Removal of Mpl or Tpo in JAK2V₆₁₇F⁺ MPN mouse models rescues normal hematopoiesis. (A) Platelet, (B) neutrophil counts, and (C) hematocrit were monitored for 16 weeks after birth in WT, JAK2V₆₁₇F⁺ (VF⁺), JAK2V₆₁₇F⁺Mpl^+/− (VF⁺Mpl^+/−), JAK2V₆₁₇F⁺Mpl^−/− (VF⁺Mpl^−/−), and JAK2V₆₁₇F⁺Tpo^−/− (VF⁺Tpo^−/−) mice. Data are presented as mean ± standard error of the mean (SEM); n = 3 to 9 mice per time point. (D) Plasma TPO levels in Mpl and Tpo transgenic mice. Plasma was collected from 16-week-old WT, JAK2V₆₁₇F⁺ (VF⁺), Mpl^+/−, JAK2V₆₁₇F⁺Mpl^+/− (VF⁺Mpl^+/−), Mpl^−/−, JAK2V₆₁₇F⁺Mpl^−/− (VF⁺Mpl^−/−), Tpo^−/−, and JAK2V₆₁₇F⁺Tpo^−/− mice, and TPO levels were quantified by enzyme-linked immunosorbent assay. Each data point represents a single mouse, and bars are presented as mean ± SEM; asterisks indicate significance compared with WT. (E) Representative spleens and (F) weights of spleens harvested from 16-week-old mice. Scale bar, 3 mm.