gjb2 mutation spectrum in inner mongolia and its comparison with other asian populations

Mutations in the GJB2 gene are the most frequently found mutations in patients with nonsyndromic hearing impairment. However, the mutation spectrum and prevalence of mutations vary among different ethnic groups. Every year, 30,000 babies are born with congenital hearing impairment in China. In order to provide appro-pilate genetic testing and counseling to the family, we investigated the molecular etiology of nonsyndromic deafness in 135 unrelated school children attending Chifeng Municipal Special Education School in Inner Mongolia, China. The coding exon of the GJB2 gene was PCR amplified and sequenced. In addition, the 12S rRNA gene and tRNAser UCN of mitochondrial genome were screened for mutations responsible for hearing impairment. Sixty four GJB2 mu-tant alleles, including 60 confirmed pathogenic alleles and 4 unclassified variants, were identified in 31.1% (42/135) of the subjects. Twenty two subjects carried two pathogenic mutations and 20 subjects carried one mutant allele, in-cluding one subject with one autosomal dominant mutation. The 235delC was the most common mutation account-ing for 65.6%(42/64) GJB2 mutant alleles. When compared to other Asian populations, our subject cohort had high-er frequency of 235delC mutation than the Japanese population. The GJB2 mutant alleles account for 23.7% (64/270) of all chromosomes responsible for nonsyndromic heating impairment. Testing of the 4 most prevalent deleterious frame shift mutations(235delC, 299_300delAT, 176191_del16, and 560_605ins46) in this cohort detect-ed 90% of all GJB2 mutant alleles. These results demonstrate that effective genetic testing of the GJB2 gene for pa-tients and families with nonsyndromic hearing impairment is possible in the Chinese population. Since the most common 309kb GJB6 deletion is not detected and only one 1555 A>G mutation in mitochondrial DNA is detected in our patients, investigation of mutations in other nuclear genes and/or environmental factors responsible for non-syndromic heating impairment in the Chinese population is necessary.     

GJB2 mutations in hearing impairment: identification of a broad clinical spectrum for improved genetic counseling

OBJECTIVES/HYPOTHESIS: Hearing impairment has a high prevalence affecting approximately 1 in 1000 newborn children. Alterations in the gap junction protein beta 2 (GJB2) and gap junction protein beta 6 (GJB6) are associated with nonsyndromic hearing impairment and should have a significant impact on genetic counseling. STUDY DESIGN: Various cases of nonsyndromic hearing impairment were screened for alterations in GJB2 and GJB6 in this clinical study. METHODS: The prevalence of mutations in GJB2 encoding for connexin 26 in a patient group with nonsyndromic hearing impairment comprising 45 families and 57 sporadic cases was initially determined by sequencing. The role of GJB2 was then assessed in individuals with hearing impairment (3 families and 20 sporadic cases) who are usually excluded from analysis because of the presence of additional symptoms or in cases in which a role for nongenetic factors cannot be eliminated. In hearing-impaired individuals with heterozygous GJB2 mutations the recently identified 342-kb deletion truncating GJB6 called del(GJB6-D13S1830) as a digenetic component in hearing impairment was excluded by polymerase chain reaction. RESULTS: Autosomal recessively inherited GJB2 mutations induced hearing impairment in 25.5% of individuals in the nonsyndromic hearing impairment group. GJB2 alterations were also seen in 17.4% of individuals in whom additional symptoms or a role for nongenetic involvement could not be excluded. In all, 15 different alterations in GJB2 were detected, including the previously unknown 154G>C, 557C>T, and 682C>T mutations, and these were correlated to clinical parameters. CONCLUSION: Improved genetic counseling can be performed by screening for GJB2 alterations in patients with nonsyndromic hearing impairment including patients within groups for which a role for exogenetic factors cannot be excluded. Specific genetic counseling for GJB2-linked hearing impairment in heterozygotes will depend on future research.     

江苏南通地区非综合征性耳聋GJB2基因突变分析

目的 研究南通地区非综合征性耳聋GJB2基因突变情况。方法 收集南通地区海安县和如皋县聋哑学校学生100名和健康对照组50名，利用PCR扩增及限制性内切酶酶切分析初筛GJB2 235delC突变者，然后再行DNA直接测序。结果 耳聋组中共发现三种突变：235delC、176—191del16、299—300delAT。235delC是主要突变方式．约30％的患者携带此突变；299—300delAT和176-191del16突变检出率分别为9％和8％。对照组未发现这些突变。结论 南通地区非综合征性耳聋GJB2基因突变率较高，因此在南通地区进行广泛的生育前耳聋基因筛查工作有重要意义。     

