Human Mitochondria and Mitochondrial Genome Function as a Single Dynamic Cellular Unit

• Published in: The Journal of cell biology 1994-04, Vol.125 (1), p.43-50
• Main Authors: Hayashi, Jun-Ichi, Takemitsu, Masakazu, Goto, Yu-ichi, Nonaka, Ikuya
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Cell separation; Cell structures and functions; Cells; Cellular biology; Deoxyribonucleic acid; Diffusion; DNA; DNA, Mitochondrial - genetics; DNA, Mitochondrial - metabolism; Electron Transport Complex IV - metabolism; Fluorescence; Fundamental and applied biological sciences. Psychology; Genes; Genetics; genomes; HeLa Cells; Humans; interaction; intercellular; L cells; man; Mitochondria; Mitochondria - physiology; Mitochondria and cell respiration; Mitochondrial DNA; Mitochondrial Swelling; Molecular and cellular biology; Molecules; RNA, Messenger - metabolism; Sequence Deletion; Somatic cells; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.125.1.43

ρ 0 HeLa cells entirely lacking mitochondrial DNA (mtDNA) and mitochondrial transfection techniques were used to examine intermitochondrial interactions between mitochondria with and without mtDNA, and also between those with wild-type (wt) and mutant-type mtDNA in living human cells. First, unambiguous evidence was obtained that the DNA-binding dyes ethidium bromide (EtBr) and 4′,6-diamidino-2-phenylindole (DAPI) exclusively stained mitochondria containing mtDNA in living human cells. Then, using EtBr or DAPI fluorescence as a probe, mtDNA was shown to spread rapidly to all ρ 0 HeLa mitochondria when EtBr- or DAPI-stained HeLa mitochondria were introduced into ρ 0 HeLa cells. Moreover, coexisting wt-mtDNA and mutant mtDNA with a large deletion (Δ-mtDNA) were shown to mix homogeneously throughout mitochondria, not to remain segregated by use of electron microscopic analysis of cytochrome c oxidase activities of individual mitochondria as a probe to identify mitochondria with predominantly wt- or Δ-mtDNA in single cells. This rapid diffusion of mtDNA and the resultant homogeneous distribution of the heteroplasmic wt- and Δ-mtDNA molecules throughout mitochondria in a cell suggest that the mitochondria in living human cells have lost their individuality. Thus, the actual number of mitochondria per cell is not of crucial importance, and mitochondria in a cell should be considered as a virtually single dynamic unit.