Using cluster analysis for grouping partial autosomal haplotypes derived from single sperm STR profiling

Abstract

Abstract Background and objective The use of single cell STR profiling for mixture deconvolution is increasingly being discussed in forensics; however, studies regarding STR profiling of single sperm are relatively rare. Considering that each sperm cell exclusively contains a haploid genome, STR profiling as well as grouping profiles from each single contributor to derive consensus profiles seems to be difficult. Thus, so far, the information obtained from gonosomal markers partially combined with previously performed whole genome amplification was used. For this study, we wanted to determine the quality of individual sperm analysis using our routine workflow and, assuming the results provided sufficient profiles, to establish means to cluster them. Material and methods In terms of a feasibility study, STR profiles of single sperm cells were examined using different multiplex kits and amplification conditions. Based on this database, a cluster analysis for grouping partial haploid autosomal profiles was successfully developed. Simulations were carried out to increase the database. Furthermore, the correlation between successful cluster analysis and the number of sperm, the quality of the profiles obtained and the number of contributors was investigated. Results and conclusion From a pool of partial haploid profiles of 2–5 individuals, generally reliable grouping can be obtained by cluster analysis and diploid profiles can be derived for each contributor. When examining 40 sperm per contributor, in 92.2% (2 person mixture) and 71.6% (5 person mixture) complete and correct profiles could be deconvoluted; however, the fewer sperm per person are available for analysis, the more the completeness of the haploid profile affects the quality of the cluster analysis and therefore the correctness of the deconvoluted profile.