GJB2 gene mutations in childhood deafness

The Frequency of childhood deafness is estimated at 1:1,000 and at least ha lf of these cases are genetic. Recently, mutations in the GJB2 gene have be en found in a great number of familial and sporadic cases of congenital dea fness in Caucasians. The most common mutation (70%) is the frameshift mutat ion of a single guanine in position 35 (35delG). More than 20 mutations in the GJB2 gene are associated with DFNB1, a prevalent type of autosomal rece ssive non-syndromic neurosensory deafness. Last year we initiated a systema tic screening programme to evaluate the causes of deafness in the populatio n of prelingually deaf children who are referred to our cochlear implant pr ogramme. All of the deaf children and their parents undergo a comprehensive medical review, directed to identify causes of acquired deafness and manif estations of syndromic hearing impairment. DNA is extracted from the blood of all of the children. The technique AS-PCR (allele-specific polymerase ch ain reaction) is used for the identification of the mutation 35delG. Screen ing for other GJB2 gene mutations is carried out by single-strand conformat ion polymorphisms (SSCP). Our results on the identification of DFNB1 will h e presented, as well as a discussion on the implications of an aetiological diagnosis in cochlear implantation.