p63RhoGEF-mediated formation of a single polarized lamellipodium is required for chemotactic migration in breast carcinoma cells

► Six Rho-GEFs are required for serum-induced chemotaxis in MDA-MB-231 cells. ► Knockdown of p63RhoGEF suppresses serum-induced RhoA activation and chemotaxis. ► Knockdown of p63RhoGEF produces multipolar lamellipodia upon serum stimulation. ► p63RhoGEF promotes chemotaxis by limiting lamellipodium formation to one direction.