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.     

中国非综合征遗传性聋人群GJB6基因突变分析

目的：研究GJB6基因[连接蛋白30（Cx30）-]在中国非综合征遗传性聋人群中的突变情况。方法：用特定引物对372例非综合征遗传性聋患者（其中295例分子病因不明，77例携带GJB2病理性单等位基因突变）和182例正常对照者进行聚合酶链反应，检测GJB6基因的342kb大片段缺失del（GJB6〉D13S1830），并进行GJB6基因编码区扩增，以产物直接测序方法进行突变检测及鉴定。结果：372例耳聋患者中未发现GJB6 del（GJB6〉D13S1830），其中1例发现携带GJB6基因点突变404C〉A，导致了氨基酸的错义改变T135K，多物种Cx30氨基酸序列进化分析证实该点位于Cx30高度保守的第3跨膜区。对照组中未发现同样突变。结论：GJB6基因突变在中国耳聋人群中整体发生频率较低，GJB6基因可暂不列为第一线耳聋基因检测项目。     

陕西省非综合征型耳聋患者GJB2基因突变分析

目的：分析陕西省非综合征型耳聋患者GJB2基因的突变类型及突变频率。方法采集陕西省800例散发非综合征型耳聋患者和104例听力正常者外周血,提取基因组DNA,采用聚合酶链反应扩增GJB2基因全部编码区并进行测序,序列与GJB2基因标准序列进行比对分析。结果共检出29种突变类型,包括5种多态性改变、19种病理性突变以及5种未见报道的突变类型。耳聋患者与对照组间235delC和299_300delAT的检出率差异具有统计学意义。153例患者由于携带GJB2基因纯合/复合杂合突变致聋。结论 GJB2基因235delC、299_300delAT以及176_191del16为陕西省非综合征型耳聋患者最常见的三种突变类型。     

中国散发耳聋患者GJB6基因的突变筛查

目的研究中国散发耳聋患者与缝隙连接蛋白beta-6基因(gap junction protein beta 6 gene,GJB6)突变的相关性。方法分别设计扩增GJB6基因编码区和大片缺失后产物的引物各1对,应用PCR产物直接测序方法对各种感音神经性耳聋患者214例、正常听力者86例进行GJB6基因的突变检测及鉴定。结果没有发现在欧美耳聋人群中常见的GJB6大片段缺失,在214例患者中仅发现GJB6基因一种杂合错义突变,为一个新的突变形式233(C→A),进一步的各物种多种连接蛋白氨基酸序列进化分析证实该突变位点位于C×30高度保守的第二跨膜区。86例正常对照组中未发现同样突变。结论通过研究发现GJB6突变不是中国散发耳聋患者中的常见致病因素,为下一步开展耳聋相关基因和临床基因诊断研究打下了基础。     

GJB2基因致病突变杂合携带者核心启动子的研究

目的：探讨GJB2基因致病突变杂合携带的语前聋患者在核心启动子区域是否存在影响功能的碱基突变。方法从前期收集的1750例耳聋患者中选取20例GJB2基因致病突变杂合携带的语前感音神经性耳聋患者和20例GJB2基因无致病突变的语前聋患者，同时选取22例听力表型正常人作为对照。利用其外周血白细胞基因组DNA作模板，运用聚合酶链反应(PCR)的方法对耳聋患者和对照组GJB2基因第一外显子和核心启动子区域进行扩增，扩增产物纯化后进行测序，运用DNAStar软件对测序结果进行生物信息学分析、比对。结果40例患者在GJB2基因第一外显子区未发现突变。20例GJB2致病突变杂合携带者中12例患者在转录起始位点上游-229位点存在T>C碱基改变，呈杂合携带形式；20例GJB2基因无致病突变的耳聋患者中7例在转录起始位点上游-229位点存在T>C碱基改变，呈杂合携带形式，7例在-229位点存在T>C纯合携带形式；22例听力正常对照者10例在转录起始位点上游-229位点存在T>C碱基改变，呈杂合携带形式，3例在转录起始位点上游-229位点存在T>C纯合携带形式。结论本研究发现的GJB2基因转录起始位点上游出现的-229位点T>C碱基改变不是致病突变，目前GJB2致病基因杂合携带的耳聋患者中GJB2基因与耳聋的关系尚难确定。     

