Tcap gene mutations in hypertrophic cardiomyopathy and dilated cardiomyopathy

OBJECTIVES: We sought to explore the relationship between a Tcap gene (TCAP) abnormality and cardiomyopathy. BACKGROUND: Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) cause severe heart failure and sudden death. Recent genetic investigations have revealed that mutations of genes encoding Z-disc components, including titin and muscle LIM protein (MLP), are the primary cause of both HCM and DCM. The Z-disc plays a role in establishing the mechanical coupling of sarcomeric contraction and stretching, with the titin/Tcap/MLP complex serving as a mechanical stretch sensor. Tcap interacts with the calsarcin, which tethers the calcineurin to the Z-disc. METHODS: The TCAP was analyzed in 346 patients with HCM (236 familial and 110 sporadic cases) and 136 patients with DCM (34 familial and 102 sporadic cases). Two different in vitro qualitative assays-yeast two-hybrid and glutathion S-transferase pull-down competition-were performed in order to investigate functional changes in Tcap's interaction with MLP, titin, and calsarcin-1 caused by the identified mutations and a reported DCM-associated mutation, R87Q. RESULTS: Two TCAP mutations, T137I and R153H, were found in patients with HCM, and another TCAP mutation, E132Q, was identified in a patient with DCM. It was demonstrated by the qualitative assays that the HCM-associated mutations augment the ability of Tcap to interact with titin and calsarcin-1, whereas the DCM-associated mutations impair the interaction of Tcap with MLP, titin, and calsarcin-1. CONCLUSIONS: These observations suggest that the difference in clinical phenotype (HCM or DCM) may be correlated with the property of altered binding among the Z-disc components.     

Inherited and de novo mutations in the cardiac actin gene cause hypertrophic cardiomyopathy

Mutations in genes encoding sarcomeric proteins cause hypertrophic cardiomyopathy (HCM). The sarcomeric protein actin plays a central, dual role in cardiac myocytes, generating contractile force by interacting with myosin and also transmitting force within and between cells. Two missense mutations in the cardiac actin gene (ACTC), postulated to impair force transmission, have been associated with familial dilated cardiomyopathy (DCM). Recently, a missense mutation in ACTC was found to cosegregate with familial HCM. To further test the hypothesis that mutations within functionally distinct domains of ACTC cause either DCM or HCM, we performed mutational analyses in 368 unrelated patients with familial or sporadic HCM. Single strand conformation polymorphism and sequence analyses of genomic DNA were performed. De novo mutations in ACTC were identified in two patients with sporadic HCM who presented with syncope in early childhood. Patients were heterozygous for missense mutations resulting in Pro164Ala and Ala331Pro amino acid substitutions, adjacent to regions of actin-actin and actin-myosin interaction, respectively. A mutation that cosegregated with familial HCM was also found, causing a Glu99Lys substitution in a weak actomyosin binding domain. The cardiac phenotype in many affected patients was characterized by an apical form of HCM. These findings support the hypothesis that a single amino acid substitution in actin causes either congestive heart failure or maladaptive cardiac hypertrophy, depending on its effect on actin structure and function.     

An overview of stress echocardiography in the study of patients with dilated or hypertrophic cardiomyopathy

Stress echocardiography is a useful noninvasive modality for measuring dynamic outflow gradient and contractility changes in patients with hypertrophic cardiomyopathy (HCM) or dilated cardiomyopathy (DCM). In patients with HCM, stress echocardiography may determine the degree of outflow tract obstruction at rest and with activity, can detect occult systolic dysfunction in symptomatic patients with a normal resting left ventricular ejection fraction, and can also be utilized to monitor the efficacy of treatment. In individuals suffering from DCM, stress echocardiography is an important aid in the evaluation of the etiology, diagnosis, and prognosis of the disease as well as the functional status of the patient during either exercise or simulated stress conditions. Dobutamine stress echocardiography, by providing a measurement of the myocardial reserve, is a useful tool to predict the systolic recovery and clinical outcome of patients with heart failure. The stress-induced change in the wall motion score index can also be used as an accurate alternative to predict the peak oxygen consumption rate and exercise capacity of the same patient population. Finally, stress echocardiography has also been used in the identification of the predilated phase of cardiomyopathy in individuals with high clinical suspicion of the disease.     

