PMID- 22926664 OWN - NLM STAT- MEDLINE DCOM- 20130625 LR - 20130121 IS - 1432-0533 (Electronic) IS - 0001-6322 (Linking) VI - 125 IP - 2 DP - 2013 Feb TI - Mitofusin 2 mutations affect mitochondrial function by mitochondrial DNA depletion. PG - 245-56 LID - 10.1007/s00401-012-1036-y [doi] AB - 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. FAU - Vielhaber, Stefan AU - Vielhaber S AD - Department of Neurology, University of Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany. FAU - Debska-Vielhaber, Grazyna AU - Debska-Vielhaber G FAU - Peeva, Viktoriya AU - Peeva V FAU - Schoeler, Susanne AU - Schoeler S FAU - Kudin, Alexei P AU - Kudin AP FAU - Minin, Irina AU - Minin I FAU - Schreiber, Stefanie AU - Schreiber S FAU - Dengler, Reinhard AU - Dengler R FAU - Kollewe, Katja AU - Kollewe K FAU - Zuschratter, Werner AU - Zuschratter W FAU - Kornblum, Cornelia AU - Kornblum C FAU - Zsurka, Gabor AU - Zsurka G FAU - Kunz, Wolfram S AU - Kunz WS LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20120828 PL - Germany TA - Acta Neuropathol JT - Acta neuropathologica JID - 0412041 RN - 0 (DNA, Mitochondrial) RN - 0 (Mitochondrial Proteins) RN - EC 1.3.99.1 (Succinate Dehydrogenase) RN - EC 1.9.3.1 (Electron Transport Complex IV) RN - EC 2.3.3.1 (Citrate (si)-Synthase) RN - EC 3.6.1.- (GTP Phosphohydrolases) RN - EC 3.6.1.- (MFN2 protein, human) SB - IM MH - Adult MH - Blotting, Western MH - Cell Separation MH - Cells, Cultured MH - Charcot-Marie-Tooth Disease/genetics MH - Citrate (si)-Synthase/metabolism MH - DNA Repair MH - DNA, Mitochondrial/*physiology MH - Electron Transport/genetics/physiology MH - Electron Transport Complex IV/metabolism MH - Female MH - Fibroblasts/physiology MH - GTP Phosphohydrolases/*genetics MH - Gene Dosage MH - Humans MH - Male MH - Microscopy, Electron MH - Mitochondria/*genetics/*physiology MH - Mitochondrial Proteins/*genetics MH - Muscle Fibers, Skeletal/physiology MH - Muscle, Skeletal/physiology MH - Mutation/*genetics MH - Oxygen Consumption/physiology MH - Succinate Dehydrogenase/metabolism MH - Young Adult EDAT- 2012/08/29 06:00 MHDA- 2013/06/26 06:00 CRDT- 2012/08/29 06:00 PHST- 2012/03/06 00:00 [received] PHST- 2012/08/18 00:00 [accepted] PHST- 2012/07/13 00:00 [revised] PHST- 2012/08/29 06:00 [entrez] PHST- 2012/08/29 06:00 [pubmed] PHST- 2013/06/26 06:00 [medline] AID - 10.1007/s00401-012-1036-y [doi] PST - ppublish SO - Acta Neuropathol. 2013 Feb;125(2):245-56. doi: 10.1007/s00401-012-1036-y. Epub 2012 Aug 28.