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Primordial germ cells (PGCs) are the precursors of adult germ cells and have remarkable potential in developmental biology-, disease modelling-, and drug development-related research applications 4.
Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia.Related to Primordial germ cells: spermatogenesis, teratoma, yolk sac
sex cell
Synonym(s): germ cell
germ cell
n. An ovum or a sperm cell or one of its developmental precursors.
sex cell
(seks sel)germ cell
see GAMETE.Germ cell
One of the cells that ordinarily develop into eggs or sperm (also sperm and eggs).
sex cell
(seks sel)Sperm or oocyte.
Synonym(s): germ cell.
Synonym(s): germ cell.
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Contents.Totipotency Totipotency (Lat. Totipotentia, 'ability for all things') is the ability of a single to divide and produce all of the differentiated cells in an. And are examples of totipotent cells.In the spectrum of cell potency, totipotency represents the cell with the greatest potential, being able to differentiate into any cell, as well as extraembryonic cells. In contrast, pluripotent cells can only differentiate into embryonic cells.It is possible for a fully differentiated cell to return to a state of totipotency.
This conversion to totipotency is complex, not fully understood and the subject of recent research. Research in 2011 has shown that cells may differentiate not into a fully totipotent cell, but instead into a 'complex cellular variation' of totipotency. Stem cells resembling totipotent from 2-cell stage embryos can arise spontaneously in mouse embryonic stem cell cultures and also can be induced to arise more frequently in vitro through down-regulation of the assembly activity of.The human development model is one which can be used to describe how totipotent cells arise.
Human development begins when a fertilizes an egg and the resulting fertilized egg creates a single totipotent cell, a. In the first hours after fertilization, this zygote divides into identical totipotent cells, which can later develop into any of the three germ layers of a human (, or ), or into cells of the ( or ). After reaching a 16-cell stage, the totipotent cells of the differentiate into cells that will eventually become either the 's or the outer. Approximately four days after fertilization and after several cycles of cell division, these totipotent cells begin to specialize. The inner cell mass, the source of, becomes pluripotent.Research on suggests that multiple mechanisms including may play a role in maintaining totipotency at different stages of development in some species. Work with and mammals suggest a further interplay between and (RBPs) in determining development differences.
Primordial germ cells In mouse primordial, -wide reprogramming leading to totipotency involves erasure of imprints. Reprogramming is facilitated by active involving the DNA enzymatic pathway. This pathway entails erasure of methylation (5mC) in primordial germ cells via the initial conversion of 5mC to (5hmC), a reaction driven by high levels of the ten-eleven dioxygenase enzymes. Pluripotency. A: Human stem cells (cell colonies that are not yet differentiated).B: cellsIn cell biology, pluripotency (Lat. Pluripotentia, 'ability for many things') refers to a stem cell that has the potential to into any of the three: endoderm (interior stomach lining, gastrointestinal tract, the lungs), mesoderm (muscle, bone, blood, urogenital), or ectoderm (epidermal tissues and nervous system), but not into extra-embryonic tissues like the placenta. However, cell pluripotency is a continuum, ranging from the completely pluripotent cell that can form every cell of the embryo proper, e.g., embryonic stem cells and iPSCs (see below), to the incompletely or partially pluripotent cell that can form cells of all three germ layers but that may not exhibit all the characteristics of completely pluripotent cells.Induced pluripotency.
Main article:Induced pluripotent stem cells, commonly abbreviated as iPS cells or iPSCs, are a type of pluripotent artificially derived from a non-pluripotent cell, typically an adult, by inducing a 'forced' expression of certain. These transcription factors play a key role in determining the state of these cells and also highlights the fact that these somatic cells do preserve the same genetic information as early embryonic cells. The ability to induce cells into a pluripotent state was initially pioneered in 2006 using mouse and four transcription factors, and c-; this technique, called, earned and the Nobel Prize in Physiology or Medicine 2012.
This was then followed in 2007 by the successful induction of human iPSCs derived from human dermal fibroblasts using methods similar to those used for the induction of mouse cells. These induced cells exhibit similar traits to those of embryonic stem cells (ESCs) but do not require the use of embryos. Some of the similarities between ESCs and iPSCs include, self-renewal ability, a trait that implies that they can divide and replicate indefinitely, and.factors are also thought to be involved in the actual reprogramming of somatic cells in order to induce pluripotency. It has been theorized that certain factors might actually work to clear the original somatic marks in order to acquire the new epigenetic marks that are part of achieving a state. Chromatin is also reorganized in iPSCs and becomes like that found in ESCs in that it is less condensed and therefore more accessible.
