USH2A

The USH2A gene encodes the protein usherin, which is associated with Usher syndrome, a condition characterized by hearing loss and progressive vision loss. Usher syndrome is the most common condition that affects both hearing and vision, and it is classified into three types: Usher syndrome type I, type II, and type III. The USH2A gene is primarily associated with Usher syndrome type II (USH2), which is the most common form of the syndrome.

Function

The USH2A gene provides instructions for making a protein called usherin. Usherin is found in the inner ear and the retina, which is the light-sensitive tissue at the back of the eye. In the inner ear, usherin is thought to be involved in the development and maintenance of hair cells, which are sensory cells that help process sound and maintain balance. In the retina, usherin is believed to play a role in the structure and function of photoreceptor cells, which are responsible for converting light into electrical signals that are interpreted by the brain as vision.

Genetic Mutations

Mutations in the USH2A gene can lead to the production of an abnormal usherin protein or prevent the production of any usherin protein. These mutations disrupt the function of hair cells in the inner ear and photoreceptor cells in the retina, leading to the characteristic symptoms of Usher syndrome type II. More than 400 mutations in the USH2A gene have been identified in people with Usher syndrome type II.

Clinical Significance

Individuals with Usher syndrome type II typically experience moderate to severe hearing loss from birth and progressive vision loss due to retinitis pigmentosa. The vision loss usually begins in adolescence or early adulthood and progresses over time. Unlike Usher syndrome type I, individuals with type II do not experience balance problems.

Diagnosis and Management

Diagnosis of Usher syndrome type II is based on clinical findings, audiological tests, and genetic testing to identify mutations in the USH2A gene. Management of the condition involves the use of hearing aids or cochlear implants to address hearing loss, and low vision aids and orientation and mobility training to assist with vision loss. Genetic counseling is recommended for affected individuals and their families.

Research and Future Directions

Research is ongoing to better understand the function of the USH2A gene and the mechanisms by which its mutations lead to Usher syndrome. Gene therapy and other molecular approaches are being explored as potential treatments to correct or compensate for the defective gene.

Also see

• Usher syndrome
• Retinitis pigmentosa
• Hearing loss
• Photoreceptor cells