Acts as an actin nucleation factor and promotes assembly of actin filaments together with spir. May play a role in intracellular vesicle transport along actin fibers, providing a novel link between actin cytoskeleton dynamics and intracellular transport. Interacts with wash. Interacts with spir. Recruited to membranes via its interaction with spir. Belongs to the formin homology family. Cappuccino subfamily.