MTOR controls genesis and autophagy of GABAergic interneurons during brain development

Interneuron progenitors in the ganglionic eminence of the ventral telencephalon generate most cortical interneurons during brain development. However, the regulatory mechanism of interneuron progenitors remains poorly understood. Here, we show that MTOR (mechanistic target of rapamycin [serine/threonine kinase]) regulates proliferation and macroautophagy/autophagy of interneuron progenitors in the developing ventral telencephalon. To investigate the role of MTOR in interneuron progenitors, we conditionally deleted the <i>Mtor</i> gene in mouse interneuron progenitors and their progeny by using <i>Tg(mI56i-cre,EGFP)1Kc/Dlx5/6-Cre-IRES-EGFP</i> and <i>Nkx2–1-Cre</i> drivers. We found that <i>Mtor</i> deletion markedly reduced the number of interneurons in the cerebral cortex. However, relative positioning of cortical interneurons was normal, suggesting that disruption of progenitor self-renewal caused the decreased number of cortical interneurons in the <i>Mtor</i>-deleted brain. Indeed, <i>Mtor</i>-deleted interneuron progenitors showed abnormal proliferation and cell cycle progression. Additionally, we detected a significant activation of autophagy in <i>Mtor</i>-deleted brain. Our findings suggest that MTOR plays a critical role in the regulation of cortical interneuron number and autophagy in the developing brain.