CHD7 and Usher syndrome: CHD7 gene mutations are the main cause of CHARGE syndrome,[13] and the CDH23 gene, which encodes otocadherin, plays an important role in the structure and function of hair cell stereocilia.[14] Mutations in the CDH23 gene can lead to non-syndromic hearing loss (NSHL) with only auditory manifestations or to Usher syndrome type 1D (USH1D) characterized by hearing loss, retinal pigment deposits, and vestibular dysfunction.