Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome
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...
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2020-01-01
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Online Access: | https://www.frontiersin.org/article/10.3389/fgene.2019.01300/full |
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language |
English |
format |
Article |
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DOAJ |
author |
Sonia Emperador Sonia Emperador Sonia Emperador Nuria Garrido-Pérez Nuria Garrido-Pérez Nuria Garrido-Pérez Javier Amezcua-Gil Paula Gaudó Julio Alberto Andrés-Sanz Delia Yubero Delia Yubero Ana Fernández-Marmiesse Maria M. O’Callaghan Maria M. O’Callaghan Juan D. Ortigoza-Escobar Juan D. Ortigoza-Escobar Marti Iriondo Marti Iriondo Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Angels García-Cazorla Angels García-Cazorla Mercedes Gil-Campos Mercedes Gil-Campos Rafael Artuch Rafael Artuch Julio Montoya Julio Montoya Julio Montoya María Pilar Bayona-Bafaluy María Pilar Bayona-Bafaluy María Pilar Bayona-Bafaluy |
spellingShingle |
Sonia Emperador Sonia Emperador Sonia Emperador Nuria Garrido-Pérez Nuria Garrido-Pérez Nuria Garrido-Pérez Javier Amezcua-Gil Paula Gaudó Julio Alberto Andrés-Sanz Delia Yubero Delia Yubero Ana Fernández-Marmiesse Maria M. O’Callaghan Maria M. O’Callaghan Juan D. Ortigoza-Escobar Juan D. Ortigoza-Escobar Marti Iriondo Marti Iriondo Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Angels García-Cazorla Angels García-Cazorla Mercedes Gil-Campos Mercedes Gil-Campos Rafael Artuch Rafael Artuch Julio Montoya Julio Montoya Julio Montoya María Pilar Bayona-Bafaluy María Pilar Bayona-Bafaluy María Pilar Bayona-Bafaluy Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome Frontiers in Genetics mitochondrial disease encephalomyopathic mtDNA depletion syndrome 13 F-box leucine-rich repeat protein 4 mitochondrial DNA mtDNA depletion mtDNA transcription |
author_facet |
Sonia Emperador Sonia Emperador Sonia Emperador Nuria Garrido-Pérez Nuria Garrido-Pérez Nuria Garrido-Pérez Javier Amezcua-Gil Paula Gaudó Julio Alberto Andrés-Sanz Delia Yubero Delia Yubero Ana Fernández-Marmiesse Maria M. O’Callaghan Maria M. O’Callaghan Juan D. Ortigoza-Escobar Juan D. Ortigoza-Escobar Marti Iriondo Marti Iriondo Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Eduardo Ruiz-Pesini Angels García-Cazorla Angels García-Cazorla Mercedes Gil-Campos Mercedes Gil-Campos Rafael Artuch Rafael Artuch Julio Montoya Julio Montoya Julio Montoya María Pilar Bayona-Bafaluy María Pilar Bayona-Bafaluy María Pilar Bayona-Bafaluy |
author_sort |
Sonia Emperador |
title |
Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome |
title_short |
Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome |
title_full |
Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome |
title_fullStr |
Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome |
title_full_unstemmed |
Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion Syndrome |
title_sort |
molecular characterization of new fbxl4 mutations in patients with mtdna depletion syndrome |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Genetics |
issn |
1664-8021 |
publishDate |
2020-01-01 |
description |
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. |
topic |
mitochondrial disease encephalomyopathic mtDNA depletion syndrome 13 F-box leucine-rich repeat protein 4 mitochondrial DNA mtDNA depletion mtDNA transcription |
url |
https://www.frontiersin.org/article/10.3389/fgene.2019.01300/full |
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doaj-3d23431fa04641679dcfda334d4bd9172020-11-25T02:03:46ZengFrontiers Media S.A.Frontiers in Genetics1664-80212020-01-011010.3389/fgene.2019.01300489485Molecular Characterization of New FBXL4 Mutations in Patients With mtDNA Depletion SyndromeSonia Emperador0Sonia Emperador1Sonia Emperador2Nuria Garrido-Pérez3Nuria Garrido-Pérez4Nuria Garrido-Pérez5Javier Amezcua-Gil6Paula Gaudó7Julio Alberto Andrés-Sanz8Delia Yubero9Delia Yubero10Ana Fernández-Marmiesse11Maria M. O’Callaghan12Maria M. O’Callaghan13Juan D. Ortigoza-Escobar14Juan D. Ortigoza-Escobar15Marti Iriondo16Marti Iriondo17Eduardo Ruiz-Pesini18Eduardo Ruiz-Pesini19Eduardo Ruiz-Pesini20Eduardo Ruiz-Pesini21Angels García-Cazorla22Angels García-Cazorla23Mercedes Gil-Campos24Mercedes Gil-Campos25Rafael Artuch26Rafael Artuch27Julio Montoya28Julio Montoya29Julio Montoya30María Pilar Bayona-Bafaluy31María Pilar Bayona-Bafaluy32María Pilar Bayona-Bafaluy33Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainInstituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, SpainFundación ARAID, Universidad de Zaragoza, Zaragoza, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainInstituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, SpainFundación ARAID, Universidad de Zaragoza, Zaragoza, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainClinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainGenomes&Disease Group, Molecular Medicine and Chronic Diseases Research Centre (CiMUS), Santiago de Compostela University—IDIS, Santiago de Compostela, SpainClinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainClinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainClinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainInstituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, SpainFundación ARAID, Universidad de Zaragoza, Zaragoza, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainClinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainMetabolism Unit, Reina Sofia University Clinical Hospital, Institute Maimónides of Biomedicine Investigation of Córdoba (IMIBIC), University of Córdoba, Córdoba, SpainCIBEROBN (Physiopathology of Obesity and Nutrition CB12/03/30038), Madrid, SpainClinical Biochemistry, Genetics, Pediatric Neurology and Neonatalogy Departments, Institut de Recerca Sant Joan de Déu, Barcelona, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainInstituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainDepartamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, SpainInstituto de Investigación Sanitaria de Aragón (IIS-Aragón), Zaragoza, SpainCentro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER), Madrid, SpainEncephalomyopathic 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.https://www.frontiersin.org/article/10.3389/fgene.2019.01300/fullmitochondrial diseaseencephalomyopathic mtDNA depletion syndrome 13F-box leucine-rich repeat protein 4mitochondrial DNAmtDNA depletionmtDNA transcription |