Activation delay and VT parameters in arrhythmogenic right ventricular dysplasia/cardiomyopathy: toward improvement of diagnostic ECG criteria

Introduction: Desmosomal changes, electrical uncoupling, and surviving myocardial bundles embedded in fibrofatty tissue are hallmarks of activation delay in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). Currently, generally accepted task force criteria (TFC) are used for clinical diagnosis. We propose additional criteria based on activation delay and ventricular tachycardia (VT) to improve identification of affected individuals.
Methods and Results: Activation delay and VT-related 12-lead electrocardiographic (ECG) criteria were studied, while off drugs, in 42 patients with proven ARVD/C according to TFC, and 27 controls with idiopathic VT from the RV outflow tract. Two of three measured TFC could only be identified in a small minority of ARVD/C patients. Additional ECG criteria proposed in this study included (a) prolonged terminal activation duration, an indicator of activation delay; (b) VT with LBBB morphology and superior axis; and (c) multiple different VT morphologies. These criteria were met in 30 (71%), 28 (67%), and 37 (88%) ARVD/C patients, respectively, and in one control patient (P < 0.001). Electrophysiologic studies contributed importantly to yield different VT morphologies. Pathogenic plakophilin-2 mutations were identified in 25 (60%) of ARVD/C patients and in none of the controls. In ARVD/C patients, parameters measured were not significantly different between mutation carriers and noncarriers, except for negative T waves in V1–3, occurring more frequently in patients with mutation.
Conclusions: The proposed additional criteria are specific for ARVD/C and more sensitive than the current TFC. Therefore, adding the newly proposed criteria to current TFC could improve ARVD/C diagnosis, independent of DNA analysis.     

Arrhythmogenic right ventricular cardiomyopathy caused by deletions in plakophilin-2 and plakoglobin (Naxos disease) in families from Greece and Cyprus: genotype-phenotype relations, diagnostic features and prognosis.

AIMS: To evaluate clinical disease expression, non-invasive diagnosis, and prognosis in families with dominant vs. recessive arrhythmogenic right ventricular cardiomyopathy (ARVC) due to mutations in related desmosomal proteins plakophilin-2 (PKP2) and plakoglobin (JUP), respectively. METHODS AND RESULTS: One hundred and eighty-seven individuals belonging to ARVC families, four with dominant PKP2 mutations and 12 with recessive JUP mutation underwent serial non-invasive cardiac assessment. Survival and arrhythmic events were evaluated prospectively up to 21 years (median 8.5 years). Sixteen of 22 PKP2 carriers and all 26 homozygous JUP carriers fulfilled the diagnostic criteria for ARVC, the youngest by the age of 13 years. Clinical disease expression did not differ significantly between PKP2 and JUP carriers. T-wave inversion in leads V1-V3, right ventricular wall motion abnormalities, and frequent ventricular extrasystoles were the most sensitive/specific markers for identification of mutation carriers. QRS dispersion > or =40 ms was an independent predictor of syncope but not of sudden death. CONCLUSION: Mutations in PKP2 and JUP express similar cardiac phenotype. Non-invasive family screening may largely be based on T-wave inversion, right ventricular wall motion abnormalities, and frequent ventricular extrasystoles to identify mutation carriers.     

Review on the genetics of arrhythmogenic right ventricular dysplasia.

Arrhythmogenic right ventricular dysplasia (ARVD) is a clinical and pathologic entity whose diagnosis rests on electrocardiographic and angiographic criteria; pathologic findings, replacement of ventricular myocardium with fatty and fibrous elements, preferentially involve the right ventricular (RV) free wall. There is a familial occurrence in about 50% of cases, with autosomal dominant inheritance with variable penetrance and polymorphic phenotypic expression, and is one of the major genetic causes of juvenile sudden death. When the dysplasia is extensive, it may represent the extensive form of ARVCM (arrhythmogenic right ventricular cardiomyopathy). In this review, we focus on the some candidate genes mutations and information on some genotype-phenotype correlation in the ARVD. Our findings are in agreement with those of European Society of Cardiology who stated that: genetic analysis is usefull in families with RV cardiomyopathy because whenever a pathogenetic mutation is identified, it becomes possible to establish a presymptomatic diagnosis of the disease among family members and to provide them with genetic counseling to monitor the development of the disease and to assess the risk of transmitting the disease offspring. On the basis of current knowledge, genetic analysis does not contribute to risk stratification of arrhythmogenic RV cardiomyopathy.     

Desmoglein-2 mutations in arrhythmogenic right ventricular cardiomyopathy: a genotype-phenotype characterization of familial disease.

