MINK1^−/− mice display features of unstable hemostasis in vivo. (A) Analysis of MINK1 expression in platelets from human, WT, and MINK1^−/− mice. (B) Bleeding times for WT (●) and MINK1^−/− mice (▲). Means are indicated by horizontal lines. Statistical significance was evaluated with 2-tailed Mann-Whitney U tests (*P < .05). (C) Percentages of WT and MINK1^−/− mouse bleeding times exceeded 15 minutes (□) or were within 15 minutes (▪). Results were obtained from 26 WT and 31 MINK1^−/− mice. (D) Electron microscopic images of WT and MINK1^−/− platelet ultrastructure (black arrows, dense granules; white arrows, α-granules). Scale bars, 1 μm (top) and 0.5 μm (bottom). (E) Quantification of α-granules and dense granules of WT (▪) and MINK1^−/− (□) platelets. Under ×24 000 magnification, α-granules and dense-granules in 160 platelets (80 from WT and MINK1^−/− each) were counted. The data were expressed as mean ± SEM. Statistical significance was evaluated with the Student t test. (F) Surface expression of CD41, CD42b, and GPVI, as determined by flow cytometry with FITC-conjugated anti-mouse CD41 mAb (MWReg30), FITC-conjugated anti-mouse CD42b mAb (Xia.B2), and FITC-conjugated anti-mouse GPVI mAb (JAQ1). Results are expressed as mean fluorescence intensity (MFI), and are the mean ± SEM. Statistical significance was evaluated with the Student t test.