The STRC gene provides instructions for making a protein called stereocilin. This protein is found in the inner ear and appears to be involved in hearing.
Stereocilin is associated with hairlike structures called stereocilia, which project from specialized cells called hair cells in the inner ear. Specifically, stereocilin helps to maintain the structure of stereocilia by linking their tips to one another. Stereocilia bend in response to sound waves, triggering a series of reactions within hair cells that generate a nerve impulse. Such nerve impulses are transmitted via the auditory nerve to the brain, where they are interpreted as sound.
Researchers have identified a few STRC gene mutations in individuals 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 nonsyndromic hearing loss called DFNB16. This form of hearing loss can either be present before a child learns to speak (prelingual) or begin after a child learns to speak (postlingual). The hearing loss ranges from mild to profound and particularly affects the ability to hear high-frequency sounds.
The STRC gene mutations that cause nonsyndromic hearing loss add a small amount of DNA to the STRC gene or delete DNA from the gene. In many cases, the mutation deletes a piece of chromosome 15 that includes the entire STRC gene. Mutations in this gene lead to the production of a nonfunctional version of stereocilin or prevent any of this protein from being produced. A loss of functional stereocilin likely alters the structure of stereocilia, preventing them from reacting normally to sound waves. As a result, hair cells cannot convert sound into electrical impulses, which leads to hearing loss in people with DFNB16.
Sensorineural deafness and male infertility is a condition caused by a deletion of genetic material on the long (q) arm of chromosome 15. This condition is characterized by the combination of hearing loss and an inability to father children.
The chromosomal region that is typically deleted contains multiple genes, including the STRC gene. People with this condition have the deletion in both copies of chromosome 15 in each cell. As a result of the deletion, affected individuals are missing both copies of the STRC gene, and no stereocilin protein is produced. A lack of stereocilin likely interferes with the normal function of stereocilia and impairs how these structures respond to sound waves, resulting in hearing loss. The loss of another gene, CATSPER2, in the same region of chromosome 15 is responsible for infertility in affected males.
- deafness, autosomal recessive 16
- Biochemistry (fifth edition, 2002): Hair Cells Use a Connected Bundle of Stereocilia to Detect Tiny Motions
- Molecular Biology of the Cell (fourth edition, 2002): Auditory Hair Cells Have to Last a Lifetime
- Neuroscience (second edition, 2001): Hair Cells and the Mechanoelectrical Transduction of Sound Waves