Spectrum and frequency of GJB2 mutations in a cohort of 264 Portuguese nonsyndromic sensorineural hearing loss patients

Abstract

Objective: To assess the spectrum and prevalence of mutations in the GJB2 gene in Portuguese nonsyndromic sensorineural hearing loss (NSSHL) patients. Design: Sequencing of the coding region, basal promoter, exon 1, and donor splice site of the GJB2 gene; screening for the presence of the two common GJB6 deletions. Study sample: A cohort of 264 Portuguese NSSHL patients. Results: At least one out of 21 different GJB2 variants was identified in 80 (30.2%) of the 264 patients analysed. Two mutant alleles were found in 53 (20%) of these probands, of which 83% (44/53) harboured at least one c.35delG allele. Twenty-seven (10.2%) of the probands harboured only one mutant allele. Subsequent analysis revealed that the GJB6 deletion del(GJB6-D13S1854) was present in at least 7.4% (2/27) of the patients carrying only one mutant GJB2 allele. Overall, one in five (55/264) of the patients were diagnosed as having DFNB1-related NSSHL, of which the vast majority (53/55) harboured only GJB2 mutations. Conclusions: This study provides clear demonstration that mutations in the GJB2 gene are an important cause of NSSHL in Portugal, thus representing a valuable indicator as regards therapeutical and rehabilitation options, as well as genetic counseling of these patients and their families.

Key Words::

• GJB2
• GJB6
• DFNB1
• connexin 26
• hearing loss
• hereditary
• genetic
• deafness
• mutation

Acknowledgements

The authors would like to thank the patients and their families for their collaboration to this investigation.

Declaration of interest: The authors report no declarations of interest. This study was supported by the Fundação para a Ciência e a Tecnologia POCTI/ESP/42078/2001, SFRH/BD/19988/2004, RIPD/SAU-ESP/63720/2005, and by the Secretariado Nacional de Reabilitação e Integração das Pessoas com Deficiência (Program CITE IV). Note that Maria do Céu Correia is presently retired.