中国人黏多糖贮积症ⅣA型家系GALNS基因新突变的鉴定

目的 研究黏多糖贮积症ⅣA型(mucopolysaccharidosis type ⅣA,MPS ⅣA)患者发病的分子遗传学机制,揭示其基因型与表现型的相互关系,为产前基因诊断等创造必要的前提条件.方法 采用尿糖胺聚糖(glycosaminoglycans,GAGs)定性检测法对疑似MPS ⅣA型的先证者进行初诊,然后采用PCR及扩增产物直接测序法对先证者及其家庭成员进行突变检测.在检出GALNS基因c.1567T＞G新突变后,先后建立XspⅠ酶切鉴定法和扩增阻碍突变系统(amplification refractory mutation system,ARMS)快速特异鉴定法,对随机采集的110名正常对照与先证者及其家庭成员的GALNS基因第14外显子进行序列分析,同时采用生物信息学方法对蛋白质二级、三级结构进行预测,以及直接测定患儿GALNS酶活性的方法,对该新突变进行致病性鉴定.结果 先证者尿检呈弱阳性GAGs(±),其GALNS基因第14外显子内存在杂合的c.1567T＞G终止密码突变,第4外显子存在杂合的c.374C＞T错义突变,为两种突变的复合杂合子.其妹突变类型与先证者完全相同,其母仅在第14外显子存在杂合的终止密码突变,为该病的携带者,其父仅在第4外显子存在杂合的错义突变,也为杂合子;第14外显子的PCR产物经XspⅠ酶切后,正常对照组切出28 bp、120 bp、399 bp 3条带,而患者和携带者的母亲均切出28 bp、120 bp、148 bp和399 bp 4条带;用ARMS特异引物扩增后,正常对照组均扩增阴性,而患者及携带者均扩增阳性;蛋白质二级、三级结构预测结果显示:c.1567T＞G变异导致终止密码(TAG)突变为谷氨酸(GAG),使多肽链延长了92个氨基酸残基,导致蛋白质二、三级结构发生明显改变,而正常对照无此变化.酶活性测定的结果显示:患者的GALNS酶活性仅为8.3 nmol/17 h/mg pr,明显低于正常值(正常参考值为41.9～92.1 nmol/17h/mg pr).结论 c.1567T＞G变异是一种新的致病性突变,是引起该家系患儿发病的根本原因.

Abstract：

Objective To study the molecular genetic mechanism of mucopolysaccharidosis type ⅣA(MPS ⅣA), and reveal the relationship between the genotype and phenotype, and provide a basis for prenatal gene diagnosis in the future. Methods A preliminary diagnosis was made by qualitative detection of urinary glycosaminoglycans of the suspected MPS ⅣA proband. Then, mutation detection was performed on the proband and her family members with PCR and direct sequencing of the PCR products. After a novel c.1567T＞G mutation was detected,XspⅠrestriction enzyme digestion and amplification refractory mutation system(ARMS) fast specific identification were established to analyze the sequences of exon 14 in GALNS gene, including 110 randomly selected healthy controls, the proband and other pedigree members. At the same time, bioinformatic approaches for protein secondary, tertiary structure prediction were applied to identify the novel pathologic mutation. Results The proband's urine GAGs test was a weak positive(±),and a c.1567T＞G heterozygous termination codon mutation in exon 14 and a c.374C＞T heterozygous missense mutation in exon 4 were found. The proband was compound heterozygous of the two mutations, so was her younger sister. Her mother was a carrier with only a c.1567T＞G heterozygous mutation in exon 14. Her father had a heterozygous mutation of c.374C>T in exon 4. After XspⅠrestriction enzyme digestion, healthy controls had three bands including 28 bp, 120 bp and 399 bp, while the proband and her mother had four bands consisting of 28 bp, 120 bp,148 bp and 399 bp. For amplification by ARMS specific primers, it was negative for the controls,while it was positive for the proband and the carrier. The results of protein secondary and tertiary structure prediction showed that the c.1567T＞G mutation located in the stop codon, resulted in stop codon (TAG) changing to glutamic acid (GAG), with the peptide chain extending 92 amino acid residues, and secondary and tertiary protein structure change, which were not found in the controls. The result of enzyme assay showed that the activity of GALNS enzyme in the affected child was 8.3 nmol/17h/mg pr, which was obviously lower than the normal value (the normal range is 41.9-92.1 nmol/17h/mg pr). Conclusion These results illustrate that the c.1567 T＞G is a novel pathologic mutation, which is the main cause of the disease in this family.     

