Over-expression of the catalytic core of mitochondrial DNA (mtDNA) polymerase in the nervous system of Drosophila melanogaster reduces median life span by inducing mtDNA depletion

• Published in: Journal of neurochemistry Vol. 105; no. 1; pp. 165 - 176
• Main Authors: Martínez-Azorín, Francisco, Calleja, Manuel, Hernández-Sierra, Rosana, Farr, Carol L, Kaguni, Laurie S, Garesse, Rafael
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.04.2008; Blackwell Publishing Ltd; Blackwell
• Subjects: Animals; Animals, Genetically Modified; apoptosis; Biochemistry; Biological and medical sciences; Catalysis; Catalytic Domain - physiology; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; DNA polymerase; DNA Polymerase gamma; DNA polymerase γ; DNA, Mitochondrial - chemistry; DNA, Mitochondrial - genetics; DNA-directed DNA polymerase; DNA-Directed DNA Polymerase - metabolism; Drosophila melanogaster; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Gene Expression - physiology; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Insects; Male; Medical sciences; Mitochondria; Mitochondrial Diseases - physiopathology; Mitochondrial DNA; NADH Dehydrogenase - metabolism; Nervous System - metabolism; Neurology; oxidative phosphorylation; oxidative stress; Oxidative Stress - physiology; Survival Analysis; Time Factors; Vascular diseases and vascular malformations of the nervous system; Human; Catalytic subunit; Oxidative stress; Factor analysis; Insecta; Central nervous system; Nervous system; Activation; DNA polymerase γ; Protein; Drosophilidae; Mitochondria; Depletion; Endogenous; Oxidative phosphorylation; Arthropoda; Invertebrata; Transcription factor; Drosophila melanogaster; Diptera; Apoptosis
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2007.05122.x

DNA polymerase γ (pol γ) is the sole DNA polymerase devoted to mitochondrial DNA (mtDNA) replication. We have characterized the molecular and physiological effects of over-expression of the catalytic subunit of pol γ, pol γ-α, in the nervous system of Drosophila melanogaster using the upstream activation sequence (UAS)/yeast transcriptional activator by binding to UAS (GAL4) system. Tissue-specific over-expression of pol γ-α was confirmed by immunoblot analysis, whereas the very low levels of endogenous protein are undetectable in UAS or GAL4 control lines. The transgenic flies over-expressing pol γ-α in the nervous system showed a moderate increase in pupal lethality, and a significant decrease in the median life span of adult flies. Moreover, these flies displayed a decrease in the rate of synthesis of mtDNA, which is accompanied by a significant mtDNA depletion, and a corresponding decrease in the levels of mitochondrial transcription factor A (mtTFA). Biochemical analysis showed an oxidative phosphorylation (OXPHOS) defect in transgenic flies, which were more susceptible to oxidative stress. Although we did not detect apoptosis in the nervous system of adult transgenic flies, brains of larvae over-expressing pol γ-α showed evidence of increased cell death that correlates with the observed phenotypes. Our data establish an animal model that mimics some of the features of human mtDNA depletion syndromes.