Mutation Screening Of The KCNQ4 And GJB3 Gene In High Frequencies Hearing Loss Population

Hereditary hearing loss has high genetic heterogeneity. There are hundreds of genes act on hearing system. Presently 39 genes that associated with nonsyndromic hearing impairment have been cloned. In which, 13 genes act on high frequencies hearing impairment population.In the 13 genes associated with high frequencies postlingual deafness, wefound KCNQ4 and GJB3 located in the same locus——DFNA2. KCNQ4 codinga kind of K+ channel protein take part in cochlear function, and which could almost be described as a "hearing K+ channel".GJB3 coding a kind of gap connexion protein. According inner physiology, we know K~+ is a crucial factor for the producing of hearing, and K~+ channel and connexion protein maintain the steady state of K~+ in the inner K~+ cycles.KCNQ4 and GJB3 coding proteins which have different functions, but their mutations can lead to high frequencies hearing loss. In our study, we use molecular genetics measures study the patients with special phenotype of high frequencies hearing loss. That may have important means in understanding and discussing the factor of these diseases.In our study, candidate approach was performed on the genotype and phenotype interaction in the cases with high frequencies hearing loss as well as in other hearing loss cases and normal hearing controls. Mutation screening was carried out in the genes of KCNQ4 and GJB3. The present study was composed of two parts as below.PART1: clinical recruitmentAudiological examination data of sporadic cases of high frequencies hearing impairment, and some normal controls were described in this part. The general physical examination results were included.PART 2: screening the mutation of KCNQ4 and GJB3 gene in high frequencies hearing impairment population.The mutations in the KCNQ4 and GJB3 gene are common causes of high frequence sensorineural hearing loss, which had been linked to loci designated DFNA2. KCNQ4 is almost exclusively expressed in the inner hair cell of cochlear base and outer hair cell of cochlear coping. Now considered the function of KCNQ4 is maintain the resting potential of endolymph, and take part in the cycles of K+ in stimulated hair cell.KCNQ4 is located on chromosome 1p34, have 14 exons which coding a polypeptide composed by 695 amino acids, molecular weight is about 77KD. GJB3 is located on the same region, composed of 6060 bp, thereinto the coding region is 812bp. GJB3 coding a kind of channel component.In the study, we designed 12 pairs of primers to amplify 14 exons of the KCNQ4 gene, and 1 pairs of primers to amplify 1 exons of the GJB3 gene. Polymerase chain reaction (PCR) and sequencing were performed to identify the mutation in PCR products of KCNQ4 and GJB3 coding sequences in the patients with the phenotype of high frequencies hearing loss and people as control.There are no reported KCNQ4 mutations. Nine mutations located on intron 2,11,12 and exon 5 were found in all subjects(33637C/T, 33637C→T, 33639C/T, 33639C→T, del47, Ins47, 35805T/C, 35805 T→C, 51219C/T, 51219C→T, 51640C>T).These mutations may not cause the amino acid changes. In which, the insert or delet of 47bp in intron 2 is consistent with the study of Wang Qiuj.In our study of GJB3, we found the reported mutation—547G>A, which caused GLU located 183 became LYS, caused deafness.ConclusionThe candidate genes of KCNQ4 and GJB3 were screened in the cases with high frequencies hearing impairment as well as in the controls. There are no mutations which may caused the amino acid changed in KCNQ4; one reported point mutations which caused the amino acid changed was found in on cases with...