title: Mitochondrial dysfunction in an Opa1(Q285STOP) mouse model of dominant optic atrophy results from Opa1 haploinsufficiency.
abstract: Mutations in the opa1 (optic atrophy 1) gene lead to autosomal dominant optic atrophy (ADOA), a hereditary eye disease. This gene encodes the Opa1 protein, a mitochondrial dynamin-related GTPase required for mitochondrial fusion and the maintenance of normal crista structure. The majority of opa1 mutations encode truncated forms of the protein, lacking a complete GTPase domain. It is unclear whether the phenotype results from haploinsufficiency or rather a deleterious effect of truncated Opa1 protein. We studied a heterozygous Opa1 mutant mouse carrying a defective allele with a stop codon in the beginning of the GTPase domain at residue 285, a mutation that mimics human pathological mutations. Using an antibody raised against an N-terminal portion of Opa1, we found that the level of wild-type protein was decreased in the mutant mice, as predicted. However, no truncated Opa1 protein was expressed. In embryonic fibroblasts isolated from the mutant mice, this partial loss of Opa1 caused mitochondrial respiratory deficiency and a selective loss of respiratory Complex IV subunits. Furthermore, partial Opa1 deficiency resulted in a substantial resistance to endoplasmic reticulum stress-induced death. On the other hand, the enforced expression of truncated Opa1 protein in cells containing normal levels of wild-type protein did not cause mitochondrial defects. Moreover, cells expressing the truncated Opa1 protein showed reduced Bax activation in response to apoptotic stimuli. Taken together, our results exclude deleterious dominant-negative or gain-of-function mechanisms for this type of Opa1 mutation and affirm haploinsufficiency as the mechanism underlying mitochondrial dysfunction in ADOA.
authors.affiliation: Immune Regulation, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Kushnareva
authors.affiliation: Immune Regulation, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Seong
authors.affiliation: Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: A Y
authors.initials: AY
authors.lastname: Andreyev
authors.affiliation: Immune Regulation, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kuwana
authors.affiliation: Immune Regulation, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
authors.forename: W B
authors.initials: WB
authors.lastname: Kiosses
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, Cardiff CF24 4LU, UK.|Cardiff Eye Unit, University Hospital Wales, Cardiff CF14 4XW, UK.
authors.forename: M
authors.initials: M
authors.lastname: Votruba
authors.affiliation: Immune Regulation, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
authors.forename: D D
authors.initials: DD
authors.lastname: Newmeyer
mesh_terms: D000483:Alleles; D000818:Animals; D030401:Cytochrome-c Oxidase Deficiency / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D003576:Electron Transport Complex IV / Q000235:genetics* / Q000378:metabolism; D004622:Embryo, Mammalian; D059865:Endoplasmic Reticulum Stress / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D020558:GTP Phosphohydrolases / Q000172:deficiency / Q000235:genetics*; D005786:Gene Expression Regulation; D057895:Haploinsufficiency; D006367:HeLa Cells; D006579:Heterozygote; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D029241:Optic Atrophy, Autosomal Dominant / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D061251:Primary Cell Culture; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C494827:Bax protein, mouse; D051028:bcl-2-Associated X Protein; D003576:Electron Transport Complex IV; D020558:GTP Phosphohydrolases; C498809:Opa1 protein, mouse