Targeted profiling of 5-(hydroxy)methylcytosine in genomic DNA from human livers: Next-generation sequencing of target enriched DNA reveals unexpectedly high interindividual variability of cytosine methylation and hydroxymethylation

So far, bisulfite sequencing has been considered as the “gold standard” method for the detection of DNA methylation. The results of whole-genome bisulfite next-generation sequencing (WG-BS-Seq) allowed scientists to conclude that the vast majority of CpG sites in genomic DNA from human and animal tissues are invariably hypermethylated. Only a small proportion (≤ 10-15%) of CpG sites was found to manifest variable degree of methylation between different tissues or among individuals. Moreover, such variably methylated CpG sites were believed to occur almost exclusively within extended clusters (differentially methylated regions, or DMRs).