Random point mutations with major effects on protein-coding genes are the driving force behind premature aging in mtDNA mutator mice.
The mtDNA mutator mice have high levels of point mutations and linear deletions of mtDNA causing a progressive respiratory chain dysfunction and a premature aging phenotype. We have now performed molecular analyses to determine the mechanism whereby these mtDNA mutations impair respiratory chain function. We report that mitochondrial protein synthesis is unimpaired in mtDNA mutator mice consistent with the observed minor alterations of steady-state levels of mitochondrial transcripts. These findings refute recent claims that circular mtDNA molecules with large deletions are driving the premature aging phenotype. We further show that the stability of several respiratory chain complexes is severely impaired despite normal synthesis of the corresponding mtDNA-encoded subunits. Our findings reveal a mechanism for induction of aging phenotypes by demonstrating a causative role for amino acid substitutions in mtDNA-encoded respiratory chain subunits, which, in turn, leads to decreased stability of the respiratory chain complexes and respiratory chain deficiency.
Edgar
Daniel
D
Division of Metabolic Diseases, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
Shabalina
Irina
I
Camara
Yolanda
Y
Wredenberg
Anna
A
Calvaruso
Maria Antonietta
MA
Nijtmans
Leo
L
Nedergaard
Jan
J
Cannon
Barbara
B
Larsson
Nils-Göran
NG
Trifunovic
Aleksandra
A
D019588:Aging, Premature / Q000235:genetics*; D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics*; D042967:Electron Transport Complex I / Q000378:metabolism; D014450:Electron Transport Complex III / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D017353:Gene Deletion; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D017354:Point Mutation
D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III