Melanocyte stem cells∗

Pigmentation of mammalian hairs is mediated by specialized pigment-producing cells referred as melanocytes. Hair pigmentation is tightly linked with hair regeneration cycles, where melanocytes proliferate and differentiate during the hair growth phase, but depleted by apoptosis during the regression phase. This periodical appearance of melanocytes is maintained by a small pool of immature stem cells residing in the hair follicle. Melanocyte stem cells offer an advantageous model by which to elucidate molecular basis of stem cell regulation, since genetic alterations affecting melanocyte regulation result in visible and yet viable phenotypes. Hence, by integrating melanocyte-specific in vivo gene manipulation approach and the subsequent phenotype analysis, melanocyte stem cell system provide an irresistible clue to identify key molecules for the stem cell regulation. Consolidation of such data would ultimately reveal an entire molecular network underlying the regulation of stem cells, which would not only contribute complete understanding of stem cell biology, but also provide valuable insights into medical application of stem cells. Copyright: C 2009 Masatake Osawa. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.