Identification of two heterozygous deafness mutations in SLC26A4 (PDS) in a Chinese family with two siblings

Abstract

Objective: To detect genetic cause of two Chinese siblings (patient 1 and 2) with Pendred syndrome. Design: Patients and their parents underwent clinical and genetic evaluations. To identify genetic mutations, sequencing of SLC26A4 was carried out. Study sample: Two siblings and their parents. Results: Clinical evaluations showed that patient 1 suffered from bilateral postlingual progressive sensorineural hearing loss with enlarged vestibular aqueduct and slight diffuse multinodular goiter with euthyroid, and patient 2 suffered from bilateral prelingual progressive sensorineural hearing loss with enlarged vestibular aqueduct and no goiter with euthyroid. Furthermore, the sequence analysis of SLC26A4 indicated that either of the two siblings presented a compound heterozygote for the c.919A>G mutation in the splice site of intron 7 and for the c.1548insC mutation in exon 14. Their mother was a heterozygous carrier of the splice site mutation in intron 7, and their father was a heterozygous carrier of the insertion mutation in exon 14. Conclusions: Mutation analysis identified a compound heterozygous mutation (c.919A>G/c.1548insC) in SLC26A4 in two Chinese siblings with Pendred syndrome. Also, c.1548insC was first reported in the Chinese population. Although the two siblings from the same family carried the same genotype, they presented different phenotypes.     

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。     

线粒体DNA1555位点和GJB2基因及SLC26A4基因的诊断方法及临床应用

目的建立常见耳聋基因如线粒体DNA（mtDNA）1555位点、GJB2基因、SLC26A4（Pendren’s syndrome gene，PDS gene）基因突变的临床检测方法。方法来自门诊的散发耳聋患者367例，有母系家族遗传史耳聋患者60例（27个家系），来自聋哑学校的先天性聋患者20例，来自门诊经高分辩CT证实双侧前庭水管扩大患者3例，无感音神经性聋病史的对照个体50例。应用线粒体基因A1555G突变检测试剂盒检测线粒体基因1555位点的突变情况；针对20例语前聋患者进行GJB2全序列分析；针对3例大前庭水管综合征的患者，应用变性高效液相色谱技术进行SLC26A4基因的全部外显子筛查，出现异常波形之外显子行序列分析。结果在26个家系的59例患者和5例散发患者中发现mtDNA A1555G突变；20例先天性聋中发现2例GJB2 235delC纯合突变，酶切加测序发现1例235delC＋299-300delAT复合突变，均为先天性聋的肯定原因，另外2例具有109G-A杂合突变；3例大前庭水管综合征患者的变性高效液相色谱技术筛查均发现包含第7、8外显子的扩增子具有异常波形，测序证实1例为杂合的SLC26A4 G316X突变；另2例为919-2 A-G纯合突变。结论耳聋基因诊断具有显著的临床意义，可操作性强，在不远的将来耳聋的基因诊断可能会正式列为耳科临床检测项目。     

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。     

福州市特教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 对福州市聋哑学校非综合征性耳聋的患儿进行聋病分子病因学分析。方法 对福州市153名聋哑学校学生进行耳聋病因问卷调查、纯音听阈测试，并对150名非综合征性感音神经性耳聋患者进行GJB2和线粒体DNA 12SrRNAA 1555G基因突变检测。结果 150例感音神经性耳聋患者中13例（8．67％）为GJB2 235delC纯合突变，10例（6．67％）为GJB2 235delC杂合突变，1例（0．67％）存在线粒体DNA 12SrRNA A1555G点突变。在分子水平能够明确诊断者达16％。结论 福州地区G口2突变发生率低于其他学者报告的数据。线粒体DNA 12SrRNA A1555G突变低于全国平均水平。GJB2基因突变分析用于产前诊断可以降低耳聋的发病率。线粒体DNA 12SrRNA A1555G点突变检测是预防药物性耳聋的有效途径。     

Compound Heterozygosity for Two Novel SLC26A4 Mutations in a Large Iranian Pedigree with Pendred Syndrome

Objectives

The aim of this study was to detect the genetic cause of deafness in a large Iranian family. Due to the importance of SLC26A4 in causing hearing loss, information about the gene mutations can be beneficial in molecular detection and management of deaf patients.

