The rs6265 polymorphism might not affect the secretion of BDNF protein directedly

Abstract

Tinnitus is an auditory disorder with ringing, buzzing, and hissing of the ears. Tinnitus occurs by perceiving sounds without attribution of external sources and has various risk factors such as loss of hearing, anxiety, depression, and hypertension. While there is a wide range of factors contributing to tinnitus, the precise molecular mechanism is poorly appreciated. Recent studies on tinnitus evoked potential evidence for the contribution of neurological factors in the progress of tinnitus. Here we used PCR-RFLP to assess a single nucleotide polymorphism in Brain-Derived Neurotrophic Factor (BDNF), which substitutes valine 66 to methionine amino acid (known as the rs6265). The BDNF functions in the development of the inner ear and has a crucial role in the central auditory pathway. The rs6265 causes a functional missense mutation that inhibits the secretion of BDNF from the synapses. Here we tested 127 Iranian subjects from the city of Yazd (90 normal subjects and 37 patients) to analyze the rs6265 polymorphism in the BDNF gene. Our analysis found no association between the investigated polymorphism of the BDNF gene and the presence of tinnitus in Iranian patients. Further, we proposed a hypothesis that SORT1 and TRAF6 might facilitate the BDNF secretion, and this process might be independent of the rs6265 polymorphism. Therefore, this study indicates that other genetic factors may be relevant to the development of tinnitus disease.