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Abstract: Objective: Mutations in GJB2 and GJB6 which comprise DFNB1 locus cause up to half of all cases of the prelingual autosomal recessive non-syndromic hearing loss (ARNSHL) worldwide. This study has intended to assess the spectrum and frequency of GJB2/GJB6 mutations in northwest of Iran. Methods: 508 Patients with presumed ARNSHL were analyzed by applying ARMS-PCR, SSCP, PCR-RFLP and sequencing assays. Results: Seventy-five (14.7%) different homozygous and eighty-seven (17.1%) different compound heterozygous genotypes were detected in this cohort. Concerning the GJB2 gene, c.35delG was the most prevalent mutation, accounting for 16.4% of the samples. In addition 29 sequence variations other than c.35delG mutation were distinguished in GJB2; namely, delE120, Ins A 290-291, R143Q, V37I, R32H, Y155X, V27I+T123N, F154F, 167delT, 312del14, 299-300delA, T8M, W24X, E114G+V27I, 235delC, R184P, V153I, S139N, A171T, M163V (unknown mutation), G127V, E147X, R127H, 35insG, R143W, V27I, G160S, E114G and IVS1+1G>A. Moreover, the IVS1+1G>A was accounted as a second common mutation. Conclusions: Overall, the frequency of GJB2 mutations (≥31%) is in agreement with other white population. These findings highlight the importance of the study of GJB2 gene in the diagnosis to provide early treatment and genetic counseling. [Copyright &y& Elsevier]

Abstract: Objective: Determine the prevalence of 35delG mutation in GJB2 gene in patients with prelingual deafness of no defined etiology whose underwent cochlear implant in the Otolaryngology Department at the Hospital de Clínicas de Porto Alegre and compare the speech recognition index using an open-set of sentences according to the presence or absence of the 35delG mutation. Methods: Cross-sectional study nested in a cohort. Were analyzed 37 patients with indeterminate etiology for deafness that underwent to cochlear implant. DNA was extracted and the mutations were studied using Polymerase Chain Reaction followed by gene sequencing. Results: The prevalence of 35delG mutation was 11%. The speech recognition index was 72% in the group with 35delG mutation, and 30% in the group without this mutation (p >0.05). Conclusions: Prevalence of 35delG mutation in this study confirmed findings in the Brazilian literature. There was a clinically significant difference in hearing performance in patients with 35delG. Absence of statistical significance in this result might be attributed to the small number of patients with 35delG in our sample. [Copyright &y& Elsevier]

Abstract: Objective: Nonsyndromic hearing loss is one of the most abundant human sensory disorders, and can be found in 1 out of 1000 newborns. In 60–70% of the cases this disorder is hereditary. The phenotype varies from moderate hearing loss to almost complete deafness, often only revealed in late childhood. Early detection of hearing related genetic variations in the first few weeks of life would allow planning of the audiological and logopedical procedures to maintain the children''s normal audiological and speech development, and if required a cochlear implantation can be planned in time. We wanted to evaluate, whether the blood samples collected from neonates onto Guthrie cards (dried blood spots, or DBS), and blood collected from people of various ages into blood collecting tubes is equally usable for genetic testing. The quality of the samples on DBS''s for genetic tests after an extended period of storage was evaluated. The methods for sample preparation and analysis were also evaluated. Methods: Two DNA extraction methods were compared on the samples. We extracted DNA from whole blood with the Versagene Blood Kit from Gentra, and from DBS''s with boiling. Allele-specific PCRs (AS-PCR) were carried out on each sample. Samples were analyzed with AS-PCR and sequencing, for the 35delG mutation in the GJB2 (Cx26) gene. Freshly drawn and dried blood spot samples stored for several years were used in the experiments. Results: An AS-PCR method for detecting 35delG mutation on DNA extracted from Guthrie cards was validated. Blood samples up to 10 years of storage were applicable in the screen. 84 patients were found with 35delG mutations, both heterozygous (with no detected hearing related phenotypical discrepancies), and homozygous (phenotipically with moderate to severe hearing loss) forms. Conclusions: The dried blood spots on Guthrie cards require only three drops of blood to be collected from children, which causes less stress than taking 3ml of blood. The blood stored on Guthrie cards can be used to store DNA samples for at least 10 years. Even under suboptimal storage conditions the samples’ DNA remains intact for genetic testing. Compared to blood collection tubes Guthrie cards cost less, are easier to transport and store. [Copyright &y& Elsevier]