AIMS: Mutations in the desmoglein-2 (DSG2) gene have been reported in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) but clinical information regarding the associated phenotype is at present limited. In this study, we aimed to clinically characterize probands and family members carrying a DSG2 mutation. METHODS AND RESULTS: We investigated 86 Caucasian ARVC patients for mutations in DSG2 by direct sequencing and detected eight novel mutations in nine probands. Clinical evaluation of family members with DSG2 mutations demonstrated penetrance of 58% using Task Force criteria, or 75% using proposed modified criteria. Morphological abnormalities of the right ventricle were evident in 66% of gene carriers, left ventricular (LV) involvement in 25%, and classical right precordial T-wave inversion only in 26%. Sustained ventricular arrhythmia was present in 8% and a family history of sudden death/aborted sudden death in 66%. CONCLUSION: Mutations in DSG2 display a high degree of penetrance. Disease expression was of variable severity with LV involvement a prominent feature. The low prevalence of classical ECG changes highlights the need to expand current diagnostic criteria to take account of LV disease, childhood disease expression, and incomplete penetrance.     

Arrhythmogenic right ventricular cardiomyopathy due to a novel plakophilin 2 mutation: Wide spectrum of disease in mutation carriers within a family

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial disease, with male preponderance, characterized by progressive fibrofatty replacement of the right ventricle and ventricular arrhythmias. Mutations in plakophilin-2 (PKP2), a desmosomal protein, have been reported to underlie familial ARVC. We report a novel ARVC PKP2 mutation and present the clinical findings in three female mutation carriers. METHODS: We sequenced PKP2 from genomic DNA isolated from peripheral blood lymphocytes in a female proband who presented with cardiac arrest and in her four first-degree relatives. Clinical testing and diagnosis of ARVC was based on International Task Force criteria. RESULTS: The proband was diagnosed with ARVC due to right ventricular enlargement and regional hypokinesis, along with repolarization abnormalities and frequent ventricular ectopy. A novel 28 bp insertion in exon 11 of the PKP2 gene was found which causes a frameshift in the coding region. This results in a change in the amino acid sequence of the protein with a premature stop codon at position 740. Of the four relatives, only the mother and younger sister were identified as mutation carriers. The mother was phenotypically normal, while the younger sister has repolarization abnormalities and frequent ventricular ectopy. CONCLUSIONS: We report a novel PKP2 mutation that causes familial ARVC. All mutation carriers in this kindred group were women, and the family showed incomplete penetrance and variable expression of ARVC. Premature truncation of the plakophilin-2 protein appears to be the predominant mechanism whereby PKP2 mutations elicit the ARVC phenotype.     

Shared Desmosome Gene Findings in Early and Late Onset Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited form of cardiomyopathy with low penetrance and variable expressivity. Dominant mutations and rare polymorphisms in desmosome genes are frequently identified. We reasoned that individuals with earlier onset disease would have more frequent desmosome gene mutations and rare polymorphisms. Three groups were compared: Young with symptoms attributable to ARVD/C or a diagnosis of ARVD/C at age of 21 years or earlier, Middle with first symptoms or diagnosis age of 22–49 years, and Late with first symptoms or diagnosis at age of 50 or more years. deoxyribonucleic acid (DNA) sequence analysis was performed on five cardiac desmosome genes, and the presence of mutations and rare missense polymorphisms was compared among the three groups. In the entire Young cohort, 20 (67%) had one or more cardiac desmosome gene mutations. The prevalence of cardiac desmosome gene mutations was similar in the Middle (48%) and Late (53%) cohorts (P?=?0.23). Similar numbers of individuals in each cohort had more than one desmosome gene mutation, although the numbers are too small for statistical comparisons. The prevalence of certain rare missense DNA variants was not different among the cohorts (P?=?0.71), yet these rare missense alleles were more prevalent in the overall study cohort of 112 ARVD/C participants compared to 100 race-matched controls (P?=?0.027). The presence of these variants did not associate with the age of onset of ARVD/C or ventricular tachycardia. These findings highlight the complex interplay of environmental and genetic factors contributing to this condition.     

Yield of Serial Evaluation in At-Risk Family Members of Patients With ARVD/C

Background

Incomplete penetrance and variable expressivity of arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) complicate family screening.

Objectives

The objective of the present study was to determine the optimal approach to longitudinal follow-up regarding: 1) screening interval; and 2) testing strategy in at-risk relatives of ARVD/C patients.

Methods

We included 117 relatives (45% male, age 33.3 ± 16.3 years) from 64 families who were at risk of developing ARVD/C by virtue of their familial predisposition (72% mutation carriers [92% plakophilin-2]; 28% first-degree relatives of a mutation-negative proband). Subjects were evaluated by electrocardiography (ECG), Holter monitoring, signal-averaged ECG, and cardiac magnetic resonance (CMR). Disease progression was defined as the development of a new criterion by the 2010 Task Force Criteria (not the “Hamid criteria”) at last follow-up that was absent at enrollment.

Results

At first evaluation, 43 subjects (37%) fulfilled an ARVD/C diagnosis according to the 2010 Task Force Criteria. Among the remaining 74 subjects (63%), 11 of 37 (30%) with complete re-evaluation experienced disease progression during 4.1 ± 2.3 years of follow-up. Electrical progression (n = 10 [27%], including by ECG [14%], Holter monitoring [11%], or signal-averaged ECG [14%]) was more frequently observed than structural progression (n = 1 [3%] on CMR). All 5 patients (14%) with clinical ARVD/C diagnosis at last follow-up had an abnormal ECG or Holter monitor recording, and the only patient with an abnormal CMR already had an abnormal ECG at enrollment.

