HMGA2 binds to the promoters of its target genes, and ectopic expression of some HMGA2 target genes increases CFU-Mk colonies and megakaryocytic cell proliferation in Jak2^V617Fmouse BM. (A) HMGA2-specific ChIP followed by RT-qPCR showed binding of HMGA2 in the promoters of CXCL12, FZD2, IFI27, GATA3, MEIS1, and TGF-βR2 genes in JAK2^V617F-positive SET-2 cells. Results from 3 independent experiments are presented as mean ± SEM in bar graphs. The RT-qPCR products were loaded onto 2% agarose gel. Representative pictures from agarose gel are shown in the bottom panels. (B) Total levels of Cxcl12 in the serum of WT-vector, WT-Hmga2, Jak2^VF/+-vector, and Jak2^VF/+-Hmga2 mice at 32 weeks after BMT were assessed by ELISA (n = 6-7). (C) Stimulation with Cxcl12 (100-200 ng/mL) significantly increased CFU-Mk formation in the BM of Jak2^V617F mice (n = 4-8 for each concentration). (D) Ectopic expression of Cxcl12, Ifi27l2a, or Fzd2 significantly increased CFU-Mk colonies and (E) enhanced megakaryocytic proliferation in the BM of Jak2^V617F mice compared with vector control (n = 4-7 for each construct). Megakaryocytic cell proliferation was assessed by viable cell counts every other day over 6 days. Data from 3 independent experiments are shown in graphs as mean ± SEM. *P < .05; **P < .005.