A stop-codon mutation in the human mtDNA cytochrome c oxidase I gene disrupts the functional structure of complex IV

Claudio Bruno, Andrea Martinuzzi, Yingying Tang, Antoni L. Andreu, Francesco Pallotti, Eduardo Bonilla, Sara Shanske, Jin Fu, Carolyn M. Sue, Corrado Angelini, Salvatore DiMauro, Giovanni Manfredi

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We have identified a novel stop-codon mutation in the mtDNA of a young woman with a multisystem mitochondrial disorder. Histochemical analysis of a muscle-biopsy sample showed virtually absent cytochrome c oxidase (COX) stain, and biochemical studies confirmed an isolated reduction of COX activity. Sequence analysis of the mitochondrial-encoded COX-subunit genes identified a heteroplasmic G→A transition at nucleotide position 6930 in the gene for subunit I (COX I). The mutation changes a glycine codon to a stop codon, resulting in a predicted loss of the last 170 amino acids (33%) of the polypeptide. The mutation was present in the patient's muscle, myoblasts, and blood and was not detected in normal or disease controls. It was not detected in mtDNA from leukocytes of the patient's mother, sister, and four maternal aunts. We studied the genetic, biochemical, and morphological characteristics of transmitochondrial cybrid cell lines, obtained by fusing of platelets from the patient with human cells lacking endogenous mtDNA (ρ0 cells). There was a direct relationship between the proportion of mutant mtDNA and the biochemical defect. We also observed that the threshold for the phenotypic expression of this mutation was lower than that reported in mutations involving tRNA genes. We suggest that the G6930A mutation causes a disruption in the assembly of the respiratory-chain complex IV.

Original languageEnglish
Pages (from-to)611-620
Number of pages10
JournalAmerican Journal of Human Genetics
Issue number3
Publication statusPublished - 1999


ASJC Scopus subject areas

  • Genetics

Cite this

Bruno, C., Martinuzzi, A., Tang, Y., Andreu, A. L., Pallotti, F., Bonilla, E., Shanske, S., Fu, J., Sue, C. M., Angelini, C., DiMauro, S., & Manfredi, G. (1999). A stop-codon mutation in the human mtDNA cytochrome c oxidase I gene disrupts the functional structure of complex IV. American Journal of Human Genetics, 65(3), 611-620. https://doi.org/10.1086/302546