Mutational analysis for GJB2, GJB6, and GJB3 genes in Campania within a universal neonatal hearing screening programme

OBJECTIVE: To determine the incidence of GJB2 and GJB3 mutations and of two deletions upstream of the GJB6 gene in infants of the Campania region of southern Italy. DESIGN: DNA samples from non-syndromic hearing-impaired infants enrolled in a neonatal screening programme for sensorineural hearing loss were analysed by PCR and by direct sequencing. The audiological features of infants with biallelic GJB2 mutations were also examined to identify genotype-phenotype correlations. STUDY SAMPLE: Molecular analyses were carried out in 129 affected and five unaffected infants. RESULTS: A genetic etiology of hearing loss was identified in 28% of infants, including several at environmental risk of hearing loss. Neither GJB6 nor GJB3 (a gene not previously investigated in the Campania population) mutations were found. CONCLUSIONS: This study confirms the importance of universal neonatal hearing screening. The identification of a genetic cause in infants at environmental risk indicates that such infants should be included when investigating etiology. We confirm that also in our geographical area, c.35delG homozygotes tend to have severe symmetrical hearing loss, whereas hearing impairment is milder in compound heterozygotes.