Cell potency
Research on Caenorhabditis elegans suggests that multiple mechanisms including RNA regulation may play a role in maintaining totipotency at different stages of development in some species.
[10] Work with zebrafish and mammals suggest a further interplay between miRNA and RNA-binding proteins (RBPs) in determining development differences.
[11] In mouse primordial germ cells, genome-wide reprogramming leading to totipotency involves erasure of epigenetic imprints.
[12] 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
'ability for many [things]')[14] refers to a stem cell that has the potential to differentiate into any of the three germ layers: endoderm (gut, lungs and liver), mesoderm (muscle, skeleton, blood vascular, urogenital, dermis), or ectoderm (nervous, sensory, epidermis), but not into extra-embryonic tissues like the placenta or yolk sac.
[17] The ability to induce cells into a pluripotent state was initially pioneered in 2006 using mouse fibroblasts and four transcription factors, Oct4, Sox2, Klf4 and c-Myc;[18] this technique, called reprogramming, later earned Shinya Yamanaka and John Gurdon the Nobel Prize in Physiology or Medicine.
Some of the similarities between ESCs and iPSCs include pluripotency, morphology, self-renewal ability, a trait that implies that they can divide and replicate indefinitely, and gene expression.
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.
However, iPSCs were found to be potentially tumorigenic, and, despite advances,[16] were never approved for clinical stage research in the United States until recently.
[22] Setbacks such as low replication rates and early senescence have also been encountered when making iPSCs,[23] hindering their use as ESCs replacements.
[24] This result challenges the terminal nature of cellular differentiation and the integrity of lineage commitment; and implies that with the proper tools, all cells are totipotent 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.
[27] Primed pluripotent stem cells from different species could be reset to naive state using a cocktail containing Klf4 and Sox2 or "super-Sox" − a chimeric transcription factor with enhanced capacity to dimerize with Oct4.
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 X-inactivation.
[40] MSCs may prove to be a valuable source for stem cells from molars at 8–10 years of age, before adult dental calcification.
