Targeted Next-Generation Sequencing Facilitates Genetic Diagnosis and Provides Novel Pathogenetic Insights into Deafness with Enlarged Vestibular Aqueduct.

Enlarged vestibular aqueduct (EVA) is an inner-ear malformation associated with sensorineural hearing impairment. Most EVAs are associated with Pendred syndrome and nonsyndromic autosomal recessive deafness-4 (DFNB4), two autosomal-recessive disorders caused by mutations in SLC26A4. However, many EVA patients cannot have a confirmed diagnosis by screening common SLC26A4 mutations, constituting an enigma in genetic diagnosis. To enable comprehensive genetic examination and explore the etiologies of EVA, we designed a next-generation sequencing panel targeting the entire length of 3 Pendred syndrome/DFNB4 genes (SLC26A4, FOXI1, and KCNJ10) and exons of 10 other genes related to EVA and performed genetic testing in 50 EVA families without confirmative results on screening for SLC26A4 hotspots (c.919-2A>G and p.H723R). Bi-allelic SLC26A4 mutations were identified in 34 families and EYA1 mutations in two families, yielding a diagnostic rate of 72% (36 of 50). In addition, two variants were identified in KCNJ10 and FOXI1, but findings did not support the previous hypothesis that mutations in these two genes are probable contributors to EVA through recessive inheritance or digenic inheritance with SLC26A4. Of note, a large SLC26A4 deletion was confirmed in one step using our panel. These results show the utility of a next-generation sequencing-based panel to address EVA families by identifying various types of gene mutations with satisfactory diagnostic yields and provide novel insights into the pathogenesis of EVA.