BACKGROUND AND OBJECTIVE: Hearing loss is the most common sensory deficit in humans. The aim of this study was to clarify the genetic aetiology of nonsyndromic hearing loss in the Moravian-Silesian population of the Czech Republic. PATIENTS AND METHODS: This study included 200 patients (93 males, 107 females, mean age 16.9 years, ranging from 4 months to 62 years) with nonsyndromic sensorineural hearing loss. We screened all patients for mutations in GJB2 and the large deletion del(GJB6-D13S1830). We performed further screening for additional genes (SERPINB6, TMIE, COCH, ESPN, ACTG1, KCNQ4, and GJB3) with Sanger sequencing on a subset of patients that were negative for GJB2 mutations. RESULTS: We detected biallelic GJB2 mutations in 44 patients (22%). Among these patients, 63.6%, 9.1% and 2.3% exhibited homozygous c.35delG, p.Trp24*, and p.Met34Thr mutations, respectively. The remaining 25% of these patients exhibited compound heterozygous c.35delG, c.-23+1G>A, p.Trp24*, p.Val37Ile, p.Met34Thr, p.Leu90Pro, c.235delC, c.313_326del14, p.Ser139Asn, and p.Gly147Leu mutations. We found a monoallelic GJB2 mutation in 12 patients (6.6%). We found no pathogenic mutations in the other tested genes. Conclusions: One fifth of our cohort had deafness related to GJB2 mutations. The del(GJB6-D13S1830), SERPINB6, TMIE, COCH, ESPN, ACTG1, GJB3, and KCNQ4 mutations were infrequently associated with deafness in the Moravian-Silesian population. Therefore, we suggest that del(GJB6-D13S1830) testing should be performed only when patients with deafness carry the monoallelic GJB2 mutation.

Department of Epidemiology and Public Health Faculty of Medicine University of Ostrava Syllabova 19 703 00 Ostrava Zábřeh Czech Republic Department of Otorhinolaryngology Hospital of Havířov Dělnická 1132 24 736 01 Havířov Czech Republic

Department of Medical Biophysics Faculty of Medicine and Dentistry Palacky University Olomouc Hnevotinska 3 775 15 Olomouc Czech Republic

Department of Medical Genetics University Hospital Ostrava 17 listopadu 1790 708 52 Ostrava Czech Republic

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