IVS8+1 DelG, a Novel Splice Site Mutation Causing DFNA5 Deafness in a Chinese Family / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Nonsyndromic hearing loss (NSHL) is highly heterogeneous, in which more than 90 causative genes have currently been identified. DFNA5 is one of the deafness genes that known to cause autosomal dominant NSHL. Until date, only five DFNA5 mutations have been described in eight families worldwide. In this study, we reported the identification of a novel pathogenic mutation causing DFNA5 deafness in a five-generation Chinese family.</p><p><b>METHODS</b>After detailed clinical evaluations of this family, the genomic DNA of three affected individuals was selected for targeted exome sequencing of 101 known deafness genes, as well as mitochondrial DNA and microRNA regions. Co-segregation analysis between the hearing loss and the candidate variant was confirmed in available family members by direct polymerase chain reaction (PCR)-Sanger sequencing. Real-time PCR (RT-PCR) was performed to investigate the potential effect of the pathogenic mutation on messenger RNA splicing.</p><p><b>RESULTS</b>Clinical evaluations revealed a similar deafness phenotype in this family to that of previously reported DFNA5 families with autosomal dominant, late-onset hearing loss. Molecular analysis identified a novel splice site mutation in DFNA5 intron 8 (IVS8+1 delG). The mutation segregated with the hearing loss of the family and was absent in 120 unrelated control DNA samples of Chinese origin. RT-PCR showed skipping of exon 8 in the mutant transcript.</p><p><b>CONCLUSIONS</b>We identified a novel DFNA5 mutation IVS8+1 delG in a Chinese family which led to skipping of exon 8. This is the sixth DFNA5 mutation relates to hearing loss and the second one in DFNA5 intron 8. Our findings provide further support to the hypothesis that the DFNA5-associated hearing loss represents a mechanism of gain-of-function.</p>

Single nucleotide polymorphisms and haplotypes analysis of DFNB1 locus in Chinese sporadic hearing impairment population / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The DFNB1 locus, which contains the gap junction beta-2 (GJB2) and gap junction beta-6 (GJB6) genes, plays a key role in the nonsyndromic and sporadic hearing impairment. Mutations of DFNB1 result in autosomal recessive nonsyndromic hearing impairment (ARNSHI). Previous researches have identified mutations in GJB2 and GJB6, but single nucleotide polymorphisms (SNPs) of DFNB1 locus have not been studied. So we chose five SNPs to evaluate whether there is difference between deafness people and normal-hearing people in Han Chinese.</p><p><b>METHODS</b>Five SNPs in the DFNB1 region were examined using a case-control association study between cases with sporadic hearing impairment and controls with normal hearing. The HWEsoft and SHEsis softwares were used to analyze the results.</p><p><b>RESULTS</b>Single-locus association analysis showed a positive association for three SNPs: rs9315400, rs2274084 and 235delC. When we compared the distributions of the haplotypes, we also found significant differences between cases and controls in the haplotype combination of rs2274084 and rs2274083 (chi(2) = 12.978, df = 3, global P = 0.004719).</p><p><b>CONCLUSIONS</b>The haplotypes composed of rs2274084 and rs2274083 suggested that C-C may be a risk haplotype for the sporadic hearing impairment while T-T may be protective against hearing impairment. From that point of view, we can conclude that the SNPs of DFNB1 locus also plays an important role in sporadic hearing impairment cases.</p>