应用等位基因特异性扩增检测经典型苯丙酮尿症PAH基因第6外显子基因突变

目的建立快速简便、特异灵敏的鉴定PAH基因第6外显子c.611A〉G突变热点的基因诊断方法。方法针对突变频率较高的PAH基因第6外显子的突变热点c.611A〉G,设计等位基因特异性扩增（amplification refractory mutationsystem,ARMS）的特异引物,对山西省已经临床确诊的70例经典型PKU患儿、c.611A〉G突变患儿的家长及50例正常儿童进行第6外显子扩增,扩增产物测序验证。结果在受检的山西省患儿中,PAH基因第6外显子c.611A〉G突变位点ARMS检测结果和测序结果完全相符。结论 ARMS技术操作简便,重复性和稳定性好,可作为PAH基因热点突变的快速灵敏检测方法。     

眼皮肤白化病Ⅰ型产前基因诊断

目的对已生育过眼皮肤白化病Ⅰ型（oculocutaneous albinism type Ⅰ，OCA1）患儿的两个家系进行酪氨酸酶（tyrosinase，TYR）基因TYR的突变研究和产前基因诊断。方法应用PCR技术扩增TYR基因各外显子、外显子．内含子交界区及启动子区，直接以DNA序列测定技术分析先证者或其父母的基因突变，明确致病性突变后，检测胎儿TYR基因相应位点的DNA序列，获知胎儿的基因型。结果家系1的先证者为R278X和929insC突变复合杂合子；胎儿未获得这2种突变等位基因，基因型和表型均正常。家系2先证者的父母分别为IVS4＋3A→T和G253E突变的杂合子，胎儿只获得了父源性的IVS4＋3A→T突变等位基因，未获得母源性G253E突变等位基因，胎儿为表型正常的致病基因携带者。结论此为中国大陆首次真正意义上的OCA1产前基因诊断；应用上述基因分析方法进行OCA1产前基因诊断是可行的。     

眼皮肤白化病Ⅰ型产前基因诊断二例

目的对生育过眼皮肤白化病（oculocutaneous albinism,OCA）患儿的2个家系进行基因诊断分型,并在此基础上提供产前基因诊断。方法采用PCR扩增先证者OCA 1型疾病相关基因TYR的所有5个编码外显子,PCR产物直接测序,在确定致病突变的基础上对及家系成员进行综合分析。结果 2个OCA先证者均携带TYR基因复合杂合突变,确定2例先证者均为OCA1型患者。TYR基因共检测到3种突变：c.71G〉A,c.896G〉A和c.929ins C。产前诊断：第1个家系提示胎儿基因型与先证者一致,家属选择终止妊娠;第2个家系中胎儿为TYR基因野生型携带者,继续妊娠至足月分娩,新生儿随访正常。结论利用基因检测可为眼皮肤白化病患者提供确切的临床分型,并在此基础上提供有效的产前基因诊断。     

