Abstract A010: Dnmt3a2 ensures proper enhancer DNA methylation during embryonic development

Abstract Proper enhancer function and switching is essential for the development of vertebrates and is known to be controlled by DNA cytosine methylation. We used isoform-specific knockouts of the two known DNA methyltransferase variants, Dnmt3a1 and Dnmt3a2 to probe their roles in enhancer methylation in embryogenesis and in postnatal development. Mouse embryos lacking Dnmt3a1 showed minimal loss of genomic methylation confirming that this isoform is not required for embryonic development. However, they were smaller than their littermates and died about 4 weeks after birth with considerable demethylation in the brain as has been previously reported. On the other hand, embryos lacking Dnmt3a2 showed widespread genomic hypomethylation which was particularly prevalent in enhancers and imprinted genes. Interestingly these methylation deficits were largely repaired after birth, presumably by the remaining Dnmt3a1 isoform. The mice were viable; however, they showed an increased prevalence of sporadic phenotypes including anophthalmia, hydronephrosis, hydrocephalus and male infertility which have previously been observed in laboratory mice. Hypomethylation of several imprinted genes was also observed in sperm which might potentially explain the infertility phenotype. There is therefore an interplay between the 2 isoforms which is developmentally regulated and a key role for Dnmt3a2 might be the stabilization of enhancer states which lessening the chance of sporadic phenotypes arising after birth. Citation Format: Minmin Liu, Guillermo A Urrutia, Rachel Shereda, Gangning Liang, Peter A Jones. Dnmt3a2 ensures proper enhancer DNA methylation during embryonic development [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Methylation, Clonal Hematopoiesis, and Cancer; 2025 Feb 1-4; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2025;85(3 Suppl):Abstract nr A010.