screening of gjb2 mutations in chinese population

The GJB2 gene(connexin 26) has been shown to be responsible for DFNB1 and DFNA3. We screened the GJB2 gene in 488 patients with prelingual deafness(Group 1), 124 with postlingual deafness(Group 2), and 117 normal hearing subjects(Group 3). We found that, in Group 1, 65 patients(13.32%) were homozygotes or compound heterozygotes and 51 patients (10.45%) carried a single pathogenic mutation. The 235delC mutation was the most frequent mutation, accounting for 73.22% of the known pathogenic alleles in Group 1. No homozygotes or compound heterozygotes were detected in Group 2 or Group 3. Some postlingual deaf patients (2.42%) and normal hearing subjects(4.27%) were 235delC carriers. Our preliminary data indicate that 235delC, the most frequent mutation identified in this study, is a major cause for prelingual deafness.     

Cochlear implantation for children with GJB2-related deafness

OBJECTIVES/HYPOTHESIS: Mutations in GJB2 are a common cause of congenital sensorineural hearing loss. Many children with these mutations receive cochlear implants for auditory habilitation. The purpose of the study was to compare the speech perception performance of cochlear implant patients with GJB2-related deafness to patients without GJB2-related deafness. STUDY DESIGN: Retrospective case review. METHODS: Pediatric cochlear implant recipients who have been tested for GJB2 mutation underwent chart review. All patients received cochlear implantation at a tertiary referral center, followed by outpatient auditory habilitation. Charts were reviewed for cause and duration of deafness, age at time of cochlear implantation, intraoperative and postoperative complications, duration of use, and current age. Results of standard tests of speech perception administered as a part of the patients' auditory habilitation were reviewed. RESULTS: Twenty patients with GJB2 mutations were compared with 27 patients without GJB2 mutations. There was no statistical difference between patients with and without GJB2-related congenital sensorineural hearing loss with regard to open-set and closed-set speech recognition performance at 12, 24, and 36 months after cochlear implantation. Surgical complications were uncommon. CONCLUSION: Pediatric patients with congenital sensorineural hearing loss without other comorbid conditions (eg, developmental delay, inner ear malformations) perform well when they receive cochlear implantation and auditory habilitation. The presence or absence of GJB2 mutation does not appear to impact speech recognition performance at 12, 24, and 36 months after implantation.     

Auditory responses in cochlear implant users with and without GJB2 deafness

OBJECTIVE/HYPOTHESIS: It is reasonable to suppose that the pattern of sensorineural damage along the length of the cochlea depends on the etiology of a hearing loss (HL). In GJB2-related deafness, we hypothesize that gap junction deficits are uniformly distributed and will result in similar damage along the length of the cochlea as compared with non-GJB2 subjects. We assessed this by measuring patterns of neural activity and hearing from apical versus basal cochlear implant electrode regions. STUDY DESIGN: This was a prospective, blind, controlled study. METHODS: Blood from 301 pediatric cochlear implant users was analyzed for mutations in GJB2 by direct sequencing. After exclusion of patients with monoallelic GJB2 mutations, associated syndromes, or risk factors for HL that were not congenital, 39 children with biallelic GJB2 mutations and 58 without GJB2 mutations were evaluated. Hearing was measured before implantation at frequencies ranging from 250 Hz to 8 kHz. After implantation, neural activity at the apical and basal ends of the implanted array was measured using electrically evoked compound action potentials of the auditory nerve (ECAPs) and evoked stapedius reflexes (ESRs). RESULTS: GJB2 and non-GJB2 groups were not significantly different with respect to sex, age at implantation, duration of auditory deprivation, hearing aid use, duration of aided hearing, ear implanted, implant model, or depth of insertion (P>.05). Children with GJB2-related HL had greater similarities between low- and high-frequency residual hearing and between neural activity electrically evoked at apical and basal regions of the cochlea as compared with children with non-GJB2-related HL who demonstrated larger deficits in basal regions. CONCLUSION: Results suggest more consistent spiral ganglion survival along the length of the cochlea in GJB2-related HL as compared with non-GJB2-related HL, which appears to involve a decreasing gradient of spiral ganglion survival from the apex to the base of the cochlea. Our findings support our premise that in GJB2-related HL, dysfunction of gap junctions likely occurs to a similar degree in the apical and basal regions of the cochlea. This knowledge might be used to customize implantable devices for patients with HL in the future.     

