomes into the genomes of germ cells. Mutation within these retro-transcribed sequences can inactivate the viral genome. Over 8% of the human genome is made up of (mostly decayed) endogenous retrovirus sequences, as part of the over 42% fraction that is recognizably derived of retrotransposons, while another 3% can be identified to be the remains of DNA transposons. Much of the remaining half of the genome that is currently without an explained origin is expected to have found its origin in transposable elements that were active so long ago (> 200 million years) that random mutations have rendered them unrecognizable.
Females can produce full clones of themselves through a modification of the normal meiosis process used to produce haploid egg cells for sexual reproduction. The female's germ cells undergo a process of premeiotic genome doubling, or endoreduplication, so that two consecutive division cycles in the process of meiosis result in a diploid, rather than haploid, genome. Whereas homologous chromosomes pair and separate during meiosis I in sexual species, identical duplicate sister chromosomes, produced through premeiotic replication, pair and separate during meiosis I in true parthenotes. Pairing of identical sister chromosomes, in comparison to the alternative of pairing homologous chromosomes, maintains heterozygosity in obligate parthenotes.
Bonnevie took her examen artium in 1892, began studying zoology in 1892, later switching to biology. She completed her doctoral dissertation, "Undersøgelser over kimcellerne hos Enteroxenos østergreni" (studies on the germ cells of Enteroxenos østergreni) in 1906. She also studied under Arnold Lang in Zürich from 1898 to 1899, under Theodor Boveri in Würzburg from 1900 to 1901, and under Edmund Beecher Wilson at Columbia University in New York from 1906 to 1907. She succeeded Johan Hjort as leader of the Zootomic laboratory in 1900. She was a professor at Royal Frederick University from 1912 to 1937, and founded the Institute of Inheritance Research in 1916.
GnIH-R expression in the pituitary and other brain regions implies GnIH acts directly on the pituitary to downregulate gonadotropin production, impacting reproductive behaviors. This neurohormone also acts on the hypothalamus to inhibit the expression of GnRH, which may further inhibit gonadotropin secretion, and kisspeptin, which may inhibit kisspeptin-mediated stimulation of GnRH neurons prior to the preovulatory hormonal surge. GnIH also spurs the production of cytochrome P450 aromatase, promoting the synthesis of neuroestrogen in the brains of quails and reducing aggressivity in reproductive behaviors. In male vertebrates, GnIH reduces testis size, lowers testosterone secretion, and increases the incidence of apoptosis in germ cells and Sertoli cells of the seminiferous tubules.
Among other mechanisms, her laboratory discovered that a polyadenylated tail is not required for gene regulation. Lehmann continued to focus her research efforts on germ cell differentiation well into the early 2000s. She played a substantial role in the discovery of germ cell migratory pathways (namely those involving gap junctions, G protein-coupled receptors like Tre-1, and isoprenoids), particularly those concerning migration into the ovaries and testis. In 2005, Lehmann’s laboratory published a paper relating the lipid phosphatases Wunen and Wunen 2 to germ cell migration and elimination, suggesting that germ cells are sorted into the gonads by a type of repellent mechanism.
This discovery was hailed as the people's choice for the scientific breakthrough of 2016 by Science magazine. The knowledge she gained through her work on how the embryo develops during the blastocyst to gastrula transition, allowed her to mimic these developmental processes with different types of stem cells in vitro. This led her to the pioneering success of constructing embryo-like structures from pluripotent embryonic and multipotent extra-embryonic (trophoblast) stem cells in a 3D scaffold of extra-cellular matrix proteins in vitro. These "synthetic embryos" recapitulate the natural architecture of the embryo and their patterns of gene expression leading to the specification of the germ layers and germ cells.
During implantation, the trophoblast gives rise to extraembryonic membranes and cell types that will eventually form most of the fetal placenta, the specialized organ through which the embryo obtains maternal nourishment necessary for subsequent exponential growth. The specification of the trophoblast is controlled by the combination of morphological cues arising from cell polarity with differential activity of signaling pathways such as Hippo and Notch, and the restriction to outer cells of lineage specifiers such as CDX2. In the mouse, primordial germ cells are specified from epiblast cells, a process that is accompanied by extensive genome-wide epigenetic reprogramming. Reprogramming involves global DNA demethylation and chromatin reorganization resulting in cellular totipotency.
The specification of primordial germ cells in mammals is mainly attributed to the downstream functions of two signaling pathways; the BMP signaling pathway and the canonical WNT/β-catenin pathway. Bone morphogenetic protein 4 (BMP4) is released by the extra-embryonic ectoderm (ExE) at embryonic day 5.5 to 5.75 directly adjacent to the epiblast and causes the region of the epiblast nearest to the ExE to express Blimp1 and Prdm14 in a dose-dependent manner. This is evident as the number of PGCs forming in the epiblast decreases in proportion to the loss of BMP4 alleles. BMP4 acts through its downstream intercellular transcription factors SMAD1 and SMAD5.
