[N-WASP regulates cortical neuron migration through its polyPro and VCA domains].

Cortical neuron migration in the developing mouse forebrain is a complex process, which contains several steps related to cytoskeleton dynamics and remodeling. Neural Wiskott-Aldrich syndrome protein (N-WASP), a member of the WASP-WAVE family, regulates actin cytoskeleton reorganization through the binding of its VCA domain to the Arp2/3 complex. Here we report expression patterns of N-WASP gene in the mouse developing embryonic cortex (E12.5~ E18.5) and find its expression levels are decreased during embryonic development. By using in utero electroporation (IUE) method, we find that either N-WASP overexpression or knockdown impairs cortical neuron migration, and the defects of cortical neuron migration caused by N-WASP overexpression are much more severe than that by its knockdown. N-WASP protein contains four domains: WH1, GBD, polyPro, and VCA. We generated a series of dominant negative N-WASP mutants by modifying these domains. Overexpression of N-WASP mutant lacking domain polyPro, VCA, or WH1, impairs cortical neuron migration. However, overexpression of N-WASP with the H208D point mutation, which abolishes the Cdc42 binding to N-WASP, causes only a marginal defect of cortical neuron migration. Finally, overexpression of the individual domain polyPro or VCA, but not WH1, can recapitulate the defects by N-WASP overexpression. However, overexpression of WH1-GBD fragment has no apparent effect on cortical neuron migration. In conclusion, our data demonstrate that N-WASP regulates cortical neuron migration mainly through its polyPro and VCA domains.