Modifications are also common which is also consistent with the state of found in ESCs.Due to their great similarity to ESCs, iPSCs have been of great interest to the medical and research community. IPSCs could potentially have the same therapeutic implications and applications as ESCs but without the controversial use of embryos in the process, a topic of great bioethical debate. In fact, the induced of into was originally hailed as the end of the of. However, iPSCs were found to be potentially, and, despite advances, were never approved for clinical stage research in the United States. Setbacks such as low replication rates and early senescence have also been encountered when making iPSCs, hindering their use as ESCs replacements.Additionally, it has been determined that the somatic expression of combined can directly induce other defined somatic cell fates ; researchers identified three neural-lineage-specific transcription factors that could directly convert mouse (skin cells) into fully functional. This result challenges the terminal nature of and the integrity of lineage commitment; and implies that with the proper tools, all cells are and may form all kinds of tissue.Some of the possible medical and therapeutic uses for iPSCs derived from patients include their use in cell and tissue transplants without the risk of rejection that is commonly encountered.
IPSCs can potentially replace animal models unsuitable as well as in vitro models used for disease research. Naive human pluripotent stem cell colony here seen growing on feeder cells (mouse). Primed pluripotency states Recent findings with respect to before and after implantation have produced proposals for classifying pluripotency into two distinct phases: 'naive' and 'primed'. The baseline stem cells commonly used in science that are referred as Embryonic stem cells (ESCs) are derived from a pre-implantation epiblast; such epiblast is able to generate the entire fetus, and one epiblast cell is able to contribute to all cell lineages if injected into another blastocyst. On the other hand, several marked differences can be observed between the pre- and post-implantation epiblasts, such as their difference in morphology, in which the epiblast after implantation changes its morphology into a cup-like shape called the 'egg cylinder' as well as chromosomal alteration in which one of the X-chromosomes under random inactivation in the early stage of the egg cylinder, known as. During this development, the egg cylinder epiblast cells are systematically targeted by, signaling, and other inductive factors via the surrounding yolk sac and the trophoblast tissue, such that they become instructively specific according to the spatial organization.Another major difference that was observed, with respect to cell potency, is that post-implantation epiblast stem cells are unable to contribute to blastocyst, which distinguishes them from other known pluripotent stem cells. Cell lines derived from such post-implantation epiblasts are referred to as which were first derived in laboratory in 2007; despite their nomenclature, that both ESCs and EpiSCs are derived from epiblasts, just at difference phases of development, and that pluripotency is still intact in the post-implantation epiblast, as demonstrated by the conserved expression of, and in EpiSCs, until and can be reversed midway through induced expression of.
Multipotency. Hematopoietic stem cells are an example of multipotency. When they differentiate into myeloid or lymphoid progenitor cells, they lose potency and become oligopotent cells with the ability to give rise to all cells of its lineage.Multipotency describes which have the gene activation potential to differentiate into discrete cell types. For example, a multipotent stem cell —and this cell type can differentiate itself into several types of blood cell like, etc., but it is still ambiguous whether possess the ability to differentiate into, or other non-blood cell types. New research related to multipotent cells suggests that multipotent cells may be capable of conversion into unrelated cell types. In another case, human umbilical cord blood stem cells were converted into human neurons.
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Research is also focusing on converting multipotent cells into cells.Multipotent cells are found in many, but not all human cell types. Multipotent cells have been found in, adipose tissue, cardiac cells, bone marrow, and (MSCs) which are found in the.MSCs may prove to be a valuable source for stem cells from molars at 8–10 years of age, before adult dental calcification. MSCs can differentiate into osteoblasts, chondrocytes, and adipocytes. Oligopotency In biology, oligopotency is the ability of to differentiate into a few.
It is a degree of. Examples of oligopotent stem cells are the lymphoid or myeloid stem cells.A lymphoid cell specifically, can give rise to various blood cells such as B and T cells, however, not to a different blood cell type like a red blood cell.
Examples of progenitor cells are vascular stem cells that have the capacity to become both or smooth muscle cells.Unipotency.
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