DNA profiling of single sperm cells after whole genome amplification

• Published in: Forensic Science International. Reports 2021-11, Vol.4, p.100240, Article 100240
• Main Authors: Theunissen, Glenn M.G., Gibb, Andrew, Lin, Paul Kong Thoo, Rolf, Burkhard, Forat, Sophia, Jäger, Richard
• Format: Article
• Language: English
• Subjects: DNA typing; Forensic genetics; Micromanipulation; Sexual assault; Short tandem repeat (STR); Sperm cell; Whole genome amplification; X-STR; Y-STR
• ISSN: 2665-9107; 2665-9107
• DOI: 10.1016/j.fsir.2021.100240

Intimate swabs taken for examination in sexual assault cases typically yield mixtures of sperm and epithelial cell types. While powerful, differential extraction protocols to overcome such cell type mixtures by separate lysis of epithelial cells and spermatozoa can still prove ineffective, in particular if only few sperm cells are present or if swabs contain sperm from more than one individual leading to complex low level DNA mixtures. A means to avoid such mixtures consists in the analysis of single micromanipulated sperm cells. However, the quantity of DNA from single sperm cells is not sufficient for conventional STR analysis. Here, we describe a simple method for micromanipulating individual sperm cells from intimate swabs and show that whole genome amplification can generate sufficient amounts of DNA from single cells for subsequent DNA profiling. We recovered over 80% of alleles of haploid autosomal STR profiles from the majority of individual sperm cells. Furthermore, we demonstrate that in mixtures of sperm from two contributors, Y-STR and X-STR profiles of individual sperm cells can be used to sort the haploid autosomal profiles to develop the diploid consensus STR profiles of the individual donors. Finally, by analyzing single sperm cells from mock sexual assault swabs with one or two sperm donors, we showed that our protocols enabled the identification of the unknown male contributors. •Micromanipulation of single sperm cells from intimate swabs using tungsten needle.•Whole genome amplification (WGA) facilitates STR typing of single sperm cells.•Haplotyping Y-STRs and X-STRs allows for reconstruction of diploid profiles.•Method proposed for swabs with low sperm count or sperm cells from multiple donors.