[Study of a mutation in connexin 26 gene associated with congenital sensorineural deafness]

So far, at least 39 deafness gene loci have been mapped in human chromosome including the connexin 26 gene coding for a gap-junction protein. This gene is thought to be linked to hereditary non-syndromic sensorineural hearing loss. About 80% of cases of DFNB1 hereditary deafness carry a 30 mer G mutation of connexin 26.

To investigate this relationship, we obtained DNA samples from 15 cases with autosomal recessive and autosomal dominant forms of non-syndromic deafness. In addition, DNA samples were obtained from 252 unrelated subjects with sporadic hearing loss; parents of these subjects were symptom free. We analyzed the coding region for the connexin 26 gene for mutation using PCR-SSCP and sequence analysis and PCR-mediated site-directed mutagensis.

We detected 46 mutations with SSCP. The PCR products that of 5 cases mutations had similar abnormalities in their electrophoresis bands were sequenced. Results from 2 cases of families with hereditary hearing loss and 3 cases of sporadic hearing loss had a G-to-A transversion at nucleotide 79. In addition, 2 cases sporadic hearing loss with 251 delT and 233 delC were found, 35 delG was not detected in 46 cases abnormal PCR products using PSDM assay.

High mutation rates were found in China deafness population of connexin 26 gene, but the mutation loci is different from those previously reported. Finding hot spot of connexin 26 gene mutation in China population is important for deafness etiologic diagnosis and affect genetic counseling.