遗传性长QT综合征HERG基因及SCN5A基因新突变

目的:研究长QT综合征患者基因突变、致病机制及其与临床表型之间的关系.方法:分析长QT综合征患者的临床表脱、心电图特点,应用聚合酶链式反应(PCR)扩增长QT综合征的常见突变基因KCNQ1,HERG,SCN5A的全部外显了及外显子与内含子连接部位,DNA直接测序检测基因突变位点.应用实时定量PCR方法测定一个家系的成员基因表达量,以探讨其可能的致病机制.结果:在5个长QT综合征家系中,发现2个HERG基因突变位点及1个SCN5A基因突变位点,分别为HERG基因C1848A、G1120T和SCN5A基因G638T.其中HERG基因C1848A突变引起616位酪氨酸转变为终止密码子(Y616X),G1120T突变引起374位缬氨酸转变为苯丙氨酸(V374F);SCN5A基因G638T突变引起213位甘氨酸转变为缬氨酸(G213V).HERG基因Y616X突变患者家族成员外周血mRNA表达量分析,发现其HERG基因mRNA表达量明显低于无突变者.结论:发现3个长QT综合征相关的基因新突变位点,两个突变位于HERG基因,另一个位于SCN5A基因.基中HERG基因无义突变Y616X引起mRNA表达量减少,可能受无义突变介导的RNA降解(Nonsense Mediated Decay,NMD)机制有关,从而引起较轻微的临床症状.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

一个短指家系临床特征调查及其致病基因的定位

目的 通过对山东省一个A1型短指(brachydactyly type A1,BDA1)家系的临床特征及致病基因分析,确定该病的遗传类型及其发生机制.方法 经家系调查及临床检查确定疾病类型;通过致病基因微卫星多态位点进行连锁分析;采用修饰引物产生引入酶切位点的方法来区分突变基因.结果 该家系的短指症为A1型,常染色体显性遗传;发病原因为位于染色体2q35-2q36的IHH基因(indian hedgehog gene)发生了G298A(D100N)错义突变.结论 中国山东A1型短指家系的发病机理是IHH基因发生了G298A(D100N)错义突变所致.     

A novel locus for autosomal dominant cone-rod dystrophy maps to chromosome 10q

Here we report recruitment of a three-generation Romani (Gypsy) family with autosomal dominant cone-rod dystrophy (adCORD). Involvement of known adCORD genes was excluded by microsatellite (STR) genotyping and linkage analysis. Subsequently, two independent total-genome scans using STR markers and single-nucleotide polymorphisms (SNPs) were performed. Haplotype analysis revealed a single 6.7-Mb novel locus between markers D10S1757 and D10S1782 linked to the disease phenotype on chromosome 10q26. Linkage analysis gave a maximum LOD score of 3.31 for five fully informative STR markers within the linked interval corresponding to the expected maximum in the family. Multipoint linkage analysis of SNP genotypes yielded a maximum parametric linkage score of 2.71 with markers located in the same chromosomal interval. There is no previously mapped CORD locus in this interval, and therefore the data reported here is novel and likely to identify a new gene that may eventually contribute to new knowledge on the pathogenesis of this condition. Sequencing of several candidate genes within the mapped interval led to negative findings in terms of the underlying molecular pathogenesis of the disease in the family. Analysis by comparative genomic hybridization excluded large chromosomal aberrations as causative of adCORD in the pedigree.     

