50. Rodriguez CI, Buchholz F, Galloway J, Sequerra R, Kasper J, et al. (2000) High- efficiency deleter mice show that FLPe is an alternative to Cre-loxP. Nat Genet 25: 139–140. 51. Muller-Rover S, Handjiski B, van der Veen C, Eichmuller S, Foitzik K, et al. (2001) A comprehensive guide for the accurate classification of murine hair follicles in distinct hair cycle stages. J Invest Dermatol 117: 3–15. Misu Regulates Stem Cell Fate 52. Bruhn L, Munnerlyn A, Grosschedl R (1997) ALY, a context-dependent coactivator of LEF-1 and AML-1, is required for TCRalpha enhancer function. Genes Dev 11: 640–653. PLoS Genetics | www.plosgenetics.org 14 December 2011 | Volume 7 | Issue 12 | e1002403