Notch signaling in astrocytes and neuroblasts of the adult subventricular zone in health and after cortical injury.

The postnatal subventricular zone (SVZ) is a niche for continuous neurogenesis in the adult brain and likely plays a fundamental role in self-repair responses in neurodegenerative conditions. Maintenance of the pool of neural stem cells within this area depends on cell-cell communication such as that provided by the Notch signaling pathway. Notch1 receptor mRNA has been found distributed in different areas of the postnatal brain including the SVZ. Although the identity of Notch1-expressing cells has been established in the majority of these areas, it is still unclear what cell types within the SVZ are expressing components of this pathway. Here we demonstrate that most of expression of Notch1 in the adult SVZ occurs in polysialylated neural cell adhesion molecule (PSA-NCAM)-positive neural precursors and in glial fibrillary acidic protein-positive SVZ astrocytes. Notch1 was also found in PSA-NCAM-positive neuroblasts located within the rostral migratory stream (RMS) but much less in those that have reached the olfactory bulb. We show that two of the naturally occurring Notch1 activators, Jagged1 and Delta1, are also expressed in the SVZ and within the RMS in the adult mouse brain. Finally, using a model of cortical stab wound, we show that the astrogliogenic response of the SVZ to injury is accompanied by activation of the Notch pathway. Copyright (c) 2006 S. Karger AG, Basel.