RESUMO
OBJECTIVES: Mutations in connexin26 (GJB2) are one of the most frequent causes of prelingual hearing impairment. Several different types of one-base deletions in exon2 were the most common type of GJB2 mutation regardless of ethnicity, including 35delG in American-European populations, 235delC in Japanese population and 167delT in Ashkenazi Jewish population. Various types of one-base substitutions were also considered to be causative mutations of GJB2 associated hearing impairment. This article describes a rapid and high-throughput screening procedure for the detection of one-base deletion/substitution in GJB2 with less invasive sampling procedure in the implication for the clinical application. METHODS: 53 hearing-impaired children and 50 healthy controls were admitted to take part in this study program. DNA samples obtained from buccal swab were used to amplify the exon2 of GJB2, and single run with an automated sequencer was used to identify the one-base deletion. Single-base substitutions were also screened by primer-extension procedure with dye terminators. The presence of both types of mutations was confirmed by direct sequence of the GJB2 exon2. RESULTS: Two of 50 controls (4%) included one-base deletion in GJB2 as heterozygote. 14 of 53 hearing impaired cases (26.4%) contained deletion in GJB2 either as homozygote (five cases) or heterozygote (nine cases) form. Sequencing analysis of whole exon2 of GJB2 identified all these deletions as 235delC. Primer-extension analysis revealed additional mutations with single base substitutions in three cases with compound heterozygote with 235delC. CONCLUSIONS: Rapid screening procedure of GJB2 can be potentially useful for the identification of prelingual deafness.
