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Zereg E, Chaussenot A, Morel G, Bannwarth S, Sacconi S, Soriani MH, Attarian S, Cano A, Pouget J, Bellance R, Tranchant C, Lannes B, de Paula AM, Saadi Ait-El-Mkadem S, Chafino B, Berthet M, Fragaki K, Paquis-Flucklinger V, Rouzier C. Single-fiber studies for assigning pathogenicity of eight mitochondrial DNA variants associated with mitochondrial diseases. Hum Mutat 2020; 41:1394-1406. [PMID: 32419253 DOI: 10.1002/humu.24037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/29/2020] [Accepted: 04/19/2020] [Indexed: 12/21/2022]
Abstract
Whole mitochondrial DNA (mtDNA) sequencing is now systematically used in clinical laboratories to screen patients with a phenotype suggestive of mitochondrial disease. Next Generation Sequencing (NGS) has significantly increased the number of identified pathogenic mtDNA variants. Simultaneously, the number of variants of unknown significance (VUS) has increased even more, thus challenging their interpretation. Correct classification of the variants' pathogenicity is essential for optimal patient management, including treatment and genetic counseling. Here, we used single muscle fiber studies to characterize eight heteroplasmic mtDNA variants, among which were three novel variants. By applying the pathogenicity scoring system, we classified four variants as "definitely pathogenic" (m.590A>G, m.9166T>C, m.12293G>A, and m.15958A>T). Two variants remain "possibly pathogenic" (m.4327T>C and m.5672T>C) but should these be reported in a different family, they would be reclassified as "definitely pathogenic." We also illustrate the contribution of single-fiber studies to the diagnostic approach in patients harboring pathogenic variants with low level heteroplasmy.
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Affiliation(s)
- Elamine Zereg
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Annabelle Chaussenot
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Godelieve Morel
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Sylvie Bannwarth
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Sabrina Sacconi
- Department of Clinical Neurosciences, Neuromuscular Diseases Centre, Nice Teaching Hospital, Nice, France
| | - Marie-Hélène Soriani
- Department of Clinical Neurosciences, Neuromuscular Diseases Centre, Nice Teaching Hospital, Nice, France
| | - Shahram Attarian
- Neurology Department, Referral Center for ALS and Neuromuscular Diseases, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Aline Cano
- Pediatric Neurology Department, Reference Center for Inherited Metabolic Diseases, Timone Hospital, Marseille, France
| | - Jean Pouget
- Neurology Department, Referral Center for ALS and Neuromuscular Diseases, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Rémi Bellance
- Neuromyology Department, Neuromuscular Reference Center, Fort-de-France Teaching Hospital, Fort-de-France, France
| | - Christine Tranchant
- Department of Movement Pathology, Strasbourg Teaching Hospital, Strasbourg, France
| | - Béatrice Lannes
- Pathology Department, Hôpitaux Universitaires de Strasbourg, Hôpital de Hautepierre, Strasbourg, France
| | - André Maues de Paula
- Pathology Department, Timone University Hospital, Aix-Marseille University, Marseille, France
| | - Samira Saadi Ait-El-Mkadem
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Bernadette Chafino
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Mathieu Berthet
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France
| | - Konstantina Fragaki
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Véronique Paquis-Flucklinger
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
| | - Cécile Rouzier
- Department of Medical Genetics, National Center for Mitochondrial Diseases, Nice Teaching Hospital, Nice, France.,Inserm U1081, CNRS UMR7284, IRCAN, Université Côte d'Azur, Nice, France
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