title: Genetic mosaic analysis of a deleterious mitochondrial DNA mutation in Drosophila reveals novel aspects of mitochondrial regulation and function.
abstract: Various human diseases are associated with mitochondrial DNA (mtDNA) mutations, but heteroplasmy—the coexistence of mutant and wild-type mtDNA—complicates their study. We previously isolated a temperature-lethal mtDNA mutation in Drosophila, mt:CoI(T300I), which affects the cytochrome c oxidase subunit I (CoI) locus. In the present study, we found that the decrease in cytochrome c oxidase (COX) activity was ascribable to a temperature-dependent destabilization of cytochrome a heme. Consistently, the viability of homoplasmic flies at 29°C was fully restored by expressing an alternative oxidase, which specifically bypasses the cytochrome chains. Heteroplasmic flies are fully viable and were used to explore the age-related and tissue-specific phenotypes of mt:CoI(T300I). The proportion of mt:CoI(T300I) genome remained constant in somatic tissues along the aging process, suggesting a lack of quality control mechanism to remove defective mitochondria containing a deleterious mtDNA mutation. Using a genetic scheme that expresses a mitochondrially targeted restriction enzyme to induce tissue-specific homoplasmy in heteroplasmic flies, we found that mt:CoI(T300I) homoplasmy in the eye caused severe neurodegeneration at 29°C. Degeneration was suppressed by improving mitochondrial Ca(2+) uptake, suggesting that Ca(2+) mishandling contributed to mt:CoI(T300I) pathogenesis. Our results demonstrate a novel approach for Drosophila mtDNA genetics and its application in modeling mtDNA diseases.
authors.affiliation: Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Yun
authors.initials: Y
authors.lastname: Qi
authors.affiliation: Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, Bethesda, MD 20892.
authors.forename: Stephanie
authors.initials: S
authors.lastname: French
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Guofeng
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, Bethesda, MD 20892.
authors.forename: Raúl
authors.initials: R
authors.lastname: Covian Garcia
authors.affiliation: Laboratory of Cardiac Energetics, National Heart, Lung, and Blood Institute, Bethesda, MD 20892.
authors.forename: Robert
authors.initials: R
authors.lastname: Balaban
authors.affiliation: Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20892 hong.xu@nih.gov.
authors.forename: Hong
authors.initials: H
authors.lastname: Xu
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D054910:Compound Eye, Arthropod / Q000473:pathology; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000737:chemistry*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D003576:Electron Transport Complex IV / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D054629:Genome, Mitochondrial; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008957:Models, Genetic
chemical_list: D004272:DNA, Mitochondrial; D029721:Drosophila Proteins; D003576:Electron Transport Complex IV