DELTA (GJB6-D13S1830) IS NOT A COMMON CAUSE OF NONSYNDROMIC HEARING LOSS IN THE IRANIAN POPULATION

Background: Mutations in the gene that encodes the gap-junction protein connexin 26 (GJB2) at the DFNB1 locus on chromosome 13q12 are the major cause of autosomal recessive nonsyndromic sensorineural deafness (ARNSD) in many different populations. A fraction of patients with GJB2 mutations have only one mutant allele, and in some familial cases with linkage to the DFNB1 locus, no mutations in GJB2 are reported. Recently, a large deletion involving the GJB6 gene encoding connexin 30, which is also located at the DFNB1 locus delta(GJB6-D13S1830), has been reported to cause ARNSD in homozygotes for this mutation and in compound heterozygotescarrying deafness-causing allele variants of GJB2 on the opposite allele. To date, different papers have been published reporting the presence or absence of this deletion in various populations. Methods: Three hundred eighty-five probands segregating presumed autosomal recessive nonsyndromic deafness were screened for GJB2 mutations using an allele-specific polymerase chain reaction (PCR) assay to detect 35delG mutation. Direct sequencing was performed following DHPLC analysis of all patients except 35delG homozygotes. Screening for Δ (GJB6-D13S1830) was completed using PCR primers that amplified the breakpoint junction of this deletion in all patients heterozygous for only one GJB2 mutation and 116 probands with normal GJB2 alleles. Results: GJB2-related deafness was diagnosed in 70 probands (18.2%). Sixteen patients were found to carry only one GJB2 mutant allele. Additionally, we found three novel GJB2 allele variants. Δ (GJB6-D13S1830) was not detected in the subjects screened for this mutation. Conclusion: Our finding indicates that Δ (GJB6-D13S1830) is not a common cause of deafness in Iran and suggests that this mutation is not widespread in the world.