Mitochondrial 12S rRNA gene A827G in two pedigrees with nonsyndromic deafness / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the relationship of associating mitochondrial DNA 12S rRNA gene mutations with non-syndromic and aminoglycoside-induced hearing loss happening to Chinese families.</p><p><b>METHODS</b>The diagnosis was validated by hearing tests. Blood samples were collected from 20 family members (13 subjects from pedigree A and 7 from pedigree B) and 32 sporadic deafness cases. DNA was extracted from the leukocytes in blood samples. The gene fragments of mitochondrial DNA 12S rRNA, tRNA(Ser(UCN)) and GJB(2) were amplified by polymerase chain reaction (PCR). PCR products were analyzed by sequencing.</p><p><b>RESULTS</b>The target gene fragments of all individuals were successfully amplified by PCR. The mitochondrial DNA 12S rRNA 827 A to G transition was detected from all maternal members including 12 patients with hearing loss, which was the homoplasmic mutation. Non-maternal members in two pedigrees did not carry this mutation. However, the tRNA(Ser(UCN)) A7445G, 12SrRNA A1555G and GJB2 gene mutations were not found from both the family members of two pedigrees and sporadic patients. One sporadic individual (1/32) who was diagnosed as aminoglycoside-induced hearing impairment carried A827G mutation too.</p><p><b>CONCLUSION</b>It is confirmed that the mitochondrial DNA 12S rRNA gene is a hot spot for mutations associated with non-syndromic inherited hearing loss. The 12S rRNA nt827 A to G mutation may play a pivotal role in the pathogenesis of hearing impairment in two Chinese pedigrees.</p>

Epidemiologic study on hearing impairment and ear diseases in old people / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To investigate the prevalence of hearing impairment and ear diseases in old people and provide scientific data for drawing up the prevention and treatment strategies.</p><p><b>METHODS</b>Using the probability proportion to size (PPS) method, 1261 people over 60 years were investigated in 40 clusters in Jiangsu Province with the WHO protocol.</p><p><b>RESULTS</b>The prevalence of hearing impairment was 58.1% (the standardized rate: 59.5% in the whole country, 60.9% in Jiangsu province). Degrees of hearing impairment were mild (33.1%), moderate (17.8%), severe (5.9%) and profound (1.3%). The prevalence of hearing disability was 25.0% (the standardized rate: 26.6% in the whole country, 28.1% in Jiangsu province). There were significant difference of the prevalence between male and female, as well as urban and rural, and different ages. The prevalence of the ear diseases was auricle malformation (0.2%), wax (1.7%), otitis externa (0.1%), fungi (0.5%), serous otitis media (1.2%), chronic suppurative otitis media (1.6%), dry perforation of tympanic membrance (2.3%). The causes of hearing impairment were ear diseases (2.9%), non-infectious condition (92.6%), genetic condition (0.3%) and undetermined causes (4.2%). Of which, 31.1% of persons needed hearing aids while 2.3% of persons needed medicine treatment, but 0.9% of persons needed non-urgent surgery and 1.0% of persons needed other treatment.</p><p><b>CONCLUSIONS</b>The prevalence of hearing impairment and disability in the old rised obviously than the last investigation in 1987. It was a heavy burden for social development in China. The government and the whole society should take more concern about the problem. The scientific strategies of prevention and treatment were urgently needed and implemented.</p>

Sequence analysis of the connexin 26 genes from a deafness family with A1555G mutation in Huaiyin / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To ascertain whether connexin 26 (Cx26) gene was a nuclear modifier gene in an extensive family with matrilineal nonsyndromic deafness associated with A1555G mutation in Huaiyin, China.</p><p><b>METHODS</b>Following PCR-restriction fragment length polymorphism (PCR-RFLP) with ApaI restriction enzyme, Cx26 genes from 26 cases, with A1555G mitochondrial mutations in this family, and 62 controls (including 2 patrilineal relatives, 10 spouse controls and 50 unrelated controls), were sequenced.</p><p><b>RESULTS</b>Compared with the reference sequence of Cx26 gene, totally four kinds of nucleotide changes,79G -->A, 109G-->A, 341G-->A and 235delC, were detected in a heterozygous form. However, the former three were previously reported polymorphisms, and only the 235delC was a previously described recessive mutation associated with most autosomal nonsyndromic sensorineural hearing loss in Japan and China. Further study showed that the heterozygous 235delC mutation existed in both one individual with mild hearing loss and two individuals with normal hearing. Clinical characterization showed that 235delC mutation did not seem to modify the deafness phenotype due to the A1555G mutation. Moreover, this 235delC mutation was deduced to derive from a married-in control. Finally, there were no co-segregation between the phenotypes of hearing loss and the genotypes for Cx26 genes based on the four kinds of nucleotide changes.</p><p><b>CONCLUSIONS</b>The heterozygous 235delC mutation of the Cx26 gene may not modulate the severity of hearing loss associated with A1555G mutation and Cx26 gene is unlikely to be a modifier gene for hearing loss due to A1555G mitochondrial mutation in this Chinese family.</p>

