一个中国神经性肌强直家系致病基因初步研究

目的对一遗传性神经性肌强直家系2个已知致病基因进行初步筛查。方法应用外显子高通量测序分析方法对家系患者的KCNA1基因和KCNQ2基因进行DNA测序。结果基因检测未发现KCNA1基因和KCNQ2基因外显子突变。结论该神经性肌强直家系的发病与KCNA1基因和KCNQ2基因无关。     

中国遗传性神经性肌强直家系调查和遗传学特征分析

目的寻找遗传性神经性肌强直表型缺陷,并进行家系分析。方法对家系成员进行实地调查,并绘制系谱图;对调查的家系成员进行病史、神经系统检查3,例患者进行了肌电图检查。结果收集到一个5代53人的遗传性神经性肌强直家系1,7人患有该病症,其中男性13人,女性4人,发病年龄为10～20岁。临床主要表现为肌肉强直和肌肉颤搐,受累肌群包括颈部、腹部、四肢和咽喉肌肉,无发作性共济失调和癫痫发作。家系分析表明为常染色体显性遗传。结论该家系为常染色体显性遗传,主要累及周围神经系统,无中枢神经系统异常表现。受累肌肉广泛,包括极为罕见的咽喉肌。不能除外为新的致病基因所致。     

SCN4A基因突变导致的一个先天性副肌强直家系研究

目的分析一个疑似先天性副肌强直家系致病突变,为产前分子诊断提供依据。方法针对该家系临床表型进行分析,确定待测基因。用PCR-直接测序法分析目标基因的外显子及其侧翼序列,寻找致病突变。对筛查出的突变用Poly Phen和NCBI网站进行致病性与保守性分析,同时结合家系分析评估突变位点的致病性。结果对目标基因SCN4A进行突变分析,发现家族中患者均存在c.3473CT杂合突变,健康成员均未发现该突变,属于常染色体显性遗传;生物信息学分析该突变位点编码氨基酸由脯氨酸变成亮氨酸,突变所在区域高度保守,该突变具有高度致病性。结论证实了一个先天性副肌强直家系中SCN4A基因的新致病突变c.3473CT,为患者选择胚胎植入前诊断健康婴儿提供了依据。     

中国西北地区102例儿童Duchenne型肌营养不良基因突变及家系分析研究

目的　了解西北地区Duchenne型肌营养不良症(DMD)患者基因突变特点。方法　收集2014年7月～2020年6月的102例DMD患者作为研究对象,采用多重连接依赖探针扩增（multiplex ligationdependent probe amplification, MLPA）技术、二代基因测序（next-generation sepuencing, NGS)技术及Sanger测序方法进行基因检测,分析西北地区DMD患者基因缺失突变、重复突变、点突变的分布区域特点,且对2个DMD家系基因特点进行分析。结果　102例DMD患者,72.5%来源于遗传,27.5%为新发突变。基因突变类型中,85.3%为片段缺失,6.9%为片段重复,7.8%为点突变。片段缺失突变中,≤5个数目的外显子缺失最为常见,占比为66.6%;外显子44~54是最常见的缺失区域,外显子2是最常见的重复区域。2个家系研究,家系1中突变位点为缺失突变的热点区域,外显子45~51区域;家系2中主要是重复突变,集中在外显子2和17~18区域。结论　大样本对西北地区DMD患者及家系的基因分析,可以进一步了解DMD患者基因谱,为基因治疗建立基础。     

