Romiplostim rescues thrombocytopenia in G6b-deficient mice. (A) Platelet counts and (B) volumes of WT and G6b KO mice were measured before (day 0) and after 8, 15, and 21 days of administration of 100 μg/kg body weight romiplostim. Romiplostim increased platelet counts in G6b KO mice but did not affect platelet volume. (C) GPVI and (D) α2β1 platelet surface expression in WT and G6b KO mice measured by flow cytometry before (vehicle) and after 21 days of romiplostim administration. Results are expressed as the mean fluorescent intensity (MFI) ± SEM. In WT mice, romiplostim induces a 40% reduction in GPVI expression and 25% reduction in α2β1 expression. However, romiplostim induced a 5-fold increase in GPVI expression in G6b KO mice but had no effect on α2β1 expression. n = 8 mice per condition. ∗P < .05, ∗∗∗P < .001, 2-way ANOVA Tukey’s test.