Mitofusin 2 mutations affect mitochondrial function by mitochondrial DNA depletion

被引:0
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作者
Stefan Vielhaber
Grazyna Debska-Vielhaber
Viktoriya Peeva
Susanne Schoeler
Alexei P. Kudin
Irina Minin
Stefanie Schreiber
Reinhard Dengler
Katja Kollewe
Werner Zuschratter
Cornelia Kornblum
Gábor Zsurka
Wolfram S. Kunz
机构
[1] University of Magdeburg,Department of Neurology
[2] DZNE German Centre for Neurodegenerative Diseases,Division of Neurochemistry, Department of Epileptology and Life & Brain Center
[3] University of Bonn Medical Center,Department of Neurology
[4] Hannover Medical School,Department of Neurology
[5] Leibniz Institute for Neurobiology,undefined
[6] University of Bonn,undefined
来源
Acta Neuropathologica | 2013年 / 125卷
关键词
Mitofusin 2; Mitochondrial DNA; Depletion; Deletion; Charcot–Marie–Tooth neuropathy type 2A;
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摘要
Charcot–Marie–Tooth neuropathy type 2A (CMT2A) is associated with heterozygous mutations in the mitochondrial protein mitofusin 2 (Mfn2) that is intimately involved with the outer mitochondrial membrane fusion machinery. The precise consequences of these mutations on oxidative phosphorylation are still a matter of dispute. Here, we investigate the functional effects of MFN2 mutations in skeletal muscle and cultured fibroblasts of four CMT2A patients applying high-resolution respirometry. While maximal activities of respiration of saponin-permeabilized muscle fibers and digitonin-permeabilized fibroblasts were only slightly affected by the MFN2 mutations, the sensitivity of active state oxygen consumption to azide, a cytochrome c oxidase (COX) inhibitor, was increased. The observed dysfunction of the mitochondrial respiratory chain can be explained by a twofold decrease in mitochondrial DNA (mtDNA) copy numbers. The only patient without detectable alterations of respiratory chain in skeletal muscle also had a normal mtDNA copy number. We detected higher levels of mtDNA deletions in CMT2A patients, which were more pronounced in the patient without mtDNA depletion. Detailed analysis of mtDNA deletion breakpoints showed that many deleted molecules were lacking essential parts of mtDNA required for replication. This is in line with the lack of clonal expansion for the majority of observed mtDNA deletions. In contrast to the copy number reduction, deletions are unlikely to contribute to the detected respiratory impairment because of their minor overall amounts in the patients. Taken together, our findings corroborate the hypothesis that MFN2 mutations alter mitochondrial oxidative phosphorylation by affecting mtDNA replication.
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页码:245 / 256
页数:11
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