ZASP基因与特发性扩张型心肌病相关性研究

目的 探讨成都地区特发性扩张型心肌病(IDCM)人群中是否存在z带选择性缝接PDZ基序蛋白(ZASP)基因突变以及与该地区IDCM患者的相关性.方法 2006年1月至2007年12月在四川大学华西医院采用聚合酶链反应-单链构象多态性技术(PCR-SSCP)结合DNA测序方法,筛检成都地区无血缘关系汉族人群(包括120例IDCM患者,100名健康对照者)ZASP基因外显子4、6、10的可能突变位点.结果 在IDCM组和正常对照组中,ZASP基因外显子4、6单链构象多态性(SSCP)电泳图谱未发现差异;但外显子10 SSCP电泳图谱发现差异,经DNA测序证实为G216T杂合子与T216T纯合子.G216T杂合子在IDCM组检出28例,对照组检出12例;T216T纯合子在IDCM组检出9例,对照组检出4例.G/T基因型及T等位基因频率在IDCM组和对照组中差异有统计学意义(P<0.05).结论 ZASP基因外显子10 G216-T多态性与成都地区汉族IDCM患者遗传易感性相关;提示T等位基因为扩张型心肌病的易感基因.     

心脏型肌球蛋白结合蛋白C与肥厚型心肌病

心脏型肌球蛋白结合蛋白C（cMYBPC）不仅参与正常肌小节和肌丝的组装，稳定肌小节的结构。而且通过磷酸化等调节横桥循环参与肌肉的收缩和舒张包括。编码肌小节结构蛋白的基因突变是家族性肥厚型心肌病的主要致病原因，其中编码cMYBPC的基因是肥厚型心肌病的最为常见的致病基因之一，本文就cMYBPC以及编码基因的结构、功能以及致病基因型、表型和可能的致病机制进行了较全面的阐述。     

063 结合蛋白基因突变是家族性扩张型心肌病的病因[英]／Li DX…／／Circulation

扩张型心肌病(DCM)中约50％是特发性的，而至少20％是家族性的。但它的遗传病因研究进展较慢。直至1998年，Olsor等才发现肌动蛋白基因突变是特发性扩张型心肌病的病因。该研究通过候选基因途径对44个家族性扩张型心肌病的先证者的结合蛋白基因和肌动蛋白基因进行分析。     

"最后共同通路"假说与遗传性心血管疾病

近几年来一些遗传性心血管疾病,如长QT综合症、肥厚型心肌病和扩张型心肌病等的分子遗传机制已逐步被阐明,尽管大部分这些疾病由于不同遗传机制产生相似或相同的表现型(遗传异质性),但它们也具有共同特点,即每一种疾病类型都具有编码功能相似或编码参与共同级联通路蛋白质的基因参与发病。据此,人们提出了“最后共同通路”假说。在心律失常疾病中,长QT综合征、Brugada综合征的分子机制是编码离子通道蛋白质的基因包括钾离子通道(KVLQTl、HERG、mink)和钠离子通道(SCNSA)发生突变所致。根据“最后共同通路”假说,把这些疾病归类为“离子通道病”;而肥厚性心肌病是由于编码肌小节蛋白的基因包括β-肌球蛋白重链、α-原肌球蛋白、肌钙蛋白T、I和β-肌球蛋白重链结合位点近端的肌动蛋白突变所致,可归类为“肌小节病”;扩张型心肌病主要是编码心肌骨架蛋白的基因包括抗肌萎缩蛋白、抗肌萎缩蛋白相关的糖蛋白复合物、肌纤维膜糖蛋白复合物等发生了突变,称为“细胞骨架病”。     

扩张型心肌病的遗传因素及其分子机制

扩张型心肌病病因不明,家族聚集现象的存在提示遗传在其发病中发挥一定的作用。家族性扩张型心肌病的遗传方式不同,其基因异常可发生于心肌肌凝蛋白基因、线粒体基因及细胞癌基因等。本文总结了近年该领域的研究进展。     

肥厚型心肌病病因学研究进展

肥厚型心肌病是以心室壁心肌的非对称性肥厚为特征的一种特发性心肌疾病,目前被认为是一种基因突变所导致的常染色体疾病。在人类,在编码与构成肌小节有关的蛋白质的基因中,现在发现至少有11种基因,超过200种不同的基因突变类型与肥厚型心肌病有关。另外,一些与肌小节无关的基因突变也参与了该病的发生。     

肌联蛋白截断导致扩张型心肌病

《新英格兰医学杂志》（New England Journal of Medicine）在2012年2月16日发表了一项肌联蛋白截断与扩张型心肌病的相关性研究。该项研究表明TTN（肌小节肌联蛋白的编码基因）截断突变是一个扩张型心肌病的常见原     

