DNA methylation in Vav-IDH1-KI mouse haematopoietic stem cells. Mus musculus

Mutations in isocitrate dehydrogenase-1 (IDH1 R132) and -2 (IDH2 R140 and R172), which confer neomorphic enzymatic activity converting αKG (α-ketoglutarate) to D-2-hydroxyglutarate (D2HG), occur commonly in acute myeloid leukemia (AML). Mutant IDH1 alters epigenetics and increases haematopoietic progenitors in vivo, consistent with D2HG-mediated inhibition of TET2 5-methylcytosine hydroxylase. As TET2 mutations are mutually exclusive with IDH1/2 mutations and confer a similar phenotype, it has been widely believed that the oncogenicity of mutant IDH1/2 is due to TET2 inhibition. However, IDH1/2 mutations may have additional effects explaining the clinical features of MDS/MPN/AML. Here we show that mutant IDH1 downregulates ATM, thereby inhibiting DNA damage responses and increasing genomic instability. To investigate potential mechanisms of ATM downregulation, we examined ATM promoter DNA methylation in Vav-IDH1-KI long term haematopoietic stem cells (LT-HSC), short term haematopoietic stem cells (ST-HSC) and multipotent progenitors (MPP). Overall design: LT-HSC, ST-HSC, and MPP were sorted from pooled bone marrow of aged male Vav-IDH1-KI mice and control litermates (n=6/groups) and subjected to enhanced reduced representation bisulfite sequencing (eRRBS).