Prevalence of GJB2 causing recessive profound non-syndromic deafness in Japanese children

Objective

GJB2 (gap junction protein, beta 2, 26 kDa: connexin 26) is a gap junction protein gene that has been implicated in many cases of autosomal recessive non-syndromic deafness. Point and deletion mutations in GJB2 are the most frequent cause of non-syndromic deafness across racial groups. To clarify the relation between profound non-syndromic deafness and GJB2 mutation in Japanese children, we performed genetic testing for GJB2.

Methods

We conducted mutation screening employing PCR and direct sequencing for GJB2 in 126 children who had undergone cochlear implantation with congenital deafness.

Results

We detected 10 mutations, including two unreported mutations (p.R32S and p.P225L) in GJB2. We identified the highest-frequency mutation (c.235delC: 44.8%) and other nonsense or truncating mutations, as in previous studies. However, in our research, p.R143W, which is one of the missense mutations, may also show an important correlation with severe deafness.

Conclusion

Our results suggest that the frequencies of mutations in GJB2 and GJB6 deletions differ among cohorts. Thus, our report is an important study of GJB2 in Japanese children with profound non-syndromic deafness.     

GJB2相关非综合征性感音神经性聋人工耳蜗植入后的疗效观察

目的：评价携带GJB2基因突变的儿童人工耳蜗植入后的疗效。方法：对40例携带GJB2基因突变的人工耳蜗植入患儿进行疗效评估,测试内容包括：声场助听听阈测试、（婴幼儿）有意义听觉整合量表、听觉行为分级标准评分、言语可懂度分级标准评分及普通话早期言语感知测试。以80例未检出已知热点突变者为对照组。结果：携带GJB2基因突变的患儿术后声场助听听阈优于对照组,其余测试与对照组比较差异无统计学意义（P〉0．05）。结论：携带GJB2基因突变的非综合征性感音神经性聋患儿适于行人工耳蜗植人手术,术后效果满意。     

特发性突聋患者GJB2 235delC突变分析

目的：分析GJB2 235delC突变在特发性突聋患者中的发生频率,探寻其与特发性突聋发病的可能相关性。方法：收集234例特发性突聋患者,以同期听力正常的80例体检人员为对照组。分别采外周静脉血,提取基因组DNA,经聚合酶链反应扩增GJB2基因编码区后,用限制性内切酶酶切的方法筛查235delC位点突变,同时对特发性突聋患者的临床资料汇总分析。结果：234例特发性突聋患者中,5例检测出GJB2 235delC杂合突变,突变检出率为2.1%,未检测出235delC纯合突变;对照组中未检出GJB2 235delC突变。2组人群235delC突变检出率差异无统计学意义（P〉0.05）。结论：特发性突聋患者中GJB2 235delC突变检出率低,提示该突变位点可能与特发性突聋的发病无相关性。     

The effect of GJB2 allele variants on performance after cochlear implantation

OBJECTIVES/HYPOTHESIS: It has been hypothesized that etiology of hearing loss may serve as an independent variable in performance after cochlear implantation. To test this hypothesis, the authors identified pediatric cochlear implant recipients with gap junction protein beta2 (GJB2)-related deafness. The study examines performance outcomes associated with GJB2 deafness-causing allele variants. STUDY DESIGN: Pediatric cochlear implant patients were screened for GJB2 allele variants; statistical comparisons were made with prospectively obtained performance measures. METHODS: From 181 children who participated in a nationwide cochlear implant research program, 122 children were identified with congenital nonsyndromic sensorineural hearing loss and invited to participate. Screening for GJB2 allele variants was completed for 55 children. The children were homogeneous with respect to age (8 or 9 y) and age at implant (before age 5 y). All patients have previously undergone a prospective regimented battery of performance measures. RESULTS: Performance measures were compared between 22 children with and 33 children without mutations to determine whether GJB2 status was a significant predictor of cochlear implant outcomes. Reading and cognitive outcomes were significantly dependent on connexin status. The group of children who tested positive for GJB2-related deafness scored significantly higher on a nonverbal cognitive measure, Block Design, and on a measure of reading comprehension. CONCLUSION: The isolated insult to the cochlea created by GJB2 allele variants allows for preservation of central cognitive function. Better reading performance is seen in children with GJB2-related deafness.     

