mTORC1 signaling in mouse osteoblasts regulates megakaryopoiesis and platelet (PLT) formation. (A) Platelet count and MPV in 3-week-old OSX-TSC1 and OSX-Raptor mice and control littermates (n = 8, Student unpaired t test). (B) BM of a femur and a tibia collected from OSX-TSC1 and OSX-Raptor mice stained with Wright and Giemsa dyes. Total numbers of MKs were counted (n = 8, Student unpaired t test). (C) Quantification of FACS analysis of the fraction of CD41⁺ MK lineage cells in OSX-TSC1 and OSX-Raptor mouse BM (n = 6, Student unpaired t test). (D) Femur sections of OSX-TSC1 and OSX-Raptor mice stained for VWF. Cells positive for VWF were counted under a microscope. Results represent mean MK number/mm² (± standard error of the mean) for each group analyzed (40 sections from 8 mice) (n = 8, Student unpaired t test). Scale bar = 100 μm. (E) Western blot analysis of p-S6 (S235/236) expression in primary osteoblasts isolated from OSX-TSC1, OSX-Raptor, and control mice. S6 was used as a loading control. Data are representative of 3 independent experiments and are represented as mean ± standard deviation (SD). *P < .05; **P < .01; ***P < .001. NS, not significant; T.Ar, tissue area.