Further studies revealed that the events that specify T/Bra expression in gastruloids mimic those in the embryo. After seven days gastruloids exhibit an organization very similar to a midgestation embryo with spatially organized primordia for all mesodermal (axial, paraxial, intermediate, cardiac, cranial and hematopoietic) and endodermal derivatives as well as the spinal cord. They also implement Hox gene expression with the spatiotemporal coordinates as the embryo. Gastruloids lack brain as well as extraembryonic tissues but characterisation of the cellular complexity of gastruloids at the level of single cell and spatial transcriptomics, reveals that they contain representatives of the three germ layers including neural crest, Primordial Germ cells and placodal primordia.
In the mouse, primordial germ cells arise from a layer of cells in the inner cell mass of the blastocyst (the epiblast) as a result of extensive genome-wide reprogramming. Reprogramming involves global DNA demethylation facilitated by the DNA base excision repair pathway as well as chromatin reorganization, and results in cellular totipotency. Before gastrulation, the cells of the trophoblast become differentiated into two strata: The outer stratum forms a syncytium (i.e., a layer of protoplasm studded with nuclei, but showing no evidence of subdivision into cells), termed the syncytiotrophoblast, while the inner layer, the cytotrophoblast or "Layer of Langhans", consists of well- defined cells.
There are currently two proposed models for the formation of the spermatogonial lineage during neonatal development. Both models theorize that the gonocyte population develops from a subset of post migratory germ cells (PGCs) but, differ in the proposed subsets of derived gonocytes. One of the models proposes that the PGCs give rise to a single subset of pluripotent gonocytes that either become SSCs from which progenitors then arise or differentiate into type A spermatogonia directly. The other model proposes that the PGCs give rise to multiple predetermined subsets of gonocytes that produce the foundational SSC pool, initial progenitor spermatogonial population, and initial differentiating type A spermatogonia.
Lindsley concludes: "Now suppose--just suppose--that the pseudopsyche is a piece of ancestral memory that's gotten carried along in the germ cells ... and suppose that something happens to substitute this carried-over memory for the case's real one. You'd think you're the ancestor whose memory you've been carrying around. For obvious reasons, it would end at a point before the time when the said ancestor's child from whom you're descended was conceived." The manager of the "Venus" strip club, despondent over the drop-off in business, looks on in astonishment as Betty Fiorelli, the current performer, suspends her strip tease and begins declaiming in classical Greek.
Because these genes are expressed throughout the body, Page further concluded that these genes give rise to differences in the biochemistry of male and female tissues. In super- resolution studies of the sex chromosomes, Page has found evidence of an evolutionary "arms race" between the X and Y chromosomes for transmission to the next generation. In one study, Page found that human X and mouse Y chromosomes have converged, independently acquiring and amplifying gene families expressed in testicular germ cells. Another study found that the mouse Y chromosome had acquired and massively amplified genes homologous to the testis-expressed gene families on the mouse X chromosome.
The exact function of this nitrogen base is still not fully elucidated, but it is thought that it may regulate gene expression or prompt DNA demethylation. This hypothesis is supported by the fact that artificial DNA that contains 5-hydroxymethylcytosines (5hmC) can be converted into unmodified cytosines once introduced into mammalian cells. Moreover, 5hmC is highly enriched in primordial germ cells, where it apparently plays a role in global DNA demethylation. Additionally, 5-Formylcytosine, an oxidation product of 5-Hydroxymethylcytosine and possible intermediate of an oxidative demethylation pathway was detected in DNA from embryonic stem cells, although no significant amounts of these putative demethylation intermediates could be detected in mouse tissue.
Turner syndrome, also known as 45,X or 45,X0, is a chromosomal abnormality characterised by a partial or completely missing second X chromosome giving a chromosomal count of 45, instead of the correct count of 46 chromosomes. Dysregulation in meiosis signalling to germ cells during embryogenesis may result in nondisjunction and monosomy X from separation failure of chromosomes in either the parental gamete or during early embryonic divisions. The aetiology of Turner syndrome phenotype can be the result of haploinsufficiency, where a portion of critical genes are rendered inactive during embryogenesis. Normal ovarian development requires these vital regions of the X chromosome that are inactivated.
