Usher syndrome type I can be caused by mutations in any one of several different genes: "CDH23, MYO7A, PCDH15, USH1C" and "USH1G". These genes function in the development and maintenance of inner ear structures such as hair cells (stereocilia), which transmit sound and motion signals to the brain. Alterations in these genes can cause an inability to maintain balance (vestibular dysfunction) and hearing loss. The genes also play a role in the development and stability of the retina by influencing the structure and function of both the rod photoreceptor cells and supporting cells called the retinal pigmented epithelium. Mutations that affect the normal function of these genes can result in retinitis pigmentosa and resultant vision loss.