一例类孟买血型的家系分析和分子机制研究

目的 对1例类孟买血型个体及其家系进行表型鉴定和分子机制研究.方法 应用血清学方法检测ABO、H抗原;应用PCR技术扩增FUT1编码区序列.PCR产物经双酶切后进行直接测序分析.结果 先证者红细胞与抗H血清不凝集,血清学鉴定为Bmh.直接测序显示其FUT1基因编码区序列第547-552位A、G两碱基为纯合型缺失(CAGAGAG-CAGAG),第814位为A/G杂合,因此推测其单倍型分别为547 552delAG、547-552 delAG和814A＞G复合突变.先证者母亲、姐姐、妹妹血型均为B型,母亲、姐姐的FUT1基因分别为814A/G杂合和547-552 del/AG杂合,而妹妹为FUT1 547-552 del/AG杂合.先证者的FUT1 547-552 AG缺失和814A＞G复合突变均遗传自母亲.结论 在类孟买血型个体中首次发现FUT1 547-552delAG和814A＞G复合突变.     

高分辨熔解曲线技术在Wilson病致病基因突变鉴定中的应用

目的在一个肝豆状核变性(WD)家系中进行致病突变鉴定和产前基因诊断。方法酚-氯仿法提取外周全血或妊娠13周胎儿绒毛组织基因组DNA;利用PCR-Sanger测序技术对先证者ATP7B基因外显子及外显子/内含子衔接区序列进行突变分析;针对先证者携带的突变位点,应用聚合酶链反应(PCR)-高分辨熔解曲线(HRM)方法对先证者家系4名成员进行突变鉴定,并在此基础上为患儿母亲提供产前基因诊断。结果先证者ATP7B基因第8外显子存在纯合致病突变c.2333GT(p.R778L);该家系5名成员和4名群体正常样本分属于3种不同熔解曲线。HRM分析结果与测序结果一致,即:患儿本人为R778L的纯合子,其父母、姐姐和母亲产前诊断的胎儿均为突变杂合子,4名群体正常对照为纯合野生型。结论在一个WD家系中检测到ATP7B基因热点突变c.2333GT(p.R778L),并针对该突变建立了一种基于PCR-HRM技术的快速突变鉴定方法,成功为家系提供产前基因诊断。     

1个中央轴空病家系RYR1基因的突变分析

目的 对一个常染色体显性遗传的中央轴空病(CCD)家系进行基因诊断,探讨家系中CCD患者可能的致病机制以及基因型与表现型的关系.方法 对先证者进行病史和家族史询问以及详细的临床检查.采集先证者及其家属的外周血样本,用PCR方法扩增理阿诺碱受体1(RYR1)基因C端突变热点区(外显子90-104)的编码序列,进行序列测定,与数据库中的参考序列进行比对分析.结果 先证者及其母亲、妹妹RYR1基因第102外显子均发生了第14690位碱基G到A的点突变,此突变会导致氨基酸改变,即G4897D,家系内正常成员以及家系外的50名正常对照均未发现该突变位点.结论 本实验所研究的家系中,RYR1基因第102外显子G14690A的杂合突变为致病基因,该基因突变可能导致不同的临床表现和病理改变.     

Ⅰ型成骨不全一家系的分子诊断

目的 对Ⅰ型成骨不全(osteogenesis imperfecta,OI)1个家系进行分子诊断.方法 从先证者的基因组DNA人手,自行设计30对引物,扩增产物涵盖全部COL1A1基因52个外显子及启动子区域,并以相应引物对PCR产物进行直接测序.针对突变位点,设计扩增阻滞突变系统(amplification refractory mutation system,ARMS)引物,在60名无关对照中进行突变筛查.结果 在先证者的其中1条COL1A1等位基因上存在突变,即COL1A1基因第1441位(位于第52外显子,P30)发生了GAT→CAT改变.使原来编码的天冬氨酸被组氨酸取代(D1441H);其母亲的其中1条COL1A1等位基因上也存在相同突变,而正常对照相应的COL1A1基因序列与GenBank参考序列相同.ARMS分析显示,在60个无关对照中均未检测到D1441H突变.查阅国内外相关文献及COL1A1基因突变数据库,未发现有关COL1A1基因D1441H突变的报道.结论 建立了基于COL1A1基因突变分析的成骨不全分子诊断方法 ,并在中国人Ⅰ型成骨不全患者中发现1个新的COL1A1基因D1441H突变.     

