Improved locus-specific unmethylated controls for MS-HRM analysis derived from 5-aza-2-deoxycytidine-treated DNA.

We report two restriction enzyme-based approaches for generating clean locus-specific unmethylated controls for methylation-sensitive high-resolution melting (MS-HRM) analyses. These unmethylated standards are derived from DNA treated with the demethylating agent 5-aza-2-deoxycytidine (5-Aza-dc). By using them, we overcome a limitation of 5-Aza-dc treatment - incomplete demethylation at various genomic regions. When 5-Aza-dc-treated DNA is used directly as unmethylated MS-HRM standard, partially demethylated DNA can give false methylation results. MS-HRM assay differentiates between methylated and unmethylated bisulfite-treated DNA based on the different melting profiles of PCR products amplified from them. To estimate test sample methylation levels, test sample melting profiles are compared to those of methylation standards. With our pure unmethylated controls, adequate standards of known methylation levels can be prepared for single-locus MS-HRM.