Methods

We investigated the genetic etiology in a large consanguineous family with 9 deaf patients from Fars province of Iran with no GJB2 mutations. Initially, linkage analysis was performed by four DFNB4 short tandem repeat markers. The result showed linkage to DFNB4 locus. Following that, DNA sequencing of all 21 exons, their adjacent intronic sequences and the promoter of SLC26A4 was carried out for mutation detection.

Results

Two novel mutations (c.863-864insT and c.881-882delAC) were identified in exon 7 of the gene, in both homozygous and compound heterozygous state in patients.

Conclusion

Our results supported the importance of the SLC26A4 mutations in the etiology of hearing loss among the Iranian patients and therefore its mutation screening should be considered after GJB2 in the molecular diagnostics of hearing loss, especially when enlarged vestibular aqueduct or goiter is detected.     

采用第二代测序技术发现一个中国耳聋家庭SLC26A4基因突变

目的 明确一例非综合征型耳聋患者的致病基因.方法 收集患儿及其父母的血样,提取基因组DNA,采用SNaPshot技术和第二代测序技术进行耳聋基因检测,采用聚合酶链反应(PCR)直接测序方法对检测出的SLC26A4基因突变进行验证.结果 该耳聋患儿的SLC26A4基因存在p.V306GfsX24和p.P516PfsX11复合杂合突变,其父亲存在p.V306GfsX24杂合突变,母亲存在p.P516PfsX11杂合突变.结论 SLC26A4基因p.V306GfsX24和p.P516PfsX11复合杂合突变是导致该患者耳聋发生的原因.第二代测序技术可准确检测耳聋基因的新突变,具有一定的临床应用价值.     

遗传性耳聋家系的SLC26A 4 IVS7-2A>G基因突变分析

目的检测常染色体隐性遗传耳聋家系SLC26A4IVS7-2A〉G基因突变情况,寻找耳聋患者的发病原因,为患者提供遗传咨询。方法收集耳聋家系及散发病例的临床资料,对患者进行纯音电测听检查;应用聚合酶链反应（polymerase chain reaction,PCR）和直接测序法,对2个家系的7名患者和35名散发病例进行SLC26A4exon7＋exon8基因突变检测。结果2个家系中发现SLC26A4IVS7-2A〉G突变,其中1个家系发生SLC26A4IVS7-2A〉G杂合性突变;1个系发生SLC26A4IVS7-2A〉G纯合性突变,该突变患者为极重度感音神经性耳聋。另外,在35名散发病例中发现1例携带IVS7-2A〉G杂合性突变。结论SLC26A4IVS7-2A〉G纯合性突变为致病突变。该位点具有较高的突变率,是导致常染色体隐性遗传的常见病因之一。     

