OPINIONEpidermal homeostasis: do committed progenitors work while stem cells sleep?

Tracking the fate of cells in murine epidermis in vivo has revealed that a committed progenitor cell population can maintain normal adult tissue in the long term without support from a long-lived, self-renewing population of stem cells. Here, we argue that these results challenge the dogma that stem-cell proliferation is required for the cellular homeostasis of the epidermis and other adult tissues, with important implications for tissue physiology and disease.

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