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We isolated stable cell lines, designated as mitochondrial cells, from cybrids obtained by fusing mitochondria-less HeLa cells with platelets from patients with Leigh syndrome, a subtype of mitochondrial encephalomyopathy. The cells contain a pathogenic point mutation, T9176C, in the mitochondrial DNA. Hematoxylin–eosin staining, confocal fluorescent microscopy and flow cytometry in fixed or living cells showed that the majority of these mitochondrial cells lack nuclear DNA and nuclei, but contain active mitochondria. Despite the absence of nuclear DNA, these cells can be continuously generated in culture. Therefore, it is likely that they arise from the minority of cells which possess a nucleus. [Copyright &y& Elsevier]

We applied stimulated emission depletion (STED) imaging with subdiffraction resolution to submitochondrial structures in mitochondria. Their shapes depend on both a cell's type and its physiological state. Staining with a cationic fluorescent dye, tetramethylrhodamine methyl ester (TMRM), unveiled intriguing details of lamellar structure, consisting of rapidly changeable, curtain-like formations. The TMRM-positive structure colocalized with neither proteins in the matrix nor on the outer membrane, but partially localized with the nucleoid. Suppression of a component in the mitochondrial contact site disrupted the lamellar TMRM-positive structure. Uncoupling of the oxidative phosphorylation system released TMRM from the inner membrane without any alteration in the matrix structure. STED images further showed that complexes of the electron transport chain are located on the surface of TMRM-positive structures. The approach presented here provides novel insights into the in vivo nature of submitochondrial structures, and can be used for further functional investigations of these complex structures. [ABSTRACT FROM AUTHOR]