Klf9 regulates neural stem cell activation and expansion in the adult hippocampus

Experience governs neurogenesis from radial-glial neural stem cells (RGLs) in the adult hippocampus to support memory. Transcription factors in RGLs integrate physiological signals to dictate quiescence-activation decisions and self-renewal divisions. Whereas asymmetric RGL self-renewal drives neurogenesis during favorable conditions, symmetric divisions prevent premature neurogenesis during unfavorable conditions while amplifying RGLs to anticipate neurogenic demands when conditions become favorable. Here, we show that the transcription factor Kruppel-like factor 9 (Klf9) is enriched in quiescent RGLs and inducible, bidirectional modulation of Klf9 biases RGL quiescence-activation decisions. Clonal lineage tracing and longitudinal intravital two-photon imaging of RGLs following cell-autonomous Klf9 deletion directly demonstrated increased symmetric self-renewal. In vivo translational profiling of RGLs identified a Klf9-dependent blueprint for genetic and metabolic programs instructing RGL quiescence and expansion. Thus, experience dependent regulation of Klf9 in RGLs may ensure self-preservation of neural stem cells while anticipating future demands for neurogenesis and astrogenesis to support hippocampal functions. Overall design: Analysis of WT and Klf9 CKO (Gli1+ RGls)