Do Filopodia Enable the Growth Cone to Find Its Way?

Ena/VASP family proteins are required for accurate axon pathfinding in developing Drosophila, Caenorhabditis elegans, and mouse nervous systems. Recent papers by Bear et al. and Svitkina et al. provide evidence that Ena/VASP proteins regulate actin filament elongation in the lamellipodia and filopodia of nonneuronal cells. Neuronal growth cones use filopodia as their "sensory organs" that steer the growth cone by reading guidance cues in the environment. Together, these studies suggest that Ena/VASP proteins regulate axon guidance by controlling the formation or rearrangement of growth cone filopodia.