Evaluation of new generation sequencing methodologies (NGS) for differentiation of monozygotic twins for forensic application

Abstract

DNA analysis for forensic investigations is based on the concept that each individual is genetically unique, except in cases of monozygotic twins (MZ). The DNA obtained from biological samples is able to individualize this material by comparing the genetic profile of the unknown biological sample (questionable sample) with the profile of a reference sample. The most used markers in the forensic area, considered gold standard, are the STRs (Short Tandem Repeats), analyzed by capillary electrophoresis. The advent of new generation sequencing (NGS) and the development of kits for human identification with this methodology have shown that this application starts to be part of forensic laboratories around the world. Studies have been carried out to validate the use of these new NGS kits in cases of human identification, in situations of mixture and little amount of DNA, but there is no reference to the potential of this application for differentiating MZ twins. Other approaches using NGS have been the target of studies in an attempt to differentiate MZ twins in the forensic area, such as genome methylation pattern and mitochondrial DNA (mtDNA) variants. With the advent of mtDNA kits for NGS, a few studies have reported the observation of SNPs and heteroplasmies capable of differentiating MZ twins. Since, to date, there is no publication evaluating the application of the new STR NGS kits for eventual differentiation of MZ twins, this project aims to evaluate the possibility to differentiate MZ twins using the NGS approach. As specific objectives we propose: a) to study 32 pairs of monozygotic twins using The Precision ID GlobalFiler " NGS STR Panel v2 kit (Thermo Fisher Scientific), by analyzing the internal variations of the STRs (isoalleles) and the adjacent variants (SNPs); b) to compare the STR profiles generated with standard methodology in capillary electrophoresis with the STR profiles generated by NGS to assess the frequency of isoalleles, as a preliminary analysis in our population, since there is no report on the use of this kit in the Brazilian population. (AU)