Contribution of de novo point mutations to the overall mutational burden in mitochondrial DNA of adult rats

M. Khaidakov, N. Chavannes-Turesky, C. A. Cooney, E. E. Dupont-Versteegden, R. H. Kennedy, E. R. Siegel, G. Khaidakova, R. J. Shmookler Reis

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

This study analyzed the incidence of point mutations in mitochondrial DNA of brain and muscle tissues from young (6-month) and old (24-month) male F344 rats. Coding sequence mutations in subunit 5 of the NADH dehydrogenase gene were detected after high-fidelity PCR amplification and cloning by denaturing gradient gel electrophoresis (DGGE) assay followed by sequencing of detected mutants. In total, almost a thousand individual clones were analyzed both in brain and muscle samples. On average, mtDNA from brain tissue showed a 66% increase with age in mutation frequencies (2.3±1.9 vs. 3.8±4.5×10-4 mutations/bp, mean±SD), which failed to reach statistical significance (p=0.45). Muscle tissues yielded substantially fewer mutants with average mutant frequencies for both young and old rats almost 10 times lower than the corresponding values in the brain tissue (0.3±0.4 and 0.5±0.6×10-4, respectively). The difference in mutation accumulation between muscle and brain was highly significant in both the younger group (Chi-squared=9.7, p≤0.01) and in older animals (Chi-squared=10.9, p≤0.001). Molecular analysis of the mutated sequences revealed that almost half were identical sequences recurring in different samples and tissues. Our findings indicate that the process of mutation accumulation in mitochondria begins in the germ-line and/or during earlier stages of life, contributing up to half of the total mutational burden, whereas de novo spontaneous formation of point mutations in adulthood is far less than was anticipated.

Original languageEnglish
Pages (from-to)396-402
Number of pages7
JournalExperimental Gerontology
Volume40
Issue number5
DOIs
StatePublished - May 2005

Bibliographical note

Funding Information:
This research was supported by a grant-in-aid from the American Heart Association—Heartland Affiliate (to RHK), by a grant for Methylation, Epigenetics and Longevity from Life Extension Foundation (to CAC) and by NIA/NIH P01AG20641 (to RJSR).

Keywords

  • Aging
  • Brain
  • Mitochondrial DNA
  • Muscle
  • Point mutations
  • Rats

ASJC Scopus subject areas

  • Biochemistry
  • Aging
  • Molecular Biology
  • Genetics
  • Endocrinology
  • Cell Biology

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