Journal Article

Mutations in <i>AAC2</i>, equivalent to human adPEO-associated ANT1 mutations, lead to defective oxidative phosphorylation in <i>Saccharomyces cerevisiae</i> and affect mitochondrial DNA stability

Flavia Fontanesi, Luigi Palmieri, Pasquale Scarcia, Tiziana Lodi, Claudia Donnini, Anna Limongelli, Valeria Tiranti, Massimo Zeviani, Iliana Ferrero and Anna Maria Viola

in Human Molecular Genetics

Volume 13, issue 9, pages 923-934
Published in print May 2004 | ISSN: 0964-6906
Published online March 2004 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddh108
Mutations in AAC2, equivalent to human adPEO-associated ANT1 mutations, lead to defective oxidative phosphorylation in Saccharomyces cerevisiae and affect mitochondrial DNA stability

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Autosomal dominant and recessive forms of progressive external ophthalmoplegia (adPEO and arPEO) are mitochondrial disorders characterized by the presence of multiple deletions of mitochondrial DNA in affected tissues. Four adPEO-associated missense mutations have been identified in the ANT1 gene. In order to investigate their functional consequences on cellular physiology, we introduced three of them at equivalent positions in AAC2, the yeast orthologue of human ANT1. We demonstrate here that expression of the equivalent mutations in aac2-defective haploid strains of Saccharomyces cerevisiae results in (a) a marked growth defect on non-fermentable carbon sources, and (b) a concurrent reduction of the amount of mitochondrial cytochromes, cytochrome c oxidase activity and cellular respiration. The efficiency of ATP and ADP transport was variably affected by the different AAC2 mutations. However, irrespective of the absolute level of activity, the AAC2 pathogenic mutants showed a significant defect in ADP versus ATP transport compared with wild-type AAC2. In order to study whether a dominant phenotype, as in humans, could be observed, the aac2 mutant alleles were also inserted in combination with the endogenous wild-type AAC2 gene. The heteroallelic strains behaved as recessive for oxidative growth and petite-negative phenotype. In contrast, reduction in cytochrome content and increased mtDNA instability appeared to behave as dominant traits in heteroallelic strains. Our results indicate that S. cerevisiae is a suitable in vivo model to study the pathogenicity of the human ANT1 mutations and the pathophysiology leading to impairment of oxidative phosphorylation and damage of mtDNA integrity, as found in adPEO.

Journal Article.  8327 words.  Illustrated.

Subjects: Genetics and Genomics

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