EHMT2 represses germline genes via DNA methylation in mouse embryos. (A) Comparison of RNA-seq expression levels for RefSeq genes in WT and Ehmt2−/− embryos. Genes of the Magea family and differentially expressed genes are highlighted in colors. (B) Preferential tissue of expression of genes up-regulated at least threefold in Ehmt2−/− embryos. (C) Examples of RNA-seq profiles at the Cyct and Asz1 genes in two biological replicates of WT and Ehmt2−/− embryos. (D) Activation of germline genes in Ehmt2−/− and Dnmt3b−/− E8.5 embryos. The heatmap on the bottom indicates CpG methylation measured by RRBS in the corresponding promoters in Ehmt2−/− and Dnmt3b−/− E8.5 embryos. (E) ChIP-qPCR analysis of H3K9me2 in WT and Dnmt3b−/− E8.5 embryos (mean ± SEM, n = 3 embryos for WT, n = 4 embryos for Dnmt3b−/−), showing that the reduced DNA methylation does not impact the deposition of H3K9me2. (F) Model: EHMT2 deposits H3K9me2 and facilitates cytosine methylation at a subset of gene promoters in embryos. The inactivation of EHMT2 inhibits H3K9me2 and leads to reduced cytosine methylation, leading to aberrant gene activation. In Dnmt3b−/− embryos, EHMT2 is able to bind to its target promoters but can no longer recruit cytosine methylation, which leads to incomplete gene silencing.
