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Novel biallelic mutations in POLG gene: large deletion and missense variant associated with PEO. Neurol Sci 2021; 42:4271-4280. [PMID: 34189666 DOI: 10.1007/s10072-021-05380-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 06/03/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Mitochondrial disorders are clinically heterogeneous diseases associated with impaired oxidative phosphorylation (OXPHOS) activity. POLG, which encodes the DNA polymerase-γ (Polγ) catalytic subunit, is the most commonly mutated nuclear gene associated with mitochondrial disorders. METHODS We carried out whole-exome sequencing (WES) to identify the gene associated with progressive external ophthalmoplegia (PEO). We then performed histopathological analyses, assessed mitochondrial biology, and executed functional studies to evaluate the potential pathogenicity of the identified genetic mutations. RESULTS Novel biallelic POLG mutations, including a large deletion mutation (exons 7-21) and a missense variant c.1796C>T (p.Thr599Ile) were detected in the proband. Histopathological analysis of a biopsied muscle sample from this patient revealed the presence of approximately 20% COX-negative fibers. Bioinformatics analyses confirmed that the detected mutations were pathogenic. Furthermore, levels of mitochondrial complex I, II, and IV subunit protein expressions were found to be decreased in the proband, and marked impairment of mitochondrial respiration was evident in cells harboring these mutations. CONCLUSION This study expands the spectrum of known POLG variants associated with PEO and advances current understanding regarding the structural and functional impacts of these mutations.
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Santacatterina F, Torresano L, Núñez-Salgado A, Esparza-Molto PB, Olive M, Gallardo E, García-Arumi E, Blazquez A, González-Quintana A, Martín MA, Cuezva JM. Different mitochondrial genetic defects exhibit the same protein signature of metabolism in skeletal muscle of PEO and MELAS patients: A role for oxidative stress. Free Radic Biol Med 2018; 126:235-248. [PMID: 30138712 DOI: 10.1016/j.freeradbiomed.2018.08.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 08/15/2018] [Accepted: 08/17/2018] [Indexed: 12/13/2022]
Abstract
A major challenge in mitochondrial diseases (MDs) is the identification of biomarkers that could inform of the mechanisms involved in the phenotypic expression of genetic defects. Herein, we have investigated the protein signature of metabolism and of the antioxidant response in muscle biopsies of clinically and genetically diagnosed patients with Progressive External Ophthalmoplegia due to single large-scale (PEO-sD) or multiple (PEO-mD) deletions of mtDNA and Mitochondrial Encephalopathy Lactic Acidosis and Stroke-like episode (MELAS) syndrome, and healthy donors. A high-throughput immunoassay technique that quantitates the expression of relevant proteins of glycolysis, glycogenolysis, pentose phosphate pathway, oxidative phosphorylation, pyruvate and fatty acid oxidation, tricarboxylic acid cycle and the antioxidant response in two large independent and retrospectively collected cohorts of PEO-sD, PEO-mD and MELAS patients revealed that despite the heterogeneity of the genetic alterations, the three MDs showed the same metabolic signatures in both cohorts of patients, which were highly divergent from those of healthy individuals. Linear Discriminant Analysis and Support Vector Machine classifier provided a minimum of four biomarkers to discriminate healthy from pathological samples. Regardless of the induction of a large number of enzymes involved in ameliorating oxidative stress, the down-regulation of mitochondrial superoxide dismutase (SOD2) and catalase expression favored the accumulation of oxidative damage in patients' proteins. Down-regulation of SOD2 and catalase expression in MD patients is not due to relevant changes in the availability of their mRNAs, suggesting that oxidative stress regulates the expression of the two enzymes post-transcriptionally. We suggest that SOD2 and catalase could provide specific targets to improve the detoxification of reactive oxygen species that affects muscle proteins in these patients.
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Affiliation(s)
- Fulvio Santacatterina
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain
| | - Laura Torresano
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain
| | - Alfonso Núñez-Salgado
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Spain
| | - Pau B Esparza-Molto
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain
| | - Montse Olive
- Servicio de Anatomía Patológica, Unidad Patología Neuromuscular, IDIBELL-Hospital Universitario de Bellvitge, Spain
| | - Eduard Gallardo
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Elena García-Arumi
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Laboratorio de Patología Mitocondrial y Neuromuscular, Área de Genética Clínica y Molecular, Hospital Universitari Vall d'Hebron Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Alberto Blazquez
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain; Laboratorio de Enfermedades Mitocondriales y Neuromusculares, Hospital Universitario, 12 de Octubre, Madrid, Spain
| | - Adrián González-Quintana
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain; Laboratorio de Enfermedades Mitocondriales y Neuromusculares, Hospital Universitario, 12 de Octubre, Madrid, Spain
| | - Miguel A Martín
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain; Laboratorio de Enfermedades Mitocondriales y Neuromusculares, Hospital Universitario, 12 de Octubre, Madrid, Spain
| | - José M Cuezva
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Spain; Instituto de Investigación Hospital, 12 de Octubre (i+12), Madrid, Spain.
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