Embryonic diversification of adult neural stem cells and ependymal cells

Both adult neural stem (type B) cells and ependymal (type E) cells in the mouse ventricular-subventricular zone (V-SVZ) are derived from slowly dividing (or quiescent) embryonic neural stem-progenitor cells (NPCs) that are set aside during development. However, it has remained unclear whether fate diversification between adult type B and type E cells actually occurs during embryogenesis. Here we performed single-cell transcriptomic analysis of slowly dividing embryonic NPCs and identified cell subpopulations transcriptionally similar to adult type B or type E cells. The type B- like embryonic cells appeared to emerge before embryonic day (E) 13.5, whereas the type E-like cells became evident between E13.5 and E16.5. Genes differentially expressed in B-like embryonic cells (versus E-like cells) included Tmem100, Cadm2, and bone morphogenetic protein (BMP)-induced genes. Forced expression of an active form of BMP receptor (ALK2QD), TMEM100, or CADM2 in embryonic NPCs resulted in preferential generation of adult type B cells relative to type E cells in the postnatal brain. Moreover, knockdown of TMEM100 resulted in relative enrichment of type E cells over type B cells. Our results indicate that the embryonic origin of adult type B cells and that of type E cells have already diverged molecularly during embryogenesis, and they have identified key molecular players in this fate bifurcation.