Fig. 7. Filopodial formation and elongation. (A) WAVE localizes at the distal ends of actin bundles. WAVE localized at the initiation site of filopodia and moved along the leading edge (small arrows) with the lateral motion of actin bundles through lamellipodium cytoplasm as indicated by large arrows. (B) Filopodia formation and elongation. Several actin bundles are fused at the WAVE-concentrated points and form the filopodium core. Actin polymerization via WAVE at the barbed ends elongates the microspikes and filopodia in the direction indicated by the arrows. Some proximal portions of actin bundle extend radially into the actin network and others reach the microtubule in the cytoplasm. (C) Filopodia and lamellipodia retraction. When WAVEs diffuse into the cytoplasm from the leading edge and filopodial tips, actin bundles are detached from the membrane, and then lamellipodia and filopodia retract as indicated by the arrows.