[Detection with restriction enzyme for mutation 233delC of the connexin26 gene]

Connexin26, a gap junction protein that spreads in the inner ear, is thought to be mainly responsible for nonsyndromic hereditary deafness. In the Caucasian population, 30delG is the most frequent mutation. 233delC is the most frequent, however, in the Japanese population. We studied 233delC mutations with restriction enzyme Apa I.

Subjects were 61 patients visiting the hospital between March 1997 and October 1999 suspected of hereditary deafness. All gave written informed consent for participation.

Genomic DNA was extracted from peripheral blood cells and amplified by polymerase chain reaction (PCR) using 1 set of primers targeting the connexin26 gene (nucleotide--36 to 256). After ethanol precipitation, the PCR product was digested by restriction enzyme Apa I and analyzed through agarose gel electrophoresis. The wild gene is digested by Apa I and appeared to be shorter than the original PCR product, i.e., judged to be normal.

Three patients had 233delC mutations--1 homozygous and 2 heterozygous. These mutant alleles were confirmed to have 233delC mutations by direct sequence.

In targeting the mutation 233delC of the connexin 26 gene, restriction enzyme Apa I appears to be the most useful and economic method.