Myosin II localizes to the dorsal surface of the lamella. (A and B) Myosin IIA localizes within actin arcs on the cell’s dorsal surface. (A) Ventral view of actin filaments (red), myosin IIA–GFP, and paxillin in a U2OS cell. Open arrowheads denote DSF, open arrows denote newly formed actin arcs, and closed arrows denote ventral stress fibers. (B) Dorsal view showing mature actin arcs (open arrow) and DSF (open arrowheads). Broken lines denote the sides of the cell and the circle denotes the position of the nucleus (N). Bar, 10 µm.