The exact function of CTAG1B remains to be unknown. Studies have suggested its role in cell cycle progression and growth, although not being elusive, through the analysis of CTAG1B's structure and expression pattern. The coexpression of CTAG1B with melanoma antigen gene C1 (MAGE-C1), another CTA, further supports its involvement in cell cycle regulation and apoptosis, due to the role of MAGE proteins in these processes. Moreover, its restricted expression pattern in male germ cells suggests its role in germ cell self-renewal or differentiation, supported by the nuclear localization of CTAG1B in mesenchymal stem cells in contrast to its cytoplasmic expression in cancer cells.
DAZ family of proteins are mRNA translation regulators with a characteristic recognition motif for binding target mRNAs and a sequence of 24 amino acids that is characteristic to the family, named DAZ repeats. The characteristic structure of the protein family is a single RRM-like RNA- binding domain at the N-terminus (amino terminus) and amino acid repeats in the C-terminus (carboxy terminus). DAZ protein family is one of the few examples of a tissue-specific RNA-binding protein that acts as a developmental regulator. In mice and humans, DAZ protein is non-uniformly distributed in the cytoplasm of pre-meiotic germ cells due to its oligomerisation with itself.
The mutation frequencies for cells throughout the different stages of spermatogenesis in mice is similar to that in female germline cells, that is 5 to 10-fold lower than the mutation frequency in somatic cells Thus low mutation frequency is a feature of germline cells in both sexes. Homologous recombinational repair of double-strand breaks occurs in mouse during sequential stages of spermatogenesis, but is most prominent in spermatocytes. The lower frequencies of mutation in germ cells compared to somatic cells appears to be due to more efficient removal of DNA damages by repair processes including homologous recombination repair during meiosis. Mutation frequency during spermatogenesis increases with age.
FSH plays a role in the spermatogenic capacity of the adult male as it controls the proliferation of Sertoli cells during either the perinatal or pubertal period, or both. However, testosterone has been found to be the most important hormone that is responsible for both the initiation and the maintenance of spermatogenesis. It is known that spermatogenesis is under the control of androgens, but germ cells (that will become gametes), do not express a functional androgen receptor, which are activated by the binding of androgenic hormones. It has been found through studies that spermatogenetic arrest tends to occur in the late spermatocyte/spermatid stage when the androgen receptor activation in Sertoli cells is interrupted or affected in some way.
Transgenesis is the same as gene therapy in the sense that they both transform cells for a specific purpose. However, they are completely different in their purposes, as gene therapy aims to cure a defect in cells, and transgenesis seeks to produce a genetically modified organism by incorporating the specific transgene into every cell and changing the genome. Transgenesis will therefore change the germ cells, not only the somatic cells, in order to ensure that the transgenes are passed down to the offspring when the organisms reproduce. Transgenes alter the genome by blocking the function of a host gene; they can either replace the host gene with one that codes for a different protein, or introduce an additional gene.
By using cells from a closely related species to the extinct species, genome editing can play a role in the de-extinction process. Germ cells may be edited directly, so that the egg and sperm produced by the extant parent species will produce offspring of the extinct species, or somatic cells may be edited and transferred via somatic cell nuclear transfer. This results in a hybrid between the two species, since it is not completely one animal. Because it is possible to sequence and assemble the genome of extinct organisms from highly degraded tissues, this technique enables scientists to pursue de-extinction in a wider array of species, including those for which no well-preserved remains exist.
Meiosis is the general process in eukaryotic organisms by which germ cells are formed, and it is likely an adaptation for removing DNA damages, especially double-strand breaks, from germ line DNA. (Also see article Meiosis). Homologous recombinational repair employing BRCA1 is especially promoted during meiosis. It was found that expression of 4 key genes necessary for homologous recombinational repair of DNA double-strand breaks (BRCA1, MRE11, RAD51 and ATM) decline with age in the oocytes of humans and mice, leading to the hypothesis that DNA double-strand break repair is necessary for the maintenance of oocyte reserve and that a decline in efficiency of repair with age plays a role in ovarian aging.
In those with healthy or preserved SSCs but without a cellular environment to support them, in vitro spermatogenesis could be used following transplant of the SSCs into healthy donor tissue. Another group that could be helped by in vitro spermatogenesis are those with any form of genetic impediment to sperm production. Those with no viable SSC development are an obvious target, but also those with varying levels of spermatogenic arrest; previously their underdeveloped germ cells have been injected into oocytes, however this has a success rate of only 3% in humans. Finally, in vitro spermatogenesis using animal or human cells can be used to assess the effects and toxicity of drugs before in vivo testing.
