[Screening of hot-spot deafness gene mutations among 277 cochlear implantation patients in Sichuan province]

Objective:To investigate the spectrum and incidence of the hot-spot deafness gene mutations of 277 patients with cochlear implantation in Sichuan province, and to provide information of the prevention and treatment for clinical application. Method: The data of the hotspot deafness gene mutations screening of 277 patients with cochlear implantation was analyzed retrospectively. A deafness related gene mutations detection kit was used to detect 9 mutation sites in four deafness-associated genes,including GJB2(35delG,176del16,235delC,299delAT), GJB3(538C＞T),SLC26A4(2168A＞G, IVS7-2A＞G), Mitochondrial 12SrRNA(1494C＞T, 1555A＞G). Result: ① A total of 122 patients with hot-spot Deafness Gene Mutations were detected in 277 cochlear implantation patients(44.04%),among which there were 39 patients were GJB2235delC homozygous mutation(14.08%), 23 patients were GJB2 235delC heterozygous mutation(8.30%), 1 patient was GJB2 299delAT homozygous mutation(0.36%), 2 patients were GJB2 176del16& 235delC compound heterozygous mutation(0.72%), 13 patients were GJB2 235delC& 299delAT compound heterozygous mutation(4.69%), 2 patients were SLC26A4 2168A＞G heterozygous mutation(0.72%), 16 patients were SLC26A4 IVS7-2A＞G homozygous mutation(5.78%), 22 patient were SLC26A4 IVS7-2A＞G heterozygous mutation(7.94%), 1 patients was SLC26A4 2168A＞G& IVS7-2A＞G compound heterozygous mutation(0.36%), 2 patients were mitochondrial 12SrRNA gene 1555A＞G homogenous mutation(0.72%), 1 patient carried both GJB2 235delC homozygous mutation and SLC26A4 IVS7-2A＞G heterozygous mutation(0.36%). ②A total of 49 patients with LVAS were found in 277 cochlear implantation patients: including 15 patients with IVS7-2A＞G homozygous mutation(30.61%), 22 patients with IVS7-2A＞G heterozygous mutation(44.90%), 1 patient with 2168A＞G heterozygous mutation(2.04%), 1 patient with complex heterozygosis mutations of 2168A＞G and IVS7-2A＞G(2.04%), 1 patient with GJB2 235delC homozygous mutation(2.04%) and 1 patient with GJB2 235delC&299delAT compound heterozygous mutation(2.04%), and no hotspot deafness gene mutations were found in 8 patients. ③There were 40 out of 277 cochlear implantation patients with definite family history.There was no statistic difference of the detection rate of hot-spot deafness gene mutations between in patients with family deafness history (57.50%) and in patients without family deafness history (41.77%). ④A total of 273 patients with profound binaural deafness were found among 277 cochlear implantation patients. Three patients with profound deafness in right ear and severe deafness in left ear were found among 277 cochlear implantation patients.Two patients of three were SLC26A4 IVS7-2A＞G heterozygosis mutations, and one patient of three was GJB2 235delC heterozygosis mutations; 1 patient with profound deafness in left ear and severe deafness in right ear was found among 277 cochlear implantation patients,and was GJB2 235delC heterozygosis mutations. Conclusion:① The detection rate of hotspot deafness gene mutations in 277 cochlear implantation patients is 44.04%(122/277). GJB2 Mutation is the most common, SLC26A4 mutation takes the second place, mitochondrial 12SrRNAgene mutation is not common and GJB3 mutation is not found in this study.② SLC26A4 mutation may not be the sole pathogenic factor of LVAS. ③ The results of this study suggest that the genetic background of cochlear implants patients has little effect on the data of the hotspot deafness gene mutations screening.