MLPA技术对Duchenne肌营养不良症患者基因外显子缺失和重复的诊断价值

目的使用多重连接依赖探针扩增技术对Duchenne肌营养不良症和Becker肌营养不良症家系成员的DMD基因进行外显子缺失和重复检测,探讨多重连接依赖探针扩增技术对Duchenne肌营养不良症患者和Becker肌营养不良症患者的诊断价值。方法应用多重连接依赖探针扩增技术检测1个Duchenne肌营养不良症家系成员和1个Becker肌营养不良症家系成员DMD基因的全部外显子缺失和重复,对家系成员进行基因诊断。结果 Duchenne肌营养不良症家系患者是DMD基因外显子45~50缺失所致,Becker肌营养不良症家系患者是外显子3~4重复所致。两个家系中的患者致病基因携带者均得到明确诊断。结论在规范操作的条件下,多重连接依赖探针扩增技术检测的探针拷贝数可预示DMD基因的外显子缺失和重复,因此多重连接依赖探针扩增技术可作为临床对DMD基因外显子缺失和重复的首选检测方法。     

一例双侧肾透明细胞癌患者与家系成员VHL基因的胚系突变分析

目的　对一例家族性双侧肾透明细胞癌患者家系VHL基因的胚系突变进行分析,结合其临床特点探讨可能的分子遗传学发病机制。方法　收集病人家族史、影像学、入院诊疗和随访资料,提取患者及家系直系成员外周血DNA和RNA,采用PCR-DNA测序、荧光定量PCR,RT-PCR片段长度和序列分析等方法进行VHL基因病理性胚系突变位点的筛查和验证。结果　PCR-DNA测序分析结果显示在这家系成员中均没有发现VHL基因编码区的点突变;VHL基因外显子拷贝数的定量分析数据显示VHL基因外显子2拷贝数减少;RT-PCR产物电泳和测序结果表明先证者与其兄二人存在VHL基因第2外显子杂合性缺失所致的病理性胚系突变。结论　家族性肾细胞癌家系中VHL基因的胚系突变筛查可作为一种有效的手段预测患者的预后,并可指导临床。     

MLPA及测序技术在DMD/BMD家系分析中的应用

目的运用MLPA技术和DNA及cDNA测序技术对DMD/BMD进行家系分析,对患者、可能携带者基因诊断并探讨诊断流程的临床可行性。方法对2个DMD/BMD家系中6例患者、13例女性可能携带者、6例男性家系成员,6例女性和男性健康对照共31例采集外周血提取DNA,运用MLPA技术分析对以上31例的DMD基因79个外显子;患者取右侧腓肠肌10～30mg肌肉提取RNA,逆转录cDNA;分别进行DNA及cDNA序列测定,测序结果与MLPA结果进行比较。结果经MLPA检测,家系1的4例患者均缺失DMD基因Exon50,家系2中2例患者均缺失Exon43。以上结果经肌肉cDNA测序证实了相应外显子缺失。结论 MLPA技术结合DNA及cDNA测序技术进行DMD家系分析具有可靠的临床应用价值。     

1例植物固醇血症的家系调查及致病基因突变研究

目的探讨1例植物固醇血症家系及其致病基因突变。方法对1例诊断为植物固醇血症的患者及其家系成员进行家系调查;通过PCR扩增先证者及其家系成员基因组DNA中ABCG5及ABCG8基因的所有外显子及其侧翼序列,采用Sanger测序法对PCR产物进行基因测序;采用Polyphen2及Mutation Taster生物信息学软件预测突变的致病性。结果 Sanger测序法发现先症者及家系成员中存在多个基因突变,其中ABCG5基因发现3个突变,分别为外显子1 c.64CT(p.Q22X)杂合无义突变、外显子10 c.1336CT(p.R446X)杂合无义突变、外显子13 c.1810CG(p.Q604E)杂合错义突变;ABCG8基因发现4个突变,分别为(ATG前)-19TG纯合突变、外显子2 c.161AG(p.Y54C)纯合错义突变、外显子13 c.1895TC(p.V632A)纯合错义突变、外显子4和5间的内含子g.12902TC纯合突变。Polyphen2及Mutation Taster软件预测ABCG5基因中c.64CT及c.1336CT为致病突变,其他基因突变均为非致病性的多态性位点。结论 ABCG5基因c.64CT及c.1336CT复杂杂合突变是该植物固醇血症家系的基因发病机制。     

