Evolution Shapes Cortical Interneuron Migration
The cerebral cortex comprises excitatory neurons and inhibitory interneurons originating from distinct forebrain regions. During migration, cortical interneurons (cINs) interact dynamically with neighbouring cells and their microenvironment, contributing to cortical architecture. However, how evolutionary changes in cIN migration shape species-specific cortical development remains unclear. Comparative analyses in mouse, ferret, and human models revealed a conserved migratory sequence but distinct behaviours: human cINs migrate slower, display increased leading-process branching, and exhibit more frequent homotypic repulsive interactions than their mouse and ferret counterparts. These features promote dispersed cortical invasion of cINs in humans and ferrets, contrasting with the stream-like migration observed in mice. Mechanistically, elevated expression of the cytosolic carboxypeptidase CCP1 in human cINs reduces microtubule glutamylation and doublecortin recruitment, thereby facilitating leading-process branching. These findings identify a CCP1-dependent mechanism regulating cIN dispersion and suggest that evolutionary changes in cIN migration contribute to divergent patterns of cortical morphogenesis across mammals.