Changes in the cardiac vascular bed in dilated and hypertrophic cardiomyopathy

A complex pathomorphological examination of 46 hearts from subjects who had died of dilated (34 cases) and hypertrophic (12 cases) cardiomyopathies was performed to reveal the changes occurred in the vascular bed. For this, post-mortem coronary angiography, routine anatomic method developed by the WHO, morphometric, histological, and statistical methods were applied. In dilated cardiomyopathy, there were dilatory manifestations in the coronary arteries and vessels of microcirculation along with increased volumetric density of ventricular vascularization. Hypertrophic cardiomyopathy was characterized by a specific rearrangement in the presence of the "intensive coronarogram symptom", microvascular plexus, myocardial muscular bridges, and heterogeneous manifestations of microvessels with decreased capillarization.     

Plasma levels of A- and B-type natriuretic peptides in patients with hypertrophic cardiomyopathy or idiopathic dilated cardiomyopathy

We investigated the relation between left ventricular structure and the secretion patterns of A- and B-type natriuretic peptides (ANP and BNP) by comparing their plasma levels in patients with hypertrophic cardiomyopathy (HC) and patients with idiopathic dilated cardiomyopathy (IDC). The secretion of ANP and BNP was much higher in patients with HC than in those with IDC; this shows that left ventricular cavity size is a key factor that regulates the secretion of ANP and BNP.     

Noninvasive cardiac imaging in patients with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy and the most common cause of cardiac death in young athletes in the U.S. Noninvasive imaging plays an important role in detecting the disease, understanding its pathophysiology, and selecting as well as guiding appropriate therapy. In this review, we discuss the existing methodology with emphasis on current and emerging clinical applications in patients with HCM.     

Spectrum of clinical phenotypes and gene variants in cardiac myosin-binding protein C mutation carriers with hypertrophic cardiomyopathy

OBJECTIVES: We studied the clinical and genetic features of hypertrophic cardiomyopathy (HCM) caused by mutations in the myosin-binding protein C gene (MYBPC3) in 110 consecutive, unrelated patients and family members of European descent. BACKGROUND: Mutations in the MYBPC3 gene represent the cause of HCM in approximately 15% of familial cases. MYBPC3 mutations were reported to include mainly nonsense versus missense mutations and to be characterized by a delayed onset and benign clinical course of the disease in Japanese and French families. We investigated the features that characterize MYBPC3 variants in a large, unrelated cohort of consecutive patients. METHODS: The MYBPC3 gene was screened by single-strand conformational polymorphism analysis and sequencing. The clinical phenotypes were analyzed using rest and 24-h electrocardiography, electrophysiology, two-dimensional and Doppler echocardiography and angiography. RESULTS: We identified 13 mutations in the MYBPC3 gene: one nonsense, four missense and three splicing mutations and five small deletions and insertions. Of these, 11 were novel, and two were probably founder mutations. Patients with MYBPC3 mutations presented a broad range of phenotypes. In general, the 16 carriers of protein truncations had a tendency toward earlier disease manifestations (33 +/- 13 vs. 48 +/- 9 years; p = 0.06) and more frequently needed invasive procedures (septal ablation or cardioverter-defibrillator implantation) compared with the 9 carriers of missense mutations or in-frame deletions (12/16 vs. 1/9 patients; p < 0.01). CONCLUSIONS: Multiple mutations, which include missense, nonsense and splicing mutations, as well as small deletions and insertions, occur in the MYBPC3 gene. Protein truncation mutations seem to cause a more severe disease phenotype than missense mutations or in-frame deletions.     