携带GJB2单杂合突变非综合征型耳聋患者GJA1突变分析

目的探讨携带GJB2基因单杂合突变非综合征型耳聋患者GJA1基因突变情况。方法对205例GJB2单杂合突变的非综合征型耳聋患者进行GJA1外显子2直接测序,对照组为111例听力正常成年人。结果 205例GJB2单杂合突变患者中,GJA1c.IVS2+1insA杂合突变3例(1.45%),c.456G>A和c.717G>A各1例,都为杂合同义突变。111例对照组中,c.IVS2+1insA杂合突变3例(2.70%),c.466A>G杂合突变1例。两组c.IVS2+1insA突变率无明显差异(校正χ2=0.115,P=0.735>0.05)。结论 GJB2单杂合突变非综合征型耳聋患者中GJA1检测未见致病突变。     

山东省滨州市特教学校耳聋学生分子病因学分析——GJB2235delC突变、线粒体DNA12S Rrna A1555G突变和SLC26A4ⅣS7-2A>G突变筛查报告

目的 对山东滨州市特教学校学生进行耳聋分子流行病学调查,了解耳聋的常见分子病因.方法 对山东省滨州市阳信、无棣、惠民三县特教学校年龄5～19岁的78名重度耳聋学生进行遗传性耳聋问卷调查、全面体格检查、耳鼻咽喉专科检查以及听力学评估(纯音测听和声导抗)等,应用限制性内切酶法分别对GJB2基因235delC突变、线粒体DNA 12S rRNA基因A1555G点突变进行分析,应用直接测序法检测SLC26A4基因ⅣS7-2A>G突变.结果 非综合征性耳聋74例.其中,10例(13.51%)携带GJB2基因235delC纯合突变,1例(1.35%)携带GJB2基因235delC和299DelAT复合杂合突变,3例(4.05%)携带GJB2基因235delC杂合突变,2例(2.70%)携带GJB2基因299DeLAT杂合突变;5例(6.76%)携带线粒体DNA 12S rRNA基因A1555G点突变;3例(4.05%)携带SLC26A4基因ⅣS7-2A>G纯合突变,1例(1.35%)携带SLC26A4基因ⅣS7-2A>G杂合突变.18.92%(14/74)的非综合征性耳聋患者携带GJB2基因235delC和SLC26A4基因ⅣS7-2A>G双等位基因突变(纯合突变+复合杂合突变);8.11%(6/74)的非综合征性耳聋患者携带GJB2基因和SLC26A4基因ⅣS7-2A>G单杂合突变.4例综合征性耳聋患者在所检测范围内均未发现突变.结论 山东省滨州地区特教学校耳聋患者存在较高的GJB2基因235delC、线粒体DNA 12SrRNA基因A1555G和SLC26A4基因ⅣS7-2A>G突变发生率,线粒体DNA 12S rRNA 基因A1555G突变发生率高于全国平均水平.聋病分子流行病学调查提示山东省滨州地区23.08%的特教学校耳聋患者在分子水平能够明确诊断,另有8.97%的患者有强烈的遗传倾向.准确的耳聋早期诊断、遗传咨询、及时干预和治疗在这一地区的聋哑人群中是非常重要的.     

耳聋-掌跖皮肤角化综合征的连接蛋白基因型和表型分析

目的GJB2、GJB6、GJB3基因与遗传性耳聋及角化病有关，以GJB2、GJB6、GJB3基因为候选基因，研究1例伴有掌跖角化病的综合征型耳聋先证者的分子病因，探讨其表型及遗传特征。方法 采集先证者及其父母外周血并提取DNA，对GJB2、GJB6、GJB3基因编码区进行PCR扩增，以直接测序的方法进行突变分析。结果 先证者及其父母GJB3、GJB6基因测序未发现突变。先证者携带GJB2基因R75W单等位基因突变，其父母未携带此突变，在证实先证者与其父亲的亲子关系后明确先证者携带的R75W为新生突变。301名中国正常对照中未发现GJB2基因R75W突变。结论 在中国首次发现了GJB2基因新生突变R75W，此突变可能以显性方式遗传，导致耳聋-掌跖皮肤角化综合征。在不同种族R75W导致的耳聋多为双侧重度到极重度感音神经性聋。而皮肤表型的严重程度有所不同。     

