Notch1 deficiency reduces the number of circulating platelet and TPO production. (A) Peripheral blood was drawn to measure the number of circulating platelets by an automatic blood analyzer (mean; n = 17; unpaired student t test). (B) Notch1^fl/fl or HC Notch1^−/− mice received intraperitoneal administration of rat anti-mouse integrin GPIIb/CD41 immunoglobulin at a dose of 0.1 mg/kg, followed by monitoring the number of circulating platelets at different time points (mean ± standard error of the mean [SE]; n = 7; 2-way analysis of variance [ANOVA]). Plasma (C) or liver mRNA (D) was isolated from Notch1^fl/fl or HC Notch1^−/− mice to measure TPO level by ELISA (mean ± SE; n = 3) or quantitative real-time PCR (mean ± SE; n = 8; unpaired student t test). ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. ELISA, enzyme-linked immunosorbent assay; PCR, polymerase chain reaction.