Modulation of fate determinants Olig2 and Pax6 in resident glia evokes spiking neuroblasts in a model of mild brain ischemia.

BACKGROUND AND PURPOSE Although in vitro studies suggest that non-neurogenic regions of the adult central nervous system potentially contain multipotent parenchymal progenitors, neurons are clearly not replaced in most brain regions after injury. Here, in a well-established model of mild transient brain ischemia, we explored Olig2 antagonism and Pax6 overexpression as potential avenues to redirect endogenous progenitors proliferating in situ toward a neuronal fate. METHODS Retroviral vectors containing either Pax6 or a strong activator form of the repressor Olig2 (Olig2VP16), ie, a functionally dominant negative form of Olig2, were stereotaxically injected into the lateral striatum at 48 hours after 30 minutes middle cerebral artery occlusion (MCAo)/reperfusion. RESULTS Retroviral modulation of fate determinants resulted in a significant number of infected cells differentiating into Doublecortin (DCX)-expressing immature neurons that were not observed after injection of a control virus. Whole-cell patch-clamp recordings in acute brain slices showed that the percentage of virus-infected cells with Na(+) currents was increased by inhibition of the repressor function of Olig2 and by overexpression of Pax6. Furthermore, on retroviral transduction of fate determinants, we detected newly generated cells within the ischemic lesion that were capable of generating single action potentials and that received synaptic input. CONCLUSIONS Taken together, these data show that resident glia in the striatum can be reprogrammed toward functional neuronal differentiation following brain injury.