CDH23

Several dozen mutations in the CDH23 gene have been identified in people with nonsyndromic hearing loss, which is loss of hearing that is not associated with other signs and symptoms. Mutations in this gene cause a form of hearing loss designated as DFNB12. This type of hearing loss begins before a child learns to speak (prelingual) and is severe to profound.

Most of the mutations that cause DFNB12 change single protein building blocks (amino acids) in cadherin 23. These mutations reduce but do not eliminate the function of this protein. The altered protein disrupts development of stereocilia in the inner ear, which leads to hearing loss.

Researchers speculate that some children with apparently nonsyndromic hearing loss caused by a CDH23 mutation may actually have Usher syndrome (described below). A few children thought to have DFNB12 have developed the vision disorder retinitis pigmentosa later in life, which is characteristic of Usher syndrome.

More than 60 mutations in the CDH23 gene can cause Usher syndrome type I, which is characterized by a combination of hearing loss, vision loss, and problems with balance and coordination. Specifically, CDH23 gene mutations cause a form of the disorder known as Usher syndrome type ID (USH1D).

Most of these mutations disrupt protein production, resulting in an abnormally small, nonfunctional version of cadherin 23 or preventing the production of any of this protein. Less frequently, mutations change single amino acids in cadherin 23. All of the CDH23 gene mutations that cause Usher syndrome appear to eliminate the function of cadherin 23. A lack of this protein in the inner ear disrupts the normal development and function of stereocilia, which leads to hearing loss and difficulty with balance and coordination. A lack of this protein in the retina causes retinitis pigmentosa, a condition in which light-sensing cells of the retina gradually deteriorate, resulting in progressive vision loss.

MedlinePlus Genetics provides information about Age-related hearing loss