Cx26缺陷遗传性耳聋病理机制的研究进展

GJB2基因编码的缝隙连接蛋白26(Connexin26,Cx26)是耳蜗中最重要的一种缝隙连接蛋白(Cx),在耳蜗缝隙连接(Gap Junction,GJ)中高度表达。Cx26是最常见和危害人群最广的耳聋基因,该基因缺陷不仅导致先天性耳聋,也可引起迟发性耳聋。早前人们推测Cx26突变引起耳聋的原因可能是Cx26缝隙连接功能障碍致耳蜗内淋巴液K+循环障碍。近些年来研究发现,Cx26缺陷耳聋主要是因为耳蜗发育障碍致先天性耳聋,耳蜗主动放大障碍致迟发性耳聋。本文就近年来Cx26缺陷先天性耳聋和迟发性耳聋病理机制的研究进展予以综述。     

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。     

缝隙连接蛋白Connexin与内耳发育的关系

缝隙连接细胞间通讯（gap junction intercellar communication，GJIC）是细胞间进行直接信息物质交换的通道，它在组织的生长发育、维持细胞间的协调稳定方面起着重要的作用。内耳组织中的细胞缝隙连接系统被认为是听觉功能正常发育和维持的重要结构之一，形成这种连接的离子通道的膜蛋白称为Connexin（Cx）。已发现在内耳表达的连接蛋白有Cx26、Cx29、Cx30、Cx31、Cx32、Cx43和Cx45。不同的连接蛋白在内耳发育过程中有不同的分布及表达特征，本文将有关这一方面的研究进展进行综述。     

Cx26、Cx30与非综合征耳聋的研究现状及基因治疗的展望

遗传性耳聋可分为综合征性耳聋(syndromic hearing loss,SHL)和非综合征性耳聋(nonsyndromic hearing loss,NSHL)。目前与遗传性耳聋关系最密切的两种连接蛋白是Cx26和Cx30,二者在耳蜗的生理功能上起着举足轻重的作用。随着人们对生活质量要求的提高,众多耳聋患者的听力亟待解决,目前基因治疗被认为是耳聋治疗最有希望的方法之一。本文就连接蛋白26、30与非综合征性耳聋的研究现状及耳聋基因治疗常用载体、常用治疗基因及内耳基因转导途径等方面的最新研究进展进行综述。     

缝隙连接蛋白connexin 26基因条件性敲除小鼠血管纹超微形态研究

目的观察不同年龄缝隙连接蛋白26(Connexin 26,Cx26)基因条件性敲除小鼠血管纹的超微病理形态学改变,探索Cx26突变的致聋机制。方法将Cx26 loxP/loxP与foxg1-cre转基因小鼠进行杂交,获得Cx26条件基因敲除小鼠模型(Foxg1-Cre cCx26ko条件性敲除小鼠,简称为cCx26ko小鼠),与野生型小鼠(wild type,WT)进行对比。分离出小鼠耳蜗标本,先制作半薄切片定位,再行超薄切片,采用透射电子显微镜(transmission electron microscope,TEM)观察血管纹细胞的超微病理改变。结果血管纹各种细胞在早期未见异常;出生后120天(postnatal day 120,P120)起细胞内出现溶酶体增多,P180天见巨大吞噬细胞,P360天见色素颗粒。结论 Connexin 26基因条件性敲除小鼠出生后早期血管纹超微形态基本正常。成年转基因动物的血管纹出现超微病理学改变,推测其与细胞异常代谢和衰老有关,这可能是Cx26突变致聋的病理机制之一。     

间隙连接蛋白基因与遗传性聋的相关性研究

目的　分析中国人无综合征耳聋的间隙连接蛋白 (Connexin31,Cx31)基因突变及突变频率和特性 ,从分子水平探讨该病的发病机理。方法　收集中国人 4 7例无综合征耳聋家系先证者 ,38例散发的无综合征耳聋患者以及 10 0例健康对照 ,应用聚合酶链反应 (polymerasechainreaction ,PCR)扩增Cx31基因编码区片段 ,通过变性高效液相色谱法 (denaturinghigh performanceliquidchromatography ,DHPLC)筛查突变 ,经DNA测序证实突变。结果　Cx31基因编码区 798C→T杂合突变在耳聋患者和健康对照组发生率分别为 14 1% (12 / 85 )和 1% (1/ 10 0 ) ,两者间差异具有非常显著性意义 (P <0 0 1)。在一个常染色体显性无综合征耳聋家系中的 2例患者发现Cx31基因编码区 5 80G→A杂合突变 ,导致A194T的错义突变 ,家系中听力正常者及健康对照无此突变。在 1例散发无综合征耳聋患者Cx31基因的编码区 ,发现 2 5 0G→A杂合突变。此外 ,本科题组以往已经对本实验中的耳聋家系及散发耳聋患者和对照筛查了Cx2 6基因突变 ,并发现 2个家系存在Cx2 6基因突变。但本实验在这 2个Cx2 6基因突变引起的无综合征耳聋家系未筛查到Cx31基因突变。而Cx31基因突变者也不存在Cx2 6基因突变。结论　Cx31基因与无综合征耳聋相关 ,在本实验中未发现Cx     

