MicroRNAs (miRNAs) regulate biological function of neural progenitor cells and oligodendrocyte progenitor cells (OPCs). Our preliminary data show that stroke substantially changed miRNA expression profiles in adult neural progenitor cells and oligodendrocytes. In this application, we propose to test the hypothesis that miRNAs in neural and OPCs play a pivotal role in mediating adult neurogenesis and oligodendrogenesis in the ischemic brain. In Specific Aim 1, we will investigate the effect of inactive miRNA processes in neural progenitor cells and OPCs on stroke-induced neurogenesis and oligodendrogenesis by conditional and inducible Dicer ablation in Ascl1 lineage cells (Ascl1-CreTM/Dicerflox/flox). In Specific Aim 2, we will investigate whether the sonic hedgehog (Shh) signaling pathway interacts with the miR-17-92 cluster to increase neurogenesis and oligodendrogenesis. In Specific Aim 3, we will investigate the effect of the miR17-92 cluster on biological function of neural and oligodendrocyte progenitor cells in the ischemic brain by deletion or overexpression of the miR17-92 cluster in neural progenitor cells and OPCs after stroke. These studies will provide novel insights into miRNAs in regulating stroke-induced neurogenesis and oligodendrogenesis, which could potentially lead to new therapies to amplify neurogenesis and oligodendrogenesis in injured brain.