Abstract:

In the adult mammalian central nervous system (CNS), neural cell generation is restricted to two highly specialized germinal niches. These are the subventricular zone (SVZ) that borders the forebrain lateral ventricles and the subgranular zone of the hippocampus. In the case of the former niche, the SVZ gives rise daily to thousands of migratory neuroblasts that travel long distances to the olfactory bulb via the rostral migratory stream. Neural stem cells (NSCs) first engage through a sequence of activation phenotypes and give rise to transiently amplifying progenitors (TAPs) that subsequently differentiate into neuroblasts. Once in the olfactory bulb, they generate phenotypically distinct neurons. Most of these constitute the interneuron class that is preferentially derived from the lateral portion of the SVZ, whilst a small proportion of projection neurons are also formed from the dorsal SVZ. Similarly, although fractional in number, oligodendrocyte lineage cells and astrocytes are additionally generated from this germinal zone. Lesser is known regarding the differentiation steps regarding adult astrogenesis from the SVZ. Oligodendrocyte lineage cells diverge from TAPs and remain relatively close within the periventricular forebrain corresponding to their site generation. Oligodendrocytes generated from the SVZ will also pass through phenotypically distinct stages until they form mature oligodendrocytes. Adult NG2 glia (oligodendrocyte precursor cells) are the main proliferative population of the adult CNS outside of neurogenic niches and are supported in their capacity to restore oligodendrocyte populations following injury by SVZ derived early oligodendroglial populations.