G6b conditional KO mice partially phenocopy Shp1/2 conditional DKO mice. (A) Platelet counts and volumes of G6b KO (n = 35) and G6b WT (n = 20) mice (mean ± SEM; ***P < .001). (B) Platelet half-life and (C) platelet recovery following immune-induced thrombocytopenia in G6b KO and WT mice (n = 3-5 mice/time point/genotype; mean ± SEM; **P < .01, ***P < .001). (D) Proplatelet formation of G6b KO megakaryocytes on fibrinogen-, fibronectin-, and collagen-coated surfaces. Representative images and quantification of megakaryocyte surface area, proplatelet mean area, and percentage of megakaryocytes forming proplatelets are shown (n = 4-6 mice/genotype/condition; mean ± SEM; **P < .01, ***P < .001; scale bar: 20 μm). (E-F) Thrombopoietin (Tpo)- and integrin-mediated Erk1/2 phosphorylation in G6b KO and WT megakaryocytes. Whole cell lysates of (E) Tpo-stimulated (50 ng/mL Tpo, 10 min) and (F) bovine serum albumin (BSA) nonadherent and fibrinogen (fib)-adhered megakaryocytes were western blotted with anti-phospho-Erk1/2 (p-Erk1/2) and -pan Erk1/2 (Erk1/2) antibodies. Representative blots from n = 3 independent experiments/genotype per condition.