人工耳蜗植入患者的缝隙连接蛋白相关基因（GJB2）突变分析

目的探讨人工耳蜗植入患者的缝隙连接蛋白相关基因（gap junction protein beta 2，GJB2）突变情况，分析耳聋的遗传学发病机制。方法对接受人工耳蜗植入的241例患者进行聋病基因GJB2基因突变筛查。结果241例人工耳蜗植入患者中检测出65例GJB2基因突变，其中1例为新发现突变GJB2 235delC／598G〉A。结论人工耳蜗植入患者中GJB2基因突变的发生率为27．0％，GJB2基因突变是人工耳蜗植入人群中耳聋的主要致病因素之一。     

语前聋患儿一侧人工耳蜗对侧助听器效果分析

目的:通过对人工耳蜗植入对侧耳不同听力损失的患儿联合使用助听器与人工耳蜗语前聋患儿的听觉、语言及学习能力进行评估和比较,探索对患儿更为有效的助听方法,帮助患儿获得最大限度的言语交流。方法:将30例3～6岁语前聋患儿按照植入人工耳蜗对侧耳听力损失程度及是否佩戴助听器,分为一侧人工耳蜗+对侧重度听力损失助听器组(CI+SHA组)、一侧人工耳蜗+对侧极重度听力损失助听器组(CI+PHA组)、单耳人工耳蜗组(CI组)。评估各组在康复3、6、9、12、15、18个月时听觉、语言及学习能力,并记录结果。结果:随着术后康复时间的延长,聋儿听觉、语言及学习能力逐渐提高(P<0.05),CI+SHA组听觉能力优于CI+PHA组及CI组(均P<0.05),语言能力及学习能力无明显差异(P>0.05)。结论:语前聋患儿单耳人工耳蜗植入后,若对侧耳尚有残余听力,佩戴助听器后听觉能力效果显著,长期佩戴有助于患儿的康复。     

The clinical features of patients with the homozygous 235delC and the compound-heterozygous Y136X/G45E of the GJB2 mutations (Connexin 26) in cochlear implant recipients

Objective

This study aimed to investigate the prevalence of GJB2 gene for the 235delC mutations, the clinical features and the outcomes of patients who had undergone cochlear implantation.

Methods

We have sequenced the coding region of GJB2 gene for 135 patients with sensorineural deaf from September 2000 to May 2009. Of the 135 patients, the patients with the homozygous 235delC and the compound-heterozygous Y136X/G45E were detected and were investigated clinically.

Results

The GJB2 gene for the 235delC mutations was found in 39 alleles of 270 alleles (14.4%), especially for the homozygous of 235delC was detected in 26 alleles (9.6%), the single heterozygous of 235delC was 1 allele (0.4%), the compound heterozygous of 235delC was found in 12 alleles (4.4%). Of 16 subjects (29 alleles) with the homozygous 235delC and the compound-heterozygous Y136X/G45E, 2 subjects (4 alleles) were found to have complications. All of the subjects were found to show severe hearing loss and some of them have indicated progressive hearing loss. However, they showed better performance regarding the thresholds after implantation. The subjects with complications, although, suggested poorer performance in the auditory speech performance.

Conclusion

The findings of poorer outcomes might depend on complications and brain functions. In addition, considering the blood test parameters, an independent elevated LDH and ChE at diagnosis were found to be associated with hereditary enzyme's metabolic disease. Therefore, the value of LDH measurements in patients might be a helpful predictive parameter in hereditary diseases.     

