Functional Testing of SLC26A4 Variants—Clinical and Molecular Analysis of a Cohort with Enlarged Vestibular Aqueduct from Austria

Abstract

The prevalence and spectrum of sequence alterations in the <i>SLC26A4</i> gene, which codes for the anion exchanger pendrin, are population-specific and account for at least 50% of cases of non-syndromic hearing loss associated with an enlarged vestibular aqueduct. A cohort of nineteen patients from Austria with hearing loss and a radiological alteration of the vestibular aqueduct underwent Sanger sequencing of <i>SLC26A4</i> and <i>GJB2</i>, coding for connexin 26. The pathogenicity of sequence alterations detected was assessed by determining ion transport and molecular features of the corresponding SLC26A4 protein variants. In this group, four uncharacterized sequence alterations within the <i>SLC26A4</i> coding region were found. Three of these lead to protein variants with abnormal functional and molecular features, while one should be considered with no pathogenic potential. Pathogenic <i>SLC26A4</i> sequence alterations were only found in 12% of patients. <i>SLC26A4</i> sequence alterations commonly found in other Caucasian populations were not detected. This survey represents the first study on the prevalence and spectrum of <i>SLC26A4</i> sequence alterations in an Austrian cohort and further suggests that genetic testing should always be integrated with functional characterization and determination of the molecular features of protein variants in order to unequivocally identify or exclude a causal link between genotype and phenotype.