Some human disorders are associated with genomic imprinting, a phenomenon in mammals where the father and mother contribute different epigenetic patterns for specific genomic loci in their germ cells. The best-known case of imprinting in human disorders is that of Angelman syndrome and Prader-Willi syndrome – both can be produced by the same genetic mutation, chromosome 15q partial deletion, and the particular syndrome that will develop depends on whether the mutation is inherited from the child's mother or from their father. This is due to the presence of genomic imprinting in the region. Beckwith-Wiedemann syndrome is also associated with genomic imprinting, often caused by abnormalities in maternal genomic imprinting of a region on chromosome 11.
RA, by decreasing the overall fetal gonocyte population via apoptosis, is speculated to allow the elimination of mutated and dysfunctional germ cells. The activation of protein kinase C by phorbol ester PMA also decreased fetal gonocyte mitotic activity. There are a number of factors that influence neonatal gonocyte proliferation, including 17β‐estradiol (E2), Leukemia inhibitory factor (LIF), platelet-derived growth factor (PDGF)-BB, and RA. The production of PDGF-BB and E2 by surrounding Sertoli cells activate their respective receptors on neonatal gonocytes, triggering proliferation via an interactive, crosstalk mechanism. The regulation of LIF is speculated to allow gonocytes to become sensitive to Sertoli cell factors that trigger proliferation, such as PDGF-BB and E2.
Editing embryos, germ cells and the generation of designer babies is the subject of ethical debate, as a result of the implications in modifying genomic information in a heritable manner. Despite regulations set by individual countries’ governing bodies, the absence of a standardised regulatory framework leads to frequent discourse in discussion of germline engineering among scientists, ethicists and the general public. Arthur Caplan, the head of the Division of Bioethics at New York University suggests that establishing an international group to set guidelines for the topic would greatly benefit global discussion and proposes instating “religious and ethics and legal leaders” to impose well-informed regulations. In many countries, editing embryos and germline modification for reproductive use is illegal.
If you know the genotypes of the organisms, you can determine which alleles are dominant and which are recessive. For example, if the allele specifying tall stems in pea plants is dominant over the allele specifying short stems, then pea plants that inherit one tall allele from one parent and one short allele from the other parent will also have tall stems. Mendel's work demonstrated that alleles assort independently in the production of gametes, or germ cells, ensuring variation in the next generation. Although Mendelian inheritance remains a good model for many traits determined by single genes (including a number of well-known genetic disorders) it does not include the physical processes of DNA replication and cell division.
Sertoli cell-only syndrome is likely multifactorial, and is characterized by severely reduced or absent spermatogenesis despite the presence of both Sertoli and Leydig cells. A substantial subset of men with this uncommon syndrome have microdeletions in the Yq11 region of the Y chromosome, an area known as the AZF (azoospermia factor) region. In particular, sertoli cell only syndrome (SCO) correlates with AZFa microdeletions. It is possible to recognize two types of SCO: SCO type 1 shows total absence of spermatogonia because of an altered migration of primordial germ cells from yolk sac to gonadal ridges; SCO type 2 is instead due to a subsequent damage and shows the presence of rare spermatogonia in a minority of tubules.
After a sperm fertilizes an ovum to form a zygote, rapid DNA demethylation of the paternal DNA and slower demethylation of the maternal DNA occurs until formation of a morula which has almost no methylation. After the blastocyst is formed, methylation can begin, and with formation of the epiblast a wave of methylation then takes place until the implantation stage of the embryo. Another period of rapid and almost complete demethylation occurs during gametogenesis within the primordial germ cells (PGCs). Other than the PGCs, in the post-implantation stage, methylation patterns in somatic calls are stage- and tissue-specific with changes that presumably define each individual cell type and last stably over a long time.
Demethylation of the maternal chromosome largely takes place by blockage of the methylating enzymes from acting on maternal-origin DNA and by dilution of the methylated maternal DNA during replication (red line in Figure). The morula (at the 16 cell stage), has only a small amount of DNA methylation (black line in Figure). Methylation begins to increase at 3.5 days after fertilization in the blastocyst, and a large wave of methylation then occurs on days 4.5 to 5.5 in the epiblast, going from 12% to 62% methylation, and reaching maximum level after implantation in the uterus. By day seven after fertilization, the newly formed primordial germ cells (PGC) in the implanted embryo segregate from the remaining somatic cells.
Dr. Bradley M. Patten from the University of Michigan wrote in Human Embryology that the union of the sperm and the ovum "initiates the life of a new individual" beginning "a new individual life history." In the standard college text book Psychology and Life, Dr. Floyd L. Ruch wrote "At the time of conception, two living germ cells—the sperm from the father and the egg, or ovum, from the mother—unite to produce a new individual." Dr. Herbert Ratner wrote that "It is now of unquestionable certainty that a human being comes into existence precisely at the moment when the sperm combines with the egg." This certain knowledge, Ratner says, comes from the study of genetics.
