A large deletion in GPR98 causes type IIC Usher syndrome in male and female members of an Iranian family

Background: Usher syndrome (USH) is a clinically and genetically heterogeneous disease. The three recognised clinical phenotypes (types I, II and III; USH1, USH2 and USH3) are caused by mutations in nine different genes. USH2C is characterised by moderate to severe hearing loss, retinitis pigmentosa and normal vestibular function. One earlier report describes mutations in GPR98 (VLGR1) in four families segregating this phenotype. Objective: To detect the disease-causing mutation in an Iranian family segregating USH2C. In this family, five members had a phenotype compatible with Usher syndrome, and two others had nonsyndromic hearing loss. Methods: Mutation analysis of all 90 coding exons of GPR98. Results: Consistent with these clinical findings, the five subjects with USH carried a haplotype linked to the USH2C locus, whereas the two subjects with nonsyndromic hearing loss did not. We identified a new mutation in GPR98 segregating with USH2C in this family. The mutation is a large deletion g. 371657_507673del of exons 84 and 85, presumably leading to a frameshift. Conclusions: A large GPR98 deletion of 136 017 bp segregates with USH2C in an Iranian family. To our knowledge, this is only the second report of a GPR98 mutation, and the first report on male subjects with USH2C and a GPR98 mutation.