Chromatin and Sequence Features that Define the Fine and Gross Structure of Genomics Methylation Patterns. Chromatin and Sequence Features that Define the Fine and Gross Structure of Genomics Methylation Patterns

We report a new method for genome-wide methylation profiling that is able to probe methylation status in both single-copy DNA and interspersed repeats. This method, MethylMAPS, uses methylation-sensitive and -dependent enzymes to fractionate the genome according to methylation state. Methylated and unmethylated fragments are then sequenced with Next-Gen sequencing to map methylated and unmethylated CpG sites in the genome. We have used this method to determine the methylation status of >275 million CpG sites in human and mouse DNA from breast and brain tissues. We conclude that methylation is the default state of most CpG dinucleotides and that a combination of local dinucleotide frequencies, the interaction of repeated sequences, and the presence or absence of histone variants or modifications shields a population of CpG sites (most of which are in and around promoters) from DNA methyltransferases that lack intrinsic sequence specificity. Overall design: Genome-wide methylation mapping in two normal human breast tissues, human brain tissue and mouse brain tissue.