Discrimination Power Assessment of STR Genotyping in Parentage Investigation
OBJECTIVE Nowadays, the application of DNA-typing in laboratory medicine is increasing rapidly for paternity/maternity disputes. The goal of this study was to evaluate the use of polymorphic microsatellite marker DNA analysis and to establish this analysis as the method of choice for parentage investigations.
SUBJECTS AND METHODS Among 708 civil parentage tests addressed to our Laboratory previously examined for HLA class I (-A*,-B*,-Cw*), and class II (-DRB1*,-DQB1*,-DPB1*) alleles using PCR-SSOP and/or PCR-SSP methodologies, a cohort of 50 cases (137 individuals) of disputed parentage was selected. In these cases DNA-typing was generated from co-amplification of 15 autosomal STR DNA markers (D3S1358, HUMTH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, HUMCSF1PO, Penta D, HUMvWA, D8S1179, HUMTPOX, HUMFGA and the sex determining Amelogenin marker HUMAMEL), using fragment analysis methodology.
RESULTS The evaluation of the results showed that 15 out of 50 cases, were sufficient for exclusion of fatherhood by both approaches (HLA and STRs). In all remaining 35 non-excluded cases, the PI value using HLA genotyping ranged from 76 to 6,452,794, whereas using aSTR genotyping ranged from 15,173 to 9.2 x 1010. In one non-excluded motherless case the alleged father showed one genetic discrepancy with the child at D21S11 locus, due to a mutation event.
CONCLUSION The use of DNA-typing with 15 aSTR loci for parentage testing provides an accurate and high-sensitivity method which is simpler to perform and more rapid than an accepted standard technology, such as HLA genotyping. The analysis of aSTR loci offers a highly discriminating test suitable for trio paternity testing, increasing the W rate in comparison to HLA genotyping. Nevertheless, when a mutation event occurs in motherless cases, combination of HLA and STR polymorphisms offers high level of information, and also diminishes the possibility of false exclusion due to aSTRs mutations.
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