Human Identification Using Genetically Variant Peptides in Biological Forensic Evidence
- Fanny ChuFanny ChuForensic Science Center, Lawrence Livermore National Laboratory, Livermore, California 94550, United StatesDepartment of Chemistry, Michigan State University, East Lansing, Michigan 48824, United StatesMore by Fanny Chu
- Katelyn E. MasonKatelyn E. MasonForensic Science Center, Lawrence Livermore National Laboratory, Livermore, California 94550, United StatesMore by Katelyn E. Mason
- Deon S. AnexDeon S. AnexForensic Science Center, Lawrence Livermore National Laboratory, Livermore, California 94550, United StatesMore by Deon S. Anex
- Phillip H. PaulPhillip H. PaulMore by Phillip H. Paul
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- Bradley R. Hart*
Proteins in biological evidence offer a pathway for human identification when DNA is absent or compromised and can augment existing intact DNA evidence, as collectives of single amino acid substitutions (SAPs) within protein sequences can serve as individual-specific markers. Peptides containing SAPs are known as genetically variant peptides (GVPs). Key to using GVPs in forensics is their link to associated single nucleotide polymorphisms (SNPs) in the corresponding protein-coding DNA. As such, SNP population frequencies can be used to calculate statistics, such as random match probability (RMP), derived from protein evidence, and rules of genetic inheritance can be applied. Proteomic analysis of forensic samples guided by predictions from DNA exomic analysis (i.e., of exons in the genome) can locate these GVPs. Protein-based identification was first demonstrated in 2016 using hair shafts for a cohort of over 60 individuals, producing RMPs up to 1 in 14,000 and ancestry determination. GVPs were shown to persist in archaeological hairs over 250 years old. Subsequent studies have extended GVP capabilities to bone and tooth tissues and shed skin cells. Improved sample preparation and bioinformatics have enabled greater numbers of identified SNPs; a 12,000-fold increase in maximum discriminative power has been achieved even with 100-fold reduction in sample size, from bulk quantities to a single inch of hair. Further, independence of GVP identification from body location-specific protein expression has been demonstrated. Continued development of this technology through common or rare GVP panels and concurrent GVP and mitochondrial DNA analysis provides powerful tools for individual identification and enhanced discriminative power.
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