Mice and other mammalian species undergo epigenesis during development, where germ cells are separated from the somatic lineage during early gastrulation, occurring at embryonic day 7 in mice, and are derived directly from proximal epiblast cells relative to the extraembryonic ectoderm. Prior to gastrulation the epiblast cells are not yet set in their role as cells of the germ lineage and can act as precursors for somatic cells Matsui and Okamura, 2003. At this stage, cells transplanted to the proximal epiblast from other parts of the epiblast can also be differentiated into germ line cells. The potential germ line cells are specified by the extracellular signalling of BMP4, BMP2 and BMP8b from the extraembryonic ectoderm.
Male flower urchin (Toxopneustes roseus) releasing milt, November 1, 2011, Lalo Cove, Sea of Cortez Sea urchins are dioecious, having separate male and female sexes, although no distinguishing features are visible externally. In addition to their role in reproduction, the gonads are also nutrient storing organs, and are made up of two main type of cells: germ cells, and somatic cells called nutritive phagocytes. Regular sea urchins have five gonads, lying underneath the interambulacral regions of the test, while the irregular forms mostly have four, with the hindmost gonad being absent; heart urchins have three or two. Each gonad has a single duct rising from the upper pole to open at a gonopore lying in one of the genital plates surrounding the anus.
CT antigens can be divided by whether they are encoded on the X chromosome (X-CT antigens genes) or not (non-X-CT antigens genes). It has been estimated that 10% of genes on the X chromosome belong to X-CT antigens families. The X-CT antigens genes represent more than half of all CT antigens and often constitute multigene families organized in well-defined clusters long the X chromosome, while the genes of non-X-CT antigens are distributed throughout the genome and are mostly single-copy genes. In normal testis, X-CT antigens genes are expressed primarily on the spermatogonia that are proliferate germ cells, while non-X-CT antigens are expressed in later stages of germ-cell differentiation, such as on spermatocytes.
She focused her doctoral studies on topics such as regeneration in primitive multicellular organisms, the structure of single celled organisms, the development of sperm and eggs, germ cells of insects, and cell division in sea urchins and worms. During her graduate studies at Bryn Mawr, Stevens was named a President's European Fellow and spent a year (1901–02) at the Zoological Station in Naples, Italy, where she worked with marine organisms, and at the Zoological Institute of the University of Würzburg, Germany. Returning to the United States, her Ph.D advisor was the geneticist Thomas Hunt Morgan. In addition, Stevens' experiments were influenced by the work of the previous head of the biology department, Edmund Beecher Wilson, who had moved to Columbia University in 1891.
The increased expression of the Blimp-1 protein in B lymphocytes, T lymphocytes, NK cell and other immune system cells leads to an immune response through proliferation and differentiation of antibody secreting plasma cells. Blimp-1 is also considered a 'master regulator' of hematopoietic stem cells. Blimp1 (also known as Prdm1), a known transcriptional repressor, has a critical role in the foundation of the mouse germ cell lineage, as its disruption causes a block early in the process of primordial germ cell formation. Blimp1-deficient mutant embryos form a tight cluster of about 20 primordial germ cell-like cells, which fail to show the characteristic migration, proliferation and consistent repression of homeobox genes that normally accompany specification of primordial germ cells.
Since the germ cell lineage is not established right away by induction, there is a higher chance for mutation to occur before the cells are specified. Mutation rate data is available that indicates a higher rate of germ line mutations in mice and humans, species which undergo induction, than in C. elegans and Drosophila melanogaster, species which undergo inheritance. A lower mutation rate would be selected for, which is one possible reason for the convergent evolution of the germ plasm. However, more mutation rate data will need to be collected across several taxa, particularly data collected both before and after the specification of primordial germ cells before this hypothesis on the evolution of germ plasm can be backed by strong evidence.
The idea of the Weismann barrier, namely that changes acquired during an organism's life cannot affect its offspring, is still broadly accepted. This has been extended into molecular terms as the central dogma of molecular biology, which asserts that information written in the form of proteins cannot be fed back into genetically transmissible information encoded in nucleic acids. The Weismannian notion that the germ cells are unaffected by somatic cells or their environment is however proving not to be absolute. Chemical modification of the nucleotide bases that constitute the genetic code such as methylation of cytosines as well as modifications of the histones around which DNA is organized into higher-order structures are influenced by the metabolic and physiologic state of the organism and in some cases can be heritable.
