TALIN AND VINCULIN PLAY DISTINCT ROLES IN FILOPODIAL MOTILITY IN THE NEURONAL GROWTH CONE

Filopodial motility is critical for many biological processes, particu larly for axon guidance. This motility is based on altering the F-acti n-based cytoskeleton, but the mechanisms of how this occurs and the ac tin-associated proteins that function in this process remain unclear. We investigated two of these proteins found in filopodia, talin and vi nculin, by inactivating them in subregions of chick dorsal root gangli a neuronal growth cones and by observing subsequent behavior by video- enhanced microscopy and quantitative morphometry. Microscale chromopho re-assisted laser inactivation of talin resulted in the temporary cess ation of filopodial extension and retraction. Inactivation of vinculin caused an increased incidence of filopodial bending and buckling with in the laser spot but had no effect on extension or retraction. These findings show that talin acts in filopodial motility and may couple bo th extension and retraction to actin dynamics. They also suggest that vinculin is not required for filopodial extension and retraction but p lays a role in the structural integrity of filopodia.