87630 20210902121603.0 doi 10.3389/fgene.2019.01300 sideral 116071 ART-2020-116071 eng Emperador, Sonia Universidad de Zaragoza (orcid)0000-0001-5964-6138 Molecular characterization of new FBXL4 mutations in patients with mtDNA depletion syndrome 2020 Access copy available to the general public Unrestricted 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. info:eu-repo/grantAgreement/ES/DGA/B33-17R info:eu-repo/grantAgreement/ES/ISCIII/PI17-00021 info:eu-repo/grantAgreement/ES/ISCIII/PI17-00166 info:eu-repo/grantAgreement/ES/ISCIII-FIS/PI17-00109 info:eu-repo/semantics/openAccess by http://creativecommons.org/licenses/by/3.0/es/ 4.599 2020 GENETICS & HEREDITY 48 / 175 = 0.274 2020 Q2 T1 1.413 2020 Genetics 2020 Q2 Molecular Medicine 2020 Q2 Genetics (clinical) 2020 Q2 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Garrido-Pérez, Nuria Universidad de Zaragoza (orcid)0000-0003-0145-3020 Amezcua-Gil, Javier Universidad de Zaragoza (orcid)0000-0002-0432-0170 Gaudó, Paula Universidad de Zaragoza (orcid)0000-0002-9779-8826 Andrés-Sanz, Julio Alberto Yubero, Delia Fernández-Marmiesse, Ana O'Callaghan, Maria M Ortigoza-Escobar, Juan D. Iriondo, Marti Ruiz-Pesini, Eduardo Universidad de Zaragoza (orcid)0000-0002-0269-7337 García-Cazorla, Angels Gil-Campos, Mercedes Artuch, Rafael Montoya, Julio Universidad de Zaragoza (orcid)0000-0003-1770-6299 Bayona-Bafaluy, María Pilar Universidad de Zaragoza (orcid)0000-0002-8585-6371 1003 443 Universidad de Zaragoza Dpto. Anatom.Histolog.Humanas Area Histología 1002 060 Universidad de Zaragoza Dpto. Bioq.Biolog.Mol. Celular Área Bioquímica y Biolog.Mole. 10 (2020), 1300 1-10 Front. genet. Frontiers in Genetics 1664-8021 700789 http://zaguan.unizar.es/record/87630/files/texto_completo.pdf Versión publicada 97041 http://zaguan.unizar.es/record/87630/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:87630 articulos driver 2021-09-02-08:36:28 ARTICLE