E82K新突变对Lamin A与Emerin蛋白结合能力的影响

目的：研究Lamin A E82K突变型蛋白与Emerin蛋白结合能力的减弱是否会导致家族性扩张型心肌病。方法：构建Emerin基因野生型和Lamin A基因野生型和E82K突变型表达载体，将Emerin基因表达载体分别与Lamin A基因野生型及突变型表达载体共转染HEK293细胞，免疫共沉淀的方法检测野生型和突变型Lamin A蛋白与Emerin蛋白的结合力的差异。结果：Lamin A野生型和E82K突变型蛋白与Emerin蛋白的结合能力不存在明显差异。结论：Lamin A蛋白E82K突变所导致的家族性扩张型心肌病可能与Emerin蛋白无直接关系。     

核纤层蛋白A/C基因 Glu82Lys突变与扩张型心肌病

目的 检测中国人家族性扩张型心肌病核纤层蛋白A/C(Lamin A/C)基因突变情况。方法对1个扩张型心肌病家系进行核纤层蛋白A/C、基因突变扫描,聚合酶链反应(PCR)扩增核纤层蛋白A/L’基因1～12号外显子,测序检测突变。对照为60例正常人及9例无明显家族史的扩张型心肌病伴传导阻滞病人。结果 该家系先证者第1号外显子PCR产物测序分析表明该患者核纤层蛋白A/C基因第82密码子位置发生G→A转换,使谷氨酸(Glu)变为赖氦酸(Lys)。该患者临床表现劳力性呼吸困难、心动过缓、胸闷、夜间不能平卧,超声示左心室扩大,心电图显示Ⅲ°房室传导阻滞,现已安装起搏器治疗。患者母亲及哥哥皆有相似临床症状且都已于40余岁心衰死亡,其家属有多人死于相同症状。结论 核纤层蛋白A/C基因Glu82Lys错义突变位于核纤层蛋白的杆状结陶域,有氨基酸的极性改变,该突变表型呈现症状重,发病早,预后差的临床特点,台并Ⅱ-Ⅲ°传导阻滞,提示该突变是致扩张型心肌病的恶性突变。     

扩张型心肌病家系罕见受磷蛋白致病基因突变

目的 对一扩张型心肌病(dilated cardiomyopathy, DCM)家系行候选致病基因全外显子高通量测序,以寻找该家系的致病基因,并分析其基因型和表型的关系。方法 收集在武汉大学人民医院就诊的一位DCM患者及其家系成员的临床资料及血液标本。与先证者及其家属签订知情同意书,绘制家谱图,由我院临床分子诊断中心对先证者进行候选致病基因全外显子高通量测序,获得可疑突变后,用Sanger测序对家系其他成员进行验证,寻找致病基因。结果 家系先证者6号染色体外显子上存在受磷蛋白(phospholamban, PLN)基因的精氨酸缺失突变c.36_38delAAG (p.Arg13del),为该家系的可疑致病基因。先证者目前心脏扩大,心功能显著下降,且超声心动图提示左心室附壁血栓形成,心电图提示肢导低电压以及胸导联R波极度减低。先证者母亲及其大姐因心脏病死亡,二姐目前患有扩张型心肌病,其子女未检测到致病基因。受磷蛋白作为肌质网钙离子循环中的调节蛋白,它的基因表达、分布、功能与心室的收缩功能密切相关。结论 本研究发现DCM家系中存在PLN基因缺失突变：PLN c.36_38delAAG (p.Arg13del),是家族性扩张型心肌病的重要致病基因,此突变在汉族人群中尚属首次报道。     

Mutations in Cypher/ZASP in patients with dilated cardiomyopathy and left ventricular non-compaction

OBJECTIVES: We evaluated the role of Cypher/ZASP in the pathogenesis of dilated cardiomyopathy (DCM) with or without isolated non-compaction of the left ventricular myocardium (INLVM). BACKGROUND: Dilated cardiomyopathy, characterized by left ventricular dilation and systolic dysfunction with signs of heart failure, is genetically transmitted in 30% to 40% of cases. Genetic heterogeneity has been identified with mutations in multiple cytoskeletal and sarcomeric genes causing the phenotype. In addition, INLVM with a hypertrophic dilated left ventricle, ventricular dysfunction, and deep trabeculations, is also inherited, and the genes identified to date differ from those causing DCM. Cypher/ZASP is a newly identified gene encoding a protein that is a component of the Z-line in both skeletal and cardiac muscle. METHODS: Diagnosis of DCM was performed by echocardiogram, electrocardiogram, and physical examination. In addition, levels of the muscular isoform of creatine kinase were measured to evaluate for skeletal muscle involvement. Cypher/ZASP was screened by denaturing high performance liquid chromatography (DHPLC) and direct deoxyribonucleic acid sequencing. RESULTS: We identified and screened 100 probands with left ventricular dysfunction. Five mutations in six probands (6% of cases) were identified in patients with familial or sporadic DCM or INLVM. In vitro studies showed cytoskeleton disarray in cells transfected with mutated Cypher/ZASP. CONCLUSIONS: These data suggest that mutated Cypher/ZASP can cause DCM and INLVM and identify a mechanistic basis.     

