Olig2 acts as an inducible barrier to in vivo astrocyte-to-neuron conversion.

In vivo astrocyte-to-neuron (AtN) conversion suffers low efficiency due to pre-existing intrinsic barriers. However, it is unclear whether astrocytes have inducible barriers to reprogramming. Here, we identify Olig2, a basic helix-loop-helix (bHLH) transcription factor, as an inducible barrier to Ngn2-mediated AtN conversion. Olig2 is strongly upregulated in cortical astrocytes following the ectopic expression of bHLH neuronal reprogramming factors such as Ngn2, NeuroD1, and Ascl1, but is barely expressed in normal astrocytes. Knocking down Olig2 in Ngn2-transduced astrocytes reduces astrocyte-specific gene expression, enhances neurogenesis-related gene expression, and increases AtN conversion efficiency by approximately threefold. Further multi-omics analysis shows that astrocytic Olig2 directly binds to regulatory regions of pro-neurogenic genes, including Ngn2, inhibiting their expression and impeding the expression of neural progenitor genes. Collectively, our findings reveal Olig2 as an inducible barrier to AtN conversion, providing insights into the regulation of neuronal reprogramming.