Original Investigation

Human Genetics

, Volume 118, Issue 1, pp 29-34

First online:

Targeted disruption of mouse Coch provides functional evidence that DFNA9 hearing loss is not a COCH haploinsufficiency disorder

  • Tomoko MakishimaAffiliated withSection on Gene Structure and Function, National Institute on Deafness and Other Communication Disorders, National Institutes of Health
  • , Clara I. RodriguezAffiliated withCancer and Developmental Biology Laboratory, National Cancer Institute, National Institutes of Health
  • , Nahid G. RobertsonAffiliated withDepartment of Pathology, Brigham and Women’s Hospital and Harvard Medical School
  • , Cynthia C. MortonAffiliated withDepartment of Pathology, Brigham and Women’s Hospital and Harvard Medical School
  • , Colin L. StewartAffiliated withCancer and Developmental Biology Laboratory, National Cancer Institute, National Institutes of Health Email author 
  • , Andrew J. GriffithAffiliated withSection on Gene Structure and Function, National Institute on Deafness and Other Communication Disorders, National Institutes of HealthHearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health Email author 

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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-LacZΔneo 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.

Keywords

COCH Cochlin DFNA9 Deafness Hearing loss