Remethylation of hematopoietic cells is associated with partial correction of gene dysregulation and reduced myeloid skewing.

Mutations in the DNA methyltransferase 3A () gene are the most common cause of age-related clonal hematopoiesis (ARCH) in older individuals, and are among the most common initiating events for acute myeloid leukemia (AML). The most frequent mutation in AML patients (R882H) encodes a dominant-negative protein that reduces methyltransferase activity by ∼80% in cells with heterozygous mutations, causing a focal, canonical DNA hypomethylation phenotype; this phenotype is partially recapitulated in murine bone marrow cells. To determine whether the hypomethylation phenotype of hematopoietic cells is reversible, we developed an inducible transgene to restore expression of in transplanted bone marrow cells from mice. Partial remethylation was detected within 1 wk, but near-complete remethylation required 6 mo. Remethylation was accurate, dynamic, and highly ordered, suggesting that differentially methylated regions have unique properties that may be relevant for their functions. Importantly, 22 wk of addback partially corrected dysregulated gene expression, and mitigated the expansion of myeloid cells. These data show that restoring expression can alter the epigenetic "state" created by loss of Dnmt3a activity; this genetic proof-of-concept experiment suggests that this approach could be relevant for patients with ARCH or AML caused by loss-of-function mutations.