2 例婴儿CDKL5 基因新发突变致早发性癫痫脑病的临床特征与遗传学分析

目的　探讨细胞周期蛋白依赖性蛋白激酶5（cyclin-dependent kinase-like 5,CDKL5）基因新发突变导致患儿早发性癫痫脑病的临床特征及分子遗传学特点。方法　收集西北妇女儿童医院儿童神经内科确诊的2 例早发性癫痫脑病患儿的临床资料,应用二代测序技术对核心家系成员进行全外显子测序分析,并用Sanger 测序法进行突变验证。结果　例1 患儿出生后20 天出现强直阵挛、不典型痉挛形式的癫痫发作,两种抗癫痫药物联合治疗后效果较好;例2 患儿出生后1 个月出现全面性强直阵挛发作,并伴显著的上下肢屈曲抖动,进展为难治性痉挛发作及严重精神发育迟滞和语言运动发育障碍,多种抗癫痫药物及生酮饮食联合治疗效果差。两例患儿全基因组基因拷贝数变异（copy numbervariations, CNVs）检测未见明确致病变异。核心家系全外显子组测序结果发现,例1 患儿CDKL5 基因第12 外显子上存在一杂合新发无义突变:NM_003159.2:c.1307C>G（p. Ser436*）,其父母该位点未见异常;例2 患儿该基因第13 外显子存在c.1974_1975del（p.Val659GlyfsTer23）新发杂合移码突变,其父母该位点未见异常。根据2015 年美国医学遗传学与基因组学学会（the American College of Medical Genetics and Genomics, ACMG）指南,以上变异均为致病突变。结论　CDKL5 基因c.1307C>G 无义突变和c.1974_1975del 移码突变是先证者早发性癫痫脑病遗传学病因的新发致病变异,扩充了致病基因CDKL5 的基因变异谱。     

1例遗传性多发性外生骨疣家系的EXT基因突变检测

摘要：目的：对1例遗传性多发性外生骨疣(hereditary multiple exostoses, EXT)家系的EXT1和EXT2基因编码序列进行突变检测,寻找引起该病的致病基因突变。 方法：利用与 EXT1、EXT2紧密连锁的短串联重复序列（short tandem repeat, STR）对该家系进行连锁分析,确定候选基因,用PCR-测序法对候选基因的编码区及外显子与内含子交界处进行突变分析。 结果：DNA测序分析发现,先证者致病基因EXT2第3外显子有一新的637G>A无义突变,致使编码第192位的氨基酸的密码子提前出现终止密码,使编码蛋白成为只有191个氨基酸的截断型蛋白,其余外显子未发现突变。家系调查发现,该突变来自于先证者父亲。先证者EXT1基因未发现变异。 结论：EXT2基因637G>A突变是导致这个家系发生多发性骨疣的分子机制。     

KCNQ potassium channels: physiology, pathophysiology, and pharmacology.

KCNQ genes encode a growing family of six transmembrane domains, single pore-loop, K(+) channel alpha-subunits that have a wide range of physiological correlates. KCNQ1 (KvLTQ1) is co-assembled with the product of the KCNE1 (minimal K(+)-channel protein) gene in the heart to form a cardiac-delayed rectifier-like K(+) current. Mutations in this channel can cause one form of inherited long QT syndrome (LQT1), as well as being associated with a form of deafness. KCNQ1 can also co-assemble with KCNE3, and may be the molecular correlate of the cyclic AMP-regulated K(+) current present in colonic crypt cells. KCNQ2 and KCNQ3 heteromultimers are thought to underlie the M-current; mutations in these genes may cause an inherited form of juvenile epilepsy. The KCNQ4 gene is thought to encode the molecular correlate of the I(K,n) in outer hair cells of the cochlea and I(K,L) in Type I hair cells of the vestibular apparatus, mutations in which lead to a form of inherited deafness. The recently identified KCNQ5 gene is expressed in brain and skeletal muscle, and can co-assemble with KCNQ3, suggesting it may also play a role in the M-current heterogeneity. This review will set this family of K(+) channels amongst the other known families. It will highlight the genes, physiology, pharmacology, and pathophysiology of this recently discovered, but important, family of K(+) channels.     

