Fyn regulates multipolar-bipolar transition and neurite morphogenesis of migrating neurons in the developing neocortex

•Absence of Fyn inhibits migration of late-born neurons.•Fyn deficiency impairs migration of early-born neurons.•Fyn regulates the morphogenesis of migrating neurons.

Fyn is a non-receptor protein tyrosine kinase that belongs to Src family kinases. Fyn plays a critical role in neuronal migration, but the mechanism remains unclear. Here, we reported that suppression of Fyn expression in mouse cerebral cortex led to migration defects of both early-born and late-born neurons. Morphological analysis showed that loss of Fyn function impaired multipolar-bipolar transition of newly generated neurons and neurite formation in the early phase of migration. Moreover, Fyn inhibition increased the length of leading process and decreased the branching number of the migrating cortical neurons. Together, these results indicate that Fyn controls neuronal migration by regulating the cytoskeletal dynamics and multipolar-bipolar transition of newly generated neurons during cortical development.