云南地区非综合征性聋患儿GJB2、SLC26A4和线粒体DNA12S rRNA基因突变分析

目的　研究云南地区非综合征性聋患儿GJB2、SLC26A4和线粒体DNA12S rRNA基因的突变情况,了解其遗传特征。方法　采集2010年1月～2014年5月我院门诊散发的139例先天性重度和极重度非综合征性感音神经性聋患儿外周血,提取DNA。应用飞行质谱技术对GJB2、SLC26A4和线粒体DNA12S rRNA编码区域中8个突变位点进行检测,包括GJB2（35delG、167delT、176-191dell6、235delC、299-300delAT）,SLC26A4（281C→T、589G→A、IVs7-2A→G、1174A→T、1226G→A、1229C→T、IVSl5+5G→A、1975G→C、2027T→A、2162C→T、2168A→G）及线粒体DNA12S rRNA（1494→T、1555A→G）。结果　139例耳聋患者中共检出41例存在致聋突变（29.49%）。GJB2基因突变24例（16.11%）,其中235delC纯合突变10例,235delC单杂合突 16例,235delC/299-300delAT复合杂合突变8例;SLC26A4基因突变16例（11.51%）,其中IVs7-2A→G纯合突变5例,IVs7-2A→G杂合突变4例,IVSl5+5G→A杂合突变2例,IVs7-2A→G/1229C→T复合杂合突变3例,2027T→A杂合突变2例;线粒体DNA12S rRNA基因同质突变1例（0.72%）,位点为1555A→G。结论　GJB2基因突变是导致云南地区非综合征性聋患儿听力损失的主要原因,235delC是其最常见的突变形式,IVs7-2A→G为SLC26A4基因主要的突变形式。对本地区耳聋患者行常见基因的筛查,将为部分患儿和家庭提供分子病因学诊断和相应的遗传学咨询。     

SLC26A4基因突变与听力表型的关系

SLC26A4是导致前庭导水管扩大的主要责任基因。该基因突变引起的听力损失多为感音神经性聋,也可为传导性或混合性聋,听力损失程度多为重度或极重度,听力曲线类型主要表现为高频下降型,也可表现为上升型、平坦型、W型及岛型。本文将SLC26A4基因突变与听力表型的关系进行文献综述,可为临床耳聋基因诊断和遗传咨询提供参考。     

湖南郴州非综合征型聋患者GJB2、SLC26A4和线粒体DNA12SrRNA基因突变分析

目的探讨湖南郴州非综合征型聋患者的分子病因特点。方法采取湖南郴州154名非综合征型聋患者的外周血,提取DNA,采用基因芯片筛查GJB2、SLC26A4和线粒体DNA12SrRNA基因的热点突变,基因芯片法未确诊的样本则采用DNA测序法进一步检测。结果两种方法共在34例(22.08%,34/154)患者中检出7种GJB2基因突变,其中235delC(13.63%,21/154)发生率最高,其次是299delAT(9.09%,14/154);在8例伴有大前庭水管的患者中检测出7种SLC26A4基因突变,包括一种新突变Q696X;3例患者被检出线粒体DNA12SrRNA基因突变。结论湖南郴州非综合征型聋患者中GJB2、SLC26A4和线粒体DNA12SrRNA基因突变的发生率与中国大部分地区相似,Q696X为新发现的SLC26A4基因突变。     

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。     

Novel compound heterozygous mutations in SLC26A4 gene in a Chinese Han family with enlarged vestibular aqueduct

ObjectiveTo identify the disease-related SLC26A4 mutants in a Chinese Han pedigree associated with Enlarged vestibular aqueduct (EVA).MethodsEVA diagnosis was based on the family history, clinical examinations, systematically audiometric evaluations, high-resolution computed tomography (HRCT) of the temporal bone, and magnetic resonance imaging (MRI) of inner ear. Sanger sequencing and mutation analysis of the SLC26A4 gene were performed in all members of this family to identify the disease-related SLC26A4 mutants. Mutations in the SLC26A4 gene were compared with 200 ethnically matched control persons to exclude common polymorphism.ResultsAll members in this family were negative for systemic and thyroid diseases. There were three subjects (I-2, II-2 and II-3) with bilateral sensorineural deafness since childhood. Temporal bone HRCT scans and inner ear MRI showed bilateral enlarged vestibular aqueduct with Mondini malformation in II-2 and II-3. A novel SLC26A4 splice-site mutation c.1001 + 5G > C was identified in compound heterozygosity with the mutation c.919-2A > G in the proband and in II-2. This novel compound heterozygote of two splice site mutations was not found in 200 normal hearing Chinese Han controls.ConclusionsA novel splice site mutation of c.1001 + 5G > C was identified, and the novel compound heterozygote of two splice site mutations, c.1001 + 5G > C and c.919-2A > G, in the SLC26A4 gene has been linked to hearing impairment in EVA patients.     

