Technical strategy for monozygotic twin discrimination by single-nucleotide variants

Area of Science:

• Forensic Genetics
• Genomics
• Molecular Biology

Background:

• Monozygotic (MZ) twins are theoretically genetically identical but accumulate post-zygotic mutations.
• Distinguishing between MZ twin genomes is a significant challenge in forensic genetics.
• Single-nucleotide variants (SNVs) represent a major source of genetic variation.

Purpose of the Study:

• To investigate the utility of SNVs as biomarkers for discriminating between MZ twins.
• To identify and validate post-twinning SNVs in a pair of MZ twins.

Main Methods:

• Whole-genome sequencing (WGS) of a pair of female MZ twins (ages 27 and 33) to ~30× coverage.
• Validation of discordant SNVs using amplicon-based targeted deep sequencing and Sanger sequencing.
• Whole-exome sequencing (WES) to assess SNV locations relative to coding regions.

Main Results:

• Nine bona fide post-twinning SNVs were identified, present in the younger twin and detectable in the older twin.
• None of the identified SNVs were located within coding exons; three were found in introns.
• Reliable detection of SNVs was achieved with DNA input as low as 0.25 ng, with seven SNVs consistently detected down to 0.075 ng.

Conclusions:

• SNVs are reliable and cost-effective biomarkers for MZ twin discrimination.
• The identified SNVs can be utilized for forensic identification purposes.
• The study validates the potential of SNVs in resolving genetic identity between MZ twins.