Genome-wide characterization of DNMT-deficient mouse ESCs reveals dynamicity of differentially-methylated-regions and its impact on bivalency composition

Differentially-methylated-regions (DMRs), pivotal to the diagnosis/pathogenesis of imprinting disorders, control imprinted gene expression with histone modifications; however, their establishment, numbers, boundaries, and crosstalk with chromatin remain elusive. Herein our global profiling reveals that although de novo methyltransferases DNMT3a/3b are required for locus-specific DMR maintenance, DNMT1 is required for all known DMRs. Based on the latter and the DMR concept, we have developed two novel approaches, “no restored DMRs (NORED)” and “Tag-mosaicity,” to identify/demarcate 31 known and 7 novel DMRs from 21 known loci, and 20 novel DMRs from novel loci. Tag-mosaicity analyses reveal the expected bimodal patterns of hypo/hypermethylated tags of known and new DMRs. Using Gtl2 locus, we demonstrate that methylation of DMRs controls H3K9me3 distribution to a long- range ”DMR-territory” that extends beyond our defined DMR boundary. These findings contrast that H3K9me3 controls CG methylation in Arabidopsis and Neurospora. Our analyses reveal that promoters of imprinted genes within a DMR-territory tend to have H3K4me2 and H3K9me3 with/without H3K27me3, whereas promoters outside have H3K27me3 and H3K4me2. Lastly, we confirmed that the transient DMR of Hcn2/Polrmt locus is conserved in the human genome. Our data link transient DMRs to epilepsy and chronic pain, Parkinson’s disease, Charcot-Marie-Tooth disease, and type 2 diabetes. Overall design: Genomic DNA from DNMT1 -/- (1KO) ESCs cells with exogenous expression of DNMT1 were treated with bisulfite and sequenced with the Illumina HiSeq platform using paired end reads.