Identical but not the same: The value of DNA methylation profiling in forensic discrimination within monozygotic twins

Abstract

Monozygotic twins (MZs) show remarkable resemblance in many aspects including behavior and health, because they share identical genomic DNA. However, evidence for epigenetic differences within MZs has been accumulated. DNA methylation differences between MZs could partially account for their phenotypic discordance of behavioral traits and diseases. High throughput epigenomic microarray profiling can be a strategy of choice for identification of epigenetic differences in phenotypically different MZs. In this study, we mapped MZs DNA methylation differences in white blood cells by interrogation of the unmethylated genome on methylation Beadchip. Blood samples were taken from 22 pairs of adult MZs. Genomic DNA was bisulfite modified by EZ DNA methylation-Gold kit according to the manufacturer's protocols, consequently analyzed with Illumina's Human Methylation27 Beadchip including more than 27,000 CpG sites. The results indicated that MZs exhibited remarkable differences among their genome-wide 5-methylcytosine. According to a set of selection criteria, 377 CpG sites with significant differences of methylation status were picked out. Although DNA methylation shows only partial stability, primary results of this study strongly suggested that the CpG methylation could be a perspective biomarker to distinguish MZs from each other.