title: A novel COCH mutation associated with autosomal dominant nonsyndromic hearing loss disrupts the structural stability of the vWFA2 domain.
abstract: Mutations in COCH have been associated with autosomal dominant nonsyndromic hearing loss (DFNA9) and are frequently accompanied by vestibular hypofunction. Here, we report identification of a novel missense mutation, p.F527C, located in the vWFA2 domain in members of a Korean family with late-onset and progressive hearing loss. To assess the molecular characteristics of this cochlin mutant, we constructed both wild-type and mutant cochlin constructs and transfected these into mammalian cell lines. Results of immunocytochemistry analysis demonstrated localization of the cochlin mutant in the endoplasmic reticulum/Golgi complex, whereas western blot analyses of cell lysates revealed that the mutant cochlin tends to form covalent complexes that are retained in the cell. Biochemical analyses of recombinant vWFA2 domain of cochlin carrying the p.F527C mutation revealed that the mutation increases propensity of the protein to form covalent disulfide-bonded dimers and affects the structural stability but not the collagen-affinity of the vWFA2 domain. We suggest that the instability of mutant cochlin is the major driving force for cochlin aggregation in the inner ear in DFNA9 patients carrying the COCH p.F527C mutation.
authors.affiliation: Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Hyun-Ju
authors.initials: HJ
authors.lastname: Cho
authors.affiliation: Soree Ear Clinics, Seoul, South Korea.
authors.forename: Hong-Joon
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: Maria
authors.initials: M
authors.lastname: Trexler
authors.affiliation: Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Hanka
authors.initials: H
authors.lastname: Venselaar
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, College of Medicine, Kyungpook National University, Daegu, South Korea.
authors.forename: Kyu Yup
authors.initials: KY
authors.lastname: Lee
authors.affiliation: Departments of Obstetrics, Gynecology and Reproductive Biology, Brigham & Women's Hospital, Harvard Medical School, Boston, Ma, USA.
authors.forename: Nahid G
authors.initials: NG
authors.lastname: Robertson
authors.affiliation: Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Jeong-In
authors.initials: JI
authors.lastname: Baek
authors.affiliation: School of Life Science and Biotechnology, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Beom Sik
authors.initials: BS
authors.lastname: Kang
authors.affiliation: Departments of Obstetrics, Gynecology and Reproductive Biology, Brigham & Women's Hospital, Harvard Medical School, Boston, Ma, USA.|Department of Pathology, Brigham & Women's Hospital, Harvard Medical School, Boston, Ma, USA.
authors.forename: Cynthia C
authors.initials: CC
authors.lastname: Morton
authors.affiliation: Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Gert
authors.initials: G
authors.lastname: Vriend
authors.affiliation: Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Patthy
authors.affiliation: Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Un-Kyung
authors.initials: UK
authors.lastname: Kim
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D002460:Cell Line; D004220:Disulfides; D007758:Ear, Inner / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000502:physiology*; D005260:Female; D005799:Genes, Dominant; D006056:Golgi Apparatus / Q000378:metabolism; D034381:Hearing Loss / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense; D010375:Pedigree; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: C110668:COCH protein, human; D004220:Disulfides; D016326:Extracellular Matrix Proteins