Loss of Ezh2 enhances repopulation capacity of Jak2V617F HSC and promotes myeloid cell expansion. (A) Competitive reconstitution assay. BM cells (5 × 10⁵) from uninduced control, Jak2^VF/+, or Jak2^VF/+ Ezh2^−/− mice (CD45.2⁺) were mixed with wild-type CD45.1⁺ mice BM (5 × 10⁵) at a 1:1 ratio and transplanted into lethally irradiated CD45.1 recipient mice. Four weeks after BMT, recipient mice were treated with 5 doses of pI-pC to induce Ezh2 deletion and Jak2V617F expression simultaneously after hematopoietic reconstitution. The recipient mice were analyzed at 16 weeks after pI-pC injection. (B) The percentages and total numbers of donor-derived (CD45.2⁺) LSK cells, (C) percentages of CD45.2⁺ Gr-1⁺ myeloid cells, and (D) percentages of CD45.2⁺CD41⁺CD61⁺ megakaryocytic cells in the BM of recipient animals at 16 weeks after pI-pC induction are shown; bar graphs represent mean ± SEM (control, n = 5; Jak2^VF/+, n = 5; Jak2^VF/+ Ezh2^−/−, n = 6). One-way ANOVA was used for comparisons of all 3 groups of mice, and the Student t test was used to compare between 2 groups of mice (*P < .05; **P < .005).