phenomenon in hair and increases with age

Mitochondrial DNA (mtDNA) is believed to be particularly susceptible to oxidative damage during aging, resulting in mtDNA point muta-tions, duplications, and deletions. Although mtDNA deletions have been reported in various human tissues, e.g., the brain, heart, and skeletal muscle, little is known about the occurrence in hair. Th erefore, we screened for the presence of mtDNA bp, bp, bp, bp, bp, and bp deletions in hair samples from subjects aged days to years by using polymerase chain reaction (PCR) and investi-gated the deletion load by TaqMan probe-based real-time PCR. We detected the mtDNA bp deletion in hair samples, but none of the other deletions that were screened for. Th e proportion of mtDNA deletion carriers was . (/) and the deletion loads increased from to . ± . of the total mtDNA with an exponential increase with age (r = ., p < .). Th ese results suggest that mtDNA bp deletion is a common phenomenon in hair and increases with age. Th ese fi ndings expand our understanding of the tissue-specifi c distribution of mtDNA deletions