Demonstration of Protein-Based Human Identification Using the Hair Shaft Proteome.

Area of Science:

• Forensic Science
• Proteomics
• Genetics

Background:

• DNA analysis for human identification is limited by environmental degradation.
• Proteins are more chemically stable than DNA and persist longer.
• Proteins contain genetic variation (single amino acid polymorphisms) that can reflect DNA's genetic status.

Purpose of the Study:

• To demonstrate the utility of mass spectrometry-based shotgun proteomics for characterizing hair shaft proteins.
• To impute single nucleotide polymorphism (SNP) alleles from protein data and validate them.
• To assess the potential for identity discrimination and biogeographic inference from hair shaft proteomic profiles.

Main Methods:

• Mass spectrometry-based shotgun proteomics was used to analyze hair shaft proteins.
• 66 European-American subjects' hair shafts were characterized.
• Proteomic data was used to impute 596 SNP alleles across 32 loci in 22 genes, validated by Sanger sequencing.

Main Results:

• Accurate imputation of SNP alleles from hair shaft proteins was achieved.
• High power of discrimination (1 in 12,500) was estimated for European-American profiles in the European population.
• Imputed profiles showed population-specific frequencies, with distinct patterns between European and African ancestries.
• Genetically variant peptides were identified in hair from archaeological remains up to 260 years old.

Conclusions:

• Hair shaft protein analysis provides quantifiable measures for identity discrimination.
• This method allows for the determination of biogeographic background.
• The technique is applicable to both modern forensic samples and ancient bioarchaeological remains.