GJB2和SLC26A4基因部分罕见变异的致病性研究

目的通过对听力正常的耳聋人群亲属的基因筛查,对隐性遗传性耳聋基因部分罕见错义序列变异的致病性提出一种简单而有效的排查方法。方法收集800例具有不同程度听力障碍患者的DNA样本,通过多聚酶链反应（PCR）扩增GJB2和/或SLC26A4基因片段（包括编码外显子和邻近的侧翼区域）,并对PCR产物进行Sanger测序和序列分析。当先证者含有明确致病突变时,在取得同意的情况下进一步对其听力正常的亲属进行相应基因的突变检测。结果在3个携带GJB2或者SLC26A4基因突变的先证者亲属中,一些正常听力者以复合杂合的形式同时携带GJB2或者SLC26A4基因的一个致病性明确突变和一个致病性不明确的罕见序列变异,包括GJB2基因p.T123N/c.235delC突变(2例)和SLC26A4基因 p.A434T/c.919-2A>G突变(1例)。结论GJB2基因p.T123N和SLC26A4基因p.A434T可基本排除为外显率较高的致病性突变的可能性。以上关于隐性遗传性耳聋基因疑似突变致病性的排除方法相对简便易行,通过大样本量的基因筛查可以为临床遗传性耳聋基因诊断和遗传咨询提供更可靠、明确的依据。     

GJB2、SLC26A4基因致病性突变与内耳CT表型关系的研究

目的研究感音神经耳聋GJB2、SLC26A4基因致病性突变与内耳CT表型之间的关系,探讨这两种基因检测在诊断感音神经性耳聋患者是否存在内耳畸形方面的作用。方法按DNA测序的方法检测2686例感音神经性耳聋患者GJB2、SLC26A4基因致病性突变情况,以Sennaroglu分类为标准统计以上患者内耳CT表型情况,分析GJB2、SLC26A4基因型与CT表型之间的关系。结果 1、2686例患者中共检出GJB2基因致病性突变429例(双等位基因纯合突变220例、复合杂合突变207例、单等位基因显性突变2例),共检出SLC26A4基因致病性突变596例(双等位基因纯合突变169例、复合杂合突变427例)。2、2686例患者中内耳畸形873例(Mondini畸形371例、单纯大前庭水管338例、其它164例);内耳CT正常1813例。3、GJB2基因致病性突变99.30%(426/429)在内耳CT正常组中检出,SLC26A4基因致病性突变100%(596/596)在前庭水管扩大相关内耳畸形中检出。结论 GJB2基因致病性突变与内耳正常CT表型密切相关;SLC26A4基因致病性突变与前庭水管扩大相关内耳畸形密切相关。     

GJB2 gene mutations in newborns with non-syndromic hearing impairment in Northern China

Mutations in GJB2 account for the majority of recessive forms of prelingual hearing loss. However, in most previous studies it was not possible to distinguish between congenital (present at birth) and non-congenital prelingual hearing loss. In the present study, the frequency of GJB2 alleles in 20 newborns with bilateral severe-to-profound non-syndromic hearing impairment (NSHI) who were found at birth through newborn hearing screening and clinical examination is reported. PCR was used to amplify the coding region of GJB2 gene followed by sequencing analyses. Fifty volunteers with normal hearing were included as controls. Results showed that three cases were 235delC/235delC homozygotes; one was 235delC/605ins46 compound heterozygotes, 605ins46 mutation was a novel mutation reported in the Chinese population; another was 235delC/299-300delAT compound heterozygotes. 25% (5/20) of the deafness in newborns studied was caused by GJB2 gene mutations. The frequency of 235delC allele carrier in patients and in control group was 22.5% and 1%, respectively. One case was identified as being a 235delC heterozygote without other mutations detected. Besides, multiple polymorphisms such as V27I, V37I, E114G, T123N were also detected. In conclusion, GJB2 analysis is an important test that identifies a major cause of newborns with bilateral severe-to-profound NSHI screened by universal newborn hearing screening in Northern China. The most common pathologic mutation of GJB2 in studied cases was 235delC. Molecular analysis and genetic counseling will be extremely important for congenital deafness present at birth.     

