Totipotency is the ability of a single cell, usually a stem cell, to divide and produce all the differentiated cells in an organism, including extraembryonic tissues. For example, a plant cutting can be used to grow an entire plant. Human development begins when a sperm fertilizes an egg and creates a single totipotent cell. In the first hours after fertilization, this cell divides into identical totipotent cells. Approximately four days after fertilization and after several cycles of cell division, these totipotent cells begin to specialize. Cells in culture, stained for keratin (red) and DNA (green). ... Mouse embryonic stem cells. ... A crab is an example of an organism. ...

Totipotent cells have total potential. They specialize into pluripotent cells that can give rise to most, but not all, of the tissues necessary for fetal development. Pluripotent cells undergo further specialization into multipotent cells that are committed to give rise to cells that have a particular function. For example, multipotent blood stem cells give rise to the red cells, white cells and platelets in the blood. In cell biology, a pluripotent cell is one able to differentiate into many cell types. ... Multipotent stem cells can give rise to several other cell types, but those types are limited in number. ...

Importantly, totipotent cells must be able to differentiate not only into any cell in the organism, but also into the extraembrionic tissue associated with that organism. For example, human stem cells are considered totipotent only if they can develop into any cell in the body, or into placental cells that do not become part of the developing fetus. This is an important aspect of the stem cell controversy. The placenta is an ephemeral (temporary) organ present only in female placental vertebrates during gestation (pregnancy). ... There exists a widespread controversy over stem cell research, which arises from the techniques used in the creation and usage of stem cells. ...

Basis of totipotency

The molecular mechanisms controlling totipotency are not well understood and are a subject for current research. In particular, a February 2006 report in Science suggests that in the model organism Caenorhabditis elegans, multiple mechanisms including RNA regulation maintain totipotency at different stages of development. Binomial name Caenorhabditis elegans Maupas, 1900 Caenorhabditis elegans (pronounced see-no-rab-DYE-tis) is a free-living nematode (one of the roundworms), about 1 mm in length, which lives in a temperate soil environment. ...

See also

• Stem cell

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External links

• Epigenome NoE