Studying the Association between Sudden Hearing Loss and DNA N-Methyltransferase 1 (DNMT1) Genetic Polymorphism

The aim of the present study was to investigate whether there was any relationship between some DNA N-methyltransferase 1 (DNMT1) polymorphisms and susceptibility to idiopathic sudden sensorineural hearing loss (ISSHL) in ISSHL patients.

We investigated 90 patients diagnosed with ISSHL and a control group composed of 75 age- and gender-matched healthy individuals. DNA was extracted from the blood samples by phenol-chloroform method. Polymerase chain reaction and restriction fragment length polymorphism methods were used for the genotyping analysis of 4 regions of DNMT1.

For rs2228612 single nucleotide polymorphism (SNP), the frequency of AA, AG, and GG genotypes were 81.4%, 9.3%, and 9.3% in controls and 82.2%, 16.7%, and 1.1% in patients, respectively. We observed a significant decrease in the frequency of GG genotype in patients with ISSHL when compared with controls (p=0.027). The frequency of GG, AG, and AA genotypes for rs2228611 SNP were 20.7%, 49.3%, and 20% in controls and 20%, 47.8%, and 32.2% in patients, respectively. There was a significantly increased frequency of the AA genotype of this SNP in the DNMT1 gene, and we found that individuals with the AA genotype had 2.47 times the risk for ISSHL development than individuals with the GG genotype (p=0.41). The GAA haplotype may constitute 2.66 times the risk for ISSHL disease (OR=2.66, 95% confidence interval: 0.28-25.03).

This study's results showed that the AA genotype in rs2228611 polymorphism was a risk factor in ISSHL patients and the GG genotype could be a protective factor in rs2228612 polymorphism.