In meiosis, the chromosome or chromosomes duplicate (during interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, creating a diploid cell with a complete set of paired chromosomes. A video of meiosis I in a crane fly spermatocyte, played back at 120× the recorded speed Meiosis (; from Greek μείωσις, meiosis, meaning "lessening") is a special type of cell division of germ cells in sexually-reproducing organisms used to produce the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately result in four cells with only one copy of each paternal and maternal chromosome (haploid).
The Mecoptera and Siphonaptera (fleas) share features such as the production of the rubbery cuticle material resilin and panoistic ovarioles which have germ cells forming a continuous tube in place of the usual nurse cells. The Mecoptera are related to these other insect orders as shown in the cladogram, based on a 2008 DNA and protein analysis of 128 flea taxa from around the world. In many recent analyses, the Boreidae (snow scorpionflies) are the sister clade to the Siphonaptera, so the Mecoptera as traditionally understood is paraphyletic, though the rest of the order forms a clade. Other recent analyses, based on morphology rather than DNA, propose instead that Diptera and Siphonaptera are sister to one another, either arising from within a paraphyletic Mecoptera or together comprising the sister lineage to a monophyletic Mecoptera.
She then attended Columbia University for her MD–PhD degree. She did her doctoral work under the mentorship of Nobel Laureate Eric Kandel where she used California sea slugs (Aplysia californica) as a model organism to understand how small non-coding RNA molecules in nerve cells regulate the formation and storage of memories. During her doctoral career, she discovered a brain-specific and highly conserved micro RNA (miR-124) that is abundant in the central nervous system (CNS) of sea slugs and that is important for establishing synaptic plasticity, or the ability of neuronal connections to strengthen and weaken over time. Rajasethupathy later identified a new class of small non-coding RNAs in the CNS – piRNAs – which were thought to be present only in germ cells and germline tissues.
August Weismann made the important distinction between germ cells that give rise to gametes (such as sperm and egg cells) and the somatic cells of the body, demonstrating that heredity passes through the germ line only. Hugo de Vries connected Darwin's pangenesis theory to Weismann's germ/soma cell distinction and proposed that Darwin's pangenes were concentrated in the cell nucleus and when expressed they could move into the cytoplasm to change the cell's structure. De Vries was also one of the researchers who made Mendel's work well known, believing that Mendelian traits corresponded to the transfer of heritable variations along the germline. To explain how new variants originate, de Vries developed a mutation theory that led to a temporary rift between those who accepted Darwinian evolution and biometricians who allied with de Vries.
HOX B6 gene is only expressed in erythoid progenitor cells, which are the precursor to red blood cells used for transport of oxygen and carbon dioxide throughout the body. During development, the formation of the HOX gene factor happens in the first stages of fetal development, namely soon after the establishment of the mesoderm, which is the “middle layer” of the future embryo. However, HOX B6 is only expressed once the undifferentiated stem cells of the embryo distinguish themselves into the erythpoietic phase. The research has shown that HOX B6 is not expressed in hematopoietic stem cells located in the red bone marrow, which are the precursor cells to all types of blood cells, or primordial germ cells (PGCs), the precursor to cells passed on in each generation.
Arabidopsis thaliana is a predominantly self-fertilising plant with an out-crossing rate in the wild of less than 0.3%; a study suggested that self-fertilisation evolved roughly a million years ago or more in A. thaliana. In long- established self-fertilising plants, the masking of deleterious mutations and the production of genetic variability is infrequent and thus unlikely to provide a sufficient benefit over many generations to maintain the meiotic apparatus. Consequently, one might expect self-fertilisation to be replaced in nature by an ameiotic asexual form of reproduction that would be less costly. However the actual persistence of meiosis and self-fertilisation as a form of reproduction in long-established self-fertilising plants may be related to the immediate benefit of efficient recombinational repair of DNA damage during formation of germ cells provided by meiosis at each generation.
They worked, among other things, to correct errors and deficiencies in telecommunications equipment on Kvikk and other marine vessels, and were therefore under testing exposed to high levels of electromagnetic radiation, mostly from radarsNRK Hordaland: Stråling kan ha gitt misdannelser (Norwegian) and communications equipment. It is shown in research from the 60's and 70's that non-ionizing radiation in the microwave range can provide genotoxic mechanisms in germ cells in animals which are then relayed to the offspring, as well as practical examples have shown that radiation have led to infertility in humans,bt.no: En nysgjerrig forsker (Norwegian) but little recent research supports this. The Norwegian Navy, the Norwegian Radiation Protection Authority (NRPA) and a research group at Norwegian University of Science and Technology have concluded that there is no demonstrable link between the non-ionizing radiation on board and that the children were born with birth defects.
