Histopathology of SclCreER;V617F transgenic mice using H&E and Gömöri-stained BM samples (magnification, ×630). Transgenic mice were sacrificed 10 weeks after induction with tamoxifen. SclCre^ER;V617F;Stat1^+/+ mice (n = 6) showed more features of MPN and myelofibrosis compared with SclCre^ER;V617F;Stat1^−/− littermates (n = 3) (hypercellularity with trilineage hyperplasia, markedly increased numbers of megakaryocytes with morphologic abnormalities, hyperchromatic, hyperlobulated nuclei, and bizarre nuclear configuration, often forming clusters). Frequency of mice displaying grade 0 or grade 1-2 myelofibrosis is shown in the lower panel for each genotype.