Neural stem and progenitor cells generate the massive diversity of neurons and glia that comprise the nervous system. Understanding the regulation of how neural progenitors divide and differentiate will provide important insight into disease mechanisms and enable the development of new therapeutic approaches. Our previous studies in the developing cerebral cortex suggest that stem and progenitor cells can support the growth and differentiation of other stem and progenitor cells. The goals of this proposal are to examine whether similar support mechanisms exist in the adult brain, and to elucidate the mechanisms by which cell adhesion may regulate the adult neural stem cell microenvironment. We will use mouse models of brain development for these studies.