Examination ofthe Gene for Connexin 26 in Czech Patients with Congenital Autosomal Recessive Non-SyndromicHearing Loss

Overview

Hearing loss and deafness are the most frequent sensory defects in humans. Inbornhearing losses affect every 1000th neonate and more than half are genetically based. The majority(some 80%) of genetically conditioned, non-syndromic hearing losses are autosomally recessivelyinherited.Mutations in the gene for connexin 26 (Cx26) cause the major part (up to 50 %) of autosomalrecessive and thus also genetically conditioned heating losses. In this gene there is in the Europeanpopulation a highly prevalent mutation - deletion of base G in position 35 (35delG). The frequencyof healthy heterozygous carriers of this mutation in the hearing European population is high, almost3 % (1:31).In the submitted paper the authors present the first results of examinations of Cx26 gene in a groupof Czech patients with congenital non-syndromic hearing loss.Eleven patients from nine families with congenital hearing loss without a proved acquired causewere examined for the presence of mutations in Cx26 gene. The examination had two stages - firstfocused on the presence of the most frequent mutation - 35delG - and subsequently in all patientssequencing of the whole coding section of the Cx26 gene wasmade. In eight patients from six familiesthe most frequent mutation in 35delG in the homozygous state was proved, in three patients nodeviation as compared with the published sequence of the Cx26 gene was proved, not even by directsequencing. Their impaired hearing is thus due to a disorder of another gene or is acquired, thecause being unknown.Furthermore the authors made for the first time in the Czech Republic a prenatal examination ina family with a child with congenital hearing loss where the result in the foetus was favourable andthe parents decided for continuation of the pregnancy.The results indicate, although so far only based on a small group, that also in the Czech populationmutations in the Cx26 are in the majority of patients the cause of inborn hearing loss and thatmutation 36delGis also in our country the most frequent mutation in the Cx26 gene in these patients.K e y w o r d s: congenital hearing loss, inborn deafness, connexin 26.

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