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Mutations in GJB2, encoding gap junction beta 2 protein (connexin 26), are responsible for the commonest form of non-syndromic recessive deafness in many populations. It has been reported recently that the most common 35delG mutation in GJB2 is exceptionally low in Japanese and Korean populations, but another deletion, 235delC, is relatively frequent. Since the Chinese constitute approximately one fifth of the global population, the frequency of GJB2 mutations in the population has important implications for understanding worldwide causes of genetic deafness. To determine whether GJB2 mutations are an important cause of deafness in Chinese, we conducted mutation screening for GJB2 in 118 deaf Chinese probands, including 60 from simplex and 58 from multiplex families with non-syndromic deafness, and 150 normal hearing Chinese controls. Four mutations, including 235delC, 299–300delAT, V37I, and 35delG, were found in the patients. Thirty-nine percent of the probands had a GJB2 mutation. Of the 118 probands, 19 carried two definitely pathogenic mutations: three among the 58 multiplex cases (5.2%) and 16 among the 60 simplex cases (26.7%). Twenty-seven probands (22.9%) were found to carry only single GJB2 mutations. None of them had mutations in exon 1 of GJB2 and or the 342-kb deletion of GJB6. The 235delC mutation was the most prevalent mutation (20.3% of alleles), accounting for 81% of the pathologic alleles in multiplex cases and 67% in simplex cases. Analysis of the affected haplotypes in the patients with the homozygous 235delC mutation yielded evidence for a single origin of the mutation. The carrier frequency of the 235delC mutation in control subjects with normal hearing was 1.3%. The 35delG mutation was only noted as a heterozygous change in two simplex cases (1.2% of alleles). These results indicated that mutations in GJB2 are a major cause of inherited and sporadic congenital deafness in the Chinese population. The 235delC mutation, rather than 35delG, is the most common mutation found in the Chinese deaf population. Our data support the view that specific combinations of GJB2 mutation exist in different populations.

This work was supported by the Medical Research Council (U.K.), Defeating Deafness—the Hearing Research Trust, and SENSE and by European Community grant CT96-1324. C.H. acknowledges support from the British Retinitis Pigmentosa Society and the Birmingham Eye Foundation.

BACKGROUND Recent studies showed that aminoglycosides destroyed the cochlear cells and induced ototoxicity by producing reactive oxygen species, including free radicals in the mitochondria, damaging the membrane of mitochondria and resulting in apoptotic cell death. Bcl-x(L) is a well characterized anti-apoptotic member of the Bcl-2 family. The aim of this study was to determine the potential cochlear protective effect of Bcl-x(L) as a therapeutic agent in the murine model of aminoglycoside ototoxicity. METHODS Serotype 2 of adeno-associated virus (AAV2) as a vector encoding the mouse Bcl-x(L) gene was injected into mice cochleae prior to injection of kanamycin. Bcl-x(L) expression in vitro and in vivo was examined with Western blotting and immunohistochemistry separately. Cochlear dissection and auditory steady state responses were checked to evaluate the cochlear structure and function. RESULTS The animals in the AAV2-Bcl-x(L)/kanamycin group displayed better auditory steady state responses hearing thresholds and cochlear structure than those in the artificial perilymph/kanamycin or AAV2-enhanced humanized green fluorescent protein/kanamycin control group at all tested frequencies. The auditory steady state responses hearing thresholds and cochlear structure in the inoculated side were better than that in the contralateral side. CONCLUSIONS AAV2-Bcl-x(L) afforded significant preservation of the cochlear hair cells against ototoxic insults and protected the cochlear function. AAV2-mediated Bcl-x(L) might be an approach with respect to potential therapeutic application in the cochlear degeneration.

To conduct a molecular epidemiological survey on the mitochondrial DNA C1494T mutation in non-syndromic hearing loss patients in Chinese population.Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) were used to screen the mitochondrial DNA 12S rRNA C1494T mutation in 20 patients with aminoglycoside antibiotic induced hearing loss, 136 sporadic non-syndromic hearing loss patients and 50 probands of pedigrees with non-syndromic hearing loss.The C1494T mutation did not appear in all cases except for the positive control.Incidence of mitochondrial DNA C1494T mutation is much lower than that of mitochondrial DNA A1555G mutation in non-syndromic hearing loss of Chinese population. Mitochondrial DNA C1494T mutation may be a rare variation in non-syndromic hearing loss and is not the main cause of aminoglycoside antibiotic induced-deafness.

