Protein content in Nbeal2^−/− mouse platelets and plasma. Immunoblots comparing platelet (PLT) whole-cell lysates or plasma from WT and Nbeal2^−/− mice. MK-derived thrombospondin-1 (TSP1; A), platelet factor 4 (PF4; B), and von Willebrand factor (VWF; C) were undetectable or significantly reduced in Nbeal2^−/− in comparison with WT platelet lysates, and plasma VWF (E) and fibrinogen (F) levels were normal. (D) Plasma-derived fibrinogen (Fgn) was present in decreased amounts in Nbeal2^−/− platelets. (G) P-selectin in Nbeal2^−/− platelets was present at approximately 48% of WT levels. VPS33B (H) and VPS16B (I) were present at similar levels in WT and Nbeal2^−/− platelets. Lysate from equivalent numbers of platelets was loaded in each lane, and protein loading is indicated by probing for actin or glyceraldehyde-3-phosphate dehydrogenase (GAPDH). See the “Methods” section for antibody details.