Molecular Genetic Analysis of Connexin 26 in Korean Congenital Hearing Loss

Abstract

BACKGROUND AND OBJECTIVES: Congenital deafness is a relatively common disorder and its' incidence is as high as 1 per every 1, 000 newborn infants. In developed countries, genetic hearing loss accounts for 50% of all hearing losses. A least 20 autosomal recessive loci had been identified, and in 1997, Connexin 26, one of the gap-junction proteins, was found to be the main mutant gene of non-syndromic congenital sensorineural hearing loss. The objective of this study is the investigation of the clinical features and characteristics of connexin 26 mutation in congenital deaf patients in Korea. MATERIALS AND METHODS: Fifty-one patients who have visited the out-patient department of Ajou University Hospital and 125 patients attending two special schools for deafness were physically examined. Family history of each patient was also examined. One hundred normal hearing infants who were audiologically approved were selected as a control group. With their blood samples, we performed DNA extraction and sequenced PCR products. RESULTS: Among 176 patients, 53 patients had family history of hearing impairment, and 16 patients actually showed syndromic features. We sequenced Connexin 26 in 121 patients who have congenital non-syndromic sensorineural hearing loss. Two heterozygotes of 35delG, three heterozygotes, four homozygotes of 235delC, 35 heterozygotes, and four homozygotes of E114G were observed. CONCLUSION: Family history of deafness was relatively common among the patients and therefore it was an important factor in deciding that hearing loss was due to genetic origin. Syndromic hearing loss occupies a relatively minor portion of congenital deafness. With regard to Connexin 26 mutation, 35delG is reported as the major gene mutation in the western countries, but in our study, only 2 patients had this type of mutation. Therefore, 235 delC. and E114G can be considered as race specific gene mutations, even though further studies are need.