Neural stem cells in mammalian development.

Neural stem cells (NSCs) are primary progenitors that give rise to neurons and glia in the embryonic, neonatal and adult brain. In recent years, we have learned three important things about these cells. First, NSCs correspond to cells previously thought to be committed glial cells. Second, embryonic and adult NSCs are lineally related: they transform from neuroepithelial cells into radial glia, then into cells with astroglial characteristics. Third, NSCs divide asymmetrically and often amplify the number of progeny they generate via symmetrically dividing intermediate progenitors. These advances challenge our traditional perceptions of glia and stem cells, and provide the foundation for understanding the molecular basis of mammalian NSC behavior.