Screening for monogenetic del(GJB6-D13S1830) and digenic del(GJB6-D13S1830)/GJB2 patterns of inheritance in deaf individuals from Eastern Austria

Genetically caused congenital deafness is a common trait affecting 1 in 2000 newborn children and is predominantly inherited in an autosomal recessive fashion. Genes such as the gap junction protein beta 2 (GJB2) encoding for Connexin (Cx26) and GJB6 (Cx30) are known to cause sensorineural deafness. Autosomal recessive deafness has been linked both to the monogenetic occurrence of mutated GJB2 or the GJB6 deletion del(GJB6-D13S1830) and digenic GJB2/del(GJB6-D13S1830) inheritance. Monogenetic GJB2 alterations are responsible for 25.5% of deafness in the eastern Austrian population. An additional 9.8% are heterozygous carriers of a single GJB2 mutation which is not responsible for deafness alone. Del(GJB6-D13S1830) and GJB2/del(GJB6-D13S1830) mutations have been shown to be the second most frequent cause of deafness in different populations. To address the question of the relevance of mutations in GJB6 either as a monogenetic or a digenic GJB2/del(GJB6-D13S1830) cause of deafness in this population, 76 unrelated individuals (33 families and 43 sporadic cases) were screened using PCR strategies. Similar to studies in other hard of hearing populations with similar or lower carrier frequencies of single GJB2 mutations, the presence of del(GJB6-D13S1830) was not detected in any individual within the patient group. Data therefore exclude a digenetic association of del(GJB6-D13S1830) with heterozygous GJB2 mutations as a cause of deafness in a representative sample of the population from Eastern Austria.     

Phenotypic variability of non-syndromic hearing loss in patients heterozygous for both c.35delG of GJB2 and the 342-kb deletion involving GJB6

Mutations in GJB2, encoding the gap junction protein connexin 26, are the most common cause of inherited non-syndromic hearing loss (NSHL), with a broad spectrum of mutations leading to recessive as well as dominant forms. It has been shown that patients who are compound heterozygous for a 342-kb deletion (Delta(GJB6-D13S1830)) involving a large portion of the 5'-part of GJB6, encoding connexin 30, and a GJB2 mutation develop NSHL due to a trait with a digenic pattern of inheritance. We have used a mutation-specific polymerase chain reaction assay to screen NSHL patients for the presence of Delta(GJB6-D13S1830) and identified two families segregating both c.35delG in GJB2 and Delta(GJB6-D13S1830). Remarkably, the severity of hearing loss due to heterozygosity for c.35delG in GJB2 in conjunction with Delta(GJB6-D13S1830) is considerably different in members of the two families, ranging from congenital deafness in one to moderate/severe hearing loss with congenital onset in the other case.     

A study of GJB2 and delGJB6-D13S1830 mutations in Brazilian non-syndromic deaf children from the Amazon region

Hearing impairment affects about 1 in 1000 newborns. Mutations in the connexin 26 (GJB2) gene rank among the most frequent causes of non-syndromic deafness in different populations, while delGJB6-D13S1830 mutation located in the DFNB30 locus is known to cause sensorineural hearing loss. Despite the many studies on the involvement of GJB2 mutations in hearing impairment in different populations, there is little information on genetic deafness in Brazil, especially in the Amazon region.ObjectiveTo determine the prevalence of GJB2 mutations and delGJB6-D13S1830 in 77 sporadic non-syndromic deaf patients.MethodThe coding region of the GJB2 gene was sequenced and polymerase chain reaction was performed to detect the delGJB6-D13S1830 mutation.ResultsMutant allele 35delG was found in 9% of the patients (7/77). Mutations M34T and V95M were detected in two distinct heterozygous patients. Non-pathogenic mutation V27I was detected in 28.6% of the patients (22/77). None of the deaf patients carried the delGJB6-D13S1830 mutation.ConclusionMutant alleles on gene GJB2 were observed in 40% (31/77) of the subjects in the sample. Pathogenic variants were detected in only 12% (9/77) of the individuals. More studies are required to elucidate the genetic causes of hearing loss in miscegenated populations.     

