Radial glial identity is promoted by Notch1 signaling in the murine forebrain

In vertebrates, Notch signaling is generally thought to inhibit neural diff erentiation. However, whether Notch can also promote specific early cell fa tes in this context is unknown. We introduced activated Notch1 (NIC) into t he mouse forebrain, before the onset of neurogenesis, using a retroviral ve ctor and ultrasound imaging. During embryogenesis, NIC-infected cells becam e radial glia, the first specialized cell type evident in the forebrain. Th us, rather than simply inhibiting differentiation, Notch1 signaling promote d the acquisition of an early cellular phenotype. Postnatally, many NIC-inf ected cells became periventricular astrocytes, cells previously shown to be neural stem cells in the adult. These results suggest that Notch1 promotes radial glial identity during embryogenesis, and that radial glia may be li neally related to stem cells in the adult nervous system.