Prognostic guides in patients with idiopathic or ischemic dilated cardiomyopathy assessed for cardiac transplantation

In an attempt to identify which parameters predict survival in advanced dilated cardiomyopathy, 232 patients presenting for assessment for cardiac transplantation were investigated and followed for 10 +/- 12 months (range 2 weeks to 5 years). Etiology of dilated cardiomyopathy included ischemic heart disease (33%), idiopathic (42%) and miscellaneous (25%). In each patient, 26 parameters were recorded. Whole group survival was 68% at 1 year, 56% at 2 years, 41% at 3 years and 25% at 4 years. On Cox multivariate regression analysis, 3 parameters predicted survival: New York Heart Association symptom class (p less than 0.0001), pulmonary capillary wedge pressure (p less than 0.008) and plasma atrial natriuretic factor level (p less than 0.002). On paired testing of actuarial survival curves, plasma noradrenaline also held predictive value (p less than 0.002), as did left ventricular ejection fraction less than or equal to 20% on radionuclide ventriculography (p = 0.007) and presence of greater than or equal to 4 beats of ventricular tachycardia on Holter monitoring (p = 0.007). Treatment with amiodarone did not appear to influence survival. Conventional determinants of prognosis in cardiomyopathy (symptom class, wedge pressure, nonsustained ventricular tachycardia and ejection fraction) do not alone always adequately differentiate survival in this group of high risk patients. More attention to plasma noradrenaline and to atrial natriuretic factor levels may give important additional information in the context of assessment of patients for transplantation.     

Epidemiology of desmin and cardiac actin gene mutations in a european population of dilated cardiomyopathy.

AIMS: Although dilated cardiomyopathy is the most frequent form of cardiomyopathy, its aetiology is still poorly understood. In about 20-30% of cases the disease is familial with a large predominance of autosomal dominant transmission. Ten different chromosomal loci have been described for autosomal dominant forms of dilated cardiomyopathy. Only two genes have been associated with pure forms (without myopathy and/or conduction disorders) of the disease, the cardiac actin and the desmin genes. Our aim was to determine the proportion of dilated cardiomyopathy affected individuals carrying a mutation in one of these two genes. METHODS AND RESULTS: We performed (1) a systematic polymerase chain reaction-SSCP-sequencing screening of the coding sequences of cardiac actin on DNA samples from 43 probands of dilated cardiomyopathy families and 43 sporadic cases; (2) a systematic polymerase chain reaction-SSCP-sequencing screening of the coding sequences of desmin combined with a search for the described missense mutation (Ile451Met) by restriction fragment length polymorphism analysis on DNA samples from 41 probands of dilated cardiomyopathy families and 22 sporadic cases. CONCLUSION: None of the patients presents a mutation in any of these two genes. Consequently, the proportion of European dilated cardiomyopathy affected individuals bearing a mutation in (1) the cardiac actin gene is less than 1.2%, (2) the desmin gene is less than 1.6%.     

Noninvasive cardiac imaging in patients with hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy and the most common cause of cardiac death in young athletes in the U.S. Noninvasive imaging plays an important role in detecting the disease, understanding its pathophysiology, and selecting as well as guiding appropriate therapy. In this review, we discuss the existing methodology with emphasis on current and emerging clinical applications in patients with HCM.     

Survival after cardiac arrest or sustained ventricular tachycardia in patients with hypertrophic cardiomyopathy.

