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Stem Cell Depletion Through Epidermal Deletion of Rac1
Salvador Aznar Benitah,1Michaela Frye,1Michael Glogauer,2Fiona M. Watt1*
Mammalian epidermis is maintained by self-renewal of stem cells,but the underlying mechanisms are unknown. Deletion of Rac1,a Rho guanosine triphosphatase, in adult mouse epidermis stimulatedstem cells to divide and undergo terminal differentiation, leadingto failure to maintain the interfollicular epidermis, hair follicles,and sebaceous glands. Rac1 exerts its effects in the epidermisby negatively regulating c-Myc through p21-activated kinase2 (PAK2) phosphorylation. We conclude that a pleiotropic regulatorof cell adhesion and the cytoskeleton plays a critical rolein controlling exit from the stem cell niche and propose thatRac and Myc represent a global stem cell regulatory axis.
1 Keratinocyte Laboratory, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. 2 Faculty of Dentistry, University of Toronto, College Street, Toronto M5S 1A8, Canada.
* To whom correspondence should be addressed. E-mail: fiona.watt{at}cancer.org.uk
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