China has one of the most unrestrictive embryonic stem cell research policies in the world. In recent years, seeing the research opportunities that China's lax regulations provide, many expatriate Chinese scientists from the West are returning to China to establish stem cell research centers and laboratories there. As a result of the increased interest in this field of research, in 2003, the People's Republic of China Ministry of Science and Technology and Ministry of Health issued official ethical guidelines for human embryonic stem cell research in its territories. The guidelines strictly forbid any research aimed at human reproductive cloning and require that the embryos used for stem cell research come only from: # Spared gamate or blastocyst after in vitro fertilization (IVF) procedures; # Fetal cells from accidental spontaneous or voluntarily selected abortions; # Blastocyst or parthenogenetic split blastocyst obtained by somatic cell nuclear transfer technology; or # Germ cells voluntarily donated.
Daley's research seeks to translate insights in stem cell biology into improved therapies for genetic and malignant diseases. His laboratory has pioneered human cell culture-based and murine models of human blood disease and cancer.Biography, Stem Cell Program Leadership, Children's Hospital Boston Retrieved 2010-08-30. Important research contributions from his laboratory include the creation of customized stem cells to treat genetic immune deficiency in a mouse model (together with Rudolf Jaenisch),RIDEOUT ET AL, CELL 2002 the differentiation of germ cells from embryonic stem cells (cited as a "Top Ten Breakthrough" by Science in 2003),Biography, 2004 Recipients, NIH Director's Pioneer Award Retrieved 2010-08-30.GEIJSEN ET AL., NATURE 2003/4 the generation of disease-specific pluripotent stem cells by direct reprogramming of human fibroblasts (cited in the "Breakthrough of the Year" issue of Science magazine in 2008),Bios, Team, MPM Capital Retrieved 2010-08-30.
BMP4 is important for bone and cartilage metabolism. The BMP4 signaling has been found in formation of early mesoderm and germ cells. Limb bud regulation and development of the lungs, liver, teeth and facial mesenchyme cells are other important functions attributed to BMP4 signaling. Digit formation is influenced by BMP4, along with other BMP signals. The interdigital mesenchyme exhibits BMP4, which prevents apoptosis of the region. Tooth formation relies on BMP4 expression, which induces Msx 1 and 2. These transcription factors turn the forming tooth to become and incisor. BMP4 also plays important roles in adipose tissue: it is essential for white adipogenesis, and promotes adipocyte differentiation. Additionally, it is also important for brown fat, where it induces UCP1, related to non-shivering thermogenesis. BMP4 secretion helps cause differentiation of the ureteric bud into the ureter. BMP4 antagonizes organizer tissue and is expressed in early development in ectoderm and mesoderm tissue.
This announcement led to a dramatic increase in interest in the potential of stem cells to cure a range of currently incurable diseases.Australian Stem Cell Centre In 2002, Tounson apologised for misleading members of the Australian Parliament by attributing the recovery of a crippled rat to embryonic stem cells, when in fact the cells were germ cells from a fetal rat. In 2003 he was appointed a Personal Chair as Professor of Stem Cell Sciences at Monash University, was awarded a Doctor Honoris Causa by the Faculties of Medical Sciences and Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium,Australia Day – Victoria – What's On – Ambassadors and was named Australian Humanist of the Year.Australian Humanists Of The Year Trounson was the founder and executive vice-chairman of the National Biotechnology Centre of Excellence, Australian Stem Cell Centre, as well as Global Scientific Strategy Advisor.
The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria. These are usually treated separately as the nuclear genome, and the mitochondrial genome. Human genomes include both protein-coding DNA genes and noncoding DNA. Haploid human genomes, which are contained in germ cells (the egg and sperm gamete cells created in the meiosis phase of sexual reproduction before fertilization creates a zygote) consist of three billion DNA base pairs, while diploid genomes (found in somatic cells) have twice the DNA content. While there are significant differences among the genomes of human individuals (on the order of 0.1% due to single-nucleotide variants and 0.6% when considering indels), these are considerably smaller than the differences between humans and their closest living relatives, the bonobos and chimpanzees (~1.1% fixed single- nucleotide variants and 4% when including indels).
Research on TP63, also known as p63, has shown that this protein plays essential roles both for the proliferation and differentiation of stratified epithelial tissues as well as for the surveillance of the genetic quality in female germ cells. Investigations by CEF scientists showed that a specific isoform of p63 is highly expressed in primordial oocytes which are arrested in prophase of meiosis I. This isoform adopts a closed, inactive and only dimeric conformation in which both, the interaction with the DNA as well as with the transcriptional machinery is significantly reduced The inhibition is achieved by blocking the tetramerization interface of the oligomerization domain with a six-stranded anti-parallel beta-sheet. Activation requires phosphorylation and follows a spring-loaded, irreversible activation mechanism. These discoveries open the possibility to develop a therapy for preserving oocytes during chemotherapy which in female cancer patients usually results in infertility and the premature onset of menopause.
