Cargando…

Pathogenic mitochondrial mt-tRNA(Ala) variants are uniquely associated with isolated myopathy

Pathogenic mitochondrial DNA (mtDNA) point mutations are associated with a wide range of clinical phenotypes, often involving multiple organ systems. We report two patients with isolated myopathy owing to novel mt-tRNA(Ala) variants. Muscle biopsy revealed extensive histopathological findings includ...

Descripción completa

Detalles Bibliográficos
Autores principales: Lehmann, Diana, Schubert, Kathrin, Joshi, Pushpa R, Hardy, Steven A, Tuppen, Helen A L, Baty, Karen, Blakely, Emma L, Bamberg, Christian, Zierz, Stephan, Deschauer, Marcus, Taylor, Robert W
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4519577/
https://www.ncbi.nlm.nih.gov/pubmed/25873012
http://dx.doi.org/10.1038/ejhg.2015.73
Descripción
Sumario:Pathogenic mitochondrial DNA (mtDNA) point mutations are associated with a wide range of clinical phenotypes, often involving multiple organ systems. We report two patients with isolated myopathy owing to novel mt-tRNA(Ala) variants. Muscle biopsy revealed extensive histopathological findings including cytochrome c oxidase (COX)-deficient fibres. Pyrosequencing confirmed mtDNA heteroplasmy for both mutations (m.5631G>A and m.5610G>A) whilst single-muscle fibre segregation studies (revealing statistically significant higher mutation loads in COX-deficient fibres than in COX-positive fibres), hierarchical mutation segregation within patient tissues and decreased steady-state mt-tRNA(Ala) levels all provide compelling evidence of pathogenicity. Interestingly, both patients showed very high-mutation levels in all tissues, inferring that the threshold for impairment of oxidative phosphorylation, as evidenced by COX deficiency, appears to be extremely high for these mt-tRNA(Ala) variants. Previously described mt-tRNA(Ala) mutations are also associated with a pure myopathic phenotype and demonstrate very high mtDNA heteroplasmy thresholds, inferring at least some genotype:phenotype correlation for mutations within this particular mt-tRNA gene.