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。     

GJB2基因条件敲除小鼠的繁殖、基因型鉴定及听力检测

目的探讨GJB2基因条件敲除（conditional connexin 26 knock out ，cCx26KO）小鼠的饲养、繁殖及基因型鉴定方法，为进一步研究GJB2基因突变导致非综合征型聋的机制奠定基础。方法将引进的两对转基因小鼠Cx26loxp/loxp和Pax2-Cre/＋进行交配饲养与繁殖，选取子一代雌性Cx26loxp/-＿Pax2-Cre/＋小鼠与雄性小鼠Cx26loxp/loxp合笼交配，即获得cCx26KO小鼠。提取鼠尾组织基因组DNA ，PCR方法鉴定动物基因型。采用c-ABR检测成年cCx26KO小鼠和野生型小鼠的听力，进一步验证PCR方法的正确性。结果 cCx26KO小鼠繁殖成功后，采用 PCR 方法鉴定分析，成功获得 Cx26loxp/loxp＿Pax2Cre/＋、Cx26loxp/-＿Pax2- Cre/＋、Cx26loxp/loxp、Cx26loxp/-4种基因型小鼠，其繁殖结果符合孟德尔遗传定律。与野生型小鼠相比，cCx26KO小鼠c-ABR反应阈显著升高，约达95 dB SPL。结论 PCR方法可准确鉴定子鼠的基因型，雌性 Cx26loxp/-＿Pax2-Cre/＋小鼠与雄性Cx26loxp/loxp小鼠交配是获得cCx26KO实验小鼠的有效途径。     

非综合征型遗传性聋与GJB2的研究近况及新疆地区的研究进展

遗传性耳聋是人类最常见的遗传缺陷,可分为综合征型耳聋和非综合征型耳聋。研究已证实GJB2基因突变是导致遗传性耳聋的重要遗传因素。缝隙连接蛋白Cx26由GJB2基因编码,GJB2基因的致病突变导致Cx26结构功能的异常。既往的研究认为在常染色体隐性遗传的非综合征型耳聋中,约有50%的患者存在GJB2基因突变。由于不同人种、民族、地区等存在差异性,GJB2的突变形式呈现多样化。现就非综合征型遗传性聋与GJB2的研究情况作为基础,探讨新疆地区民族间GJB2基因突变情况予以综述。     

噪声对小鼠耳蜗外侧壁缝隙连接蛋白Connexin26表达的影响

目的 观察噪声性聋小鼠耳蜗外侧壁缝隙连接蛋白Connexin26(Cx26)表达的变化.方法 成年雄性Balb/c小鼠49只随机分为噪声组(29只)和对照组(20只).实验前两组小鼠检测听性脑干反应(ABR),随后噪声组小鼠给予高强度噪声(115 dB SPL,6小时/天,共2天12小时)暴露,并在噪声暴露后0和7天分别检测ABR.对照组不做任何处理.噪声暴露后4小时,每组取2只小鼠做耳蜗冰冻切片,18只小鼠提取耳蜗外侧壁总RNA.通过免疫组化染色法观察小鼠耳蜗外侧壁Cx26蛋白的表达,共聚焦显微镜下观察缝隙连接蛋白转运相关蛋白--β微管蛋白的表达,荧光实时定量 PCR检测小鼠耳蜗外侧壁Cx26编码基因GJB2 mRNA的表达.结果 正常小鼠耳蜗螺旋韧带可见Cx26棕黄色阳性颗粒,血管纹处未见阳性表达;噪声组小鼠耳蜗外侧壁Cx26免疫组化染色较对照组减弱;Cx26编码基因GJB2 mRNA表达量低于对照组,β微管蛋白排列稀疏紊乱,呈条索状排列,但未见明显浓集或断裂.结论 噪声可下调小鼠耳蜗外侧壁Cx26的表达,Cx26可能参与了噪声性聋的发病机制.     

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.     

Pseudodominants of two recessive connexin mutations in non-syndromic sensorineural hearing loss?

BACKGROUND: Hitherto more than hundred genes and gene loci for non-syndromic or syndromic deafness have been identified. Mutations in the connexin 26 gene (GJB2) account for up to 50 % of the cases of autosomal recessive hearing loss. The genes GJB2 (Connexin 26), GJB3 (connexin 31) and GJB6 (connexin 31) are located on chromosome 13q11-12. In the inner ear up to four different connexins are expressed. Connexins appertain to a group of gap junction proteins. These proteins can oligomerize to form single-membrane channels called connexons. Each connexon is composed of six subunits, that allow communication between adjacent cells by providing a channel for diffusion of ions, metabolites and second messengers. METHOD: Each of the exons and flanking splice regions of the connexin 26, 30, and 31 genes (GJB2, GJB3, and GJB6) have been analysed by direct sequencing. RESULTS: In the involved families three heterozygous mutations could be detected in the connexin 26 (GJB2) and connexin 30 (GJB6) genes. If a combination of two of those mutations occurs, 35DeltaG with 146/147DeltaC and 35DeltaG with GJB6-D13S1830 it results in hearing loss and deafness. CONCLUSION: By evidences of a familial background of hearing loss it is reasonable to analyse the connexin genes (GJB2, GJB3 and GJB6) for mutations, additionally to a specific hearing diagnostic, in order to enhance linguistic development through hearing aid or CI-implantation at an early stage.     

