n-cofilin–null platelets are markedly increased in size. (A) Whole platelet proteins were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and immunoblotted with anti-ADF or anti–n-cofilin antibodies. GPIIIa was used as a loading control. Results from 2 individual mice per group (control, Adf^−/−, n-cofilin–null) are shown. For the analysis of ADF/n-cofilin–null platelets, pooled platelet lysates were prepared from 6 mice. (B-C) Fluorescence-activated cell sorter analyses. (B) Peripheral platelet counts in control, Adf^−/− and n-cofilin–null mice. Values are mean ± SD (n = 6). n.s. indicates not significant. *P < .05. (C) Platelet size of control, Adf^−/− and n-cofilin–null platelets. Values are mean ± SD (n = 6). ***P < .001. FSC indicates forward scatter. (D) TEM analysis of resting platelets (top panel). Scale bar represents 2 μm. Visualization of the cytoskeleton of resting platelets on poly-L-lysine (bottom panel). Scale bar represents 1 μm.