Figure 4.

The changing roles of BMP signaling. BMP signaling is involved in numerous aspects of neural stem cell development. Initially, inhibition of BMP signaling is required for neuroectoderm induction. A gradient of BMP signaling establishes the dorsal–ventral axis and specifies neural crest cells and distinct interneuron subgroups within the spinal cord. During forebrain development, BMP signaling promotes neuronal lineage commitment while inhibiting oligodendrocyte formation. In late embryogenesis and postnatally, BMP signaling changes to promote astroglial commitment while repressing commitment to the other two neural lineages. In adulthood, a balance of BMP signaling is critical for maintenance and differentiation of neural stem cell populations in the SVZ and SGZ. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]