Platelet production in single-KO and DKO mice. (A) Platelet count in response to 5-FU, anti-platelet serum (APS), or TPO (n = 3 per genotype). Baseline platelet count (day 0) was performed just before drug administration. (B) Mean ± SEM number of bone marrow megakaryocytes in mice treated with or without TPO for 5 days (n = 3 per genotype). Student t test compared with untreated mice of the same genotype. (C) Proplatelet production from in vitro cultured megakaryocytes obtained from untreated (left panel) and TPO-treated mice (right panel). Results analyzed using two-way ANOVA with Tukey’s correction. Megs, megakaryocyte; NS. not significant. **P < .001; ***P < .0001 compared with WT mice.