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Stem cell modeling of mitochondrial parkinsonism reveals key functions of OPA1
Author(s) -
Jonikas Mindaugas,
Madill Martin,
Mathy Alexandre,
Zekoll Theresa,
Zois Christos E.,
Wigfield Simon,
KurzawaAkanbi Marzena,
Browne Cathy,
Sims David,
Chinnery Patrick F.,
Cowley Sally A.,
Tofaris George K.
Publication year - 2018
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.25221
Subject(s) - haploinsufficiency , biology , induced pluripotent stem cell , mitochondrion , mitochondrial fusion , microbiology and biotechnology , atrophy , mitochondrial dna , parkinsonism , pink1 , pathology , genetics , apoptosis , mitophagy , phenotype , autophagy , medicine , disease , embryonic stem cell , gene
Objective Defective mitochondrial function attributed to optic atrophy 1 ( OPA1 ) mutations causes primarily optic atrophy and, less commonly, neurodegenerative syndromes. The pathomechanism by which OPA1 mutations trigger diffuse loss of neurons in some, but not all, patients is unknown. Here, we used a tractable induced pluripotent stem cell (iPSC)‐based model to capture the biology of OPA1 haploinsufficiency in cases presenting with classic eye disease versus syndromic parkinsonism. Methods iPSCs were generated from 2 patients with OPA1 haploinsufficiency and 2 controls and differentiated into dopaminergic neurons. Metabolic profile was determined by extracellular flux analysis, respiratory complex levels using immunoblotting, and complex I activity by a colorimetric assay. Mitochondria were examined by transmission electron microscopy. Mitochondrial DNA copy number and deletions were assayed using long‐range PCR. Mitochondrial membrane potential was measured by tetramethylrhodamine methyl ester uptake, and mitochondrial fragmentation was assessed by confocal microscopy. Exome sequencing was used to screen for pathogenic variants. Results OPA1 haploinsufficient iPSCs differentiated into dopaminergic neurons and exhibited marked reduction in OPA1 protein levels. Loss of OPA1 caused a late defect in oxidative phosphorylation, reduced complex I levels, and activity without a significant change in the ultrastructure of mitochondria. Loss of neurons in culture recapitulated dopaminergic degeneration in syndromic disease and correlated with mitochondrial fragmentation. Interpretation OPA1 levels maintain oxidative phosphorylation in iPSC‐derived neurons, at least in part, by regulating the stability of complex I. Severity of OPA1 disease associates primarily with the extent of OPA1‐mediated fusion, suggesting that activation of this mechanism or identification of its genetic modifiers may have therapeutic or prognostic value. Ann Neurol 2018;83:915–925