Segregation of human neural stem cells in the developing primate forebrain

Many central nervous system regions at all stages of Life contain neural st em cells (NSCs). We explored how these disparate NSC pools might emerge. A traceable clone of human NSCs was implanted intraventricularly to allow its integration into cerebral germinal zones of Old World monkey fetuses. The NSCs distributed into two subpopulations: One contributed to corticogenesis by migrating along radial glia to temporally appropriate layers of the cor tical plate and differentiating into lamina-appropriate neurons or glia; th e other remained undifferentiated and contributed to a secondary germinal z one (the subventricular zone) with occasional members interspersed througho ut brain parenchyma. An early neurogenetic program allocates the progeny of NSCs either immediately for organogenesis or to undifferentiated pools for later use in the "postdevelopmental" brain.