Proteomic genotyping for individual human identification: Inferring SNPs in the absence of DNA evidence

Proteins exhibit genetic variation due to differences in the amino acid sequence of proteins within and between populations. Amongst individuals this variation is most commonly in the form of single amino acid polymorphisms (SAPs) resulting from the translation of a non-synonymous single nucleotide polymorphism (SNP). The identification of SAPs can be used to infer the presence of corresponding SNP allele genotypes. When viable DNA is absent, proteomic genotyping may be used to associate biological evidence with an individual, similarly to other genetic markers of identification. As with DNA-based genotypes, this information can achieve potentially high levels of discriminating power and provide investigative leads including ancestry or biogeographic background. In forensic investigation the use of SNPs for individual identification continues to be explored at the nucleic acid level. However, in circumstances where DNA is not recovered, poorly recovered, or recovered as a complex mixture, alternative or complementary approaches for obtaining molecular markers of genetic variation would be valuable to investigators. Variations in the amino acid sequence of chemically abundant and stable proteins provides this opportunity. Using a proteomics approach, it’s possible to determine the presence of SNPs in an individual’s genome by revealing SAPs in the amino acid sequence of polypeptides. Ongoing research aims to use this information to bridge a gap in forensic intelligence gathering by applying emerging proteomics technologies to the analysis of biological matrices, most notably hair, an underutilised type of biological evidence.