Selective enrichment of STRs for applications in forensic human identification

Abstract

Forensic human identification (HID) is currently based on determining repeat length polymorphisms located in short tandem repeat regions in the human genome. Despite the great progress made in the area of multiplex PCR-based approaches, limitations associated with challenging forensic samples such as DNA degradation, cooccurrence of inhabited microbial DNA and PCR inhibitors significantly affect the success rate of human DNA profiling. We have developed a sequence-specific pre-PCR STR enrichment method and evaluated its efficacy using DNA samples doped with various contaminants in view of its application on compromised forensic samples. This strategy has enabled us to generate complete and reproducible DNA profiles from samples doped with fivefold excess of nonhuman DNA and three to fourfold excess of various potent PCR inhibitors than that is claimed to be tolerated by some of the widely used commercial multiplex STR kits, from as little as two nanograms of degraded human DNA. The "hybrid capture"-based STR enrichment strategy described in this study is easily adaptable and offers a sensitive, efficient, and economical approach for successful human DNA profiling from compromised and recalcitrant forensic samples that are usually encountered in mass disaster incidents and missing persons' identifications.

Differential pre‐amplification of STR loci for fragmented forensic DNA profiling

“…Locus enrichment by hybridization of degraded genomic DNA with an STR locus‐specific biotinylated oligonucleotide is a powerful approach to overcome problems in STR typing of highly degraded DNA . To develop a more sensitive strategy, we examined whether pre‐amplification of STR loci with STR locus‐specific biotinylated primer pairs is an efficient way to obtain DNA profiling results from fragmented DNA.…”

“…We and others optimized the experimental conditions of hybridization‐mediated STR loci enrichment and further purification using streptavidin‐coated magnetic particles . This approach is useful for enriching STR loci and can be applied to the isolation of human DNA from a DNA mixture contaminated with bacterial DNA and other impure ingredients . Although this strategy is useful for STR analysis of fragmented DNA, relatively large amounts of genomic DNA are required to obtain clear STR DNA profiles.…”