<P> Totipotency (Lat . totipotentia, "ability for all (things)") is the ability of a single cell to divide and produce all of the differentiated cells in an organism . Spores and zygotes are examples of totipotent cells . In the spectrum of cell potency, totipotency represents the cell with the greatest differentiation potential . </P> <P> 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 blastomeres from 2 - cell stage embryos can arise spontaneously in the embryonic stem cell cultures and also can be induced to arise more frequently in vitro through down - regulation of the chromatin assembly activity of CAF - 1 . </P> <P> The human development model is one which can be used to describe how totipotent cells arise . Human development begins when a sperm fertilizes an egg and the resulting fertilized egg creates a single totipotent cell, a zygote . 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 (endoderm, mesoderm, or ectoderm), into cells of the cytotrophoblast layer or syncytiotrophoblast layer of the placenta . After reaching a 16 - cell stage, the totipotent cells of the morula differentiate into cells that will eventually become either the blastocyst's Inner cell mass or the outer trophoblasts . 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 embryonic stem cells, becomes pluripotent . </P> <P> 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 . Work with zebrafish and mammals suggest a further interplay between miRNA and RNA binding proteins (RBPs) in determining development differences . </P>

Where are totipotent stem cells found in the body
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