Deleterious mitochondrial DNA point mutations are overrepresented in Drosophila expressing a proofreading-defective DNA polymerase γ

PLoS Genet. 2018 Nov 19;14(11):e1007805. doi: 10.1371/journal.pgen.1007805. eCollection 2018 Nov.


Mitochondrial DNA (mtDNA) mutations cause severe maternally inherited syndromes and the accumulation of somatic mtDNA mutations is implicated in aging and common diseases. However, the mechanisms that influence the frequency and pathogenicity of mtDNA mutations are poorly understood. To address this matter, we created a Drosophila mtDNA mutator strain expressing a proofreading-deficient form of the mitochondrial DNA polymerase. Mutator flies have a dramatically increased somatic mtDNA mutation frequency that correlates with the dosage of the proofreading-deficient polymerase. Mutator flies also exhibit mitochondrial dysfunction, shortened lifespan, a progressive locomotor deficit, and loss of dopaminergic neurons. Surprisingly, the frequency of nonsynonymous, pathogenic, and conserved-site mutations in mutator flies exceeded predictions of a neutral mutational model, indicating the existence of a positive selection mechanism that favors deleterious mtDNA variants. We propose from these findings that deleterious mtDNA mutations are overrepresented because they selectively evade quality control surveillance or because they are amplified through compensatory mitochondrial biogenesis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aging / genetics
  • Aging / metabolism
  • Animals
  • Animals, Genetically Modified
  • DNA Polymerase gamma / genetics*
  • DNA Polymerase gamma / metabolism*
  • DNA Replication / genetics
  • DNA, Mitochondrial / genetics*
  • Dopaminergic Neurons / metabolism
  • Dopaminergic Neurons / pathology
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / cytology
  • Drosophila melanogaster / enzymology*
  • Drosophila melanogaster / genetics*
  • Genes, Insect
  • Longevity / genetics
  • Mitochondria / enzymology
  • Mitochondria / genetics
  • Motor Activity / genetics
  • Organelle Biogenesis
  • Point Mutation*


  • DNA, Mitochondrial
  • Drosophila Proteins
  • DNA Polymerase gamma