Cochlear implantation in common forms of genetic deafness

Genetic factors are among the main etiologies of severe to profound hearing loss and may play an important role in cochlear implantation (CI) outcomes. While genes for common forms of deafness have been cloned, efforts to correlate the functional outcome of CIs with a genetic form of deafness carried by the patient have been largely anecdotal to date. It has been suggested that the differences in auditory performance may be explained by differences in the number of surviving spiral ganglion cells, etiology of hearing loss, and other factors. Knowledge of the specific loci and mutations involved in patients who receive cochlear implants may elucidate other factors related to CI performance. In this review article, current knowledge of cochlear implants for hereditary hearing loss will be discussed with an emphasis on relevant clinical genotype-phenotype correlations.     

The effects of cochlear implantation in Japanese single-sided deafness patients: five case reports

Conclusion Cochlear implantation (CI) for Japanese single-sided deafness patients resulted in improved speech perception, increased sound localization accuracy, and reduced tinnitus handicap. Objectives This study reports results for five adult SSD cases with CI, focusing on the benefits they obtained in terms of speech recognition, sound localization, and tinnitus handicap. Methods Five Japanese patients meeting the eligibility criteria were included in this study. All patients were implanted with a fully inserted MED-EL Concerto FLEX28® implant (MED-EL, Innsbruck, Austria). Speech perception outcomes in noise, as well as sound localization and tinnitus disturbance, were assessed pre-surgically and at 1, 3, 6, and 12 months after CI activation. Results The Japanese monosyllable test score in noise improved gradually after implantation. In some cases, speech perception ability appeared unstable, particularly in the first 1–6 months after implantation. The sound localization ability showed marked improvement in all cases, with the disturbance to daily life caused by tinnitus also decreasing in all cases from the early post-operative period.     

Association of GJB2 gene mutation with cochlear implant performance in genetic non-syndromic hearing loss

Objective

To analyze the association of GJB2 gene mutations with cochlear implant performance in children.

Methods

Sixty-five consecutive children who underwent cochlear implantation due to congenital profound senseurineural hearing between 2006 and 2008 were included in the study. In children, GJB2 gene mutation analysis was performed. Their auditory performance was assessed using MAIS, MUSS and LittlEARS tests.

Results

Twenty-two of sixty-five patients GJB2 mutations, and 35delG was the most frequent mutation. No significant difference was found between the auditory performance of mutation positive and negative children after one year follow up (p > 0.05).

Conclusion

GJB2 gene mutations do not impact on the outcome of cochlear implantation.     

赤峰市特教学校耳聋患者GJB2和GJB3及GJB6基因突变分析

目的:利用基因诊断的方法调查内蒙古自治区赤峰市特教学校非综合征耳聋患者的常见分子病因,对GJB2、GJB3、GJB6基因编码区突变进行分析.方法:调查对象来自赤峰市特教学校非综合征耳聋患者134例(耳聋组),对照组为中国北方地区(北京、河北、内蒙、山西)听力正常者100例.所有受检者均采集外周血并提取DNA,首先进行GJB2基因编码区测序,对携带GJB2单杂合突变的患者进一步检查GJB6 del(GJB6-D13S1830)突变并进行GJB6编码区测序.对除GJB2基因、线粒体A1555G突变相关性耳聋及前庭水管扩大综合征外的分子病因不明的91例非综合征耳聋患者进行GJB3基因编码区测序.结果:134例非综合征耳聋患者及100例正常对照中共检测到6种GJB2基因新的突变方式.耳聋组41例携带GJB2病理性突变,其中双等位基因突变22例,单等位基因突变19例,在GJB2单等位基因突变的耳聋患者中未检测到GJB6 del(GJB6-D13S1830)及编码区其他突变;对照组4例携带GJB2基因病理性突变.在91例分子病因不明的耳聋患者及100例正常对照中共检测到3种GJB3基因新的突变方式.耳聋组2例携带GJB3基因病理性突变,均为杂合子,其中1例同时携带GJB2单等位基因突变235delC;对照组1例携带GJB3基因病理性突变.结论:通过GJB2、GJB6、GJB3基因编码区突变分析为赤峰市特教学校16.42%(22/134)的非综合征耳聋学生明确了分子病因;新发现的突变和多态丰富了中国人GJB2、GJB3基因突变及多态性图谱,为深入开展耳聋基因筛查奠定了基础.     