OBJECTIVES: The aim of this study was to evaluate the survival of patients with hypertrophic cardiomyopathy (HCM) after resuscitated ventricular fibrillation or syncopal sustained ventricular tachycardia (VT/VF) when treated with low dose amiodarone or implantable cardioverter defibrillators (ICDs). BACKGROUND: Prospective data on clinical outcome in patients with HCM who survive a cardiac arrest are limited, but studies conducted before the widespread use of amiodarone and/or ICD therapy suggest that over a third die within seven years from sudden cardiac death or progressive heart failure. METHODS: Sixteen HCM patients with a history of VT/VF (nine male, age at VT/VF 19 +/- 8 years [range 10 to 36]) were studied. Syncopal sustained ventricular tachycardia/ventricular fibrillation occurred during or immediately after exertion in eight patients and was the initial presentation in eight. One patient had disabling neurologic deficit after VT/VF. Before VT/VF, two patients had angina, four had syncope and six had a family history of premature sudden cardiac death. After VT/VF all patients were in New York Heart Association class I or II, three had nonsustained VT during ambulatory electrocardiography and 11 had an abnormal exercise blood pressure response. After VT/VF eight patients were treated with low dose amiodarone and six received an ICD. Prophylactic therapy was declined by two patients. RESULTS: Mean follow-up was 6.1 +/- 4.0 years (range 0.5 to 14.5). Cumulative survival (death or ICD discharge) for the entire cohort was 59% at five years (95% confidence interval: 33% to 84%). Thirteen (81%) patients were alive at last follow-up. Two patients died suddenly while taking low dose amiodarone, and one died due to neurologic complications of his initial cardiac arrest. Three patients had one or more appropriate ICD discharges during follow-up; the times to first shock after ICD implantation were 23, 197 and 1,124 days. CONCLUSIONS: This study shows that patients with HCM who survive an episode of VT/VF remain at risk for a recurrent event. Implantable cardioverter defibrillator therapy appears to offer the best potential benefit regarding outcome.     

扩张型心肌病与HLA-B*基因的多态性关系

目的探讨北方汉族人扩张型心肌病(dilated cardiomyopathy,DCM)遗传易感性与人类主要组织相容性复合体(HLA-B*)基因多态性的关系。方法采用聚合酶链反应和顺序特异性引物(PCR-SSP)基因多态性分析方法,对31例扩张型心肌病患者及29例无血缘关系健康人的HLA-B*各等位基因及亚基因进行检测分析。结果HLA-B*35基因与DCM呈正相关(相对危险度RR=3．9375,P<0．05),其他HLA-B*各等位基因未见异常,差异均无统计学意义(P>0．05)。结论HLA-B*35基因可能是北方地区汉族人DCM的致病易感基因之一,为揭示DCM的发病机制中免疫遗传学所起的作用提供了重要信息和依据。     

扩张型心肌病与MHC-DQ基因多态性的关联分析

目的　探讨扩张型心肌病 ( DCM)易感的分子机制和确立一种较为实用的 MHC- 类基因的检测方法。方法　采用聚合酶链式反应和顺序特异性引物 ( PCR- SSP)基因分析方法 ,对 31例扩张型心肌病患者及 30例无血缘关系的健康人的人类主要组织相容性复合体 ( MHC- 类 ) DQ各等位基因及亚基因进行了检测分析 ,并将该方法与其它检测 MHC- 类基因的方法进行对比。结果　结果表明 ,MHC- DQB1* 0 30 1基因与 DCM呈正相关 ( P <0 .0 1) ,其它 MHC- DQB1*其它各等位基因未见异常。结论　 MHC- DQB1* 0 30 1基因可能为北方汉族人 DCM的致病易感基因。尽管目前 MHC- 类基因分型方法已有多种 ,但所采用的方法 ( PCR- SSP)具有快速、简便、敏感、准确和可靠等优点。     

扩张型心肌病患者HLA-DQB1基因的多态性

目的 :探讨扩张型心肌病 (DCM)的遗传背景及免疫学发病机制。方法 :借助聚合酶链式反应 /序列特异性引物 (PCR/ SSP)技术对 84例 DCM患者和 143例正常人进行了 HL A- DQB1 基因型别分析。结果 :与正常对照组相比 ,HL A- DQB1 * 0 30 3等位基因频率降低 ,其 RR值为 0 .41,P <0 .0 1。结论 :研究进一步证实免疫遗传学在部分 DCM发病机制中具有重要意义。携带 HL A- DQB1 * 0 30 3等位基因的个体可能对 DCM具有抗性。     