Summary: Mutations of GJB2, the gene encoding connexin 26, have been associated with prelingual, sensorineural hearing loss of mild to profound severity. One specific mutation, the 35delG, has accounted for the majority of mutations detected in the GJB2 gene in Caucasian populations. Recent studies have described progression of hearing loss in a proportion of cases with GJB2 deafness. We report an unusual family with four 35delG homozygous members, in which the parents were deaf-mute whilst both children had a postlingual progressive hearing loss. Furthermore, the son suffered from sudden hearing loss. [Copyright &y& Elsevier]

Summary: Objective: DFNB1 locus has been reported as a major cause of autosomal recessive non-syndromic hearing loss (ARNSHL) worldwide. 35delG and del(GJB6-D13S1830) are thought to be two common mutations in this locus among Caucasians. The aim of this study is to determine the significance of these two mutations in aetiology of ARNSHL in Iran. Methods: One hundred and thirty-three unrelated patients with ARNSHL were tested by using multiplex allele-specific PCR assay after validation by positive control samples. Results: The frequency of 35delG was about 18.5%, however, del(GJB6-D13S1830) was not found in the studied patients. Parental consanguinity was observed in 50% of 35delG-mutated families. Conclusions: Our results support founder effect regarding these mutations. [Copyright &y& Elsevier]

Summary: Objective: Mutations in the GJB2 gene are a major cause of autosomal recessive and sporadic non-syndromic hearing loss in many populations. A single mutation of this gene (35delG) accounts for approximately 70% of mutations in Caucasians with a carrier frequency of 2–4% in Europe. This study aims to determine the rate of 35delG carrier frequency in Iran. Methods: Genomic DNA was extracted from a total of 550 unaffected unrelated subjects from 4 provinces of Iran following the standard phenol chloroform procedure. The one base pair deletion (35delG) was analysed using a nested PCR procedure; 35delG mutation carriers were subsequently confirmed by sequence analysis. Moreover, using the Binomial probability distribution, we compared the 35delG carrier frequency of Iranian population with the various Middle Eastern and overall European populations. Results: Of the four populations studied, we found a high carrier frequency of 2.8% in Gilan province in the north of Iran. The overall 35delG carrier frequency was found to be 1.25% in the populations studied (our present and previous data) which is similar to the overall 35delG carrier frequency detected in Middle Eastern populations, but Significantly lower than that identified in European populations. [Copyright &y& Elsevier]

Summary: Objective: Hearing loss is a complex multifactorial disorder caused by genetic and environmental factors. The 35delG mutation in the GJB2 gene is the most prevalent mutation in Caucasian patients with genetic sensorineural deafness. The A1555G mutation in the mitochondrial 12S rRNA is the main genetic alteration associated with aminoglycoside-induced deafness. The aim of this study was to evaluate the prevalence of both mutations in general population of Argentina. Methods: A total of 712 samples of unrelated healthy blood donors and 330 newborn dried blood spots were studied by PCR–RFLP. Results: The 35delG mutation was detected in 11/ 712 unrelated blood donors. The carrier frequency found in this sample (1/65) proved to be lower than that found in Southern European countries, mainly Spain and Italy, from where Argentina originally received its major immigration waves. When the populations of Southern Europe were considered altogether, this difference reached statistical significance. The A1555G mutation was not found in any of the 1042 samples tested. Conclusions: Taking into account the 35delG carrier frequency found in this study, it could be estimated that 130–160 children with congenital deafness due to mutations in the connexin genes would be born per year in Argentina. In contrast, the mitochondrial mutation A1555G appears to be infrequent in general Argentinean population. [Copyright &y& Elsevier]

Summary: Objective: Mutations in the GJB2 (connexin-26) gene are responsible for more than half of all cases of prelingual recessive inherited non-syndromic deafness in Europe. One specific mutation 35delG, accounts for up to 70% of the mutations detected in European populations and is one of the most frequent disease mutations identified so far. The aim of this study is to determine the percentage of carriers of this mutation in the Greek Cypriot population. Methods: Genomic DNA was isolated from a total of 405 healthy unrelated Greek Cypriot adults. Screening for the frameshift 35delG mutation was performed by using an allele-specific PCR protocol. Moreover, using the Poisson probability distribution, we compared the carrier frequencies of the 35delG mutation of the Greek Cypriot population to the various European and Middle Eastern populations. Results: The carrier frequency in the Greek Cypriot population was estimated to be 2.5% and is similar to that observed in other European populations. The variance estimate for 35delG mutation produces slightly wider intervals with the Poisson model when compared with Binomial probability variance estimate. [Copyright &y& Elsevier]