FAK ablation in megakaryocytes and platelets. (A) Bone marrow–derived megakaryocytes and freshly isolated platelets were lysed and FAK and PYK2 protein expression determined by Western blotting. (B) Cytospin preparations of mature bone marrow–derived megakaryocytes are shown, stained for FAK expression (green) and DNA (blue). The staining shown is representative of approximately 50 cells in each group. Relevant immunoglobulin controls are shown as insets. (C) Western blot analyses of phospho-PYK2 in response to fibrinogen and MnCl₂ in megakaryocytes and (D) in platelets in response to ADP derived from Pf4-Cre/FAK-floxed and WT mice. (E) Western blot analyses of FAK protein expression by nonmegakaryocytic tissues in Pf4-Cre/FAK-floxed and WT mice.