Loss of Asxl2 leads to myeloid malignancies in mice.

ASXL2 is frequently mutated in acute myeloid leukaemia patients with t(8;21). However, the roles of ASXL2 in normal haematopoiesis and the pathogenesis of myeloid malignancies remain unknown. Here we show that deletion of Asxl2 in mice leads to the development of myelodysplastic syndrome (MDS)-like disease. Asxl2-/- mice have an increased bone marrow (BM) long-term haematopoietic stem cells (HSCs) and granulocyte-macrophage progenitors compared with wild-type controls. Recipients transplanted with Asxl2-/- and Asxl2+/- BM cells have shortened lifespan due to the development of MDS-like disease or myeloid leukaemia. Paired daughter cell assays demonstrate that Asxl2 loss enhances the self-renewal of HSCs. Deletion of Asxl2 alters the expression of genes critical for HSC self-renewal, differentiation and apoptosis in Lin-cKit+ cells. The altered gene expression is associated with dysregulated H3K27ac and H3K4me1/2. Our study demonstrates that ASXL2 functions as a tumour suppressor to maintain normal HSC function.

ASXL2 Regulates Glucose, Lipid, and Skeletal Homeostasis.

ASXL2 is an ETP family protein that interacts with PPARγ. We find that ASXL2-/- mice are insulin resistant, lipodystrophic, and fail to respond to a high-fat diet. Consistent with genetic variation at the ASXL2 locus and human bone mineral density, ASXL2-/- mice are also severely osteopetrotic because of failed osteoclast differentiation attended by normal bone formation. ASXL2 regulates the osteoclast via two distinct signaling pathways. It induces osteoclast formation in a PPARγ/c-Fos-dependent manner and is required for RANK ligand- and thiazolidinedione-induced bone resorption independent of PGC-1ß. ASXL2 also promotes osteoclast mitochondrial biogenesis in a process mediated by PGC-1ß but independent of c-Fos. Thus, ASXL2 is a master regulator of skeletal, lipid, and glucose homeostasis.