Identification of 605ins46, a novel GJB2 mutation in a Japanese family

Connexin 26 gene (GJB2) mutations are known to be responsible for a significant portion (30–80%) of autosomal recessive congenital severe to profound deafness. More than 60 recessive mutations in GJB2 have been reported and most consist of point mutations of a nucleotide. We report here a novel insertional GJB2 mutation consisting of a long repetitive nucleotide sequence. As compound heterozygotes of this mutation with 235delC express sensorineural hearing loss of variable severity, further analysis of the phenotype–genotype relationship is required.     

Outcomes of consonant-vowel monosyllable perception and word recognition after cochlear implantation in elderly Japanese patients

Conclusion: Performance in consonant-vowel (CV) monosyllable speech perception after cochlear implantation (CI) in the elderly (≥ 65 years) is equivalent to that of young adults (18–64 years). Present data in the Japanese language supported the indication for CI in the elderly. Word recognition after CI was significantly lower in the elderly than young adults. Objective: This study compared outcomes of monosyllable perception and word recognition after CI between elderly patients and young adults with post-lingual deafness. Age-related differences in CV monosyllable speech perception in Japanese were examined. Methods: A retrospective chart review of 137 patients with post-lingual deafness who underwent CI at Okayama University Hospital during 1992–2014 [young adults aged 18–64 years (n = 96) and elderly aged ≥ 65 years (n = 41) at implantation] was conducted. CV monosyllable speech perception post-CI was compared among age groups (18–29, 30–39, 40–49, 50–59, 60–69, 70–79, 80–89). CV monosyllable perception and word recognition scores post-CI were compared between the elderly and young adults. Results: There was no significant difference in CV monosyllable speech perception among age groups. CV monosyllable speech perception in the elderly (61.4 ± 25.5%) did not differ from that of young adults (65.9 ± 24.8%). Word recognition scores were significantly lower in the elderly (64.3 ± 28.1%) than young adults (80.4 ± 25.9%) (p < 0.05).     

The deafness-causing mutation c.508_511dup in the GJB2 gene and a literature review

Conclusions: The mutation c.508_511dup in GJB2 gene has been incorrectly named as other mutations. It is essential to standardize mutation nomenclature to describe complex mutations. Objectives: This paper aimed to verify a series of patients with the frame-shift mutation c.508_511dup in the GJB2 gene and review the literature on related mutations. Methods: All the included patients with non-syndromic hearing loss (NSHL) carried the 504insAACG or c.508_511dup mutation of the GJB2 gene in the present study. Their parents were encouraged to participate. After written informed consent and clinic data had been obtained, genomic DNA was extracted from venous blood of participants. The target fragments were amplified by polymerase chain reaction (PCR) and subjected to bidirectional sequencing to identify sequence variations. Results: A total of 14 patients with prelingual NSHL and 6 normal parents were recruited. Genotyping revealed that one mutation, c.508_511dup (not 504insAACG), was homozygous in 1 patient, heterozygous in 2 patients and 3 parents, and compound heterozygous in 11 patients. Twelve patients had hearing loss caused by c.508_511dup in a homozygous or compound heterozygous form, and further study showed that it was wrongly named as 504insAACG. Additionally, according to the standard nomenclature, the previously reported mutations with distinct names from the literature review may be replaced by c.508_511dup.     

