Abstract
Self renewing epidermis are characterized by a fine balance between growth and differentiation of immature keratinocytes including stem cells. Recent progress showed various molecules that played important roles for this control. Here we focus on two molecules, cyclin-dependent kinase inhibitor p 21 and Notch receptor. First, p21 has been shown to the contribution to proliferation and differentiation of keratinocytes. Recently we know that loss of p21 function increases the pluripotent keratinocyte population with multi-potential (stem cells) . Second, Notch was identified as one of key molecules for cell fate decision in Drosophila. Even in mammalian Notch homologues have important functions for the control of cell fate decision and growth/differentiation due to cell-cell communication. In keratinocytes Notch 1 signaling leads to growth arrest via p21 activation and differentiation. These works will advance our knowledge on controlling mechanism for homeostasis and tumor formation in not only epidermis but also other epithelia tissue.
