Cell Journal (Jan 2011)
Detecting Rare Triple Heteroplasmic Substitutions in the Mitochondrial DNA Control Region:A Potential Concern for Forensic DNA Studies
Abstract
Objective: Mitochondrial DNA (mtDNA) is a useful tool for population studies, identificationof humans and forensic DNA studies. The existence of several hundreds copies ofmtDNA per cell permit its extraction from minute or degraded samples. In addition, thelevel of polymorphism in the hypervariable (HV) region is high enough to permit its usein human identity testing. However, the presence of several heteroplasmy might lead toambiguous results.Materials and Methods: This study was an experiental study. This study evaluated heteroplasmyin the HV region of mtDNA in blood samples of 30 Iranians who belonged to tenunrelated families from three sequential generations (grandmother, mother and daughter).Results: There were no heteroplasmic substitutions in the HV1 region, but analysis ofHV2 showed heteroplasmic substitutions in two out ten families. In the first family thegrandmother showed heteroplasmy (T/C) in nucleotide positions 146 and 151, howeverit was not detected in the mother and daughter. In second family, a triple heteroplasmy(T/C) was detected in the daughter in nucleotide positions 146, 151 and 295, but theseheteroplasmic substitutions were not obvious in the grandmother and mother.Conclusion: Heteroplasmy in mtDNA is not a rare phenomenon and probably exists ineveryone, but a triple heteroplasmy in one family member is a novel finding. Our resultsdemonstrate that one or two sequence differences between samples in mtDNA do notwarrant exclusion. In our study, the average nucleotide difference between unrelated personsin the HV2 region was 2.8 nucleotides, whereas there was a triple heteroplasmy inone person which was not obvious in her family.