Compound heterozygosity for mutations Asp611-->Tyr in KCNQ1 and Asp609-->Gly in KCNH2 associated with severe long QT syndrome

LQTS (long QT syndrome) is an inherited cardiac disorder characterized by prolongation of QT interval, torsades de pointes and sudden death. We have identified two heterozygous missense mutations in the KCNQ1 and KCNH2 (also known as HERG) genes [Asp611-->Tyr (D611Y) in KCNQ1 and Asp609-->Gly (D609G) in KCNH2] in a 2-year-old boy with LQTS. The aim of the present study was to characterize the contributions of the mutations in the KCNQ1 and KCNH2 genes relative to the clinical manifestations and electrophysiological properties of LQTS. Six of 11 carriers of D611Y in KCNQ1 had long QT intervals. D609G in KCNH2 was detected only in the proband. Studies on the electrophysiological alterations due to the two missense mutations revealed that the D611Y mutation in KCNQ1 did not show a significant suppression of the currents compared with wild-type, but the time constants of current activation in the mutants were increased compared with that in the wild-type. In contrast, the D609G mutation in KCNH2 showed a dominant-negative suppression. Our results suggest that the mild phenotype produced by the D611Y mutation in KCNQ1 became more serious by addition of the D609G mutation in KCNH2 in the proband.     

A candidate locus approach identifies a long QT syndrome gene mutation

Long QT syndrome is an inherited disorder that results in lengthened cardiac repolarization. It can lead to sudden onset of torsades de pointes, ventricular fibrillation, and death. The authors obtained a family history, performed electrocardiograms, and drew blood for DNA extraction and genotyping from 15 family members representing 4 generations of an affected family. Seven individuals demonstrated prolonged QT intervals. The authors used polymorphic short tandem repeat markers at known LQTS loci, which indicated linkage to chromosome 11p15.5 where the potassium channel, KCNQ1, is encoded. Polymerase chain reaction was used to amplify the coding region of KCNQ1. During survey of the KCNQ1 coding region, a G-to-A transition (G502A) was identified. DNA from all clinically affected but from none of the clinically unaffected family members carried the G-to-A transition. The candidate locus approach allowed an efficient mechanism to uncover the potassium channel mutation causing LQTS in this family.     

2型糖尿病易感基因代谢通路生物信息学研究

目的构建中国人群中2型糖尿病易感基因的代谢通路。方法采用2型糖尿病的易感基因集合,基于商用数据库Ingenutiy Pathway Analysis(后简称IPA)中的Right-Tailed Fisher′s Exact Test算法进行统计分析,找到与糖尿病相关的代谢通路,并从中筛选出15个与中国人群糖尿病相关的易感基因,根据易感基因建立代谢通路,探讨中国人群易感基因之间在生物学上的关联关系。结果 KCNQ1、PPARG、IRS1、ADIPOQ等基因位于多条代谢通路的节点位置,与多条代谢通路相关。结论 KCNQ1、PPARG、IRS1、ADIPOQ等基因在中国人群2型糖尿病的发生过程中起到了关键作用。该研究结果对基于代谢通路研究复杂性疾病具有很好的借鉴意义。     

Clinical and electrophysiological characterization of a novel mutation (F193L) in the KCNQ1 gene associated with long QT syndrome

