Autosomal recessive and sporadic non syndromic hearing loss and the incidence of Cx26 mutations in a Province of Iran

Despite the enormous heterogeneity of genetic hearing loss, mutations in the GJB2 [connexin 26] gene located on 'DFNB1' locus [13q12] account for up to 50% of cases of autosomal recessive non-syndromic hearing loss [ARNSHL] in some populations. This study describes the analysis of 100 autosomal recessive and sporadic nonsyndromic hearing loss individuals from 79 families each having at least one deaf child in Chehar Mahal va Bakhtiari province in west of Iran. We have investigated the prevalence of the connexin 26 gene mutations using nested PCR strategy to screen the predominant 35delG mutation and subsequent direct sequencing to detect other Cx26 mutations. Seven different genetic variants were detected from which one novel variant was including 363delC. The 35delG was the most common mutation found in 5 of 79 families [6.3%]. Cx26 related deafness mutations [35delG, [V27I; E114G]] and R127H] were found in 12 of 158 chromosomes studied [7.8%]. We conclude that the association of Cx26 mutations with deafness in Chehar Mahal va Bakhtiari province is low and looks like most other populations of Iran

Frequencies of mutations in the connexin 26 gene [GJB2] in two populations of Iran [Tehran and Tabriz]

While hearing loss has been considered to be a very heterogeneous disorder, mutations in Gap junction beta 2 [GJB2] gene encoding Connexin 26 [Cx26] protein are the major cause of autosomal recessive and sporadic non-syndromic deafness in many populations. In this study, we have investigated the prevalence of the GJB2 gene mutations using nested PCR pre screening strategy and direct sequencing method. Two hundred and seventy two hearing impaired subjects were studied from 210 families obtained from two large cities of Iran [Tehran and Tabriz]. Twenty four different genetic variants were identified. Cx26 mutations were found in 53 of the 210 families [25.2%] including T8M, 35delG, W24X, R32H, V37I, E47X, 167delT, delE120, Y136X, R143W, R184P, 235delC and V27I+E114G. Homozygosity and compound heterozygosity for the Cx26 mutations were found in 39 of 210 [18.5%] families. Homozygosity for the 35delG mutation was the most common that causes hearing loss in 28 [13.3%] patients. Six novel variants H16R, E101E, K102Q, G200R, 327delG and G130A were detected in this study. As a conclusion, the present survey revealed that the rate of mutation in Cx26 gene in our area is lower than in Europe; nevertheless, this rate is regarded as a considerable cause of deafness in the cited provinces in Iran

Report of a new mutation and frequency of connexin 26 gene [GJB2] mutations in patients from three provinces of Iran

Autosomal recessive and sporadic non-syndromic hearing loss [ARSNSHL] is the major form of hereditary deafness.Mutations in the GJB2 gene encoding the gap-junction protein Connexin 26 have been identified to be highly associated with ARSNSHL. In this study we have analyzed 196 deaf subjects from 179 families having one or more deaf children in 3 proviences of Iran, including Kordestan, Khuzestan and Golestan. The nested PCR prescreening strategy and direct sequencing technique were used to detect the mutations in coding exon of the gene. Altogether 3 GJB2 recessive mutations including 35delG, 167delT and V27I+E114G, were identified in 23 of 179 families [12.8%]. Fourteen of 179 families were observed to have GJB2 mutation in both alleles [7.8%]. A novel variant [R159H] also was found in a deaf family from Khuzestan. Four polymorphisms V27I, E114G, S86T and V153 I also were detected in 7 families. A polymorphism [S86T] was seen in the whole population studied. Our data indicated that the rate of connexin 26 mutations is different in this three Irainian population and is lower than the high frequency of 35delG [26%] reported from Gilan province in the north of Iran

Two novel mutations and predominant 35delG mutation in the connexin 26 gene [GJB2] in Iranian populations

Mutations in the GJB2 gene encoding Connexin 26 [Cx26] protein are a major cause for autosomal recessive non syndromic and sporadic deafness in many populations. In this study we have investigated the prevalence of the GJB2 gene mutations using nested PCR pre screening strategy and direct sequencing method. Two hundred and sixty autosomal recessive non syndromic and sporadic deaf subjects from 199 families in two provinces of Iran [Gilan and Khorasan] were studied. Altogether 14 different genetic variants were identified from which 2 were novel variant [327delG+G109G and 431insC]. Eight GJB2 mutations including 35delG, 235delC, W77X, R127H, M34T, V27I+E114G, L90P and delE120 were also found in 54 of 199 families [27%]. Four polymorphysms V27I, S86T, V153I and G160S also were detected. Thirty two of 199 families were observed to have GJB2 mutations in both alleles [16%]. The most common mutation was 35delG so that 43 out of 55 GJB2 mutations [78.2%] contained 35delG mutation

Frequency of a very rare 35delG mutation in two ethnic groups of iranian population

The 35delG mutation in the Connexin 26 gene [Cx26], at the DNFB1 locus is the most common mutation in the patients with autosomal recessive non-syndromic hearing loss [ARNSHL]. We have studied a total of 224 deaf cases from 189 families in two populations of Iran [Sistan va Bluchestan and Hormozgan provinces] by prescreening nested PCR, polyacrylamide gel electrophoresis and consequent direct sequencing method for all cases. The aim of the present work was to find prevalence of GJB2 mutations in the populations studied. Four different GJB2 mutations including 35delG, W24X, R127H and [V27I + E114 G] were identified in 11 of 189 families [5.8%]. Two polymorphisms [V27I and V153I] also were detected in 14 families. A polymorphism S86T was determined in all cases. Homozygote 35delG mutation was found only in 1 of 189 families [0.5%].The rate of Cx26 mutations found in this study was lower than other Iranian populations. So the cause of deafness in the populations studied remains to be detected in other loci or genes