TY  - JOUR
AU  - Vielhaber, Stefan
AU  - Debska-Vielhaber, Grazyna
AU  - Peeva, Viktoriya
AU  - Schoeler, Susanne
AU  - Kudin, Alexei P
AU  - Minin, Irina
AU  - Schreiber, Stefanie
AU  - Dengler, Reinhard
AU  - Kollewe, Katja
AU  - Zuschratter, Werner
AU  - Kornblum, Cornelia
AU  - Zsurka, Gábor
AU  - Kunz, Wolfram S
TI  - Mitofusin 2 mutations affect mitochondrial function by mitochondrial DNA depletion.
JO  - Acta neuropathologica
VL  - 125
IS  - 2
SN  - 0001-6322
CY  - Heidelberg
PB  - Springer
M1  - DZNE-2020-03086
SP  - 245-256
PY  - 2013
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.
KW  - Adult
KW  - Blotting, Western
KW  - Cell Separation
KW  - Cells, Cultured
KW  - Charcot-Marie-Tooth Disease: genetics
KW  - Citrate (si)-Synthase: metabolism
KW  - DNA Repair
KW  - DNA, Mitochondrial: physiology
KW  - Electron Transport: genetics
KW  - Electron Transport: physiology
KW  - Electron Transport Complex IV: metabolism
KW  - Female
KW  - Fibroblasts: physiology
KW  - GTP Phosphohydrolases: genetics
KW  - Gene Dosage
KW  - Humans
KW  - Male
KW  - Microscopy, Electron
KW  - Mitochondria: genetics
KW  - Mitochondria: physiology
KW  - Mitochondrial Proteins: genetics
KW  - Muscle Fibers, Skeletal: physiology
KW  - Muscle, Skeletal: physiology
KW  - Mutation: genetics
KW  - Oxygen Consumption: physiology
KW  - Succinate Dehydrogenase: metabolism
KW  - Young Adult
KW  - DNA, Mitochondrial (NLM Chemicals)
KW  - Mitochondrial Proteins (NLM Chemicals)
KW  - Succinate Dehydrogenase (NLM Chemicals)
KW  - Electron Transport Complex IV (NLM Chemicals)
KW  - Citrate (si)-Synthase (NLM Chemicals)
KW  - GTP Phosphohydrolases (NLM Chemicals)
KW  - MFN2 protein, human (NLM Chemicals)
LB  - PUB:(DE-HGF)16
C6  - pmid:22926664
DO  - DOI:10.1007/s00401-012-1036-y
UR  - https://pub.dzne.de/record/136764
ER  -