KCNQ1 is a gene encoding an alpha subunit of voltage-gated cardiac K(+) channels, with properties similar to the slowly activating delayed rectifier K(+) current, and one of the genes causing long QT syndrome (LQTS). However, genotype-phenotype correlations of the KCNQ1 gene mutations are not fully understood. The aims of this study were to identify a mutation in the KCNQ1 gene in patients with LQTS, and to characterize the clinical manifestations and electrophysiological properties of the mutation. We screened and identified mutations by PCR, single-strand conformational polymorphism analysis and DNA sequencing. We identified a novel mutation [Phe193Leu (F193L)] in the KCNQ1 gene in one family with LQTS. The patients with this mutation showed a mildly affected phenotype. The proband was a 17-year-old girl who had a prolonged QT interval. Her elder brother, father and paternal grandmother also had the mutation. None of them had any history of syncope. Sudden death was not found in this family. Next, we studied the electrophysiological characteristics of the F193L mutation in the KCNQ1 gene using the expression system in Xenopus oocytes and the two-microelectrode voltage-clamp technique. Co-expression of F193L KCNQ1 with the K(+) channel minK suppressed peak (by 23.3%) and tail (by 38.2%) currents compared with those obtained by the combination of wild-type (WT) KCNQ1 and minK. Time constants of current activation in F193L KCNQ1 and F193L KCNQ1+minK were significantly slower than those of WT KCNQ1 and WT KCNQ1+minK. This electrophysiological study indicates that F193L causes less severe KCNQ1 current suppression, and thereby this mutation may result in a mildly affected phenotype.     

Molecular characterization of two founder mutations causing long QT syndrome and identification of compound heterozygous patients

BACKGROUND: Mutations of at least six different genes have been found to cause long QT syndrome (LQTS), an inherited arrhythmic disorder characterized by a prolonged QT interval on the electrocardiogram (ECG), ventricular arrhythmias and risk of sudden death. AIM: The aims were to define the yet undetermined phenotypic characteristics of two founder mutations and to study clinical features in compound heterozygotes identified during the course of the study. METHODS: To maximize identification of the compound heterozygotes, we used an extended group of LQTS patients comprising 700 documented or suspected cases. Functional studies were carried out upon transient expression in COS-7 or HEK293 cells. RESULTS: The KCNQ1 IVS7-2A>G (KCNQ1-FinB) mutation associated with a mean QTc interval of 464 ms and a complete loss-of-channel function. The HERG R176W (HERG-FinB) mutation caused a reduction in current density as well as slight acceleration of the deactivation kinetics in vitro, and its carriers had a mean QTc of 448 ms. The HERG R176W mutation was also present in 3 (0.9%) out of 317 blood donors. A total of six compound heterozygotes were identified who had the HERG R176W mutation in combination with a previously reported LQTS mutation (KCNQ1 G589D or IVS7-2A>G). When present simultaneously with an apparent LQTS-causing mutation, the HERG R176W mutation may exert an additional in vivo phenotypic effect. CONCLUSIONS: The HERG R176W mutation represents a population-prevalent mutation predisposing to LQTS. Compound heterozygosity for mutant LQTS genes may modify the clinical picture in LQTS.     

Polymorphism screening in the cardiac K+ channel gene KCNA5

BACKGROUND: Common deoxyribonucleic acid polymorphisms that modulate normal cardiac electrophysiologic characteristics have previously been identified in long QT syndrome disease genes. In this study we screened an additional gene encoding the cardiac potassium channel KCNA5 (underlying I(Kur)) in 3 ethnic groups and evaluated the functional consequences of the variants identified. METHODS: The coding region was screened by single-stranded conformational polymorphism analysis and direct sequencing, and nonsynonymous variants were studied by patch-clamping transfected Chinese hamster ovary cells. Results Five synonymous and 6 nonsynonymous polymorphisms were found in KCNA5. None of these polymorphisms was present in greater than 7% of alleles screened or in all 3 ethnic groups. Expression of the nonsynonymous KCNA5 variants revealed normal gating. However, 2 variants (P532L and R578K, both in the C-terminus) were resistant to block by the prototypical inhibitor quinidine; the concentration required to block I(Kur) by 50% (IC(50)) was 8.4 micromol/L for wild type versus 54 micromol/L for R578K and 133 micromol/L for P532L (both P < .0001, versus wild type). CONCLUSION: KCNA5 displays little variability in its coding region. C-terminal KCNA5 variants displayed near-normal gating but striking resistance to drug block; thus these pharmacogenomic studies have identified a heretofore-unappreciated role of this region as a modulator of channel sensitivity to drugs. Resistance to I(Kur) blockers may be genetically determined.     

