[Frequency of 35delG mutation in GJB2 gene in non-syndromic prelingual hearing loss in 3 provinces of Iran]

Hearing loss is the most common inherited sensory disorder. At least 50% of hearing loss is inherited and about half of the genetic hearing loss is autosomal recessive non-syndromic. Mutations in GJB2 gene is the most frequent cause of autosomal recessive non-syndromic hearing loss. A single 35delG mutation is the most common allelic variant of GJB2 in most parts of the world. The aim of this study was to determine the rate of 35delG mutation in non-syndromic prelingual hearing loss in 3 provinces of Iran. In this descriptive experimental study, 240 cases with autosomal recessive non-syndromic hearing loss in 3 provinces of Iran, including Azarbaijan Sharghi [97 cases], Chaharmahal va Bakhtiari [98 cases] and Gilan [45 cases] were screened for 35delG mutation in the GJB2 gene. Blood samples [5 ml] were taken for genomic DNA extraction. The mutation was screened using Nested-PCR method and the positive results were confirmed by subsequent direct sequencing. Results of this study showed that from 240 studied patients [480 chromosomes], 35delG mutation was found in 58 chromosomes [24 patients were homozygote and 10 patients were heterozygote]. The frequency of 35delG mutation was 12.08%, including 18.04% in Azarbaijan Sharghi, 3.06% in Chaharmahal va Bakhtiari and 18.88% in Gilan province. Prevalence of 35delG mutation in Chaharmahal va Bakhtiari population was lower than other provinces studied. These results indicate that the other genes or mutations could result in autosomal recessive non-syndromic hearing loss in Chaharmahal va Bakhtiari population. However, as we found a low rate of 35delG in the populations studied, the cause of deafness remains to be detected in other loci or genes

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