两个斑驳病家系KIT基因突变研究

目的 对2个斑驳病家系进行致病基因突变分析,为患者及其家系成员提供遗传咨询和生育指导.方法 分别采集家系1两例患者(先证者及其父亲)、家系2先证者及3名表型正常家系成员的外周血,提取外周血DNA和RNA.应用PCR、逆转录PCR及测序等技术,从基因组水平和表达水平对此两家系先证者和患者进行KIT基因诊断,并初步探讨检测到的突变对KIT基因功能的影响.结果 家系l中两例患者KIT基因均存在IVS12+ 2_+7delinsACATCTTTA的杂合突变,该突变在cDNA水平导致KIT基因c.1765-1779del突变,在氨基酸水平导致p.Gly592Ala/del:E12突变,使得KIT基因剪切位点发生改变,即其中一条cDNA第12外显子被跨越、未转录.家系2中先证者KIT基因存在c.2401A＞C突变,3位表型正常的家系成员未见该突变.结论 确诊了两个斑驳病家系的致病原因.家系1患者KIT基因均存在IVS12+ 2_+ 7delinsACATCTTTA的杂合突变,该突变为人类基因突变数据库未记载的、新的剪切突变;家系2先证者KIT基因存在c.2401A＞C突变,结合3位表型正常的家系成员KIT基因未见c.2401A＞C突变,推测该突变为先证者患斑驳病的致病突变可能性大.为此两家系进行遗传咨询和产前诊断提供了理论依据.     

二代测序平台(NGS)在眼皮肤白化病I型诊断应用一例

目的借助Ion Torrent PGMTM测序平台对1例眼皮肤白化病(oculocutaneous albinism,OCA)患者的家系进行基因诊断分型。方法采用PCR扩增的方法对OCA常见的四个致病基因TYR、P、TYRP1和SLC45A2进行全长扩增(包括内含子和外显子),PCR产物二代测序,在确定致病突变的基础上对家系成员进行综合分析。结果先证者携带TYR基因的双重杂合突变:c.929ins C和c.1199GT,尽管先证者在P和SLC45A2基因上也发现了纯合突变,但是相应纯合突变在父母基因组中也被发现,而父母均未有临床症状表现,因此确定先证者为OCA1型患者。结论我们在一个白化病核心家系鉴定了1例由TYR基因双重杂合子突变引起的OCA1型白化病,应用二代测序方法可高效准确地为具有高遗传异质性的遗传病开展全面的基因筛查工作。     

一个近亲婚配家系中的一种P基因新突变

目的在DNA水平上对1个有2例患者的姨表兄妹近亲婚配家系中的眼皮肤白化病患者进行分型诊断。方法用PCR扩增先证者P基因及TYR基因各外显子、外显子-内含子交界区及3＇端和5＇端非翻译区，以DNA序列测定技术检测基因突变，以DNA测序技术和限制性内切酶酶切法检测该家系其他成员及群体中正常人的相应基因位点。结果先证者和其白化病妹妹为P基因A787T突变纯合子，其父母和表型正常的弟弟均为A787T突变杂合子。先证者TYR基因未见突变。群体中102名表型正常者中无A787T突变等位基因。结论在基因水平确定我国存在眼皮肤白化病Ⅱ型，同时发现了一种P基因病理性新突变。     

癌基因PPO及其同源性基因的结构分析

目的采用PPO(proliferation and phosphorylation oncogene)基因与其同源性基因的结构分析,推测PPO并验证其功能。方法利用PPO的蛋白序列寻找同源基因,比较其结构并利用蛋白免疫杂交方法证实其功能。结果克隆了PPO基因,找到了PPO基因与小鼠、果蝇、蚊子、线虫以及酵母等的同源基因,比较发现PPO在进化上非常保守。人和小鼠的氨基酸序列有许多与磷酸化有关的功能域,并发现其中某些氨基酸在进化上非常保守。进一步研究表明PPO能使ERK2和MEK磷酸化。结论PPO基因在进化上非常保守,与磷酸化功能有关。     