KCNH2 Gene Mutation: A Potential Link Between Epilepsy and Long QT-2 Syndrome

Long QT syndrome (LQTS) is closely associated with syncope, seizure, and sudden death but LQTS is frequently misdiagnosed as epilepsy. LQTS and epilepsy both belong to the group of ion channelopathies that manifest in the heart and brain. Therefore, genetic analysis of genes associated with potassium and sodium homeostasis and electrical disorders may reveal a link between epilepsy and lethal cardiac arrhythmia. Here, the authors report a young woman who suffered recurrent seizure episodes and syncopes that occurred while walking and also during rest. She showed electroencephalogram abnormalities and a pathological prolonged QTc interval in electrocardiogram. The patient and the patient's asymptomatic family members underwent genetic screening of the three genes most frequently associated with LQTS: KCNQ1, KCNH2, and SCN5A. The patient and the family members did not show DNA alterations in the genes KCNQ1 and SCN5A associated with LQT-1 and LQT-3, respectively. However, the patient showed a de novo mutation 2587T→C in exon 10 of KCNH2 gene associated with LQT-2. The mutation caused a stop codon substitution (R863X) in the HERG channel, leading to a 296–amino acid deletion. The patient's asymptomatic relatives did not show the KCNH2 gene mutation. R863X alteration in HERG channel may be involved in both prolonged QTc interval and epilepsy. This fact raises the possibility that R863X alteration in KCNH2-encoded potassium channel may confer susceptibility for epilepsy and cardiac LQT-2 arrhythmia.     

Genetic and physical characterization of the early-onset Alzheimer's disease AD3 locus on chromosome 14q24.3

Genetic linkage studies have provided significant evidence thata major gene defect, AD3, for familial early-onset Alzheimer'sdisease (EOAD) is located at chromosome 14q24.3, between theshort tandem repeat (STR) markers D14S52 and D14S53 defininga genetic size of 22.7 cM for the AD3 candidate region. We constructeda physical map of the AD3 region using yeast artificial chromosomes(YACs) selected from both the CEPH and megaCEPH YAC librariesusing the AD3 linked STR markers as well as new sequence-taggedsites (STSs) designed based on YAC terminal sequences. The YACmap is contiguous in the region between D14S258 and D14S53,a region of 8.2 cM, and has an estimated physical size of 4–8Mb. The YAC contig map was used as a framework to localize threeknown genes, a pseudogene and two brain expressed sequence tags(ESTs). Linkage analysis studies in two Belgian chromosome 14EOAD families AD/A and AD/B, identified obligate recombinantsin family AD/A with D14S289 and D14S61 reducing the geneticsize of the candidate AD3 region substantially. The minimalAD3 candidate region measured 6.4 cM on the genetic map andis contained within six overlapping megaCEPH YACs that covereda physical distance estimated between 2 and 6 Mb. These YACsas well as other YACs in the YAC contig map are valuable resourcesin gene cloning efforts or genomic sequencing experiments aimingat isolating the AD3 gene.     

家族性高甘油三酯血症家系的候选基因位点连锁分析

目的 对一个家族性高甘油三酯血症(familial hypertriglyceridemia,FHTG)家系进行遗传连锁定位及基因突变分析.方法 32名家系成员,其中12例为高甘油三酯血症(hypertriglyceridemia)患者.应用短串联重复(short tandem repeat,STR)片段微卫星标记物对其中的22名成员进行了16个与脂代谢有关的候选基因和(或)位点的遗传连锁分析和单倍型分析,并对其中的两个候选基因APOA2和USF1直接测序以筛查突变.结果 APOA5、LIPI、RP1、APOC2、ABC1,LMF1、APOA1-APOC3-APOA4、LPL,APOB、CETP、LCAT,LDLR,APOE等候选基因位点与该家系表型不连锁,Lod值均小于-1.0(θ=0).遗传连锁分析提示位于1q23.3-24.2染色体区域,疾病表型在D1S104至D1S196之间(遗传间距为5.87 cM)存在连锁,其中D1S194两点间最大Lod值为2.44(θ=0).对APOA2和USF1基因的序列分析未发现致病突变.结论 排除了上述候选基因为本家系的致病基因;提示在1q23.3-1q24.2染色体区域可能存在一个新的与FHTG相关的基因.     

