HMGA2 overexpression

Overexpression of high mobility group AT-hook 2 (HMGA2) associated with truncations of its 3 untranslated region (UTR) with let-7 micro RNA-complementary sequences have been identified in patients with paroxysmal nocturnal hemoglobinuria (PNH). Here, we generated transgenic mice (Hmga2 mice) with a 3UTR-trncated Hmga2 cDNA that overexpress Hmga2 mRNA and protein in hematopoietic organs. Hmga2 mice showed proliferative hematopoiesis that mimicked a myeloproliferative neoplasm (MPN)-like phenotype with increased numbers of all lineages of peripheral blood cells, hypercellular bone marrow (BM), splenomegaly with extramedullary erythropoiesis, and erythropoietin-independent erythroid colony formation compared to wild-type mice. Hmga2 BM-derived cells took over most of hematopoiesis in competitive repopulations during serial BM transplants. When we bred mice with circulating PNH cells (Piga- mice) with Hmga2 mice, the lack of GPI-linked proteins did not add an additional clonal advantage to the Hmga2+ cells. In summary, our results showed that the overexpression of a 3UTR-truncated Hmga2 leads to a proliferative hematopoiesis with clonal advantage, which may explain clonal expansion in PNH or MPN at the level of HSC.

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Ikeda K, Mason PJ, Bessler M