Gallery of platelets at early stages of shape change showing localization of Arp2/3 at the cortex and at the tips and roots of filopodia.

Representative double images of platelets fixed in the presence of detergent as in Figure 6A-B. (A) Four different platelets fixed at progressively later stages of activation from left to right and imaged for both F-actin (FITC–phalloidin, green) and Arp2/3 (Cy3, red). (B) Corresponding images of the same 4 platelets showing only the actin channel. (C) Higher magnification of the 2 filopodia indicated in panel A by an asterisk. (D) Fully spread platelet at the same magnification as the other platelets in this figure for size comparison.