Audiological profiles and gjb2, gjb6 mutations: A retrospective study on genetic and clinical data from 2003 to 2008

Abstract

In many world populations, mutations in the GJB2 gene (codifyng for Connexin 26) are the most common causes of autosomal recessive non-syndromic hearing loss and account for approximately 50% of cases. To date, more than 100 (dominant or recessive) mutations have been identified (The Connexin Deafness Homepage, 2009) and differences in frequency and distribution across the world are significant. In European and American Caucasian populations, the 35delG is the most common mutation found to account for nearly 70% of the pathological alleles. Mutations in the GJB6 gene (codifyng for Connexin 30) can co-occur in some cases (we refer to the 342-kb truncating deletion, named as GJB6-D13S1830)...... In accordance with the literature, all categories of HL were found. The severe-profound HL was predominant especially in T/T, T/NT forms. The 35delG is the most common mutation that we found, especially in profound hearing impairment. Mild-moderate HL was identified overall among NT/NT forms. Our findings confirm the importance of newborn screening, and the evaluation of genetic mutations to define genotype/phenotype correlation and clinical or audiological features useful to early diagnosis and improvement of therapeutic protocols

GJB2(Connexin 26) gene mutations among hearing-impaired persons in a Swedish cohort

“…In total, 19 persons (24%) in the present study were homozygotes for the 35delG mutation and among these 16 (84%) had a severe or profound hearing impairment. Furthermore, in an Italian study, Berto et al [12] showed that 80% of the homozygotes for CÂ35del had a severe or profound hearing impairment, hence the same result as in this study.…”

“…Several studies in Europe have shown a high rate of homozygous, compound heterozygous and heterozygous CÂ26 mutations and polymorphisms among hearing-impaired persons [12]. The frequencies of CÂ26 mutations and polymorphisms described on The Connexins and Deafness homepage (http:// davinci.crg.es/deafness) found among hearing-impaired persons in Europe varies between 30% and 50% in unselected populations [13,14].…”

Prevalence of Deafness‐Associated Connexin‐26 (GJB2) and Connexin‐30 (GJB6) Pathogenic Alleles in a Large Patient Cohort from Eastern Sicily

“…This suggests a lower involvement in Eastern Sicily of the c.−23+1G>A allele. Other studies highlighted percentages of this allele ranging from 2.89% to <1% (Cryns et al., ; Snoecks et al., ; Berto et al., ).…”

“…In our study, the HL of c.35delG homozygous patients was profound in 71.5% (20/28). In the past, this genotype was associated with a profound HL in 65.79% and 64% of patients (Snoeckx et al., ; Berto et al., ). Our findings overlap those obtained by Martines et al (), who found HL in 75% of patients homozygous for the c.35delG allele.…”

The role of gene GJB2 and connexin 26 in hearing impairment

“…This generates deploarization, which opens Ca 2+ channels. When calcium enters, neurotransmitters are realeased onto the afferent nerve [9] A B lating K + homeostasis during the normal function of hearing process, and which its mutations are responsible for most deafness cases [7]. Moreover, gap junction beta 2 is found in the long arms of chromosome 13 in positions 11 and 12, and has a length of 5.5 kilobases.…”