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Del Dotto, V.* ; Ullah, F.* ; Di Meo, I.* ; Magini, P.* ; Gusic, M. ; Maresca, A.* ; Caporali, L.* ; Palombo, F.* ; Tagliavini, F.* ; Baugh, E.H.* ; Macao, B.* ; Szilagyi, Z.* ; Peron, C.* ; Gustafson, M.A.* ; Khan, K.* ; La Morgia, C.* ; Barboni, P.* ; Carbonelli, M.* ; Valentino, M.L.* ; Liguori, R.* ; Shashi, V.* ; Sullivan, J.* ; Nagaraj, S.* ; El-Dairi, M.* ; Iannaccone, A.* ; Cutcutache, I.* ; Bertini, E.* ; Carrozzo, R.* ; Emma, F.* ; Diomedi-Camassei, F.* ; Zanna, C.* ; Armstrong, M.* ; Page, M.* ; Stong, N.* ; Boesch, S.* ; Kopajtich, R. ; Wortmann, S.B. ; Sperl, W.* ; Davis, E.E.* ; Copeland, W.C.* ; Seri, M.* ; Falkenberg, M.* ; Prokisch, H. ; Katsanis, N.* ; Tiranti, V.* ; Pippucci, T.* ; Carelli, V.*

SSBP1 mutations cause mtDNA depletion underlying a complex optic atrophy disorder.

J. Clin. Invest. 130, 108-125 (2020)
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Inherited optic neuropathies include complex phenotypes, mostly driven by mitochondrial dysfunction. We report an optic atrophy spectrum disorder, including retinal macular dystrophy and kidney insufficiency leading to transplantation, associated with mitochondrial DNA (mtDNA) depletion without accumulation of multiple deletions. By whole-exome sequencing, we identified mutations affecting the mitochondrial single-strand binding protein (SSBP1) in 4 families with dominant and 1 with recessive inheritance. We show that SSBP1 mutations in patient-derived fibroblasts variably affect the amount of SSBP1 protein and alter multimer formation, but not the binding to ssDNA. SSBP1 mutations impaired mtDNA, nucleoids, and 7S-DNA amounts as well as mtDNA replication, affecting replisome machinery. The variable mtDNA depletion in cells was reflected in severity of mitochondrial dysfunction, including respiratory efficiency, OXPHOS subunits, and complex amount and assembly. mtDNA depletion and cytochrome c oxidase-negative cells were found ex vivo in biopsies of affected tissues, such as kidney and skeletal muscle. Reduced efficiency of mtDNA replication was also reproduced in vitro, confirming the pathogenic mechanism. Furthermore, ssbp1 suppression in zebrafish induced signs of nephropathy and reduced optic nerve size, the latter phenotype complemented by WT mRNA but not by SSBP1 mutant transcripts. This previously unrecognized disease of mtDNA maintenance implicates SSBP1 mutations as a cause of human pathology.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Bioenergetics ; Genetic Diseases ; Genetics ; Mitochondria ; Ophthalmology; Dna-binding Protein; Mitochondrial Transcription Factor; D-loop; Opa1; Gene; Replication; Deletions; Phosphorylation; Instability; Twinkle
ISSN (print) / ISBN 0021-9738
e-ISSN 1558-8238
Quellenangaben Volume: 130, Issue: 1, Pages: 108-125 Article Number: , Supplement: ,
Publisher American Society of Clinical Investigation
Publishing Place 2015 Manchester Rd, Ann Arbor, Mi 48104 Usa
Reviewing status