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.     

Prevalence of GJB2 mutations and the del(GJB6-D13S1830) in Argentinean non-syndromic deaf patients

Genetically caused congenital deafness is a common trait affecting 1 in 2000 children and it is predominantly inherited in an autosomal recessive fashion. Several mutations in the GJB2 gene and a deletion of 342 kb in GJB6 (delGJB6-D13S1830) have been identified worldwide in patients with hearing impairment. The aim of this study was to determine the prevalence of these mutations in Argentina. Non-syndromic 46 probands (17 familial and 29 sporadic cases) were genetically evaluated. Mutations in GJB2 and/or delGJB6-D13S1830 were found in 19 patients, accounting for 41.3% of the sample. Of the 46 patients investigated in this study, 12 (26.1%) were diagnosed to carry sequence variations in both alleles; all but one, were considered causative for hearing impairment in those patients. In 7 out of 46 patients (15.2%) only one mutant allele was detected. Of their 38 chromosomes, 71% resulted with mutations in the GJB2 gene and 11% in GJB6. The most frequent mutation in GJB2 (24%) was c.35delG (11% homozygous and 13% heterozygous and compound heterozygous). In addition, 11 sequence variations different from c.35delG, were identified in the coding region of the GJB2 gene: T8M, V27I, M34T, E47X, R75W, W77R, I82M, L90P, E129K, V153I, M163V. The delGJB6-D13S1830 mutation was found in 4 patients (9%), 3 of them associated with GJB2 mutations, resulting in compound heterozygous for the DFNB1 locus. The present study demonstrates that mutations in the GJB2 gene and the delGJB6-D13S1830 are prevalent in the Argentinean population.     

Occurrence of del(GIB6-D13S1830) mutation in Italian non-syndromic hearing loss patients carrying a single GJB2 mutated allele

Molecular screening for GJB2 (connexin 26) mutations represents the standard diagnostic approach for the genotype definition of non-syndromic deafness. Nevertheless, a single GJB2 pathogenic mutation is detectable in a relevant number of cases, therefore failing to explain the phenotype. We aimed at assessing the occurrence of the recently described del(GIB6-D13S1830) mutation, occurring in the connexin 30 gene, in a group of Italian hearing-impaired patients carrying a single GJB2 mutated allele. A total of 59 non-syndromic hearing loss (NSHL) patients were screened for GJB2 mutations. Among these, nine NSHL patients were found to be heterozygous for a single GJB2 mutation. These patients, heterozygotes for different GJB2 mutated alleles (35delG, L90P, M34T, V153I), together with 11 additional 35delG/neg cases previously described, were studied for the presence of the del(GIB6-D13S1830) mutation. Two double heterozygotes del(GIB6-D13S1830)/35delG were identified. In both cases the degree of hearing loss was profound. Furthermore, GJB2 molecular screening led to the identification of a novel change (T55G) occurring in compound heterozygosity with the V37I mutation. In conclusion, our data suggest a significant frequency of del(GIB6-D13S1830) mutation in Italian hearing-impaired subjects (10% of unexplained GJB2 heterozygotes) similar to that reported in other European countries.     

200例非综合征型聋患者GJB3和GJB6基因突变分析

目的研究广东、湖南和广西三省非综合征型聋患者GJB3和GJB6基因突变的特征。方法选择200例来自广东、湖南和广西三省的非综合征型聋患者,提取外周血DNA,PCR扩增后,进行GJB3、GJB6基因编码区测序和GJB6大片段缺失del(GJB6-D13S1830)及del(GJB6-D13S1854)突变检测。结果 200例患者中发现GJB3 580G>A杂合突变2例,其中1例为GJB2 109G>A和GJB3 580G>A复合杂合突变,250G>A杂合突变1例,474G>A杂合突变1例,357C>T杂合突变35例,纯合突变1例,474G>A为首次发现。GJB3等位基因突变频率为1%(4/400)。未发现GJB6基因突变。结论本组广东、湖南和广西三省非综合征型聋患者GJB3基因等位基因突变率为1%;GJB6基因突变致聋罕见。     

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.     

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.