Molecular characterization of two founder mutations causing long QT syndrome and identification of compound heterozygous patients

Background. Mutations of at least six different genes have been found to cause long QT syndrome (LQTS), an inherited arrhythmic disorder characterized by a prolonged QT interval on the electrocardiogram (ECG), ventricular arrhythmias and risk of sudden death.

Aim. The aims were to define the yet undetermined phenotypic characteristics of two founder mutations and to study clinical features in compound heterozygotes identified during the course of the study.

Methods. To maximize identification of the compound heterozygotes, we used an extended group of LQTS patients comprising 700 documented or suspected cases. Functional studies were carried out upon transient expression in COS‐7 or HEK293 cells.

Results. The KCNQ1 IVS7‐2A>G (KCNQ1‐FinB) mutation associated with a mean QTc interval of 464?ms and a complete loss‐of‐channel function. The HERG R176W (HERG‐FinB) mutation caused a reduction in current density as well as slight acceleration of the deactivation kinetics in vitro, and its carriers had a mean QTc of 448?ms. The HERG R176W mutation was also present in 3 (0.9%) out of 317 blood donors. A total of six compound heterozygotes were identified who had the HERG R176W mutation in combination with a previously reported LQTS mutation (KCNQ1 G589D or IVS7‐2A>G). When present simultaneously with an apparent LQTS‐causing mutation, the HERG R176W mutation may exert an additional in vivo phenotypic effect.

Conclusions. The HERG R176W mutation represents a population‐prevalent mutation predisposing to LQTS. Compound heterozygosity for mutant LQTS genes may modify the clinical picture in LQTS.     

KCNQ1和RFX3基因表达量作为原发性痛风诊断指标的探讨

目的探讨KCNQ1和RFX3基因表达量作为原发性痛风诊断指标的临床应用。方法收集2018年1-12月广州市海珠区江海街社区卫生服务中心和广州中医药大学第三附属医院原发性痛风患者86例(原发性痛风组),包括急性期31例、间歇期44例、慢性期11例和无症状高尿酸血症患者50例(无症状高尿酸血症组),另选同期来这两家医疗机构体检且无原发性痛风症状,也无高尿酸血症的患者81例作为对照组。采用密度梯度离心法分离外周血单个核细胞(PBMC),实时荧光定量聚合酶链反应(qPCR)检测PBMC中KCNQ1和RFX3 mRNA的表达量,统计分析各组间KCNQ1和RFX3基因水平差异,绘制受试者工作特征曲线(ROC曲线)评价所观察指标的诊断效能。结果原发性痛风组的KCNQ1和RFX3 mRNA表达量显著低于对照组;原发性痛风组急性期KCNQ1和RFX3 mRNA表达量显著低于对照组,差异有统计学意义(P<0.05);无症状高尿酸血症组的KCNQ1 mRNA表达量显著低于对照组,差异有统计学意义(P<0.05);原发性痛风组急性期KCNQ1 mRNA表达量显著低于无症状高尿酸血症组,差异有统计学意义(P<0.05)。ROC曲线分析表明,KCNQ1对原发性痛风诊断性能低于RFX3。结论原发性痛风患者低表达KCNQ1和RFX3基因水平,RFX3对诊断原发性痛风比KCNQ1更灵敏,可以作为临床预测发生原发性痛风患病的阳性率的较好指标。