Vinculin mediated axon growth requires interaction with actin but not talin

Axon growth requires coordination of the actin cytoskeleton by actin-binding proteins in the growth cones of the extending neurites. The actin-binding protein vinculin (Vcl) is a major constituent of focal adhesion but its role in neuronal migration and axon growth is poorly understood. We found that vinculin deletion in mouse neocortical neurons attenuated axon growth both in vitro and in vivo. Using functional mutants of vinculin, we found that various domains of vinculin affect cell migration and axon growth differently. While expression of a constitutively active vinculin significantly enhanced axon growth, the head-neck domain had a moderate inhibitory effect. Contrary to previous findings, vinculin-talin interaction was dispensable for axon growth and neuronal migration. Strikingly, expression of the tail domain delayed neuronal migration and caused increased branching, enlarged soma and highly stunted axon both in vitro and in vivo. Inhibition of the Arp2/3 complex completely reversed the branching phenotype caused by tail domain expression without affecting axon length. Similarly, abolishing the tail domain interaction with actin reversed the enlarged cell soma and branching phenotypes but not axon length. Super-resolution microscopy showed increased mobile fraction of actin in tail domain expressing neurons. Our results provide novel insights into the role of vinculin and its functional domains in regulating neuronal migration and axon growth.