CDH23 and Usher syndrome: Mutations in the CDH23 gene were first identified in patients with Usher Syndrome (Bolz et al., 2001; Bork et al., 2001), which is a syndromic hearing loss (OMIM: 601067) The encoded protein cadherin 23 (CDH23) belongs to the cadherin superfamily, which constitutes a family of transmembrane proteins that mediate calcium-dependent cell-cell adhesion (Ramzan et al., 2020).