title: Super-resolution microscopy reveals that mammalian mitochondrial nucleoids have a uniform size and frequently contain a single copy of mtDNA.
abstract: Mammalian mtDNA is packaged in DNA-protein complexes denoted mitochondrial nucleoids. The organization of the nucleoid is a very fundamental question in mitochondrial biology and will determine tissue segregation and transmission of mtDNA. We have used a combination of stimulated emission depletion microscopy, enabling a resolution well below the diffraction barrier, and molecular biology to study nucleoids in a panel of mammalian tissue culture cells. We report that the nucleoids labeled with antibodies against DNA, mitochondrial transcription factor A (TFAM), or incorporated BrdU, have a defined, uniform mean size of ∼100 nm in mammals. Interestingly, the nucleoid frequently contains only a single copy of mtDNA (average ∼1.4 mtDNA molecules per nucleoid). Furthermore, we show by molecular modeling and volume calculations that TFAM is a main constituent of the nucleoid, besides mtDNA. These fundamental insights into the organization of mtDNA have broad implications for understanding mitochondrial dysfunction in disease and aging.
authors.affiliation: Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, D-50931 Cologne, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kukat
authors.forename: Christian A
authors.initials: CA
authors.lastname: Wurm
authors.forename: Henrik
authors.initials: H
authors.lastname: Spåhr
authors.forename: Maria
authors.initials: M
authors.lastname: Falkenberg
authors.forename: Nils-Göran
authors.initials: NG
authors.lastname: Larsson
authors.forename: Stefan
authors.initials: S
authors.lastname: Jakobs
mesh_terms: D000818:Animals; D000906:Antibodies; D004272:DNA, Mitochondrial / Q000276:immunology / Q000648:ultrastructure*; D004268:DNA-Binding Proteins / Q000276:immunology; D006801:Humans; D008853:Microscopy / Q000295:instrumentation*; D008928:Mitochondria; D024101:Mitochondrial Proteins / Q000276:immunology; D014157:Transcription Factors / Q000276:immunology
chemical_list: D000906:Antibodies; D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D014157:Transcription Factors; C422562:mitochondrial transcription factor A