Platelets assemble actin normally in the absence of WASp.

(A) Platelets isolated from a healthy human volunteer (●) and WAS patient P34 (○) were activated with 25 μM TRAP or 3 μg/mL CRP. (B) Platelets from wild-type (●) and WASp-deficient (○) mice were activated with 1 U/mL thrombin or 3 μg/mL CRP. Platelets were fixed with 3.4% formaldehyde, extracted with 0.1% Triton X-100 in PHEM buffer containing 2 μM FITC-phalloidin, and analyzed by FACS. Results shown are expressed as the ratio between the fluorescence of activated cells versus resting cells and are representative of 3 to 4 experiments.