Targeted Gene Bisulfite Sequencing Identifies Differential Methylation in p21

Next-generation sequencing (NGS) methods are widely available to assess methylation of whole-genomes, reduced representation of genomes, and target capture of many loci, but simple, flexible, and low-cost methods are needed to leverage NGS for sequencing single-locus amplicons from large numbers of samples. We developed a two-stage PCR approach, targeted gene bisulfite sequencing (TGBS) which uses the Illumina MiSeq and Bismark bisulfite mapper, to assess site specific changes in methylation of the cyclin-dependent kinase inhibitor p21 (CDKN1a) after exposure to a DNA methyltransferase inhibitor, 5-aza-2′-deoxycytidine (5-Aza) and determine the differences between human and rat p21 methylation. TGBS analysis of human embryonic kidney cells (HEK293) and human proximal tubular cells (hPT) demonstrated variation at a known methylation sensitive site (SIE-1), but not in rat kidney cells. Treatment of cells with 5-Aza altered the methylation of this site in correlation with increased p21 protein expression. We also found that human and rat p21 promoter sequences differ considerably in the amount of basal DNA methylation. These data showed the utility of TGBS for rapid analysis of DNA methylation of specific loci. We provide links to a ready-to-run Virtualbox that includes the program and commands for methylation analysis of bisulfite datasets, including step-by-step directions.