RESEARCH ARTICLE

DNA methylation study of a genome-wide analysis ao-F di os yl g context of a cytosine-guanine dinucleotide (CpG) in the mammalian genome [1]. Methylation of CpG-rich pro-are less well established [4]. On the other hand, Xiang H et al. estimate that more than 0.11 % of genomic cyto-Wang et al. BMC Medical Genomics 2014, 7:18 http://www.biomedcentral.com/1755-8794/7/18been demonstrated to be required for vertebrate early2School of Medicine, Xi’an Jiaotong University, Xi’an 710061, PR China Full list of author information is available at the end of the articlemoters is used by mammals to prevent transcriptional initiation, to ensure the inactivation of X chromosome and the silence of imprinted genes and parasitic DNAs. sines are methylcytosines, all of which probably occur in CG dinucleotides. CG methylation is substantially enriched in gene bodies and positively correlated with gene expres-sion levels, suggesting it has a positive role in gene tran-scription [5]. Recently, researchers have conducted extensive re-search on the mechanism of DNA methylation and its role in embryonic development. DNA methylation ha