Organization and dynamics of human mitochondrial DNA.
Heteroplasmic mutations of mitochondrial DNA (mtDNA) are an important source of human diseases. The mechanisms governing transmission, segregation and complementation of heteroplasmic mtDNA-mutations are unknown but depend on the nature and dynamics of the mitochondrial compartment as well as on the intramitochondrial organization and mobility of mtDNA. We show that mtDNA of human primary and immortal cells is organized in several hundreds of nucleoids that contain a mean of 2-8 mtDNA-molecules each. Nucleoids are enriched in mitochondrial transcription factor A and distributed throughout the entire mitochondrial compartment. Using cell fusion experiments, we demonstrate that nucleoids and respiratory complexes are mobile and diffuse efficiently into mitochondria previously devoid of mtDNA. In contrast, nucleoid-mobility was lower within mitochondria of mtDNA-containing cells, as differently labeled mtDNA-molecules remained spatially segregated in a significant fraction (37%) of the polykaryons. These results show that fusion-mediated exchange and intramitochondrial mobility of endogenous mitochondrial components are not rate-limiting for intermitochondrial complementation but can contribute to the segregation of mtDNA molecules and of mtDNA mutations during cell growth and division.
Legros
Frédéric
F
INSERM U582 (IFR 14, UPMC) Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, 47, Boulevard de l'Hôpital, 75651 Paris CEDEX 13, France.
Malka
Florence
F
Frachon
Paule
P
Lombès
Anne
A
Rojo
Manuel
M
D000328:Adult; D000911:Antibodies, Monoclonal / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D045744:Cell Line, Tumor; D002675:Child, Preschool; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000737:chemistry*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D012516:Osteosarcoma; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D004272:DNA, Mitochondrial; D008164:Luminescent Proteins; D024101:Mitochondrial Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D014475:Uncoupling Agents; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D003576:Electron Transport Complex IV