安阳市特教学校重度感音性聋分子病因学分析--GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变筛查报告

目的 调查河南省安阳地区重度感音神经性耳聋聋病分子病因学情况。方法对安阳市聋哑学校160名学生进行耳聋病因问卷调查、纯音听阈测试。对其中154名非综合征性感音神经性耳聋患者进行线粒体DNA 12SrDNA A1555G点突变检测和G朋12基因突变检测。结果 8例（5．19％）存在线粒体DNA 12SrDNA A1555G点突变；11例（7．14％）存在GJB2 235delC纯合突变；13例（8．44％）存在GJB2 235delC杂合突变。在分子水平能够明确诊断者占20．77％。结论 安阳地区耳聋患者存在较高的遗传性耳聋发生率。特别是线粒体DNA A1555G突变发生率高于全国平均水平，通过聋病分子诊断，可达到防聋、指导聋儿康复及评估耳聋预后等积极效果。     

Identification of mutations in members of the connexin gene family as a cause of nonsyndromic deafness in Taiwan

Connexins (Cx), a large family of membrane proteins, are key components of gap junction channels. These channels are critical intercellular pathways through which ions or small molecules are passed, regulating a variety of physiological and developmental processes. One of these processes is hearing. In the current study, a genetic survey was made on 380 Taiwanese individuals, 260 with nonsyndromic deafness and 120 with normal hearing. All the 380 Taiwanese were screened for the presence of mutations in 8 genes of the Cx gene family. These genes included Cx26 (GJB2), Cx29 (GJE1), Cx30 (GJB6), Cx30.3 (GJB4), Cx31 (GJB3), Cx32 (GJB1), Cx43 (GJA1) and pseudogene [rho] of Cx43 (rho GJA1). Mutations were identified in 7 out of the 8 screened genes of the Cx family from 62 of the 260 deaf subjects (23.85%). Of the 17 mutations observed in the Cx gene family, 11 were novel mutations. Fourteen polymorphisms that were not associated with hearing loss were identified in the Cx gene family. The first 2 most frequently occurring mutations were found in the Cx26 (28/62; 45.16%) and the rho Cx43 (17/62; 27.42%), respectively. Nine cases of mutations were found in the Cx30.3 (9/62; 14.52%). In the Cx30, 1 novel mutation was identified in 1 case (1/62; 1.61%). Two patients with mutations of each of Cx29 and Cx43 were found (2/62; 3.23%). One novel mutation of Cx31 was identified in 3 patients with nonsyndromic deafness (3/62; 4.84%). The Cx32 was the only gene without detecting any mutation or polymorphism.Our study provides information for understanding the importance of genetic factors in nonsyndromic deafness of the Taiwanese and may be of use in the improvement of genetic diagnosis of hearing loss in Taiwan.     

柳州市盲聋学校非综合征性聋分子病因学分析--GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变筛查报告

目的 分析GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变在广西壮族自治区柳州地区非综合征性耳聋（nonsyndromic hearing impairment，NSHI）患儿中的作用。方法 收集广西壮族自治区柳州聋哑学校的88例非综合征性耳聋患儿的血样，提取DNA后经聚合酶链反应（PCR）分别扩增GJB2基因编码区及线粒体DNA，ApaI酶切分析GJB2 235位点的C缺失突变、Prey—DAF药物性耳聋基因诊断试剂盒分析线粒体1555位点的A—G突变，对GJB2 235delC及线粒体DNA 12SrRNA A1555G的突变率进行统计分析。结果 88例患儿中1例（1．14％）为GJB2 235delC纯合突变；5例（5．68％）为GJB2 235delC杂合突变；4例（4．55％）存在线粒体DNA 12SrRNA A1555G点突变，其中1例同时伴有GJB2 235delC杂合突变。在分子水平能够明确诊断者占11．37％。结论 柳州地区耳聋患者常染色体隐性遗传性耳聋发生率较全国平均水平低，线粒体DNA 12SrRNA A1555G突变发生率偏高。应用基因诊断技术可以在地区性耳聋病因调查中进行快速筛查、诊断，可达到防止聋儿再生、指导聋儿康复等积极效果。     

