Establishment And Application Of Mutation Screening System Based On DHPLC For Hereditary Deafness

In recent ten years, over 120 loci have been mapped and 41 geneshave been identified in nonsyndromic hearing loss (NSHL), which showshighly genetic heterogeneity of NSHL. Genetic testing can onlyperformed on few common genes due to this heterogeneity and mostNSHL patients can't have definite gene diagnosis, resulting in thedifficulty of genetic counseling for those patients. Denaturing HighPerformance Liquid Chromatography (DHPLC) is recently reported as ahighly effective, high-throughput, low cost and easy operating method forsequence variations screening. This study is to establish a NSHL genemutation screening system based on DHPLC, to improve the geneticdiagnosis and offer more information to genetic counseling, to reduce thebirth rate of newborns with deafness through definite genetics testing andprenatal diagnosis.Mutation screening of GJB2, the most common gene of NSHL, wasperformed by DHPLC to set up the system. Then mutation screening ofCOCH and WFS1 were performed by the system in some patient withsome typical characteristics of hearing loss.Through DHPLC combined with sequencing, definite gene diagnosiswas made in 16 families with hereditary deafness. The system detected 15GJB2 variants (including 7 mutations and 8 polymorphisms), 7 COCHvariants (including 1 novel mutation, 1 novel polymorphism and 5polymorphisms) and 19 WFS1 variants (including 1 published mutation, 1pending variant, 2 novel polymorphisms and 17 polymorphisms).GJB2 mutations were major causes of prelingual deafness; twocausative mutations were found in 28.6％of prelingual recessive and in20.7％of prelingual sporadic NSHL patients in this study, both of whichare obviously less than the 50％of the population in Europe and America.The 235delC mutation was the most common, accounting for 76.3％ofthe GJB2 mutant alleles. The allele frequency of the three polymorphisms79G＞A, 109G＞A and 341A＞G were 21.3％, 9.6％and 17.8％,respectively, which are the three most common GJB2 polymorphismsamong Chinese population. The COCH are frequently associated with autosomal dominant progressive hearing loss with vestibular dysfunction,and WFS1 mutations are common seen in autosomal dominantlow-frequency sensorineural deafness.DHPLC could be an effective mutation screening method to thosemulti-exon NSHL genes with characteristic phenotyps. But highfrequency of polymorphisms in GJB2 found in this research suggestsDHPLC is not suitable for GJB2 mutation screening in Chinesepopulation.