Morphological and functional alterations in ventricular myocytes from male transgenic mice with hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (FHC) is a human genetic disorder caused by mutations in sarcomeric proteins. It is generally characterized by cardiac hypertrophy, fibrosis, and myocyte disarray. A transgenic mouse model of FHC with mutations in the actin-binding domain of the alpha-myosin heavy chain (MyHC) gene displays many phenotypes similar to human FHC. At 4 months, male transgenic (TG) mice present with concentric cardiac hypertrophy that progresses to dilation with age. Accompanying this latter morphological change is systolic and diastolic dysfunction. Left ventricular (LV) myocytes from male TG and wild-type (WT) littermates at 5 and 12 months of age were isolated and used for morphological and functional studies. Myocytes from 5- and 12-month-old TG animals had shorter sarcomere lengths compared with WT. This sarcomere length difference was abolished in the presence of 2,3-butanedione monoxime, suggesting that the basal level of contractile element activation was increased in TG myocytes. Myocytes from 12-month-old TG mice were significantly longer than those from age-matched WT controls, and TG myocytes exhibited Z-band disorganization. When cells were paced at 0.5 Hz, TG myocyte relengthening and the fall in intracellular [Ca2+] were slowed when compared with cells from age-matched WT controls. Moreover, an increased amount of beta-myosin heavy chain protein was found in hearts from TG compared with WT. Thus, myocytes from the alpha-MyHC TG mouse model display many morphological and functional abnormalities that may help explain the LV dysfunction seen in this TG mouse model of FHC.     

A polymorphic modifier gene alters the hypertrophic response in a murine model of familial hypertrophic cardiomyopathy.

Familial hypertrophic cardiomyopathy (FHC), an autosomal dominant disorder caused by mutationally altered dominant-acting sarcomere proteins, exhibits significant clinical heterogeneity. To determine whether genetic background could influence the expression of this disease, we studied a murine model for this human condition. Hypertrophic responses to the Arg403Gln missense mutation in a cardiac myosin heavy chain gene were compared in 129SvEv (inbred; designated 129SvEv- alpha MHC403/+) and Black Swiss (outbred; designated BSw- alpha MHC403/+) strains. At 30-50 weeks of age all 129SvEv- alpha MHC403/+ showed left ventricular hypertrophy, while left ventricular wall thickness was increased in only half of BSw- alpha MHC403/+ mice demonstrating that a polymorphic modifier gene can determine the hypertrophic response to this dominant-acting sarcomere protein mutation. Further analysis suggests that SJL/J mice bear a recessive allele of this modifier gene that prevents a hypertrophic response to the Arg403Gln missense mutation. We conclude that genetic modifiers in mice, and presumably in man, can alter the hypertrophic response to sarcomere protein gene missense mutations.     

High-risk hypertrophic cardiomyopathy associated with a novel mutation in cardiac Myosin-binding protein C

Hypertrophic cardiomyopathy is an autosomal dominant inherited disease characterized by ventricular hypertrophy and myofibril disarray. Mutations responsible for hypertrophic cardiomyopathy have been identified in 11 genes that encode for cardiac sarcomere proteins. Traditionally, hypertrophic cardiomyopathy due to mutation of the myosin-binding protein C gene (MYBPC3) has been thought to follow a benign course. We report a family with several members affected by hypertrophic cardiomyopathy in which there was a high incidence of sudden death. Disease was presumably caused by the substitution of cytosine by guanine at nucleotide 269 of MYBPC3 mRNA. This mutation, which has not previously been described, modifies codon 79, which encodes for the incorporation of a tyrosine, and gives rise to a stop codon. The mutation described here appears to confer a higher risk than that previously associated with hypertrophic cardiomyopathy due to MYBPC3 gene mutation.     

