Surface expression of activated but not wild-type α2 integrins is lost during platelet production in vivo. (A) Expression of surface α2 integrins and GFP in platelets from wild-type C57 Bl/6 mice and lethally irradiated mice reconstituted with hematopoietic stem cells lacking both α2 and GPVI that were transduced with GFP-expressing vector (vector) or vectors expressing the indicated α2 integrins and GFP. (B) Quantitation of platelet surface α2 integrin levels. Mean fluorescence intensity (MFI) was measured in the indicated platelets after staining with anti-α2 antibody. N = 3-5; mean and SD are shown. **P < .01 compared with vector control. (C) Immunoblot analysis of α2 integrins and GFP in total platelet lysate derived from the chimeric animals shown in panels A and B and in α2-deficient animals. (D) The ratio of platelet α2 integrin/GFP protein expression for the indicated animals is shown. N = 3; mean and SD are shown. *P < .05, **P < .01 compared with vector control.