Number, morphology, and GP expression in β3(R760C) KI platelets. (A) Peripheral blood was obtained from 8- to 10-week-old male mice. Giant platelets are indicated by yellow arrows in murine peripheral blood films stained with the May-Grünwald Giemsa stain (upper panel). Platelet counts in each phenotype are presented as the mean and standard deviation (SD; n = 6 each; lower left panel). Platelet size in each phenotype was determined as the mean of forward scatter (FSC) of CD42b⁺ cells via flow cytometry (lower right panel). Data are presented as the mean and SD (n = 6 each). (B) Surface GP expression was determined via flow cytometry. Data are shown as percentage expression in comparison with the mean of the WT. Data are presented as mean and SD (n = 6 each). (C). Soluble GPVI concentration in murine plasma was measured using an enzyme-linked immunosorbent assay (ELISA) kit. Measurements were taken from 3 mice of each phenotype in 2 independent experiments. The data are presented as the mean and SD. (D) Total GP expression in KI mouse platelets. Lysates obtained from the washed platelets were separated via sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by immunoblotting using specific antibodies. GPV expression levels were additionally determined as the internal control in the same membrane. ∗∗∗P < .001, ∗∗P < .01, and ∗P < .05 (1-way analysis of variance [ANOVA]). MFI, mean fluorescence intensity; ns, not significant.