USH2A and Usher syndrome: Consistent with previous work25, 26, Usher Type I pedigrees were found to be predominantly (80%) caused by MYO7A mutations, while Usher Type II pedigrees were most commonly (74%) caused by mutations in USH2A. No causative mutations could be found in patients with atypical Usher syndrome, although two mutations were identified in the CLRN1 gene in a patient with type III Usher syndrome.