Many tissues contain adult stem cells that could provide sources of cells for cell-based therapies. For example, adult neural stem cells (NSCs), which are found in brain regions such as the subependymal zone (SEZ), could be used to treat nervous system disorders. Little is known, however, about the intrinsic specification of adult NSCs or how dependent this specification is on the local niche. To understand the biology of NSCs better, Benedikt Berninger and co-workers have been using continuous live imaging to follow the cell divisions and lineage progression of cells isolated from the adult mouse SEZ (see p. ). They now report that SEZ cells cultured at low density without growth factors are primarily neurogenic, and that adult NSCs progress through stereotypic lineage trees consisting of asymmetric stem cell divisions, symmetric transit-amplifying divisions and final symmetric neurogenic divisions. The researchers conclude from these results that lineage progression from stem cell to neuron is cell-intrinsic and is independent of the local niche to a surprising degree.
