Cochlear mitochondrial DNA3867bp deletion in aged mice.

Objectives: To study the status of cochlear mitochondrial DNA (mtDNA) and to determine the location of mtDNA deletion in aged mice.
Methods: We detected cochlear mtDNA in 2, 7 - 10 and 17 - 19 month old mice by nested polymerase chain reaction (PCR) and DNA sequencing.
Results: mtDNA3867bp deletions were found in the cochleae of aged mice. The deletion occurred within nt9103-nt12970 and were flanked by 15 base pair direct repeats. Comparing the incidence of mtDNA3867bp deletions, 17 - 19 month old mice (7/8) were significantly higher than 7 - 10 month old mice (4/16). The deletion was not observed in 2 month old mice (0/7). The ratio of deleted mtDNA/total mtDNA in 17 - 19 month old mice was higher than in 7 - 10 month old mice (P < 0.001).
Conclusion: Cochlear mtDNA 3867bp deletion in aged mice may be related to presbycusis.