肌联蛋白基因突变与中国人扩张型心肌病

目的 肌联蛋白是由单基因编码的最大蛋白,普遍存在于心肌和骨骼肌,被称为第三肌丝,具有复杂的牛物力学性质和牛物化学功能.2002年日本研究人员报道r肌联蛋白基因(TTN)第3、14、49号外显子的4个基凶突变町能与扩张型心肌病(DCM)发病相关,我国未见相关报道.本研究通过寻找我同DCM患者是否存在TTN的突变,探讨在中国人基因背景下可能存在的TTN的突变及其与我国DCM发病的关系.方法 采用聚合酶链反应-单链构象多态件(PCR-SSCP)方法、聚丙烯酰胺凝胶电泳及DNA序列测定等方法对117例DCM患者和120例健康对照者TTN的第3、14、49号外显子的多个位点进行检测、分析.结果 在我国DCM患者和健康对照者中未发现与日本DCM患者相同位点的基因突变,而在2例有明显DCM家族史的儿章患者(1.7%)中新发现了位于TTN第49号外显子的13053位点基凶突变--G→A突变(G13053A),其导敛第4351位点氨基酸由甘氨酸变为大冬氨酸(Gly4351Asp),在健康对照组巾未发现此改变.结论 本研究首次在中国DCM患者中发现存在于TTN第49号外显子的基因错义突变,该突变可能是DCM重要的病因学机制,尤其可能与早发DCM相关.     

Hemochromatosis gene variants in patients with cardiomyopathy.

Iron depletion was suggested to be protective against the development of ischemic heart disease. Population studies have led to conflicting results, and such an association has not been addressed in patients with heart failure due to cardiomyopathy. We studied the distribution of hemochromatosis-related mutations in 319 patients with heart failure due to cardiomyopathy of different etiologies. The genotypic distribution showed a significantly higher prevalence of heterozygotes for the C282Y mutation in patients with ischemic cardiomyopathy than in patients with cardiomyopathy of nonischemic etiologies (p = 0.0036). The frequency of the D63 mutation was not significantly different between ischemic versus nonischemic groups. In multiple logistic regression models adjusted for age, sex, ethnicity, and different degrees of disease progression, there was a strong and significant association of the C282Y mutation with ischemic cardiomyopathy compared with the nonischemic group (odds ratio 6.64, 95% confidence interval 1.71 to 25.73, after adjustment). In our sample, genetic variation in the HFE gene was associated with ischemic cardiomyopathy. Such association merits further study regarding its value as a prognostic marker in patients with ischemic heart disease.     

Mutations in the cardiac troponin T gene show various prognoses in Japanese patients with hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant disorder resulting from mutations in genes for at least 15 various sarcomere-related proteins including cardiac β-myosin heavy chain, cardiac myosin-binding protein C, and cardiac troponin T. The troponin T gene (TNNT2) mutation has the third incidence of familial HCM, and the genotype–phenotype correlation of this gene still remains insufficient in Japanese familial HCM. Therefore, in the present study, we focused on screening the TNNT2 mutation in 173 unrelated Japanese patients with familial HCM, and found three reported mutations and a new mutation of TNNT2 in 11 individuals from four families. In these families, two individuals from one family had double mutations, Arg130Cys and Phe110Ile, six individuals from two other families had an Arg92Trp mutation, and one individual of another family had a new mutation, Ile79Thr, of TNNT2. The phenotype of each family was often different from reported cases, even if they had the same genetic mutation. In addition, families with the same genetic mutation showed a similar trend in the phenotype, but it was not exactly the same. However, sudden death in youth was observed in all of these families. Although the type of genetic mutation is not useful for predicting prognosis in HCM, the possibility of sudden cardiac death remains. Therefore, the prognosis of individuals bearing the TNNT2 mutation with familial HCM should be more carefully observed from birth.