Mutations in SCN9A, encoding a sodium channel alpha subunit, in patients with primary erythermalgia

Primary erythermalgia is a rare autosomal dominant disease characterised by intermittent burning pain with redness and heat in the extremities. A previous study established the linkage of primary erythermalgia to a 7.94 cM interval on chromosome 2q, but the causative gene was not identified. We performed linkage analysis in a Chinese family with primary erythermalgia, and screened the mutations in the two candidate genes, SCN9A and GCA, in the family and a sporadic patient. Linkage analysis yielded a maximum lod score of 2.11 for both markers D2S2370 and D2S2330. Based on critical recombination events in two patients in the family, we further limited the genetic region to 5.98 cM between D2S2370 and D2S2345. We then identified two missense mutations in SCN9A in the family (T2573A) and the sporadic patient (T2543C). Our data suggest that mutations in SCN9A cause primary erythermalgia. SCN9A, encoding a voltage-gated sodium channel alpha subunit predominantly expressed in sensory and sympathetic neurones, may play an important role in nociception and vasomotor regulation.     

Sodium channel abnormalities are infrequent in patients with long QT syndrome: identification of two novel SCN5A mutations.

Long QT syndrome (LQTS) is a heterogeneous disorder caused by mutations of at least five different loci. Three of these, LQT1, LQT2, and LQT5, encode potassium channel subunits. LQT3 encodes the cardiac-specific sodium channel, SCN5A. Previously reported LQTS-associated mutations of SCN5A include a recurring three amino acid deletion (DeltaKPQ1505-1507) in four different families, and four different missense mutations. We have examined the SCN5A gene in 88 index cases with LQTS, including four with Jervell and Lange-Nielsen syndrome and the remainder with Romano-Ward syndrome. Screening portions of DIII-DIV, where mutations have previously been found, showed that none of these patients has the three amino acid deletion, DeltaKPQ1505-1507, or the other four known mutations. We identified a novel missense mutation, T1645M, in the DIV; S4 voltage sensor immediately adjacent to the previously reported mutation R1644H. We also examined all of the additional pore-forming regions and voltage-sensing regions and discovered another novel mutation, T1304M, at the voltage-sensing region DIII; S4. Neither T1645M nor T1304M were seen in a panel of unaffected control individuals. Five of six T1304M gene carriers were symptomatic. In contrast to previous studies, QT(onset-c) was not a sensitive indicator of SCN5A-associated LQTS, at least in this family. These data suggest that mutations of SCN5A are responsible for only a small proportion of LQTS cases.     

A fourth locus for hereditary hemorrhagic telangiectasia maps to chromosome 7

Hereditary hemorrhagic telangiectasia (HHT) is a genetically and clinically heterogeneous multisystem vascular dysplasia. Mutations of the endoglin and ACVRL1 genes are known to cause HHT. However, existence of HHT families in which linkage to these genes has been excluded has suggested that other gene(s) can cause HHT in some families. Recently, a family was reported to be linked to chromosome 5q, the HHT3 locus. Here we report on linkage results on a family with classic features of HHT, albeit a less severe phenotype with regards to epistaxis and telangiectases, in which linkage to HHT1, HHT2, and HHT3 is ruled out. Whole genome linkage analysis and fine mapping results suggested a 7 Mb region on the short arm of chromosome 7 (7p14) between STR markers D7S2252 and D7S510. We obtained a maximum two point LOD score of 3.60 with the STR marker D7S817. This region was further confirmed by haplotype analysis. These findings suggest the presence of another gene causing HHT (HHT4). The features in this family that strongly suggest the presence of a hereditary, multisystem vascular dysplasia would be easily missed during the typical evaluation and management of a patient with an AVM. This family helps emphasize the need to obtain a very detailed, targeted medical and family history for even mild, infrequent but recurring nosebleed, subtle telangiectases. Further studies of the candidate region and the identification of the gene responsible for the vascular anomalies in this family will add to our understanding of vascular morphogenesis and related disorders.     

