Epigenetic Discrimination of Lebanese Monozygotic Twins as a Promising Forensic Approach

Abstract

Standard forensic genetics is foremost prominent by its power of discrimination. Yet, classical DNA profiling is ineffective when having monozygotic twins (MZs) as suspects in criminal casework. Arising from a single fertilized egg, monozygotic twins share the same genotype. This critical dilemma imposes an urgent challenge in forensics. The aim of this study is to distinguish between Lebanese MZs using DNA methylation as a promising epigenetic alternative. Twenty-eight unrelated pairs of Lebanese male and female MZs were recruited in this study. Participants signed an informed consent and filled a well-designed questionnaire. DNA was extracted using the PureLink Genomic DNA Mini kit, genotyped using the Identifiler Plus kit, and separated on 3500 Genetic Analyzer to confirm the monozygosity status. Extracted DNA was treated with bisulfite using the Epitect Bisulfite kit followed by a real time-polymerase chain reaction (RT-PCR) using the Epitect HRM PCR kit targeting 19 CpG residues distributed over Alu-Sp & Alu-E2F3 elements. High-Resolution Melting Curve (HRMC) analysis was performed at the endpoint of the amplification using the Rotor-Gene Q instrument. Discrimination between MZs is based on the expected different methylation patterns of Alu-Sp & Alu-E2F3 CpGs. Our results show significant differences among males (78.56%) and females (78.56%) MZs along the Alu-Sp element. The differences were 100% among males and 85.7% among female MZs targeting Alu-E2F3. Both Alu-Sp & Alu-E2F3 methylation patterns detected by HRMC were shown to be helpful with Alu-E2F3 being more discriminative. In conclusion, epigenetic discrimination of Lebanese MZs tends to offer a new powerful forensic perspective.