The role of gene GJB2 and connexin 26 in hearing impairment

Abstract

Gap Junction Beta 2 (GJB2) gene mutations are the leading causes of hereditary hearing impairment. This gene encodes various gap junction proteins such as connexin 26 (Cx26), which facilitate K + homeostasis inside the cochlea in the inner ear. It is as well identified in non-syndromic deafness, which is not accompanied with other abnormalities in the body and contributes to 75% of the cases. The protein connexin 26 is composed of four transmembrane helices and two extracellular loops, in which each has three specific, highly preserved, cysteine residues held by intramolecular disulfide bridges. Moreover, 35delG and Cys169Tyr are the most common mutations of GJB2, where the former results in a shortened Cx26 protein due to the termination of coding sequence, and the latter leads to a destabilized protein structure as one of the three cysteine residuals that are affected. This short review gives further insights on how these two types of mutations lead to hearing loss.