Characterization of platelets from β1 integrin mouse mutants. Platelet β1 integrin surface expression of wild-type (WT; β1^+/+), HT (β1^+/−), KO (β1^−/−), TTAA (β1^TTAA), and Hpm (β1^Hpm) β1 integrin mice were analyzed by flow cytometry. (B) Geometric mean values of β1 integrin expression shown in panel A were corrected for isotype control and expressed as % of WT β1-integrin surface levels (n = 6 per group). (C) Platelet lysates were subjected to immunoblotting for β1-integrin, talin-1, kindlin-3, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). (D) Surface expression of β3 integrin, GPVI, and GPIX on platelets of indicated mouse strains. (E) Platelet β1 integrin activation was determined with the conformation-specific 9EG7 antibody via the use of flow cytometry upon stimulation with 50 ng/mL CVX, 0.1 U/mL thrombin, or 5 mM U46619. Acquired mean fluorescence intensity values were normalized to total β1 integrin expression levels and are shown as arbitrary unit (n = 3 for TTAA and Hpm, n = 4 for all other groups; bars represent mean values ± SEM; significance levels are indicated; *P < .05; **P < .01; n.s., not significant). (F) Active β3 integrins were determined with JON/A antibody after platelet stimulation with indicated stimuli. No significant difference between all tested groups was determined (n = 5 for HT and WT, n = 4 for all other groups; bars represent geometric mean values ± SEM).