DFNB1-associated deafness in Portuguese cochlear implant users: prevalence and impact on oral outcome.
OBJECTIVE
Hearing loss is a condition that interferes with the development of the child at a cognitive and language level. Therefore, early diagnosis of deafness is important for (re)habilitation, namely through the use of cochlear implant (CI). The present study aimed at screening CI Portuguese individuals for the presence of mutations in the genes GJB2 and GJB6 (DFNB1 locus), and searching a possible correlation between the genotype and the oral habilitation outcome following implantation.


METHODS
Our sample included 117 CI individuals implanted longer than 5 years. Sequencing of GJB2 entire coding region was first performed. The presence of deletions del(GJB6-D13S1830) and del(GJB6-D13S1854) was subsequently tested by multiplex PCR. To assess the oral outcome of these individuals, a global score is calculated through a formula that integrates the results of a battery of speech and audiological tests routinely used in ORL services. This global oral performance score was used to test whether individuals with DFNB1-associated deafness perform significantly better than individuals without DFNB1-associated deafness.


RESULTS
In 35% of the cases, deafness was clearly associated to DFNB1. The most common mutated allele was c.35delG (85%). Other variants have also been found, namely p.Gly130Ala, p.Asn206Ser, p.Val37Ile, p.Glu47X, p.Arg184Trp, p.Trp24X and the two common GJB6 deletions, del(GJB6-D13S1854) and del(GJB6-D13S1830), the last one identified for the first time in our population. Regarding the oral outcome, after testing the homogeneity of the two groups it could be observed that, in mean, the individuals with DFNB1-associated deafness perform significantly better (p=0.012) than the individuals without DFNB1-associated deafness.


CONCLUSIONS
This first screening of DFNB1 genes in the Portuguese CI population provides clear evidence of the high proportion of DFNB1-associated deafness amongst the Portuguese implanted individuals. DFNB1 status is significantly associated to higher oral performance scores, with DFNB1 individuals performing, on average, 6% better than the individuals without DFNB1-associated deafness.
Chora
Joana Rita Gaspar de Barros Martinho
JR
BioFIG, Center for Biodiversity, Functional and Integrative Genomics, University of Lisbon, C2, Faculty of Science of the University of Lisbon Campus, 1749-016 Lisbon, Portugal.
Matos
Tiago Daniel Morim
TD
Martins
Jorge Humberto Ferreira
JH
Alves
Marisa Costa
MC
Andrade
Susana Margarida Sousa
SM
Silva
Luis Filipe dos Santos
LF
Ribeiro
Carlos Alberto dos Reis
CA
Antunes
Marília Cristina de Sousa
MC
Fialho
Maria Graça Monteiro Azevedo
MG
Caria
Maria Helena de Figueiredo Ramos
MH
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D019929:Cochlear Implantation; D003054:Cochlear Implants; D015331:Cohort Studies; D000072259:Connexin 26; D000075302:Connexin 30; D017630:Connexins / Q000235:genetics*; D003638:Deafness / Q000235:genetics* / Q000628:therapy; D005260:Female; D006801:Humans; D007223:Infant; D007804:Language Development; D008297:Male; D009154:Mutation; D011174:Portugal; D015995:Prevalence; D013065:Speech Intelligibility; D013067:Speech Perception
D000075302:Connexin 30; D017630:Connexins; C000607042:GJB2 protein, human; C491020:GJB6 protein, human; D000072259:Connexin 26