Identification of a p.R143Q dominant mutation in the gap junction beta-2 gene in three Chinese patients with different hearing phenotypes

Prelingual Sensorineural Hearing Loss Caused by a Novel GJB2 Dominant Mutation in a Chinese Family

Background

GJB2 mutation is the most common cause of genetic deafness. Many pathogenic variations have already been identified, and thus, fewer and fewer novel pathogenic variations remain to be identified. Here, we describe a novel pathogenic variation associated with dominant hereditary deafness in a Chinese family.

Methods

In this study, we examined four generations of a Chinese family (M127) with hearing loss. Temporal CT scan, complete physical examination (including skin and hair), and audiological tests were performed. Targeted next-generation and Sanger sequencing were used to identify pathogenic mutations in affected individuals.

Results

All patients exhibited prelingual nonsyndromic sensorineural hearing loss, with severity ranging from moderate to severe. A novel dominant pathogenic variant c.205T > C (p.Phe69Leu) was identified in all patients in this family.

Conclusions

c.205T > C (p.Phe69Leu) was identified as a novel dominant pathogenic variant of GJB2 associated with prelingual nonsyndromic sensorineural hearing loss.GJB2 mutation is the most common cause of genetic deafness. Many pathogenic variations have already been identified, and thus, fewer and fewer novel pathogenic variations remain to be identified. Here, we describe a novel pathogenic variation associated with dominant hereditary deafness in a Chinese family.

Frequency of GJB2 mutations, GJB6-D13S1830 and GJB6-D13S1854 deletions among patients with non-syndromic hearing loss from the central region of Iran

Background

In the present study, we investigate the prevalence of the GJB2 gene mutations, and deletions in the GJB6 gene, namely del (GJB6‐D13S1830) and del (GJB6‐D13S1854), in patients with autosomal recessive non‐syndromic hearing loss (ARNSHL) from the central region of Iran.

Methods

One hundred and thirty‐one unrelated ARNSHL cases from the central part of Iran were recruited. Among them, 81% (106 cases) had at least two affected relatives. Coding and noncoding regions of the GJB2 gene were sequenced. Multiplex PCR was used for analysis of del (GJB6‐D13S1830) and del (GJB6‐D13S1854) deletions in GJB6.

Results

The GJB2 variants were found in 16.79% (22/131) of the patients. The pathogenic variants were 21/131 (16.03%). The nonpathogenic variants were 1/131 (0. 07%). Allele frequency of the c.35delG as the pathogenic variant was the most common with 59.52% (25/42). The remaining pathogenic variants were c.235delC, p.T8M, p.R32H, p.R143Q, p.R143W, c‐23+1G>A. The only nonpathogenic variant was polymorphism p.V27I. Further segregation analysis showed that variant of p.R143Q might have incomplete penetrance. None of the patients had targeted deletions in the GJB6 gene.

Conclusion

In comparison with reports from other areas of Iran, c.35delG demonstrates the highest frequency within the central region (accounting for 57.14% of cases), probably resulting from the founder effect and consanguineous marriage. The pathology of ARNSHL in such patients could be attributed to defects in Connexin 26 encoded by GJB2.

R75Q de novo dominant mutation of GJB2 in a Chinese family with hearing loss and palmoplantar keratoderma

OBJECTIVES

Mutations in the GJB2 gene encoding connexin 26 (Cx26) are major causes of hereditary deafness. This study aimed to characterize the mutation profiles of the GJB2 gene in a Chinese family with sensorineural hearing loss.

METHODS

A Chinese family that included three individuals with sensorineural hearing loss and palmoplantar keratoderma underwent complete physical examinations, audiological examinations including pure tone audiometry and auditory brainstem response, skin pathological examination, and temporal CT scans. The entire coding region of GJB2, GJB3, GJB6, and the coding exons (exon7+8 and 19) of SLC26A4, mitochondrial 12SrRNA, and tRNA Ser (UCN) were sequenced. Structural analysis was performed to detect the effects of mutation on the tertiary structure of Cx26.

RESULTS

A dominant GJB2 mutation, c.224G>A (p.Arg75Gln, p.R75Q), was detected in the family. No other mutation was identified in GJB2, GJB3, GJB6, or the coding exons (exon7+8 and 19) of SLC26A4, mitochondrial 12SrRNA, and tRNA Ser (UCN). Structural analysis revealed that the p.R75Q mutation likely affects the structural stability and permeation properties of the Cx26 gap junction channel.

CONCLUSION

Our findings provide further evidence of a correlation between the p.R75Q mutation in Cx26 and a syndromic hearing impairment with palmoplantar keratoderma.

Compound heterozygosity for dominant and recessive GJB2 mutations in a Tunisian family and association with successful cochlear implant outcome

OBJECTIVES

Mutations of GJB2 encoding connexin 26 are the most common cause of hearing loss. They are responsible for up to 50% of ARNSHL. The pathogenic mutations in this gene are generally inherited recessively. Dominant mutations in GJB2 also cause hearing loss, either in isolated non-syndromic form or as part of a syndrome associated with various skin disorders.

METHODS

We screened a Tunisian child affected by congenital, bilateral, profound, sensorineural hearing loss for mutations in GJB2 gene using PCR and direct sequencing.

RESULTS

The proband was found to be compound heterozygous for recessive and dominant GJB2 mutations respectively p.V37I (c.109G > A) and p.R143Q (c.428G > A). Surprisingly the hearing mother is a carrier for this dominant GJB2 mutation. This proband underwent a cochlear implant at four years old. The evaluation using APCEI and IT-MAIS tests at six months post implantation indicates a successful cochlear implant outcome since the deaf child began to acquire language abilities and auditory sensation.

CONCLUSIONS

The p.R143Q mutation was described for the first time in Tunisia. We confirm the low penetrance of this mutation since the proband mother is a carrier despite her normal hearing. We show the effectiveness of cochlear implant to restore the communication abilities and auditory sensation for our patient.