武汉地区非综合征性聋分子病因学分析--GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变筛查报告

目的 分析武汉地区非综合征性耳聋（nonsyndromic hearing impairment，NSHI）患儿GJB2 235delC突变率和线粒体DNA A1555G突变率。方法 收集武汉市艺萌听力康复中心的94例耳聋患儿血样，非综合征性耳聋患儿88例，提取DNA后经聚合酶链反应（PCR）分别扩增GJB2基因编码区及线粒体DNA，ApaI酶切分析GJB2 235位点的C缺失突变，Prev—DAF药物性耳聋基因诊断试剂盒分析线粒体1555位点的A—G突变，对GJB2 235ddC及线粒体DNA A1555G的突变率进行统计分析。结果 88例患儿中9例（10．23％）为GJB2 235delC纯合突变，7例（7．96％）为GJB2 235delC杂合突变；2例（2．27％）存在线粒体DNA A1555G点突变。在分子水平能够明确诊断者占20．46％。结论 武汉地区耳聋患者存在较高的遗传性耳聋发生率，应用基因诊断技术可以在耳聋患者病因调查中进行快速诊断筛查，达到防止再生育聋儿、指导聋儿康复等积极效果。     

中国西北地区线粒体DNA12SrRNAA1555G和GJB2基因突变

目的研究mtDNA 12SrRNA A1555G突变和GJB2突变在西北地区非综合征型感音神经性聋患者中的流行情况,探讨GJB2基因与mtDNA A1555G点突变的关系。方法收集本地区221例非综合征感音神经性聋患者的基因组DNA,多聚酶链反应扩增线粒体DNA和GJB2基因目的片断,Alw26Ⅰ限制性内切酶检测A1555G点突变,对酶切阳性病例和全部的GJB2基因的PCR产物进行DNA测序。结果21例患者检出mtDNA 12SrRNA A1555G突变;发现GJB2基因11种序列改变,有44例患者检出GJB2致病突变,235delC占携带致病突变患者的54．54％：在21例A1555G突变患者中,11例为GJB2基因多态改变,9例未检出GJB2基因序列改变,1例为109G→A（V371）突变。结论mDNA 12SrRNA A1555G在这一地区人群中有较高的发生频率．235delC是本地区GJB2基因突变的主要形式,GJB2基因突变不是mtDNA A1555G突变致聋的主要修饰因素。     

与非综合征型聋相关缝隙连接蛋白31及线粒体12SrRNA基因突变

 耳聋是影响人类健康和造成人类残疾的常见疾病,它主要由遗传因素和环境因素引起。遗传性聋包括综合征型聋和非综合征型聋,其中非综合征型聋约占70%。 GJB3及线粒体12SrRNA基因突变和非综合征型聋密切相关。本文就GJB3及线粒体12SrRNA基因突变与非综合征型聋的相关性进行综述,进一步明确其发病的相关性,在明确部分非综合征型聋病因的同时,更好的为患者及其家族成员提供准确的遗传咨询和指导,为临床防聋治聋提供依据及策略。     

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.     

非综合征型聋患者GJB2 235delC及线粒体DNA A1555G突变分析

目的 对非综合征型聋患者进行聋病分子病因学分析。方法 对北京第三聋哑学校学生进行耳聋病因问卷调查、纯音测听检查，应用PCR扩增及限制酶切方法对158名非综合征型感音神经性聋患者进行GJ-B2和线粒体DNA12SrRNAA1555G基因突变的检测。结果 在158例感音神经性聋患者中，5例（3．16％）存在线粒体DNA12SrRNAA1555G点突变，其中2例有明确的氨基糖甙类抗生素用药史；24例（15．18％）存在GJB2235delC纯合性突变；12例（7．59％）存在GJB2 235delC杂合性突变。在基因水平明确诊断或强烈提示遗传性聋者占25．93％。结论 对GJ-B2 235delC突变和线粒体DNA12SrRNAA1555G突变的基因筛查可以明确或提示部分非综合征型聋的病因，对防聋、指导聋儿家庭婚育及评估人工耳蜗手术预后起到重要作用。     

赤峰市特教学校重度感音性聋分子病因学分析--GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变筛查报告

目的 调查内蒙古赤峰市聋哑学校重度感音性耳聋病因学情况。方法 对赤峰市聋哑学校140名学生进行耳聋病因问卷调查、纯音听阈测试。所有受检学生均采集外周血并提取DNA．进行线粒体DNA 12SrRNA A1555G点突变检测、GJB2基因突变检测。结果 1例（0．71％）存在线粒体DNA A1555G点突变；16例（11．43％）存在GJB2 235delC纯合突变，19例（13．57％）存在GJB2 235delC杂合突变。结论 赤峰市耳聋患者存在较高的遗传性耳聋发生率，并呈现明显的地域特点。通过聋病分子诊断，可达到防聋、指导聋儿康复及评估耳聋预后等积极效果。     

运城市聋哑学校重度感音性聋分子病因学分析--GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变筛查报告

