The search of a genetic basis for noise-induced hearing loss (NIHL)

Abstract

Background and aim: Knowledge about the genetic factors responsible for noise-induced hearing loss (NIHL) is still limited. This study investigated whether genetic factors are associated or not to susceptibility to NIHL.

Subjects and methods: The family history and genotypes were studied for candidate genes in 107 individuals with NIHL, 44 with other causes of hearing impairment and 104 controls. Mutations frequently found among deaf individuals were investigated (35delG, 167delT in GJB2, Δ_rm;(GJB6- D13S1830), Δ_rm;(GJB6- D13S1854) in GJB6 and A1555G in MT-RNR1 genes); allelic and genotypic frequencies were also determined at the SNP rs877098 in DFNB1, of deletions of GSTM1 and GSTT1 and sequence variants in both MTRNR1 and MTTS1 genes, as well as mitochondrial haplogroups.

Results: When those with NIHL were compared with the control group, a significant increase was detected in the number of relatives affected by hearing impairment, of the genotype corresponding to the presence of both GSTM1 and GSTT1 enzymes and of cases with mitochondrial haplogroup L1.

Conclusion: The findings suggest effects of familial history of hearing loss, of GSTT1 and GSTM1 enzymes and of mitochondrial haplogroup L1 on the risk of NIHL. This study also described novel sequence variants of MTRNR1 and MTTS1 genes.

Keywords::

• Genetic susceptibility
• deafness genes
• mitochondrial mutations
• mitochondrial haplogroups

Acknowledgements

The collaboration of the bus drivers and the workers from the printing facility and the metallurgical plant is deeply acknowledged. We thank Dr Mara Gandara for referring patients, Claudia Blanes Angeli for helping with the statistical analysis, Martha Lima-Cozzo and all professionals from Centro de Estudos do Genoma Humano for technical support in DHPLC and sequencing analysis. We also thank the ‘Sindicato dos Motoristas e Trabalhadores em Transporte Rodoviário Urbano de São Paulo’ and CEREST/SP (‘Centro de Referência em Saúde do Trabalhador de São Paulo’) for allowing contact with subjects.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.