Epigenetic and transcriptomic alterations in Dnmt3a mutants
DNMT3A mutations are overrepresented in haematologic malignancies. Our mouse model introduced the murine homologue (R878H) of the human 'hotspot' R882H mutation into the mouse DNMT3A locus, resulting in reduced DNA methylation throughout the organism. Mice with germline heterozygous R878H mutations were susceptible to irradiation induced thymic lymphoma, suggesting a vulnerability to stress stimuli in Dnmt3aR878H/+ cells. In competitive transplantations, Dnmt3aR878H/+ LSK (Lin-Sca-1+Kit+) cells had a competitive advantage, indicating a self-renewal phenotype at the expense of differentiation. RNA-sequencing of Dnmt3aR878H/+ LSKs exposed to low dose gamma irradiation showed downregulation of the p53 pathway. Reduced PUMA expression in irradiated Dnmt3aR878H/+ bone marrow was further observed by flow cytometry. Our results offer new insights as to how DNMT3A mutations cause subtle changes in the transcriptome of LSK cells which contribute to their increased self-renewal phenotypes and propensity for malignant transformation.