The aims of this study were to evaluate the expression of enhanced green fluorescent protein (EGFP) driven by 6 different promoters, including cytomegalovirus IE enhancer and chicken beta-actin promoter (CAG), cytomegalovirus promoter (CMV), neuron-specific enolase promoter (NSE), myosin 7A promoter (Myo), elongation factor 1alpha promoter (EF-1alpha), and Rous sarcoma virus promoter (RSV), and assess the dose response of CAG promoter to transgene expression in the cochlea. Serotype 1 adeno-associated virus (AAV1) vectors with various constructs were transduced into the cochleae, and the level of EGFP expression was examined. We found the highest EGFP expression in the inner hair cells and other cochlear cells when CAG promoter was used. The CMV and NSE promoter drove the higher EGFP expression, but only a marginal activity was observed in EF-1alpha promoter driven constructs. RSV promoter failed to driven the EGFP expression. Myo promoter driven EGFP was exclusively expressed in the inner hair cells of the cochlea. When driven by CAG promoter, reporter gene expression was detected in inner hair cells at a dose as low as 3x10(7) genome copies, and continued to increase in a dose-dependent manner. Our data showed that individual promoter has different ability to drive reporter gene expression in the cochlear cells. Our results might provide important information with regard to the role of promoters in regulating transgene expression and for the proper design of vectors for gene expression and gene therapy.

To explore the mutations of Wolfram syndrome I gene (WFS1) in families affected by non-syndromic low frequency sensorineural hearing loss (NS-LFSNHL).Twenty eight individuals from 6 pedigrees with hereditary non-syndromic low frequency sensorineural hearing loss as a dominant trait and cases of control were collected in the present study. The coding sequence of WFS1 gene was amplified by polymerase chain reaction (PCR), and direct DNA sequencing was performed to screen the entire coding region of the WFS1 gene for mutations in the WFS1.Three heterozygous missense mutations (2016 G--T, 2379 G--4A, 2766 G--A) in the WFS1 gene were found in two families. Mutations in WFS1 were identified in all patients tested of the two pedigrees. None of the mutations was found in at least 280 control chromosomes and normal individuals of the families. These missense mutations affecting conserved amino acids in two pedigrees.Mutations in WFS1 are one of causes of non-syndromic low frequency sensorineural hearing loss, and the majority of mutations are missense mutations. Genetic counseling and genetic testing may be useful in the management of patients with this type of hearing loss.

To study the relation between hereditary nonsyndromic hearing impairment (NSHI) in Chinese and mutation in Connexin 31 (Cx31) gene and to explore the pathogenic mechanism.Forty-seven pedigrees with hereditary NSHI, 38 Children with sporadic NSHI and cases of control were collected in present studies. The coding sequence of Cx31 gene was amplified by polymerase chain reaction (PCR), screened by denaturing high-performance liquid chromatography (DHPLC) and confirmed by direct sequencing.The mutation rate of heterozygous mutation C --T at position 798 of Cx31 cDNA in patient group and in control were 14.1% (12/85) and 1% (1/100) respectively. Significant difference was found between the two group (P0.01). Heterozygous mutation G --A at position 580 of GJB3 cDNA, which results in a missense mutation (A194T), was found in two members of one pedigree with autosomal dominant NSHI. The mutation was not found in numbers with normal hearing of this pedigree and controls. Heterozygous mutation G --A at position 250 of Cx31 cDNA was found in one child with sporadic congenital NSHI. In our previous studies, Cx26 gene mutations have been screened among the patient with hereditary NSHI and sporadic NSHI and the control of our test, and two Cx26 gene mutations were found in two pedigrees. But the two NSHI pedigrees which were confirmed to have Cx26 gene mutation were not found to have Cx31 mutation. The patient and the control which were confirmed to have Cx31 gene mutations were not found to have Cx26 mutations.Cx31 gene was associated with nonsyndromic hearing impairment There was no cross and cooperative effect between Cx26 gene and Cx31 gene.