Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome
Por:
Emperador S, Garrido-Pérez N, Amezcua-Gil J, Gaudó P, Andrés-Sanz JA, Yubero-Siles D, Fernández-Marmiesse A, O'Callaghan-Gordo M, Ortigoza-Escobar JD, Iriondo-Sanz M, Ruiz-Pesini E, Garcia-Cazorla A, Gil-Campos M, Artuch-Iriberri R, Montoya C and Bayona-Bafaluy MP
Publicada:
8 ene 2020
Ahead of Print:
8 ene 2020
Resumen:
Encephalomyopathic mitochondrial DNA (mtDNA) depletion syndrome 13 (MTDPS13) is a rare genetic disorder caused by defects in F-box leucine-rich repeat protein 4 (FBXL4). Although FBXL4 is essential for the bioenergetic homeostasis of the cell, the precise role of the protein remains unknown. In this study, we report two cases of unrelated patients presenting in the neonatal period with hyperlactacidemia and generalized hypotonia. Severe mtDNA depletion was detected in muscle biopsy in both patients. Genetic analysis showed one patient as having in compound heterozygosis a splice site variant c.858+5G>C and a missense variant c.1510T>C (p.Cys504Arg) in FBXL4. The second patient harbored a frameshift novel variant c.851delC (p.Pro284LeufsTer7) in homozygosis. To validate the pathogenicity of these variants, molecular and biochemical analyses were performed using skin-derived fibroblasts. We observed that the mtDNA depletion was less severe in fibroblasts than in muscle. Interestingly, the cells harboring a nonsense variant in homozygosis showed normal mtDNA copy number. Both patient fibroblasts, however, demonstrated reduced mitochondrial transcript quantity leading to diminished steady state levels of respiratory complex subunits, decreased respiratory complex IV (CIV) activity, and finally, low mitochondrial ATP levels. Both patients also revealed citrate synthase deficiency. Genetic complementation assays established that the deficient phenotype was rescued by the canonical version of FBXL4, confirming the pathological nature of the variants. Further analysis of fibroblasts allowed to establish that increased mitochondrial mass, mitochondrial fragmentation, and augmented autophagy are associated with FBXL4 deficiency in cells, but are probably secondary to a primary metabolic defect affecting oxidative phosphorylation.
Filiaciones:
Emperador S:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, Spain
Fundación ARAID, Universidad de Zaragoza, Zaragoza, Spain
Garrido-Pérez N:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, Spain
Fundación ARAID, Universidad de Zaragoza, Zaragoza, Spain
Amezcua-Gil J:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Gaudó P:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Andrés-Sanz JA:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Yubero-Siles D:
Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Fernández-Marmiesse A:
Genomes&Disease Group, Molecular Medicine and Chronic Diseases Research Centre (CiMUS), Santiago de Compostela University-IDIS, Santiago de Compostela, Spain
O'Callaghan-Gordo M:
Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Ortigoza-Escobar JD:
Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Iriondo-Sanz M:
Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Ruiz-Pesini E:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, Spain
Fundación ARAID, Universidad de Zaragoza, Zaragoza, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Garcia-Cazorla A:
Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Gil-Campos M:
Metabolism Unit, Reina Sofia University Clinical Hospital, Institute Maimónides of Biomedicine Investigation of Córdoba (IMIBIC), University of Córdoba, Córdoba, Spain
CIBEROBN (Physiopathology of Obesity and Nutrition CB12/03/30038), Madrid, Spain
Artuch-Iriberri R:
Clinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Montoya C:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
Bayona-Bafaluy MP:
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
Instituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, Spain
Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, Spain
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