TGF-βs are known to promote withdrawal of keratinocytes from the cell cycle [41]. Hence, when TGF-β2 protein was detected at the transition between the growing and destructive phases of the adult hair cycle, research initially and naturally focused on a role for this family member in cessation of growth and/or triggering apoptosis ([42] and references therein). However, in contrast to TGF-β1-null skin, which exhibits an extended growing phase of postnatal hair follicles, TGF-β2-null skin displays an embryonic block in follicle bud progression [32]. Although this phenotype is consistent with TGF-β2's embryonic expression patterns [33], about 50% of TGF-β2 null buds appear unable to progress to the down-growth phase, a feature that cannot be explained readily on the basis of previously established effects of TGF-βs.