Biological determinism, also known as genetic determinism, is the belief that human behaviour is directly controlled by an individual's genes or some component of their physiology, generally at the expense of the role of the environment, whether in embryonic development or in learning.Feminist Frontiers, Ninth Edition, by Taylor, Whittier, and Rupp; How Societies Work, Fourth Edition, by Joanne Naiman Genetic reductionism is a similar concept, but it is distinct from genetic determinism in that the former refers to the level of understanding, while the latter refers to the supposedly causal role of genes. Biological determinism has been associated with movements in science and society including eugenics, scientific racism, and the debates around the heritability of IQ, the basis of sexual orientation, and sociobiology. In 1892, the German evolutionary biologist August Weismann proposed in his germ plasm theory that heritable information is transmitted only via germ cells, which he thought contained determinants (genes).
In 1988, the United States Patent and Trademark Office (USPTO) granted (filed Jun 22, 1984, issued Apr 12, 1988, expired April 12, 2005) to Harvard College claiming “a transgenic non-human mammal whose germ cells and somatic cells contain a recombinant activated oncogene sequence introduced into said mammal…” The claim explicitly excluded humans, apparently reflecting moral and legal concerns about patents on human beings, and about modification of the human genome. Remarkably, there were no US courts called to decide on the validity of this patent. Two separate patents were issued to Harvard College covering methods for providing a cell culture from a transgenic non-human animal (; filed Mar 22, 1988, issued Feb 11, 1992, expired Feb 11, 2009) and testing methods using transgenic mice expressing an oncogene (; filed Sep 19, 1991, issued Jul 20, 1999, expires July 20, 2016). The patent has been found to expire in 2005 by the USPTO.
By analyzing the differential expression of two existing, viable alleles for the X-linked enzyme glucose-6-phosphate dehydrogenase (G6PD) gene, Beutler observed that the inactivation of the gene was heritable across passaged generations of the cells. This pattern of dosage compensation, caused by random X-inactivation, is regulated across development in female mammals, following concerted patterns throughout development; for example, at the beginning of most female mammal development, both X chromosomes are initially expressed, but gradually undergo epigenetic processes to eventually achieve random inactivation of one X. In germ cells, inactivated X chromosomes are then once again activated to ensure their expression in gametes produced by female mammals. Thus, dosage compensation in mammals is largely achieved through the silencing of one of two female X chromosomes via X-inactivation. This process involves histone tail modifications, DNA methylation patterns, and reorganization of large-scale chromatin structure encoded by the X-ist gene.
In 1988, the United States Patent and Trademark Office (USPTO) granted (filed Jun 22, 1984, issued Apr 12, 1988, expired April 12, 2005) to Harvard College claiming a mouse (the "oncomouse") as “a transgenic non-human mammal whose germ cells and somatic cells contain a re-combinant activated oncogene sequence introduced into said mammal…”See Oncomouse. The European Patent Office (EPO) concluded that the usefulness of the oncomouse in furthering cancer research satisfied the likelihood of substantial medical benefit, and outweighed moral concerns about suffering caused to the animal.Article 6 of the EC's Directive 98/44/EC (the "E.U. Biotechnology Directive") excludes from patentability inventions that are contrary to ordre public or morality. These inventions include processes for modifying the genetic identity of animals that are “likely to cause them suffering without any substantial medical benefit to man or animal.” In the original application, the claims referred to animals in general, but in the course of the proceedings, the patent was amended and finally maintained with claims limited to mice.
Horizontal gene transfer poses a possible challenge to the concept of the last universal common ancestor (LUCA) at the root of the tree of life first formulated by Carl Woese, which led him to propose the Archaea as a third domain of life. Indeed, it was while examining the new three-domain view of life that horizontal gene transfer arose as a complicating issue: Archaeoglobus fulgidus was seen as an anomaly with respect to a phylogenetic tree based upon the encoding for the enzyme HMGCoA reductase—the organism in question is a definite Archaean, with all the cell lipids and transcription machinery that are expected of an Archaean, but whose HMGCoA genes are of bacterial origin. Scientists are broadly agreed on symbiogenesis, that mitochondria in eukaryotes derived from alpha- proteobacterial cells and that chloroplasts came from ingested cyanobacteria, and other gene transfers may have affected early eukaryotes. (In contrast, multicellular eukaryotes have mechanisms to prevent horizontal gene transfer, including separated germ cells.) If there had been continued and extensive gene transfer, there would be a complex network with many ancestors, instead of a tree of life with sharply delineated lineages leading back to a LUCA.

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