GJB2 c.-23+1G>A mutation is second most common mutation among Iranian individuals with autosomal recessive hearing loss.

GJB2 mutation analysis is used routinely as a first step in genetic testing for autosomal recessive non-syndromic sensorineural hearing loss. Although most GJB2 mutations can be detected by sequencing of the exon 2 of this gene, a prevalent splice mutation, c.-23+1G>A (IVS1+1G>A), is not usually included in the analyzed region. In this study, we have developed an ARMS-PCR strategy for detection of this mutation among Iranian deaf individuals. A total of 418 Iranian individuals with hearing loss consistent with autosomal recessive non-syndromic sensorineural hearing loss based on audiological test result, medical history, physical examination and pedigree of the family, were included in this study. c.35delG and c.-23+1G>A mutations were detected by using ARMS-PCR. Direct sequencing of the exon 2 of the GJB2 gene was performed for mutation analysis of the coding region of this gene. Among 418 investigated cases, a total of 81 patients (~19.4 %) with biallelic pathogenic mutations in the GJB2 gene and 13 cases with only one pathogenic mutant allele were identified. The total allele frequencies of the two most frequent mutations, c.35delG and c.-23+1G>A, among mutated alleles were found to be around 59 and 15.7 %, respectively. High frequency of the c.35delG and c.-23+1G>A mutations among Iranian deaf individuals shows the importance of developing rapid and cost-effective methods for primary mutation screening methods before performing direct sequencing.

Revisiting a Complex Rearrangement Involving a 619 Base Pairs Deletion, 6 Nucleotide Insertion Followed by a A > G Substitution Causing ß°-Thalassemia.

One of the prevalent inherited blood disorders is thalassemia syndrome that characterized by reduction (ß+) or absence (ß0) of ß globin chain synthesis. The ß globin (HBB) gene map in the short arm of chromosome 11 and most of the mutations in this gene are single nucleotide substitutions, insertions or deletions of nucleotides. Nucleotide sequence analysis of a partially deleted ß-globin gene from an Iranian carrier of ß-thalassemia displayed a complex rearrangement involving a 619 base pairs (bp) deletion. This rearrangement had originally been named as the 619 bp deletion and later on as the 619 bp deletion with a 7 bp insertion. In our study, using by single chain sequencing, we have shown that the actual rearrangement involves a 619 bp deletion, a 6 bp insertion followed by a G > A substitution deleting the exon 3 of the ß-globin gene. This clarification has to be inserted into the relevant databases as some of them still site the original 619 bp deletion with wrong breakpoints.