First report of prevalence c.IVS1+1G>A and del (GJB6-13S1854) mutations in Syrian families with non-syndromic sensorineural hearing loss.

OBJECTIVE: Mutations in GJB2 and GJB6 genes are a frequent cause of congenital non-syndromic hearing loss (NSHL). Mutational screening has usually focused on coding region of GJB2 gene. A few studies have been conducted on the non-coding region and exon 1. c.IVS1+1G>A (a splice site mutation in GJB2 gene have been detected as disruptive mutation. Del (GJB6 D13S1830) is found in many populations, but del (GJB6 D13S1854) is reported from a few restricted countries. This study was carried out to investigate the prevalence of splice site mutation c.IVS1+1G>A and two common deletions in GJB6 gene as the genetic etiology of hearing impairment in 70 Syrian families.

METHODS: The frequency of the c.IVS1+1G>A mutation and two deletions were determined by PCR-RFLP and A multiplex PCR assay.

RESULT: Our results showed a high prevalence of IVS1+1G>A mutation (20%) and del(GJB6-D13S1854) (15.7%) in deaf families. The homozygous genotype (c.IVS1+1G>A/c.IVS1+1G>A) was observed in one family and the compound heterozygous genotypes (c.35delG/c.IVS1+1G>A) and (c.IVS1+1G>A/V153I) were observed in 7 families and one family respectively. Also, the heterozygous state (c.IVS1+1G>A/unknown) was detected in 5 families. The study of del((GJB6-D13S1854) was showed a compound heterozygous genotype del((GJB6-D13S1854)/c.IVS1+1G>A) in the same families (5 families) having heterozygous genotype of c.IVS1+1G>A mutation. Also, del(GJB6-D13S1854) is combined with c.35delG mutation in 2 families and it was observed in the heterozygous state del(GJB6-D13S1854)/unknown) in 4 families. In contrast, the del(GJB6-D13S1830) described in many population was absent in our patients.

CONCLUSION: Our findings indicate to significant contribution of the splice site mutation and del(GJB6-D13S1854) in our deaf families and these mutations were important causes of hearing impairment.