Clinical study of acute low-tone sensorineural hearing loss / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To explore the etiology, clinical aspects, diagnosis and therapeutic strategies of acute low-tone sensorineural hearing loss (ALHL).</p><p><b>METHODS</b>Thirty patients (31 ears) with ALHL were selected for this study. Detailed history collection, otological examination and systematic audiological evaluations were conducted. The hearing tests included pure tone audiometry, acoustic immittance, auditory brainstem response (ABR) and otoacoustic emissions (OAE). All cases received therapeutic trial of corticosteroid for 15 days with 6 to 14 months' following-up.</p><p><b>RESULTS</b>ALHL mainly affected young people. Low-tone tinnitus, a sensation of ear fullness and hearing impairment were the frequent complains. Otological examinations showed normal results. Mild to moderate sensorineural hearing loss at low frequencies and type "A" tympanograms were found in all patients. Acoustic stapedial reflexes were elicited in 26 of 31 affected ears, and 14 of them had positive results on the Metz test. ABR responses were normal in all 20 tested ears. In 14 out of 20 ears, TEOAEs were absent and DPOAE grams at low frequencies (0.5, 0.75 kHz) were abnormal on the first visit. After steroid therapy, 24 ears demonstrated complete recovery, but 4 ears showed partial recovery and 3 ears unchanged. The total improvement rate was 90.3%.</p><p><b>CONCLUSIONS</b>ALHL patients are clinically characterized by low-tone tinnitus, aural fullness and hearing loss, which mainly involved unilateral ear. Audiological findings indicate a cochlear impairment, which only invades low frequency region. The basic pathological feature may be endolymphatic hydrops involves immune response. Conflicting data exist on whether ALHL is an independent disorder or a subtype of Meniere's disease. Ideal therapeutic strategy has not been established by now and corticosteroid is probably an effective agent.</p>

Nonsyndromic inherited hearing impairment caused by mtDNA double mutations of A1555G and 961 insC / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the genotypes of mitochondrial DNA mutations of a large nonsyndromic inherited hearing impairment pedigree.</p><p><b>METHODS</b>The diagnosis was validated by hearing test. Blood samples from the branch pedigree (33 members) and 6 sporadic patients were obtained. DNA was extracted from the leukocytes. The mitochondrial DNA target fragments were amplified by polymerase chain reaction(PCR). The 1555G, 3243G and 7445G mutations were detected by BsmA I, Apa I and Xba I restriction endonuclease digestion respectively. Some PCR products were analyzed by sequencing.</p><p><b>RESULTS</b>Restriction endonuclease digestion identified that 17 patients from the pedigree carried 1555G mutation. All pedigree members, including patients and sporadic patients, did not have 3243G and 7445G mutation. In 6 patients of the pedigree DNA sequence analysis revealed double mutations, an A>G transition at position 1555 and a C insertion at position 961, whereas the unaffected relatives of the pedigree and sporadic patients did not have such mutations. None of them carried 3243G and 7445G mutation.</p><p><b>CONCLUSION</b>Double mutations of A1555G and 961 insC in mitochondrial DNA 12S rRNA gene region may play a pivotal role in the pathogenesis of hearing loss in the large nonsyndromic inherited hearing impairment pedigree.</p>