目的 调查山西省运城地区重度感音性耳聋病因学情况。方法 对运城市聋哑学校142名学生进行耳聋病因问卷调查、纯音听阈测试，对其中139名非综合征性感音神经性耳聋患者进行线粒体DNA 12SrRNA A1555G点突变检测和GJB2基因突变检测。结果 7例（5．04％）存在线粒体DNA A1555G点突变，8例（5．76％）存在-GJB2 235delC纯合突变，14例（10．07％）存在 -GJB2 235delC杂合突变，在分子水平能够明确诊断者占20．87％。结论 运城地区耳聋患者存在较高的遗传性耳聋发生率，特别是线粒体DNA 12SrRNA A1555G突变发生率高于全国平均水平，通过聋病分子诊断，可达到防聋、指导聋儿康复及评估耳聋预后等积极效果。     

Molecular analysis of the GJB2, GJB6 and SLC26A4 genes in Korean deafness patients

OBJECTIVES: Mutations in the GJB2, GJB6 and SLC26A4 genes are a frequent cause of hearing loss in a number of populations. However, little is known about the genetic causes of hearing loss in the Korean population. METHODS: We sequenced the GJB2 and GJB6 genes to examine the role of mutations in these genes in 22 hearing loss patients. We also sequenced the SLC26A4 gene in seven patients with inner ear malformations, including enlarged vestibular aqueduct (EVA) revealed by computer tomography. RESULTS: Coding sequence mutations in GJB2 were identified in 13.6% of the patients screened. Two different mutations, 235delC and T86R were found in three unrelated patients. The 235delC was the most prevalent mutation with an allele frequency of 6.9% in our patient group. No mutations, including 342-kb deletion, were found in GJB6 gene. Three different variants of SLC26A4 were identified in the EVA patients, including one novel mutation. Four EVA patients carried two mutant alleles of SLC26A4, and at least one allele in all patients was the H723R mutation, which accounted for 75% of all mutant alleles. CONCLUSIONS: Our results suggest that GJB2 and SLC26A4 mutations together make up a major cause of congenital hearing loss in the Korean population. Further studies may be able to identify other common variants that account for a significant fraction of hearing loss in the Korean population.     

GJB2 mutations in the Swiss hearing impaired

OBJECTIVE: Mutations in the GJB2 gene encoding connexin 26 (Cx26) protein are a major cause for nonsyndromic autosomal recessive and sporadic deafness. However, its contribution to hearing impairment in Switzerland remains undefined. To determine the frequency and type of GJB2 mutations in the Swiss hearing-impaired population diagnosed under the age of 2 yr and at 2 yr and older and to assess the effectiveness of denaturing high-performance liquid chromatography (DHPLC) in screening for mutation in GJB2. METHODS: Thirty-four patients with hearing impairment underwent mutation screening of the single coding exon of GJB2 with DHPLC followed by bidirectional sequencing to identify sequence alterations. RESULTS: GJB2 mutations were more common in children diagnosed with hearing impairment under the age of 2 yr compared to the group 2 yr and older. In patients under age 2 yr, 9 of 20 (45%) harbored 13 GJB2 mutations including a common 313del14nt mutation; four of these patients were homozygous or compound heterozygous for GJB2 mutations. In contrast, 2 of 14 patients in the 2 yr and older group (14%) had a single mutation in GJB2. The 35delG mutation was exclusively found in 5 patients under the age of 2 yr. DHPLC for mutation screening was 100% sensitive and 83% specific for detecting sequence alterations in GJB2. CONCLUSIONS: In Switzerland, GJB2 mutations are a major cause of nonsyndromic hearing impairment in children under the age of 2. Similar to other populations, GJB2 mutations are uncommon in the affected Swiss patients identified after 2 yr. Although 35delG mutation is common in the hearing-impaired children under the age of 2, it was absent in patients diagnosed with hearing impairment after the age of 2. DHPLC is a highly sensitive tool for detection of GJB2 mutations.     

Kongenitale Schwerhörigkeit

BACKGROUND: About 50% of congenital non-syndromic hearing impairment is caused by genetic factors. Research on the genetics of deafness has revealed a vast number of relevant genes. Mutations in the GJB2 gene have been shown to be the most common in several populations. METHODS: Mutation analysis of the genes for connexin 26, 30 and 31 (GJB2, GJB6 and GJB3) was performed in 67 patients with profound hearing loss. RESULTS: Of the participants, 9% had two pathogenic mutations in the GJB2 gene. Pedigree information indicates that in these families further offspring have a 25% to a 100% chance of having hearing impairment. CONCLUSIONS: Patients with non-syndromic hearing impairment should be offered molecular diagnostics of the GJB2 gene. Genetic counseling is mandatory for mutation carriers in order to advise them on the individual consequences of the gene test results.     

