Prevalence of GJB2 mutations among patients with autosomal recessive non syndromic hearing loss in Sistan and Baloochestan province

Background: Hereditary hearing impairment is a heterogeneous disability showing different
pattern of inheritance and involving a multitude of different genes. Mutations in the GJB2 gene,
especially the 35delG mutation, have been established as a major cause of inherited and sporadic
non-syndromic deafness in various ethnic groups. Because population-specific differences are not
uncommon, in this study we sought to determine the prevalence and spectrum of GJB2 mutations in
two isolated ethnic groups of Balooch and Sistani in southeastern Iran.
Methods and Materials: In this study in 2004 2005 we analyzed one hundred families belonging to
the Balooch and Sistani populations suffering from autosomal recessive non-syndromic hearing
impairment. Mutation screening of GJB2 was performed by an allele-specific PCR assay to detect
the 35delG mutation. The negative or heterozygous cases for the 35delG mutation were screened by
denaturing high performance liquid chromatography (DHPLC) and sequencing analysis.
Results: 35delG mutation which is the most common GJB2 mutation in the white population as
well as other parts of Iran was not found in any of the patients. We identified GJB2 mutant alleles
in 18 chromosomes (9%) including R127H, K122I, W24X, 167delT and M93I. Among them W24X
had the highest frequency.
Conclusions: Based on these data, the hot-spot mutations in the GJB2 gene in the Balooch
population with non-syndromic hearing loss may be different from other ethnic groups in Iran.