Reduced Syk activity rescues macrothrombocytopenia and GPVI expression in G6b-deficient mice. (A) Platelet counts and (B) volumes of WT, G6b KO, G6b-/-R41A+/+Cre+, and G6b-/-R41Afl/flCre+ mice were measured, n = 9 to 43 mice/genotype. (C) GPVI and (D) α2β1 platelet surface expression of WT, G6b KO, G6b-/-R41A+/+Cre+, and G6b-/-R41Afl/flCre+ mice were measured by flow cytometry n = 5 to 18 mice per genotype. ∗∗∗P < .001, 1-way ANOVA with Dunnett’s test, mean ± SEM. (E-J) G6b KO mice received BI1002494 (30 mg/kg per bid) orally via gavage twice a day for 5 days. (E) Platelet counts and (F) volumes of G6b KO mice were monitored before (day 0) and every day for 5 days, n = 10 to 15 mice per genotype. ∗∗P < .01, ∗∗∗P < .001, 2-way ANOVA Tukey’s test, mean ± SEM. (G) GPVI and (H) α2β1 platelet surface expression of WT and G6b KO mice were measured 5 days after BI1002494 administration (30 mg/kg per bid) by flow cytometry, n = 6 to 10 mice per genotype. (I) Hemostatic response was measured 5 days after BI1002494 administration, in saline tail bleeding assay by an excision of a 3 mm portion of the tail tip followed by immersion of the tail in 0.9% isotonic saline at 37 °C. Plotted is the time to complete the arrest of bleeding. Each symbol represents 1 animal. (J) Blood loss was measured using colorimetric dosage of hemoglobin. Experiments were conducted in a double-blinded manner, n = 7 mice per genotype per condition. 1-way ANOVA with Sidak’s test, mean ± SD. ns, non-significant.
