title: NDUFA4 mutations underlie dysfunction of a cytochrome c oxidase subunit linked to human neurological disease.
abstract: The molecular basis of cytochrome c oxidase (COX, complex IV) deficiency remains genetically undetermined in many cases. Homozygosity mapping and whole-exome sequencing were performed in a consanguineous pedigree with isolated COX deficiency linked to a Leigh syndrome neurological phenotype. Unexpectedly, affected individuals harbored homozygous splice donor site mutations in NDUFA4, a gene previously assigned to encode a mitochondrial respiratory chain complex I (NADH:ubiquinone oxidoreductase) subunit. Western blot analysis of denaturing gels and immunocytochemistry revealed undetectable steady-state NDUFA4 protein levels, indicating that the mutation causes a loss-of-function effect in the homozygous state. Analysis of one- and two-dimensional blue-native polyacrylamide gels confirmed an interaction between NDUFA4 and the COX enzyme complex in control muscle, whereas the COX enzyme complex without NDUFA4 was detectable with no abnormal subassemblies in patient muscle. These observations support recent work in cell lines suggesting that NDUFA4 is an additional COX subunit and demonstrate that NDUFA4 mutations cause human disease. Our findings support reassignment of the NDUFA4 protein to complex IV and suggest that patients with unexplained COX deficiency should be screened for NDUFA4 mutations.
authors.affiliation: MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK.
authors.forename: Robert D S
authors.initials: RD
authors.lastname: Pitceathly
authors.forename: Shamima
authors.initials: S
authors.lastname: Rahman
authors.forename: Yehani
authors.initials: Y
authors.lastname: Wedatilake
authors.forename: James M
authors.initials: JM
authors.lastname: Polke
authors.forename: Sebahattin
authors.initials: S
authors.lastname: Cirak
authors.forename: A Reghan
authors.initials: AR
authors.lastname: Foley
authors.forename: Anna
authors.initials: A
authors.lastname: Sailer
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Hurles
authors.forename: Jim
authors.initials: J
authors.lastname: Stalker
authors.forename: Iain
authors.initials: I
authors.lastname: Hargreaves
authors.forename: Cathy E
authors.initials: CE
authors.lastname: Woodward
authors.forename: Mary G
authors.initials: MG
authors.lastname: Sweeney
authors.forename: Francesco
authors.initials: F
authors.lastname: Muntoni
authors.forename: Henry
authors.initials: H
authors.lastname: Houlden
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Taanman
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hanna
mesh_terms: D020121:5' Untranslated Regions; D001483:Base Sequence; D015153:Blotting, Western; D019295:Computational Biology; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D059472:Exome; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree
chemical_list: D020121:5' Untranslated Regions; D003576:Electron Transport Complex IV; C577147:NDUFA4 protein, human