Comparative Studies Of DNA Microarray And Sequencing In Genetic Diagnosis On The Patients With Enlarged Vestibular Aqueduct Syndrome

Objective:To study the genotype and molecular epidemiologic characteristic of Enlarged vestibular aqueduct syndrome (EVAS) in Chinese, we detected mutations in relative gene SLC26A4 and FOXI 1 by the method of DNA microarray and sequencing, then we discussed gene diagnostic strategy appropriated for EVAS patients in Chinese.Methods:30 cases of EVAS and 50 control individuals with normal hearing were included in this study. Their genomic DNA samples were extracted from peripheral blood, and detected with the DNA microarray which was able to perform mutation detection of 2 hot-spot mutations in SLC26A4 gene, including IVS7-2A>G and 2168A>G simultaneously. Meanwhile, the results were confirmed with the traditional methods of DNA sequencing. We stopped the examining process if mutations梙omozygous or composite heterotic—were detected through DNA microarray,or examined the rest exons until a gene mutation was found if no mutation or only pure heterozygosity was detected.Meantime, mutation detection was carried out by DNA sequencing on 2 exons of FOX11 gene and their consecutive part of introns.Then we used the software of DNA Star to analyze the sequence.Results:In the group of EVAS,25 of 30 patients were found to have SLC26A4 gene mutations by DNA microarray, detection rate was 83.33%. We found a heterozygosis mutation of IVS7-2A>G in the normal control group. The detection rate was significantly different in the two groups (X2 test,P＜0.01). Checking the samples that found any mutation, there was a coincidence rate of 100%. Combining with DNA sequencing,28 patients were found gene mutation of SLC26A4 totally,with a mutation of 93.33%.But there were no statistically significant differences in the detection rate of DNA microarray and sequencing (X2 test, P>0.05).A total of 16 mutations were identified in the study including 4 novel mutations(G368X,IVS8-1G＞T,IVS13+9C＞T and Q696X).In all mutations,IVS7-2A>G was the most common mutation; H723R and T410M were another common mutations.There were 2 polymorphisms of FOXI1 in 30 EVAS patients:279 G>A and 1044T>C.Conclusions:SLC26A4 gene mutations are the primary cause of EVAS.Among these mutations,IVS7-2A>G is the most common mutation in Chinese,and H723R and T410M are another common mutations.DNA microarray can be used to generally screen hot site mutation of SLC26A4.But DNA sequencing is necessary if no mutation or only heterozygosity mutation is detected by DNA microarray.4 novel mutations which have been detected in the study are very important for the pathogenesis research and genetic diagnosis of Enlarged vestibular aqueduct syndrome.In this study, no significant mutation has been detected except two polypeptides of FOXI1,suggesting that the detection rate is low in EVAS.Moreover,other unknown morbific factors could be existed in EVAS.