Connexin 26 and connexin 30 mutations in children with nonsyndromic hearing loss

OBJECTIVES/HYPOTHESIS: Mutations in the connexin 26 (Cx26) or gap junction beta 2 gene are the leading cause of hereditary nonsyndromic sensorineural hearing loss in Caucasians. The Cx26 coding region of 68 children with nonsyndromic sensorineural hearing loss was sequenced to determine the frequency and type of Cx26 mutations in this population. Screening was also performed for a common connexin 30 (Cx30) or gap junction beta 6 mutation (del [GJB6-D13S1830]). Children also underwent audiological testing to determine whether any correlation exists between Cx26 mutations and severity of hearing loss. STUDY DESIGN: In all, 68 children with nonsyndromic sensorineural hearing loss were screened for Cx26 and Cx30 mutations by polymerase chain reaction and direct sequencing. METHODS: Genomic DNA was amplified by polymerase chain reaction using primers that flank the entire Cx26 coding region. Screening for the 342-kb Cx30 deletion was performed using primers that amplified the breakpoint junction of the deletion. The amplicons were then sequenced in both directions and analyzed for mutations. Audiometric testing, including pure-tone audiometry and auditory evoked brainstem response, was also performed to determine the degree of hearing loss. RESULTS: Twenty-seven of 68 children tested had mutations in Cx26 with 35delG being the most prevalent. Ten additional Cx26 mutations were detected including a novel compound heterozygote. Two children were heterozygous for the Cx30 del (GJB6-D13S1830) mutation. CONCLUSION: Cx26 and Cx30 mutations were present in 41.2% of children tested in the study population. Audiometric data supported previous studies demonstrating a greater degree of hearing loss in subjects who are homozygous for the 35delG mutation.     

Lack of association between Connexin 31 (GJB3) alterations and sensorineural deafness in Austria

Mutations in the gap junction protein beta 3 (GJB3) gene encoding Connexin 31 (Cx31) are known to cause autosomal inherited sensorineural deafness, erythrokeratodermia and neuropathy. The role of Cx31 mutations has not been described in familial cases of non-syndromic hearing impairment (NSHI) in central European populations. To identify mutations in the Austrian population, highly selected familial (n=24) and sporadic (n=21) cases of isolated NSHI were screened by analysis of the complete coding sequence of Cx31, after exclusion of a common Cx26 causing deafness. Three different variations occurring in a total of 37% of all cases were identified. A C94T (R32W) missense mutation was seen in 4.4% of cases and two silent alterations C357T and C798T were detected in 8.9% and 24.4% of cases exclusively in a heterozygous pattern. No correlation between Cx31 alterations and deafness was found. To investigate the role of heterozygous Cx31 variations for a possibly combination allelic disease inheritance with Cx26 mutations as shown for Connexin 30 and Connexin 26, patients with Cx26 variations were tested. Our data suggest that Cx31 alterations are common but have no or a low genetic relevance in the Austrian hearing impaired population with or without Cx26 alterations.     

GJB2突变相关的迟发性遗传性聋研究进展

GJB2基因突变是引发非综合征型遗传性聋最常见的原因之一.GJB2编码缝隙连接蛋白26(Connex-in26,Cx26),其表达在来源于外胚层的皮肤和耳蜗中.不同于以往的共识:GJB2基因突变导致先天性听力损失,近年来的分子遗传学研究发现GJB2基因突变也导致迟发性、渐进性听力损失.且听力损失常开始于高频,然后累及中...     

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.     

Connexin 26 as a cause of hereditary hearing loss

Connexin 26 (Cx26) is an inner ear protein that forms part of the potassium recycling pathway used to maintain the osmotic balance essential for normal auditory function. Mutations in the GJB2 gene, which encodes for the Cx26 protein, recently have been implicated as the cause of up to 50% of hereditary prelingual severe-to-profound nonsyndromic hearing loss. A single mutation that results in the loss of a guanosine nucleotide at position 35, the 35delG mutation, is involved in approximately 97% of cases of Cx26-related deafness. In persons with prelingual severe-to-profound nonsyndromic hearing loss, genetic testing for Cx26-related deafness can establish a diagnosis and obviate the need for a more expensive evaluation. However, if this type of testing is considered, appropriate genetic counseling must be provided and the nuances and limitations of genetic testing must be understood.