Neural Stem Cell Relay from B1 to B2 cells in the adult mouse Ventricular-Subventricular Zone

Neurogenesis and gliogenesis continue in the Ventricular-Subventricular Zone (V-SVZ) of the adult rodent brain. B1 cells are radial glia-derived astroglial cells that function as primary progenitors or neural stem cells (NSCs) in the V-SVZ. B1 cells, which have an apical contact with the ventricle, decline during early postnatal life, yet neurogenesis continues into adulthood. We found that a second population of V-SVZ astroglial cells (B2 cells), that do not contact the ventricle, function as NSCs in the adult brain. B2 cell numbers increase postnatally, remain constant in 12-month-old mice, and decrease by 18 months. Transcriptomic analysis revealed differences between B1 and B2 cells and shows that like B1 cells, B2 cells can be quiescent or activated. Transplantation and lineage tracing of B2 cells demonstrate their function as primary progenitors for adult neurogenesis. This study reveals that NSC function is relayed from B1 to B2 progenitors to maintain adult neurogenesis.