Analysis of SclCreER;V617F transgenic and control mice. (A) Stat1 protein expression in spleen homogenates was assessed by immunoblot analysis. (B) Blood counts 10 weeks after induction with tamoxifen (SclCre^ER;V617F;Stat1^+/+, n = 11; SclCre^ER;V617F;Stat1^+/−, n = 27; SclCre^ER;V617F;Stat1^−/−, n = 22; controls: WT and Stat1^−/−, n = 6). One-way ANOVA is shown for comparisons. *P ≤ .05, **P ≤ .01, ***P ≤ .001. (C) Follow-up of blood counts. Genotypes and coloring of the lines is the same as in panel B. The Student t test was used for the comparisons between SclCre^ER;V617F;Stat1^−/− and SclCre^ER;V617F;Stat1^+/+ mice; *P ≤ .05. (D) Spleen weight assessment in transgenic mice 10 weeks after induction with tamoxifen. (SclCre^ER;V617F;Stat1^+/+, n = 3; SclCre^ER;V617F;Stat1^+/−, n = 6; SclCre^ER;V617F;Stat1^−/−, n = 6; WT, n = 4; and Stat1^−/−, n = 4). The Student t test was used. Error bars represent SEM. HCT, hematocrit; MCV, mean corpuscular volume; WT, wild type.