甲基丙二酸尿症一家系MMACHC基因突变分析

目的 研究甲基丙二酸尿症(methymalonic aciduria,MMA)MMACHC基冈的突变.方法 应用聚合酶链反应及DNA直接测序技术对甲基丙二酸尿症一家系进行MMACHC基因突变位点检测,并与50名健康人的MMACHC基冈进行对照.结果 患者及其父亲的MMACHC基因中检测到一个新的整码突变,MMACHC基因第2外显子146_154缺失CCTTCCTGG,导致P.49_51位缺失丙氨酸苯丙氨酸亮氨酸(AFL),50名对照者的等位基因无此突变.结论 MMACHC基因的146_154缺失CCTTCCTGG也可能是该家系引起甲基丙二酸尿症的病因.     

X-连锁迟发性脊椎骨骺发育不良家系基因突变研究

目的 研究X-连锁迟发性脊椎骨骺发育不良(X-linked spondyloepiphyseal dysplasia tarda,SEDL)患者的发病机理,并探讨该病的快速基因诊断方法.方法 应用逆转录聚合酶链反应,结合序列分析方法,对一个X-SEDL家系2例患者及育龄女性进行SEDL基因突变分析.结果 cDNA序列分析显示患者为G209A突变,并对突变所在第4外显子进行PCR扩增并测序进一步证实.患者女儿为该突变的携带者.结论 由于SEDL基因较小,直接对患者提取总RNA,逆转录后直接进行PCR扩增、测序,可直接发现基因阅读框内的多种类型的突变,相对于针对每一个外显子单独扩增检测更加直接、快速.     

先天性长QT综合征一家系的突变分析

目的对1个先天性长QT综合征(long QT syndrome，LQTS)家系的突变进行检测与分析。方法根据先证者的临床表现及心电图先对其致病基因初步判断，然后采用聚合酶链反应以及直接测序法对其进行KCNQ1基因检测以发现致病突变。结果根据先证者的临床表现及心电图将其致病基因初步定位于KCNQ1基因上，且在KCNQ1基因上发现一错义突变940(G—A)(G314S)，此突变在欧美及日本人群中均有发现，为长QT综合征的突变热点。结论在中国长QT综合征患者中有与国外患者同样的突变热点。     

一个视网膜色素变性家系致病基因定位和CA4基因突变分析

目的通过对一个常染色体显性视网膜色素变性(autosomal dominant retinitis pigmentosa,adRP)家系致病基因的定位和基因突变分析,以确定该家系的致病基因及其突变形式。方法对15个已知的常染色体显性视网膜色素变性致病基因所在染色体位点进行连锁分析,以确定该家系与疾病连锁的染色体区域,对该区域附近候选基因进行直接序列分析。结果连锁分析提示在D17S701和D17S1604为正的连锁值(logofodds,LOD),分别为Zmax=2.107和Zmax=1.806。其余14个adRP染色体位点的微卫星标记两点LOD值均为负数。单倍型分析进一步将该家系致病基因定位于微卫星标记D17S916和D17S794之间的RP17位点,该位点adRP候选基因碳酸酐酶Ⅳ(carbonic anhydrase4,CA4)直接序列分析在其编码区未发现基因突变。结论将一个中国人常染色体显性视网膜色素变性家系的致病基因定位于RP17位点,但未发现该位点内的CA4基因突变,该家系是否存在CA4基因复杂突变或RP17位点是否存在新的视网膜色素变性致病基因有待于进一步研究。     

Transient expression assay in a baculovirus system using firefly luciferase gene as a reporter

