Base specific variation rates at mtDNA positions 16093 and 16183 in human hairs

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• Mitochondrial DNA (mtDNA) analysis is crucial in forensic casework.
• Interpreting mtDNA results is complicated by small variations between an individual's tissues.
• Hair and buccal swabs are common sample types, necessitating understanding of tissue-specific mtDNA differences.

Purpose of the Study:

• To characterize variations at specific mitochondrial DNA (mtDNA) nucleotide positions (16093, 16182, 16183) between hair and buccal cells.
• To assess the impact of uninterrupted HV1 poly-C stretches on intra-individual mtDNA variation.
• To provide insights for forensic practitioners comparing hair and reference samples.

Main Methods:

• Sanger sequencing was performed on 25-28 hair strands from 15 individuals.
• Individuals were selected based on specific mitochondrial DNA (mtDNA) haplotypes in their buccal cells (16093C/Y or uninterrupted HV1 polyC-stretch).
• Results were evaluated alongside previous findings on mtDNA variation.

Main Results:

• No variation was found in hair strands from individuals with T16093 in buccal cells.
• Individuals with 16093C or 16093Y in buccal cells showed variations (T16093, 16093C, 16093Y) in hair strands.
• Specific variations were observed at positions 16182 and 16183 in hair strands depending on the buccal cell haplotype.

Conclusions:

• Mitochondrial DNA (mtDNA) variations between hair and buccal cells are position-dependent and influenced by specific haplotypes.
• Understanding these intra-individual variations is critical for accurate forensic mtDNA analysis.
• These findings can improve the interpretation of mtDNA evidence in forensic casework, particularly when comparing hair samples to reference material.