佛山地区耳聋儿童GJB2 235delC突变和线粒体DNA A1555G突变的研究

目的研究佛山地区先天性聋儿中GJB2突变和线粒体DNAA1555G突变在耳聋发病中的作用。方法收集180例散发的先天性聋儿的DNA，利用聚合酶链反应一限制性片断长度多态性（PCR—RFLP）方法和Prey—DAF药物性耳聋基因诊断试剂盒对收集到的DNA进行分析，筛查患者GJB2235deIC突变和线粒体DNAA1555G突变。结果经PCR-RFLP和Prev—DAF药物性耳聋基冈诊断试剂盒分析，在所有参加检测的180名患儿中共发现GJB2235delC纯合突变14名（7．78％），GJB2235delC杂和突变7名（3．89％），线粒体DNAA1555G突变6名（3．33％）。结论应用基因检测方法可以在地区性耳聋流行病学凋查中帮助明确常见的遗传性耳聋病例，并可指导此类患者的家庭进行耳聋的预防。     

Autosomal recessive and sporadic deafness in Morocco: high frequency of the 35delG GJB2 mutation and absence of the 342-kb GJB6 variant

Deafness is a heterogeneous disorder showing different pattern of inheritance and involving a multitude of different genes. Mutations in the gene, GJB2 Gap junction type 1), encoding the gap junction protein connexin-26 on chromosome 13q11 may be responsible for up 50% of autosomal recessive nonsyndromic hearing loss cases (ARNSHL), and for 15–30% of sporadic cases. However, a large proportion (10–42%) of patients with GJB2 has only one GJB2 mutant allele. Recent reports have suggested that a 342-kb deletion truncating the GJB6 gene (encoding connexin-30), was associated with ARNSHL through either homozygous deletion of Cx30, or digenic inheritance of a Cx30 deletion and a Cx26 mutation in trans. Because mutations in Connexin-26 (Cx26) play an important role in ARNSHL and that distribution pattern of GJB2 variants differs considerably among ethnic groups, our objective was to find out the significance of Cx26 mutations in Moroccan families who had hereditary and sporadic deafness. One hundred and sixteen families with congenital deafness (including 38 multiplex families, and 78 families with sporadic cases) were included. Results show that the prevalence of the 35delG mutation is 31.58% in the family cases and 20.51% in the sporadic cases. Further screening for other GJB2 variants demonstrated the absence of other mutations; none of these families had mutations in exon 1 of GJB2 or the 342-kb deletion of GJB6. Thus, screening of the 35delG in the GJB2 gene should facilitate routinely used diagnostic for genetic counselling in Morocco.     

GJB2 (connexin 26) gene mutations in Moroccan patients with autosomal recessive non-syndromic hearing loss and carrier frequency of the common GJB2-35delG mutation

OBJECTIVE: Mutations in the connexin 26 gene (GJB2), which encodes a gap-junction protein expressed in the inner ear, have been shown to be responsible for a major part of autosomal recessive non-syndromic hearing loss in Caucasians. The aim of our study was to determine the prevalence and spectrum of GJB2 mutations, including the (GJB6-D13S1830) deletion, in Moroccan patients and estimate the carrier frequency of the 35delG mutation in the general population. METHODS: Genomic DNA was isolated from 81 unrelated Moroccan familial cases with moderate to profound autosomal recessive non-syndromic hearing loss and 113 Moroccan control individuals. Molecular studies were performed using PCR-Mediated Site Directed Mutagenesis assay, PCR and direct sequencing to screen for GJB2, 35delG and del(GJB6-D13S1830) mutations. RESULTS: GJB2 mutations were found in 43.20% of the deaf patients. Among these patients 35.80% were 35delG/35delG homozygous, 2.47% were 35delG/wt heterozygous, 3.70% were V37I/wt heterozygous, and 1 patient was E47X/35delG compound heterozygous. None of the patients with one or no GJB2 mutation displayed the common (GJB6-D13S1830) deletion. We found also that the carrier frequency of GJB2-35delG in the normal Moroccan population is 2.65%. CONCLUSIONS: These findings indicate that the GJB2-35delG mutation is the major cause of autosomal recessive non-syndromic hearing loss in Moroccan population. Two other mutations were also detected (V37I and E47X), in agreement with similar studies in other populations showing heterogeneity in the frequencies and types of mutation in connexin 26 gene.