Expression analysis of 32Dcl3 cells expressing ASXL-MT in the presence of IL-3 or G-CSF

Recurrent mutations in ASXL1 are found in various hematological malignancies and are associated with poor prognosis. In particular, ASXL1 mutations are frequently found in patients with hematological malignancies associated with myelodysplasia including myelodysplastic syndromes (MDS), and chronic myelomonocytic leukemia. Although loss-of-function ASXL1 mutations promote myeloid transformation, a large subset of ASXL1 mutations is thought to result in stable truncation of ASXL1. Here we demonstrate that C-terminal truncating ASXL1 mutations (ASXL1-MT) inhibit myeloid differentiation and induce MDS-like disease in mice, displaying all the features of human MDS including multi-lineage myelodysplasia, pancytopenia and occasional progression to overt leukemia. Concerning the molecular mechanisms, ASXL1-MT derepressed expression of Hoxa9 and miR-125a through inhibiting PRC2-mediated methylation of H3K27. miR-125a targeted expression of a surface receptor Clec5a, which was found to supports for myeloid differentiation. In addition, HOXA9 expression was high in MDS patients with ASXL1 mutations while Clec5a expression was generally low in MDS patients. Thus, ASXL1-MT induced MDS-like disease in mice via derepression of Hoxa9 and miR-125a, and Clec5a downregulation. Our data provide evidence for a novel axis of MDS pathogenesis (ASXL1 mutations-upregulation of HoxA9 and miR-125a-downregulation of Clec5a) and implicate both ASXL1 mutants and miR-125a as therapeutic targets in MDS.

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Inoue D, Kitaura J, Togami K, Nishimura K, Enomoto Y, Uchida T, Kagiyama Y, Kawabata KC, Nakahara F, Izawa K, Oki T, Maehara A, Isobe M, Tsuchiya A, Harada Y, Harada H, Ochiya T, Aburatani H, Kimura H, Thol F, Heuser M, Levine RL, Abdel-Wahab O, Kitamura T