Drebrin E regulates neuroblast proliferation and chain migration in the adult brain

F‐actin‐binding protein drebrin has two major isoforms: drebrin A and drebrin E. Drebrin A is the major isoform in the adult brain and is highly concentrated in dendritic spines, regulating spine morphology and synaptic plasticity. Conversely, drebrin E is the major isoform in the embryonic brain and regulates neuronal morphological differentiation, but it is also expressed in neurogenic regions of the adult brain. The subventricular zone ( SVZ ) is one of the brain regions where adult neurogenesis occurs. Neuroblasts migrate to the olfactory bulb ( OB ) and integrate into existing neuronal networks, after which drebrin expression changes from E to A, suggesting that drebrin E plays a specific role in neuroblasts in the adult brain. Therefore, to understand the role of drebrin E in the adult brain, we immunohistochemically analyzed adult neurogenesis using drebrin‐null‐mutant ( DXKO ) mice. In DXKO mice, the number of neuroblasts and cell proliferation decreased, although cell death remained unchanged. These results suggest that drebrin E regulates cell proliferation in the adult SVZ . Surprisingly, the decreased number of neuroblasts in the SVZ did not result in less neurons in the OB . This was because the survival rate of newly generated neurons in the OB increased in DXKO mice. Additionally, when neuroblasts reached the OB , the change in the migratory pathway from tangential to radial was partly disturbed in DXKO mice. These results suggest that drebrin E is involved in a chain migration of neuroblasts.