Introduction of disease-related mitochondrial DNA deletions into HeLa cells lacking mitochondrial DNA results in mitochondrial dysfunction.
Mutant mitochondrial DNA with large-scale deletions (delta-mtDNA) has been frequently observed in patients with chronic progressive external ophthalmoplegia (CPEO), a subgroup of the mitochondrial encephalomyopathies. To exclude involvement of the nuclear genome in expression of the mitochondrial dysfunction characteristic of CPEO, we introduced the mtDNA of a CPEO patient into clonal mtDNA-less HeLa cells and isolated cybrid clones. Quantitation of delta-mtDNA in the cybrids revealed that delta-mtDNA was selectively propagated with higher levels of delta-mtDNA correlating with slower cellular growth rate. In these cybrid clones, translational complementation of the missing tRNAs occurred only when delta-mtDNA was less than 60% of the total mtDNA, whereas accumulation of delta-mtDNA to greater than 60% resulted in progressive inhibition of overall mitochondrial translation as well as reduction of cytochrome c oxidase activity throughout the organelle population. Because these cybrids shared the same nuclear background as HeLa cells, these results suggest that large-scale deletion mutations of mtDNA alone are sufficient for the mitochondrial dysfunction characteristic of CPEO.
Hayashi
J
J
Department of Biochemistry, Saitama Cancer Center Research Institute, Japan.
Ohta
S
S
Kikuchi
A
A
Takemitsu
M
M
Goto
Y
Y
Nonaka
I
I
D000293:Adolescent; D015139:Blotting, Southern; D002478:Cells, Cultured; D002872:Chromosome Deletion; D003593:Cytoplasm / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000302:isolation & purification; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000502:physiology; D009886:Ophthalmoplegia / Q000235:genetics*; D014176:Protein Biosynthesis; D012313:RNA / Q000032:analysis / Q000235:genetics; D000077278:RNA, Mitochondrial; D012867:Skin / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D004272:DNA, Mitochondrial; D000077278:RNA, Mitochondrial; D012313:RNA; D003576:Electron Transport Complex IV