Mutations in DNA methyltransferase 3A (DNMT3A) are prevalent in various myeloid and lymphoid malignancies. The most common DNMT3A R882 mutations inhibit methyltransferase activity of the remaining wild-type DNMT3A proteins at a heterozygous state due to their dominant-negative activity. Reports and COSMIC database analysis reveal significantly different frequencies of R882 mutations in myeloid versus T-cell malignancies, inspiring us to investigate whether downregulation of DNMT3A regulates malignancies of different lineages in a dose-dependent manner. In a competitive transplant setting, the survival of recipients with KrasG12D/+ ; Dnmt3a+/- bone marrow (BM) cells was significantly shortened than that of recipients with KrasG12D/+ cells. Moreover, all of the recipients with KrasG12D/+ ; Dnmt3a+/- cells developed a lethal T-cell acute lymphoblastic leukemia (T-ALL) without significant myeloproliferative neoplasm (MPN) phenotypes, while ~20% of recipients with KrasG12D/+ cells developed MPN with or without T-ALL. This is in sharp contrast to the recipients with KrasG12D/+ ; Dnmt3a-/- cells, in which ~60% developed a lethal myeloid malignancy (MPN or acute myeloid leukemia [AML]). Our data suggest that in the context of oncogenic Kras, loss of Dnmt3a promotes myeloid malignancies, while Dnmt3a haploinsufficiency induces T-ALL. This dose-dependent phenotype is highly consistent with the prevalence of DNMT3A R882 mutations in AML versus T-ALL in human.
Keywords: DNA methylation; DNMT3A; KRAS; MPN; T-ALL.