High prevalence in the Greek population of the 35delG mutation in the connexin 26 gene causing prelingual deafness.
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Biomedical subjects
Publications and source records attributed to J Economides.
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One hundred and twenty patients (children) with Down's Syndrome were examined by the Audiological Dept. at 'Aghia Sophia' Children's Hospital during the period 1988-1990. Of these 73 (60.8%) were boys and 47 (37.2%) were girls. Their ages varied from 7-18 years of age with an average age of 14.8 years. Physical examination included otoscopy, tympanometry, and in some cases auditory brainstem audiometry. It is worth noting that a high percentage of these patients were unable to cooperate in this study, therefore making it obligatory to utilize objective measures for hearing evaluation.
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Mutations in the gene encoding the gap-junction protein connexin 26 (GJB2) on chromosome 13q11 have been shown as a major contributor to prelingual, sensorineural, nonsyndromic deafness. One specific mutation, 35delG, has accounted for the majority of the mutations detected in the GJB2 gene in Caucasian populations and is one of the most frequent disease mutations identified so far with highest carrier frequency of 3,5% in the Greek population. In a collaboration with the major referral centers for childhood deafness in Greece, patients were examined by an extensive questionnaire to exclude syndromic forms and environmental causes of deafness and by allele-specific PCR for the detection of the 35delG mutation. The 35delG mutation was found in 32.1% of the alleles in 173 unrelated cases of prelingual deafness: 50 homozygotes and 11 heterozygotes. Individuals heterozygous for the 35delG mutation were further analyzed by direct genomic sequencing of the coding region of the GJB2 gene, which revealed R184P and 486insT mutations in single alleles. We conclude that the 35delG GJB2 mutation is responsible for one third of prelingual, sensorineural deafness in Greece, which is higher than the usually quoted 20% for Caucasian populations.