Regulation of expression by single CpG methylation in downstream of transcription initiation site.

The innate immune system is an immediate defense against infectious pathogens by the production of inflammatory cytokines and other mediators. Deficiencies of epigenetic regulatory enzymes, such as and , cause dysregulation of cytokine expression. However, it is unclear if DNA methylation at a single CpG dinucleotide in a specific gene locus can regulate gene expression. In this study, we demonstrated that CpG+286 and CpG+348 in exon 2 of the gene are similar in various primary mouse cells. In lipopolysaccharide-stimulated condition, hypomethylated CpG+286 promoted expression whereas deletion of CpG+348 led to a reduction in expression associated with enhanced CTCF binding to the locus. Moreover, hypomethylation at CpG+286 in alveolar macrophages from aged mice led to higher expression in response to LPS compared with young mice. Thus, DNA methylation at specific CpG dinucleotides plays an important regulatory role in expression.