Stem cell proliferation in the skin: alpha-catenin takes over the hippo pathway.

Epithelial tissues in the human body undergo constant renewal. For example, the skin is regenerated continuously through the periodic proliferation of normally quiescent stem cells in the basal compartment of the skin. Proper balance between stem cell quiescence and proliferation is maintained over the lifetime of the organism to preserve pools of stem cells required to maintain and repair tissues. However, mechanisms controlling the rate of stem cell renewal are poorly understood. Additionally, whether deregulation of these mechanisms within epidermal stem cells leads to skin cancer is not known. The adherens junction component α-catenin has been identified as a regulator of epidermal stem cell proliferation and as a suppressor of skin cancer through its inhibition of Yap, a transcriptional effector of the Hippo growth control pathway. Understanding the pathways that regulate the proliferation of stem cells in the skin holds promise for reversing the aging process and tumor development.