Abstract
Here, we characterize the DNA methylation phenotypes of bone marrow cells from mice with hematopoietic deficiency of Dnmt3a or Dnmt3b (or both enzymes) or expressing the dominant-negative Dnmt3aR878H mutation [R882H in humans; the most common DNMT3A mutation found in acute myeloid leukemia (AML)]. Using these cells as substrates, we defined DNA remethylation after overexpressing wild-type (WT) DNMT3A1, DNMT3B1, DNMT3B3 (an inactive splice isoform of DNMT3B), or DNMT3L (a catalytically inactive "chaperone" for DNMT3A and DNMT3B in early embryogenesis). Overexpression of DNMT3A for 2 weeks reverses the hypomethylation phenotype of Dnmt3a-deficient cells or cells expressing the R878H mutation. Overexpression of DNMT3L (which is minimally expressed in AML cells) also corrects the hypomethylation phenotype of Dnmt3aR878H/+ marrow, probably by augmenting the activity of WT DNMT3A encoded by the residual WT allele. DNMT3L reactivation may represent a previously unidentified approach for restoring DNMT3A activity in hematopoietic cells with reduced DNMT3A function.