Oligodendrocyte precursors guide interneuron migration by unidirectional contact repulsion.

In the forebrain, ventrally derived oligodendrocyte precursor cells (vOPCs) travel tangentially toward the cortex together with cortical interneurons. Here, we tested in the mouse whether these populations interact during embryogenesis while migrating. By coupling histological analysis of genetic models with live imaging, we show that although they are both attracted by the chemokine Cxcl12, vOPCs and cortical interneurons occupy mutually exclusive forebrain territories enriched in this chemokine. Moreover, first-wave vOPC depletion selectively disrupts the migration and distribution of cortical interneurons. At the cellular level, we found that by promoting unidirectional contact repulsion, first-wave vOPCs steered the migration of cortical interneurons away from the blood vessels to which they were both attracted, thereby allowing interneurons to reach their proper cortical territories.