GENETIC VARIANTS OF GJB2-RELATED DEAFNESS IN NORTH CAUCASUS

Bozhkova V (1), Khashaev ZK (1), Umanskaya TM (2).

(1) Institute for Information Transmission Problems of RAS, Russia; (2) Faculty of Defectology of Moscow State Pedagogical University, Russia.

Aim and Background: Our aim was to study the etiology of hearing loss among the children living in one of a region of Russian Federation - North Caucasus (a South-East part of Europe). First, it has been confirmed that the c.35delG mutation in the GJB2 gene is the most common cause of sensorineural inherited non syndromic hearing impairment among children living in majority of European part of Russia. Among 9 young students affected by autosomal recessive non syndromic hearing loss (ARNSHL), mutations in the coding region of the GJB2 gene have been revealed for 100 percent of deaf students. The allele frequency of the c.35delG mutation appeared to be 94% of all the mutations detected in the GJB2 gene. Another mutation we have revealed was 167delT the allele frequency being 6%.

Method and Results: On the other hand, when the entire coding region of the GJB2 gene was sequenced for 12 children from North Caucasus, affected by profound prelingual ARNSHL, mutations has been detected only in 4 deaf children (33% of cases). The total number of revealed mutations was three: 35delG (two children, non-relatives, the allele frequency of 40%), delE120 – formerly known as scarce one (two children, non-relatives, the allele frequency of 40%), and a novel mutation delE187 (one child, the allele frequency of 20%). In one case, the mutations were in a compound heterozygous state (35delG/ delE120 genotype), in three others – in a heterozygous state.

Conclusion: Since the pathogenicity of the delE120 mutation is considered proven (Gabriel et al., 2001; Bruzzone et al., 2003; Baysal et al., 2008), its relatively high frequency in the North Caucasian region along with a relatively low frequency of the 35delG mutation should be taken into account when developing DNA diagnostics strategies for revealing inherited hearing loss.

E-mail: bgk@iitp.ru