Noggin antagonizes BMP signaling to create a niche for adult neurogenesis

Large numbers of new neurons are born continuously in the adult subventricu lar zone (SVZ). The molecular niche of SVZ stem cells is poorly understood. Here, we show that the bone morphogenetic protein (BMP) antagonist Noggin is expressed by ependymal cells adjacent to the SVZ. SVZ cells were found t o express BMPs as well as their cognate receptors. BMPs potently inhibited neurogenesis both in vitro and in vivo. BMP signaling cell-autonomously blo cked the production of neurons by SVZ precursors by directing glial differe ntiation. Purified mouse Noggin protein promoted neurogenesis in vitro and inhibited glial cell differentiation. Ectopic Noggin promoted neuronal diff erentiation of SVZ cells grafted to the striatum. We thus propose that epen dymal Noggin production creates a neurogenic environment in the adjacent SV Z by blocking endogenous BMP signaling.