Mutation analysis of Connexin 31 (GJB3) in sporadic non‐syndromic hearing impairment

Abstract

Mutations in GJB3, the gene encoding the gap junction protein Connexin 31 (CX31), have been pathogenically linked to erythrokeratodermia and non-syndromic autosomal dominant (DFNA2) or recessive hereditary hearing impairment (HHI). To determine the contribution of CX31 to sporadic deafness, we assessed 63 individuals with non-syndromic hearing impairment for CX31 mutations. Single coding exon of CX31 was amplified from genomic DNA and then sequenced. Single nucleotide sequence alteration was present in 15 out of 63 patients (24%), all of the positives being heterozygous for the four different single base pair changes that were detected: C94T, C201T, C357T and C798T. Of these, only C94T transition, identified in two patients, results in amino acid change, R32W, while the other three changes are single nucleotide polymorphisms (SNPs). The R32W substitution in CX31 has been previously documented and is speculated to manifest variable penetrance, similar to the polymorphic allele encoding CX26M34T. Over one-third of all samples were also screened with denaturing high-performance liquid chromatography (dHPLC). Seven out of 25 individuals screened were determined to be positive for CX31 sequence variation. Sequence analysis of the 25 individuals screened identified nucleotide alterations in all of the 7 'positives' and in none of the 16 'negatives' yielding a specificity and sensitivity of 100%. Thus, dHPLC represents a highly efficient CX31 screening technique. This study suggests that while sequence alterations are common, pathogenic mutations of CX31 are infrequent in sporadic non-syndromic hearing impairment.

Coincidence of mutations in different connexin genes in Hungarian patients

“…The new c.357C>T, c.798C>T base changes were not the result of a change of amino acid and they were likely polymorphisms since they also occurred in the control population. The c.357C>T variant occured with an incidence of ~6% (controls) to 15% (patients), a frequency comparable to other studies (17,20). The SNP c.798C>T occured in 6% (patients) to 11% (controls) of all analyzed individuals, which also concurs with other research (20).…”

“…In several studies mutations within GJB3 were described which resulted in HI (5,17,20,41). In a family with palmoplantar keratoderma and various forms of HI, Kelsell and coworkers were the first to detect the p.R32W mutation which occurred in combination with two missense mutations in GJB2 (p.M34T and p.D66H) segregating with the skin disease (41).…”

“…The coding exon of GJB3 was sequenced using primers described elsewhere (16,17). Sequences were compared with the reference sequence (GenBank no.…”

Lack of association between Connexin 31 (GJB3) alterations and sensorineural deafness in Austria

“…Common alterations in genes associated with hearing impairment such as homozygous Cx26 mutations and the 12sRNA A1555G mutation were excluded in our first patient group. Mutations in Cx31 were found in approximately 37% of the hearing impaired population under study in an exclusively heterozygous pattern with a comparable frequency to other studies (LopezBigas et al, 2000;Mhatre et al, 2003). Our findings are in contrast to the population relevance in China.…”

<b>Three-dimensional reconstruction of root cells and interdental cells in the rat inner ear by serial section scanning electron micr</b><b>oscopy </b>

“…Since then, many researchers have been interested in the localization of connexin subtypes (e.g., connexin 26, 30, 31, and 43) in the inner ear (1,8,15,23,27). The existence of hearing loss diseases that are caused by mutations of these connexin genes also supports the critical importance of K + circulation through gap junctions in normal hearing (3,19,26,29). Because root cells and interdental cells are located at both ends of the epithelial cell gap junction system and are found in close proximity to the connective tissue gap junction system, these cells are considered to play an important role in K + circulation by delivering K + from the epithelial cell gap junction system to the connective tissue one.…”