Background: The most common form of nonsyndromic neurosensory autosomal recessive deafness, DFNB1, is caused by mutations in the connexin 26 gene (GJB2) on chromosome 13. One mutation, in which one guanosine (G) residue is deleted from a run of 6 Gs (35delG), is found in 40% to 70% of DFNB1 cases and has an expected population frequency of one in 40 to one in 100.
Methods and results: Polymerase chain reaction (PCR)-based tests for the 35delG mutation were developed. They are based on mismatched PCR primers that produce novel EcoRII or DdeI restriction enzyme sites depending on the number of Gs at the 35delG locus. An EcoRII site is generated in the wild-type sequence (6 Gs), but not when the 35delG mutation is present. Alternatively, a DdeI site can be generated so that this enzyme cuts the PCR product when the 35delG mutation is present, but not the wild-type sequence.
Conclusions: These tests enable a quick and reliable screen for the common 35delG mutation.