RIT1 GTPase Regulates Sox2 Transcriptional Activity and Hippocampal Neurogenesis [Signal Transduction]

December 22nd, 2016 by Sajad Mir, Weikang Cai, Douglas A. Andres

Adult neurogenesis, the process of generating mature neurons from neuronal progenitor cells, makes critical contributions to neural circuitry and brain function under both healthy and disease states. Neurogenesis is a highly regulated process, in which diverse environmental and physiological stimuli are relayed to resident neural stem cell populations to control the transcription of genes involved in their self-renewal and differentiation. Understanding the molecular mechanisms governing neurogenesis is necessary for the development of translational strategies to harness this process for neuronal repair. Here we report that the Ras-related GTPase, RIT1, serves to control the sequential proliferation and differentiation of adult hippocampal neural/stem progenitor cells (NPCs), with in vivo expression of active RIT1 driving robust adult neurogenesis. Gene expression profiling analysis demonstrates increased expression of a specific set of transcription factors known to govern adult neurogenesis in response to active RIT1 expression in the hippocampus, including sex-determining region Y-related HMG box 2 (Sox2), a well-established regulator of stem cell self-renewal and neurogenesis. In adult hippocampal neuronal precursor cells (HNPCs), RIT1 controls an Akt-dependent signaling cascade, resulting in the stabilization and transcriptional activation of phosphorylated Sox2. Together, these studies support a role for RIT1 in relaying niche-derived signals to NPCs to control transcription of genes involved in self-renewal and differentiation.