Transient gene expression assays were developed to assess the function of the regulatory sequences of baculovirusesBombyx mori nuclear polyhedrosis virus (BmNPV) andAutographa californica nuclear polyhedrosis virus (AcNPV) in insect cells ofBombyx mori andSpodoptera frugiperda, respectively. DNA sequences encoding luciferase (luc) of the fireflyPhotinus pyralis was successfully employed in the expression assay as a reporter gene. Recombinant plasmids were constructed containing the luc gene under control of baculovirus-specific or heterologous promoters. Cotransfection ofBombyx mori andSpodoptera frugiperda cells with recombinant plasmids carrying virus-specific promoter sequences and BmNPV and AcNPV DNA, respectively, gave rise to efficient synthesis of luciferase (Luc), while heterologous promoters induced a low level of luc expression. We found that flanking sequences of the AcNPV DNA in the transfer plasmid contained an unknown promoter conferring an efficient luc expression. The activity of this promoter was modulated by the polh promoter sequences. The assay allows one to conduct highly sensitive monitoring of the transient expression of foreign genes from the transfecting plasmids prior to construction of recombinant viruses.     

The beta-globin locus control region versus gene therapy vectors: a struggle for expression

Developmental control of gene expression has a major impact on the design of beta-globin retrovirus vectors for hematopoietic stem cell gene therapy of beta-thalassemia. It is obvious that the endogenous locus control region (LCR) elements that drive beta-globin gene expression in transgenic mice must be included in these vectors. However, the specific elements to use are not clear and require an understanding of LCR action. Moreover, retrovirus vectors contain silencer elements that function in stem cells and are dominant to LCR function. Recent studies on LCRbeta-globin transgenes and retrovirus silencing suggest ways to overcome this silencing effect after transfer into stem cells and carefully designed lentivirus vectors have exciting therapeutic benefit in animal models of beta-thalassemia. By building on 15 years of development, LCRbeta-globin vectors are now being tested in preclinical animal models and may ultimately lead to the long-sought cure for this genetic disease.     

成骨不全一家系的COL1A1基因突变分析

目的探讨一个成骨不全家系的COL1A1基因的突变位点及其与临床特征的关系。方法收集一个成骨不全家系的临床资料，采用聚合酶链反应以及直接测序法对家系内成员进行COL1A1基因突变位点检测，同时对50名无血缘关系健康对照者的该位点进行限制性内切酶分析。结果该家系中成骨不全患者均存在COL1A1基因的第2461位点G→A突变（17．821S），但其临床特征不一致。而在家系内非患者及正常对照者中均未发现该突变。结论COL1A1基因突变是中国人群中成骨不全致病原因之一。成骨不全的表型不仅与基因型有关，还与遗传背景有关。     

Exome Sequencing Identifies a Novel Nonsense Mutation of MYO6 as the Cause of Deafness in a Brazilian Family

We investigated 313 unrelated subjects who presented with hearing loss to identify the novel genetic causes of this condition in Brazil. Causative GJB2/GJB6 mutations were found in 12.7% of the patients. Among the familial cases (100/313), four were selected for exome sequencing. In one case, two novel heterozygous variants were found and were predicted to be pathogenic based on bioinformatics tools, that is, p.Ser906* (MYO6) and p.Arg42Cys (GJB3). We confirmed that this nonsense MYO6 mutation segregated with deafness in this family. Only the proband and her unaffected mother exhibited the GJB3 mutation, which is in the same amino acid of a known Erythrokeratodermia variabilis mutation. None of the patients exhibited this skin disease, but the proband exhibited a more severe hearing loss. Hence, the GJB3 mutation was considered to be a variant of uncertain significance. In conclusion, we described a novel nonsense MYO6 mutation that was responsible for the hearing loss in a Brazilian family. This mutation resides in the neck domain of myosin‐VI after the motor domain. Thus, our data give further support for genotype‐phenotype correlations, which state that when the motor domain of the protein is functioning, the hearing loss is milder and has a later onset. The three remaining families without mutations in the known genes suggest that there are still deafness genes to be revealed.