Characterization of platelets from Pyk2-KO mice. (A) Platelets and WBC count in whole blood from WT (black bars) and Pyk2-KO (white bars) mice. Results are the means ± SD of determination performed in 10 different mice. (B) Analysis of Pyk2, FAK, and tubulin expression in platelets from WT and Pyk2-KO mice by immunoblotting with specific Abs as indicated on the right. (C) Surface expression of different glycoproteins on WT (black bars) and Pyk2-KO (white bars) mice determined by flow cytometric analysis with specific Abs. Data are expressed as the mean fluorescence intensity ± SD of 3 different experiments performed in duplicate. (D) Electron microscopy analysis of WT and Pyk2-deficient (Pyk2-KO) platelets. Representative images at different magnitudes (7000× and 22 000×, respectively) are reported in panel Di. Measurement of the mean platelet diameter is reported in panel Dii and quantification of α- and dense-granules is shown in panel Diii. Data have been obtained from the analysis of 50 platelets from 5 different slides for each genotype and are expressed as means ± SEM. (E) Tail bleeding time determined in groups of 13 WT and 14 Pyk2-KO mice. Each symbol represents 1 animal. Statistical analysis revealed a significant difference between the 2 groups of animals (P < .01).