Prevalence of the 35delG mutation in the GJB2 gene in two samples of non-syndromic deaf subjects from Chile

Abstract

Hearing loss is the most common inherited sensorial defi ciency in humans; about 1 in 1000 children suff er from severe or profound hearing loss at birth. Mutations in the GJB2 gene are the most common cause of prelingual, non-syndromic autosomal recessive deafness in many populations; the c.35delG mutation is the most common in Caucasian populations. The frequency of the c.35delG mutation was estimated in two samples of deaf patients from Santiago, Chile. Unrelated non-syndromic sensorioneural deaf patients were examined: Group 1 consisted of 47 unrelated individuals with neurosensory deafness referred to the Chilean Cochlear Implant Program; Group 2 included 66 school children with prelingual deafness attending special education institutions for deaf people. Individuals with profound to moderate isolated neurosensory hearing loss with unknown etiology were included. The presence of the c.35delG mutation was evaluated by the allele-specifi c polymerase chain reaction method (PCR), and in some cases it was confi rmed by direct DNA sequencing of the coding region of the GJB2 gene. Deaf relatives were present in 20.3% of the cases. We found 19.5% (22/113) patients with the c.35delG mutation, 6 of them homozygous; these rates are similar to frequencies found in other Latin American countries.

Predictive Value of GJB2 Mutation Status for Hearing Outcomes of Pediatric Cochlear Implantation

“…Additionally, the nonuniformity in molecular testing for a GJB2 mutation and the variance in the definition regarding GJB2 positivity may have contributed for these controversies. Because most patients who have a single-allele mutation are usually carriers and the presence of a single pathogenic allele does not explain the cause of deafness, 34 they may actually have other causes for their hearing loss, since carriers are more likely than noncarriers to develop hearing impairment in the presence of other genetic defects or environmental factors. 34,35 Biallelic GJB2 mutations, however, are generally less commonly accompanied by other causes.…”

“…Because most patients who have a single-allele mutation are usually carriers and the presence of a single pathogenic allele does not explain the cause of deafness, 34 they may actually have other causes for their hearing loss, since carriers are more likely than noncarriers to develop hearing impairment in the presence of other genetic defects or environmental factors. 34,35 Biallelic GJB2 mutations, however, are generally less commonly accompanied by other causes. Therefore, CI outcomes in patients with a monoallelic GJB2 mutation, which is more commonly accompanied by other genetic defects or environmental factors, would have more pronounced effects than those with biallelic GJB2 mutation.…”

Spectrum and Frequency of the GJB2 Gene Pathogenic Variants in a Large Cohort of Patients with Hearing Impairment Living in a Subarctic Region of Russia (the Sakha Republic)

“…Spectrum and allelic frequencies of the GJB2 gene vary significantly among different ethnic groups worldwide [ 3 , 4 ]. Currently, the regions of Europe [ 5 – 32 ], Asia [ 33 – 48 ], the Middle East [ 49 – 56 ], Central and North America [ 57 – 61 ], South America [ 62 – 69 ], Greenland [ 70 ], Australia [ 71 ], and some parts of Africa [ 72 – 81 ] have been characterized according to the pathogenic variant spectrum and frequency of the GJB2 gene. However, data regarding the molecular basis of HI in populations of Russia are scarce [ 7 , 16 , 82 ].…”

Relevance of Connexin 26 (GJB2) Gene Mutations With Congenital Nonsyndromic Sensorineural Hearing Loss in Lraqi Deafness Patients.

“…The GJB2 mutations account in Algeria 40%, in Lebanon 33.3%, in Palestine 23%, in Tunisia 17% and in Jordanian 16.9%. However, this mutation very rare in Asian patients and it is frequently encountered GJB2 mutation in Caucasians (17) .…”