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Published February 7, 1997 | public
Journal Article

Regulatory Mechanisms in Stem Cell Biology


Stem cells are a subject of intense and increasing interest because of their biological properties and potential medical importance. Unfortunately, the field has been difficult for the nonspecialist to penetrate, in part because of ambiguity about what exactly constitutes a stem cell. A working definition is useful in order to pose the important questions in stem cell biology. However, since different people define stem cells in different ways (for examples, see37 and 76), formulating a generally acceptable definition can lead to a conclusion similar to that of U. S. Supreme Court Justice Byron White's in regard to pornography: "It's hard to define, but I know it when I see it." A minimalist definition is that stem cells have the capacity both to self-renew and to generate differentiated progeny. Although this is in many respects inadequate, it immediately highlights some important problems: How at each cell division is a stem cell able to pass on its "stem" properties to at least one of its two daughters? And what determines whether stem cell divisions will be self-renewing, or differentiating?

Additional Information

© 1997 by Cell Press. Under an Elsevier user license. Available online 17 October 2000. We thank Tom Jessell and Irv Weissman for their helpful comments on the manuscript, and Marie-Anne Félix and Paul Sternberg for helpful discussions and for allowing reproduction of their illustration in Figure 3. S. J. M. is supported by the Guenther Foundation and the Natural Sciences and Engineering Research Council of Canada. D. J. A. is an Investigator of the Howard Hughes Medical Institute.

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