Phenotype of patients showing hearing impairment based on the 35delG mutation in the connexin 26 gene

BACKGROUND: Hereditary hearing impairment constitutes a heterogeneous class of disorders showing different patterns of inheritance and involving multiple genes. Mutations in the GJB2 gene, especially the 35delG mutation, have been established as a major cause of inherited and sporadic nonsyndromic hearing impairment in different populations. METHODS: We analyzed 14 northeast Hungarian families and 69 sporadic cases with nonsyndromic hearing impairment for the 35delG mutation. Sixty-five patients showing a homozygous 35delG mutation were examined regarding their audiologic phenotype. RESULTS: In general, these patients (70%) showed a prelingual, sensorineural, bilateral, symmetric hearing impairment without progression. The audiograms demonstrated sloping as well as flat patterns. CONCLUSIONS: The severity of hearing impairment varied in 30% of all analyzed patients, making genetic counseling difficult.     

GJB2, SLC26A4 and mitochondrial DNA A1555G mutations in prelingual deafness in Northern Chinese subjects

CONCLUSION: This genetic epidemiological study demonstrated that 26.65% of the prelingual deafness in Northern Chinese patients can be detected at younger ages by genetic testing of three common hearing loss genes (GJB2, SLC26A4 and mtDNA A1555G), and thus, early intervention measures could be undertaken to help them in language acquisition. OBJECTIVES: The GJB2, SLC26A4 and mtDNA A1555G mutations are the prevalent causes of prelingual deafness worldwide. Numerous studies have revealed that the forms and frequencies of the mutations in the three genes are largely dependent on the ethnic or geographic origins. Hence, this study aimed to characterize the mutation profiles of the three genes in prelingual deafness in Northern Chinese patients. SUBECTS AND METHODS: An investigation of 514 patients with prelingual deafness and 117 controls with normal hearing was conducted. Bidirectional sequencing (or enzyme digestion) was applied to identify sequence variations. RESULTS: This study revealed that 26.65% patients had two mutated alleles (homozygote or compound heterozygote) of GJB2 (9.14%) or SLC26A4 (8.95%) and/or an mtDNA A1555G (8.56%) mutation. In detail, 19.26% patients carried GJB2 mutations including 10.12% single mutant carriers. 235delC was the most common type, making up 69.18% of all mutants for GJB2. The mutant carrier rate for SLC26A4 was 15.2%, including 6.23% single mutant carriers. The two most common types (IVS7-2A > G and H723R) accounted for 51.61% and 33.06% mutations, respectively. Forty-five patients had mtDNA A1555G, giving a frequency of 8.75%. In the control group with normal hearing, 2.56%, 1.71% and 0% of the subjects carried a single mutant for GJB2, SLC26A4 and mtDNA A1555G, respectively.     

甘肃省375例非综合征型聋患者聋病易感基因突变检测分析

目的 通过对甘肃省部分非综合征型聋患者进行聋病易感基因筛查,从分子水平了解其遗传病因及特点.方法 采集甘肃省375例非综合征型聋患者的外周静脉血5~10 ml,提取基因组DNA,运用SNPscan技术检测GJB2基因2个外显子36个突变位点、SLC26A4基因21个外显子77个突变位点和mtDNA12SrRNA A1555G及C1494T突变.结果 375例非综合征型聋患者中,23例携带mtDNA12SrRNA A1555G均质性突变(6.13%, 23/375),2例携带mtDNA12SrRNA C1494T均质性突变(0.53%, 2/375);检出GJB2基因突变致聋者42例(11.20%, 42/375),其中纯合突变31例(8.27%, 31/375)、复合杂合突变11例(2.93%, 11/375),GJB2基因单杂合突变携带者25例(6.67%,25/375),c.235delC为最常见的突变类型,等位基因频率为8.80%(66/750);检出SLC26A4基因突变致聋者29例(7.73%, 29/375),其中纯合突变17例(4.53%, 17/375)、复合杂合突变12例(3.20%, 12/375),SLC26A4基因单杂合突变携带者14例(3.73%,14/375),c.919-2A>G和c.2168A>G为其最主要的突变类型,等位基因频率分别为5.20%(39/750)和2.0%(15/750).结论 甘肃省部分非综合征型聋患者mt DNA12SrRNA A1555G突变检出率明显高于全国水平(2.83%,57/2016),而GJB2、SLC26A4基因突变检出率与全国水平相近;三个常见聋病易感基因筛查可为25.60%的本组耳聋患者提供明确的分子病因学诊断.     

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.