Moving Beyond the Sarcomere to Explain Heterogeneity in Hypertrophic Cardiomyopathy: JACC Review Topic of the Week

Hypertrophic cardiomyopathy (HCM) has been considered a heterogeneous cardiac disease ascribed solely to single sarcomere gene mutations. However, limitations of this hypothesis suggest that sarcomere mutations alone do not adequately explain all HCM clinical and pathobiological features. Disease-causing sarcomere mutations are absent in ～70% of patients with established disease, and sarcomere gene carriers can live to advanced ages without developing HCM. Some features of HCM are also inconsistent with the single sarcomere gene hypothesis, such as regional left ventricular hypertrophy and myocardial fibrosis, as well as structurally abnormal elongated mitral valve leaflets and remodeled intramural coronary arterioles, which involve tissue types that do not express cardiomyocyte sarcomere proteins. It is timely to expand the HCM research focus beyond a single molecular event toward more inclusive models to explain this disease in its entirety. The authors chart paths forward addressing this knowledge gap using novel analytical approaches, particularly network medicine, to unravel the pathobiological complexity of HCM.     

Titin Mutation in Familial Restrictive Cardiomyopathy

Background

Familial restrictive cardiomyopathy (RCM) caused by a single gene mutation is the least common of the inherited cardiomyopathies. Only a few RCM-causing mutations have been described. Most mutations causing RCM are located in sarcomere protein genes which also cause hypertrophic cardiomyopathy (HCM).Other genes associated with RCM include the desmin and familial amyloidosis genes. In the present study we describe familial RCM with severe heart failure triggered by a de novo mutation in TTN, encoding the huge muscle filament protein titin.

Methods and results

Family members underwent physical examination, ECG and Doppler echocardiogram studies. The family comprised 6 affected individuals aged 12–35 years. Linkage to candidate loci was performed, followed by gene sequencing. Candidate loci/gene analysis excluded 18 candidate genes but showed segregation with a common haplotype surrounding the TTN locus. Sequence analysis identified a de novo mutation within exon 266 of the TTN gene, resulting in the replacement of tyrosine by cysteine. p.Y7621C affects a highly conserved region in the protein within a fibronectin-3 domain, belonging to the A/I junction region of titin. No other disease-causing mutation was identified in cardiomyopathy genes by whole exome sequencing.

Conclusions

Our study shows, for the first time, that mutations in TTN can cause restrictive cardiomyopathy. The giant filament titin is considered to be a determinant of a resting tension of the sarcomere and this report provides genetic evidence of its crucial role in diastolic function.     

Danon病临床研究进展

Danon病是一种X连锁显性遗传性溶酶体病,以肥厚型心肌病、骨骼肌病和智力障碍三联征为主要临床表现,其引起的心肌病变与典型的肥厚型心肌病相似.Ⅱ型溶酶体相关膜蛋白是一种高度糖基化的蛋白质,是溶酶体膜的重要组成成份,编码Ⅱ型溶酶体相关膜蛋白的基因突变是导致Danon病的重要病因.现对Danon病的发病机制及其临床特点作一综述.     

Cardiac Myosin-binding protein C and hypertrophic cardiomyopathy

The cardiac myosin-binding protein C (MyBP-C) is a sarcomeric protein belonging to the intracellular immunoglobulin superfamily; it has both structural and regulatory roles. The gene-encoding cardiac MyBP-C in humans is located on chromosome 11p11.2, comprises over 21,000 base pairs, and contains 35 exons. Mutations have been identified in this gene in unrelated families with familial hypertrophic cardiomyopathy. Familial hypertrophic cardiomyopathy is an autosomal dominant disease characterized by ventricular hypertrophy associated with a large degree of myocardial and myofibrillar disarray. Most mutations found in the cardiac MyBP-C gene thus far are predicted to lead to an altered mRNA sequence and to produce the C-terminal truncation of the cardiac MyBP-C polypeptides lacking the myosin-binding site and also, in some cases, the titin-binding site. One might reasonably assume that the cardiac MyBP-C mutations exert their effect by altering the multimeric complex assembly of the cardiac sarcomere via the "null allele" mechanism, potentially leading to haploinsufficiency, and/or via a dominant negative effect of a misfolded RNA on the cardiac MyBP-C translation, which could interfere with the proper assembly of sarcomeric structures. These data underline the functional importance of MyBP-C in the regulation of cardiac work and provide the basis for further studies and for the production of transgenic animals for cardiac MyBP-C that will, one hopes, help to resolve the pathogenesis of chromosome-11-associated familial hypertrophic cardiomyopathy.     

Fast Diastolic Swinging Motion of the Mitral Valve as a Clinical Marker of Familial Hypertrophic Cardiomyopathy in Genetically Affected Young Children without Left Ventricular Hypertrophy: A New Role for Noninvasive Imaging?

Structural mitral valve (MV) abnormalities are common in patients with hypertrophic cardiomyopathy (HCM). This is the first report demonstrating MV abnormalities in very young children as the sole overt clinical feature of a known HCM‐causing sarcomere protein gene mutation. Due to MV leaflet elongation, we also noticed a typical fast diastolic swinging motion of the MV in our patients. This novel echocardiographic feature may be used as a clinical marker of HCM disease in the absence of left ventricular hypertrophy.