title: Targeted disruption of mouse Coch provides functional evidence that DFNA9 hearing loss is not a COCH haploinsufficiency disorder.
abstract: Dominant progressive hearing loss and vestibular dysfunction DFNA9 is caused by mutations of the human COCH gene. COCH encodes cochlin, a highly abundant secreted protein of unknown function in the inner ear. Cochlin has an N-terminal LCCL domain followed by two vWA domains, and all known DFNA9 mutations are either missense substitutions or an amino acid deletion in the LCCL domain. Here, we have characterized the auditory phenotype associated with a genomic deletion of mouse Coch downstream of the LCCL domain. Homozygous Coch (-/-) mice express no detectable cochlin in the inner ear. Auditory brainstem responses to click and pure-tone stimuli (8, 16, 32 kHz) were indistinguishable among wild type and homozygous Coch (-/-) mice. A Coch-LacZDeltaneo reporter allele detected Coch mRNA expression in nonsensory epithelial and stromal regions of the cochlea and vestibular labyrinth. These data provide functional evidence that DFNA9 is probably not caused by COCH haploinsufficiency, but via a dominant negative or gain-of-function effect, in nonsensory regions of the inner ear.
authors.affiliation: Section on Gene Structure and Function, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD 20850, USA.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Makishima
authors.forename: Clara I
authors.initials: CI
authors.lastname: Rodriguez
authors.forename: Nahid G
authors.initials: NG
authors.lastname: Robertson
authors.forename: Cynthia C
authors.initials: CC
authors.lastname: Morton
authors.forename: Colin L
authors.initials: CL
authors.lastname: Stewart
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Griffith
mesh_terms: D000818:Animals; D001483:Base Sequence; D001933:Brain Stem / Q000503:physiopathology; D017931:DNA Primers; D016326:Extracellular Matrix Proteins; D034381:Hearing Loss / Q000235:genetics* / Q000503:physiopathology; D051379:Mice; D011506:Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C110668:COCH protein, human; C491729:Coch protein, mouse; D017931:DNA Primers; D016326:Extracellular Matrix Proteins; D011506:Proteins