USH2A and Usher syndrome: At least 9 causative genes have been found and identified to be responsible for Usher syndrome: Five for USH1 (MYO7A, USH1C, CDH23, PCDH15, and USH1G), three for USH2 (USH2A, ADGRV1, and WHRN) and one for USH3 (CLRN1).