A PCR-RFLP test for simultaneous detection of two single-nucleotide insertions in the Connexin-26 gene promoter.

Comparisons of Connexin-26 (GJB2) gene sequences available in the GenBank data base indicate the presence of a polymorphism in the promoter, but no easy method is available for the detection of this polymorphism. We have developed a PCR-RFLP test for simultaneous detection of two single nucleotide insertions (G and A) in the GJB2 promoter. The test is based on amplification of a 146-bp DNA fragment, which was digested with Mae I to detect the G insertion in the promoter. A similar digestion with Hinf I detects the A insertion. The test was validated using direct DNA sequencing of amplified DNA from 33 samples. After validation, we have used it to investigate DNA samples from 160 control subjects and 51 unrelated patients with nonsyndromic autosomal recessive deafness. All of the samples analyzed using the PCR test and DNA sequencing were found to contain both the G and A insertions in the GJB2 gene promoter. This PCR test will be useful in studying the prevalence of these two insertions in other populations.

A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) test to detect the common mutation (35delG) in the connexin-26 gene.

OBJECTIVE: To develop a polymerase chain reaction (PCR) based test for the detection of a common frame-shift mutation (35delG) in the connexin-26 (GJB2) gene, and to investigate the status of this mutation in Oman. METHOD: A PCR test, based on site-directed mutagenesis, was developed for the 35delG mutation. A mutagenesis primer generated an EcoN I site in a short (87 bp) DNA fragment amplified from the connexin-26 gene. The EcoN I site is generated only if the 35delG mutation is present. Thus, a restriction fragment length polymorphism (RFLP) analysis of the amplified DNA fragment with EcoN I allowed us to detect the 35delG mutation in the connexin 26 gene. RESULT: After validating the test using quality control DNA samples, which contained the 35delG mutation in either homozygous or heterozygous form, 120 healthy subjects and 35 unrelated Omani patients with nosyndromic autosomal recessive deafness (NARD), were screened for 35delG mutation. The mutation was not present in any individual tested. CONCLUSION: We have been able to develop a new PCR-RFLP test for detecting the 35delG common mutation in the connexin 26 gene. Our preliminary results from application of this test on a limited number of Omani patients indicate that the 35delG mutation may not be associated with NARD in Oman.