Hereditary lymphedema: evidence for linkage and genetic heterogeneity

Hereditary or primary lymphedema is a developmental disorder of the lymphatic system which leads to a disabling and disfiguring swelling of the extremities. Hereditary lymphedema generally shows an autosomal dominant pattern of inheritance with reduced penetrance, variable expression and variable age at onset. Three multigeneration families demonstrating the phenotype of hereditary lymphedema segregating as an autosomal dominant trait with incomplete penetrance were genotyped for 366 autosomal markers. Linkage analysis yielded a two-point LOD score of 6.1 at straight theta = 0. 0 for marker D5S1354 and a maximum multipoint LOD score of 8.8 at marker D5S1354 located at chromosome 5q34-q35. Linkage analysis in two additional families using markers from the linked region showed one family consistent for linkage to distal chromosome 5. In the second family, linkage to 5q was excluded for all markers in the region with LOD scores Z < -2.0. The vascular endothelial growth factor C receptor ( FLT4 ) was mapped to the linked region, and partial sequence analysis identified a G-->A transition at nucleotide position 3360 of the FLT4 cDNA, predicting a leucine for proline substitution at residue 1126 of the mature receptor in one nuclear family. This study localizes a gene for primary lymphedema to distal chromosome 5q, identifies a plausible candidate gene in the linked region, and provides evidence for a second, unlinked locus for primary lymphedema.      

The long QT syndrome family of cardiac ion channelopathies: a HuGE review.

Long QT syndrome (LQTS) refers to a group of "channelopathies"-disorders that affect cardiac ion channels. The "family" concept of syndromes has been applied to the multiple LQTS genotypes, LQT1-8, which exhibit converging mechanisms leading to QT prolongation and slowed ventricular repolarization. The 470+ allelic mutations induce loss-of-function in the passage of mainly K+ ions, and gain-of-function in the passage of Na+ ions through their respective ion channels. Resultant early after depolarizations can lead to a polymorphic form of ventricular tachycardia known as torsade de pointes, resulting in syncope, sudden cardiac death, or near-death (i.e., cardiac arrest aborted either spontaneously or with external defibrillation). LQTS may be either congenital or acquired. The genetic epidemiology of both forms can vary with subpopulation depending on the allele, but as a whole, LQTS appears in every corner of the globe. Many polymorphisms, such as HERG P448R and A915V in Asians, and SCN5A S1102Y in African Americans, show racial-ethnic specificity. At least nine genetic polymorphisms may enhance susceptibility to drug-induced arrhythmia (an "acquired" form of LQTS). Studies have generally demonstrated greater QT prolongation and more severe outcomes among adult females. Gene-gene interactions, e.g., between SCN5A Q1077del mutations and the SCN5A H558B polymorphism, have been shown to seriously reduce ion channel current. While phenotypic ascertainment remains a mainstay in the clinical setting, SSCP and DHPLC-aided DNA sequencing are a standard part of mutational investigation, and direct sequencing on a limited basis is now commercially available for patient diagnosis.     

先天性视网膜脉络膜缺损一家系基因连锁定位分析

目的 对一个连续3代常染色体显性遗传性先天性视网膜脉络膜缺损(autosomal dominant congenital retinaochoroidal coloboma)家系进行致病基因的连锁定位分析.方法 对家系所有成员进行详细的临床检查,排除其他系统疾患.提取家系成员外周血DNA,选取位于全部染色体上的398对微卫星标记物,进行全基因组扫描.经ABI3130型遗传分析仪,Genescan收集数据,Genotyper进行基因分型,Linkage软件计算两点Lod值.结果 在2号染色体长臂上的微卫星标记物D2S2382取得最大的Lod值,其Lod值为3.01.进一步在D2S2382附近选择微卫星标记物,进行连锁分析,发现微卫星标记物D2S2382-D2S301-D2S2244-D2S163与家系中所有患者疾病表型共分离.结论 将一个常染色体显性遗传性先天性视网膜脉络膜缺损家系的致病基因定位于2q34-2q35之间的3.80 cM范围内.