Balkan Journal of Medical Genetics

DETECTION OF THE GJB2 MUTATION IN IRANIAN CHILDREN WITH HEARING LOSS TREATED WITH COCHLEAR IMPLANTATION
Peyvandi AA1, Morovvati S2,*, Rabiee HR3, Ranjbar R3, Ajalloueyan M 4, Hassanalifard M4
*Corresponding Author: Saeid Morovvati, Research Center for Human Genetics, Baqiyatallah University of Medical Sciences, Tehran, POB: 19395/5487, Iran; Tel./Fax: +98-21-88620812; E-mail: morovvati@hotmail. com; morovvati@bmsu.ac.ir
page: 19

PATIENTS AND METHODS

Study Subjects. Connexin 26 gene analysis was performed on 42 children (20 males and 22 females, age range 4-12 years old, average 6 years old) with non syndromic hearing loss and with normal parents who were referred to Baqiyatallah Hospital, Tehran, Iran, for genetic consultation and CI. Clinical history was obtained and an examination conducted on each individual, with special emphasis on identifying potential environmental causes of hearing loss, such as infections, trauma, exposure to known or possible ototoxic drugs and looking for evidence of syndromic forms of deafness. All subjects were otoscopically examined and pure tone audiometry was performed on all subjects. Air conduction thresholds were measured at 250Hz, 500Hz, 1kHz, 2kHz, 4kHz, 6kHz and 8kHz. All probands had prelingual deafness (early-onset). Mutation Analysis. Genomic DNA was extracted from peripheral blood using the standard phenol-chloroform methods [14]. For mutation identification in the Cx26 gene, the coding sequence of the gene was polymerase chain reaction (PCR) amplified using primers Conn-F (5’-CTC CCT GTT CTG TCC TAG CT-3’) and Conn-R (5’-CTC ATC CCT CTC ATG CTG TC-5’). The PCR conditions were 95°C for 3 min., then 32 cycles at 94°C, 59°C and 72°C, each for 45 seconds, followed by a 7 min. extension at 72°C. The PCR products were purified on agarose gel and directly sequenced using the same forward and reverse primers. Treatment Response Assessment. Cochlear implantation was performed on all patients. Treatment response was assessed in all of them based on their speech intelligibility rating (SIR) before, and 3, 6 and 12 months after CI.

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