中国人非综合征型听力损失患者Cx26基因的突变分析

目的分析中国人遗传性非综合征型听力损失(nonsyndromic hearing impairment,NSHI)患者缝隙连接蛋白(connexin 26,Cx26)基因编码区的突变.方法对天津市聋哑学校的8个聋哑学生的家系中29例以及健康对照2例和有家族史但本人听力正常的遗传咨询者2例共33例取外周血提取DNA,经聚合酶链反应(polymerase chain reaction,PCR)扩增Cx26基因编码区片段,通过限制酶切指纹-单链构像多态性(restriction endonucleases fingerprinting-single strand conformation polymorphism ,REF-SSCP)分析法进行突变筛选,经DNA测序判断多态性改变或致病突变.结果 33例中有30例Cx26基因发生改变,改变率为90.91%(30/33).共发现8种不同形式的改变,包括79G→A、109G→A、161A→T、235delC、240G→A、341A→G、571T→C和608T→C,其中161A→T、240G→A和571T→C为新发现的突变.22例耳聋患者中有3例为235delC,突变率为13.64%(3/22).结论 Cx26基因235delC是中国人NSHI患者中主要的突变方式,NSHI患者中存在较多的多态性改变.     

氨基糖甙类抗生素致聋家系线粒体DNA12S和16S rRNA基因突变分析

目的 研究线粒体rRNA基因突变与氨基糖甙类抗生素致聋遗传易感性的关系，为建立相应的基因诊断方法提供依据。方法 收集了五个有明确氨基糖甙类抗生素应用史的耳聋家系共27名成员的外周静脉血标本。从白细胞中提取DNA，PCR扩增线粒体DNA片段。Alw26I限制性内切酶分析和DNA序列分析检测A1555G点突变，并对其中一个家系进行了线粒体DNAl2S和16SrRNA基因的全序列分析。结果家系A．C．D和E的2l份样品均为A1555G点突变阳性，家系B的6份样品为A1555G点突变阴性。家系B线粒体DNAl2S和16SrRNA基因全序列分析显示该家系存在16SrRNA基因第2227位“AA”插入突变。结论 本研究发现了一个A1555G点突变阴性的氨基糖甙类抗生素致聋家系，说明线粒体DNA A1555G点突变不是氨基糖甙类抗生素遗传易感性唯一的分子基础，对氨基糖甙类抗生素致聋遗传易感性的预测仅检测A1555G点突变是不够的。应与mtDNA其它相关突变位点的检测结合起来。     

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.     

贵阳市盲聋哑学校非综合征性耳聋分子病因学分析——GJB2 235delC突变和线粒体DNA 12SrRNA A1555G突变筛查报告

目的 进行贵州省贵阳地区非综合征性耳聋分子病因学调查。方法 对贵阳市盲聋哑学校150名聋哑学生进行耳聋病因问卷调查、纯音听阈测试，对其中139名非综合征性耳聋患者进行线粒体DNA 12SrDNA A1555G点突变和GJB2基因235delC突变限制性内切酶的分析。结果 139名非综合征性耳聋患者中。6例（4132％）存在线粒体DNA 12SrDNA A1555G点突变；17例（12．23％）存在GJB2 235delC纯合突变；9例（6．47％）存在GJB2235delC杂合突变，在分子水平能够明确诊断者占23．02％。结论 贵阳地区耳聋患者存在较高的遗传性耳聋发生率，线粒体DNA A1555G突变发生率和GJB2 235delC突变发生率均高于全国平均水平。耳聋基因诊断技术可以应用在地区性耳聋病因调查中进行快速筛查、诊断，并可达到防止再出生聋儿，指导聋儿康复等积极效果。