COCH

The COCH gene provides instructions for making a protein called cochlin. This protein is abundant in certain parts of the inner ear called the cochlea and the vestibular system. The cochlea is a snail-shaped structure that helps process sound, and the vestibular system consists of fluid-filled canals that help maintain the body's balance and orientation in space. Cochlin is exported from cells in the cochlea and vestibular system and becomes part of the extracellular matrix. The extracellular matrix is an intricate lattice that forms in the space between cells and provides structural support. Two regions of the cochlin protein, called the LCCL and vWFA domains, probably coordinate cochlin's interactions with other molecules in the extracellular matrix. These interactions are important in forming the extracellular matrix and keeping it organized. Although the exact role of cochlin remains unknown, it likely plays a role in the structure of the inner ear.

nonsyndromic deafness - caused by mutations in the COCH gene

Several COCH gene mutations have been identified in individuals with a form of nonsyndromic deafness (hearing loss without related signs and symptoms affecting other parts of the body) called DFNA9. These mutations either change or delete a protein building block (amino acid) used to make cochlin. Most of the reported COCH gene mutations affect the LCCL domain and probably impair cochlin's interactions with other molecules in the extracellular matrix. One mutation occurs outside the LCCL domain and likely affects cochlin's 3-dimensional shape.

It is not fully understood how COCH gene mutations lead to hearing loss and in some cases, problems with balance and orientation. The altered cochlin protein may fail to become part of the extracellular matrix due to impaired interactions with other molecules, or it may disrupt the organization of the extracellular matrix. Disturbing the extracellular matrix may cause structural changes in the inner ear that affect hearing and balance. Cochlin also appears to be part of abnormal deposits that form in the inner ear of people with DFNA9 deafness. These deposits may damage nerves that are critical for the hearing process.