Julie M Schultz, Rashid Bhatti, Anne C Madeo, Amy Turriff, Julie A Muskett, Christopher K Zalewski, Kelly A King, Zubair M Ahmed, Saima Riazuddin, Nazir Ahmad, Zawar Hussain, Muhammad Qasim, Shaheen N Kahn, Meira R Meltzer, Xue Z Liu, Murali Munisamy, Manju Ghosh, Heidi L Rehm, Ekaterini T Tsilou, Andrew J Griffith, Wadih M Zein, Carmen C Brewer, Riazuddin, Thomas B Friedman

Recessive mutant alleles of MYO7A, USH1C, CDH23, and PCDH15 cause non-syndromic deafness or type 1 Usher syndrome (USH1) characterised by deafness, vestibular areflexia, and vision loss due to retinitis pigmentosa. For CDH23, encoding cadherin 23, non-syndromic DFNB12 deafness is associated primarily with missense mutations hypothesised to have residual function. In contrast, homozygous nonsense, frame shift, splice site, and some missense mutations of CDH23, all of which are presumably functional null alleles, cause USH1D. The phenotype of a CDH23 compound heterozygote for a DFNB12 allele in trans configuration to an USH1D allele is not known and cannot be predicted from current understanding of cadherin 23 function in the retina and vestibular labyrinth.