Conclusions

Over a mean follow-up of 4 years, our study showed that: 1) almost one-third of at-risk relatives have electrical progression; 2) structural progression is rare; and 3) electrical abnormalities precede detectable structural changes. This information could be valuable in determining family screening protocols.     

致心律失常性右心室心肌病患者心室晚电位与室性心动过速关系

目的探讨致心律失常性右心室心肌病(arrhythmogenic right ventricular dysplasia/cardiomyopathy,ARVD/C)合并室性心动过速与心室晚电位的关系。方法ARVD/C38例,男28例,女10例,年龄(35±15)岁。心电图检查进行信号叠加,记录心室晚电位量化参数:总QRS时限(total QRS duration,QRST)、QRS终末部位电压低于40μV时限(low potential terminal signals,LPS40)、QRS最后40ms电压方根均数(root mean square of the last 40 ms,RMS40);动态心电图检查记录室性心动过速和室性期前收缩。使用χ2及Mann-Whitney秩和检验统计。结果①心室晚电位阳性25例,其中室性心动过速18例;心室晚电位阴性13例,室性心动过速3例(P=0.004);②室性心动过速阳性21例,阴性17例,QRST:室性心动过速阳性组109～233(中位数147)ms,阴性组85～158(中位数104)ms(P=0.000);LPS40:阳性组15～158(中位数53)ms和阴性...     

Frequency and clinical expression of cardiac troponin I mutations in 748 consecutive families with hypertrophic cardiomyopathy

OBJECTIVES: The aim of this study was to evaluate the potential utility of genetic diagnosis in clinical management of families with hypertrophic cardiomyopathy (HCM) caused by mutations in the gene for cardiac troponin I (TNNI3). BACKGROUND: Knowledge about the clinical disease expression of sarcomeric gene mutations in HCM has predominantly been obtained by investigations of single individuals (probands) or selected families. To establish the role of genetic diagnosis in HCM families, systematic investigations of probands and their relatives are needed. METHODS: Cardiac troponin I was investigated by direct sequencing and fluorescent (F)-SSCP analysis in 748 consecutive HCM families. Relatives of HCM probands with TNNI3 mutations were invited for cardiovascular and genetic assessment. RESULTS: The prevalence of TNNI3 mutations was 3.1%. Mutations appeared to cluster in exons 7 and 8. A total of 100 mutation carriers were identified in 23 families with 13 different mutations (6 novel). Disease penetrance was 48%. Patients were diagnosed from the second to eighth decade of life. The morphologic spectrum observed represented a wide range of HCM. Two offspring of clinically unaffected mutation carriers were resuscitated from cardiac arrest, and an additional four individuals died suddenly as their initial presentation. Six individuals experienced other disease-related deaths. CONCLUSIONS: The clinical expression of TNNI3 mutations was very heterogeneous and varied both within and between families with no apparent mutation- or gene-specific disease pattern. The data suggest that disease development may be monitored by regular assessment of cardiac symptoms and electrocardiographic abnormalities. Genetic diagnosis of TNNI3 is valuable in identifying clinically unaffected mutation carriers at risk of disease development and facilitates accurate management and counseling.     

Noninvasive detection of myocardial fibrosis in arrhythmogenic right ventricular cardiomyopathy using delayed-enhancement magnetic resonance imaging

OBJECTIVES: We evaluated the role of myocardial delayed-enhancement (MDE) magnetic resonance imaging (MRI) for noninvasive detection of fibrosis in Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy is characterized by fibro-fatty replacement of the right ventricle (RV) leading to arrhythmias and RV failure. Endomyocardial biopsy can demonstrate fibro-fatty replacement of the RV myocardium; however, the test is invasive and carries a risk of perforation. METHODS: Thirty consecutive patients were prospectively evaluated for ARVD/C. Magnetic resonance imaging was performed on a 1.5-T scanner. Ten minutes after intravenous administration of 0.2 mmol/kg of gadodiamide, MDE-MRI was obtained. Diagnosis of ARVD/C was based upon the Task Force criteria and did not include MRI findings. RESULTS: Twelve (40%) of 30 patients met the Task Force criteria for ARVD/C. Eight (67%) of the 12 ARVD/C patients demonstrated increased signal on MDE-MRI in the RV compared with none (0%) of the 18 patients without ARVD/C (p <0.001). Endomyocardial biopsy was performed in 9 of the 12 ARVD/C patients. Of the nine patients, four had fibro-fatty changes consistent with the diagnosis of ARVD/C. Each of these patients had increased RV signal on MDE-MRI. None of the patients without ARVD/C had any abnormalities either on histopathology or on MDE-MRI. Electrophysiologic testing revealed inducible sustained ventricular tachycardia (VT) in six of the eight ARVD/C patients with delayed enhancement, compared with none of the ARVD/C patients without delayed enhancement (p=0.01). CONCLUSIONS: Noninvasive detection of RV myocardial fibro-fatty changes in ARVD/C is possible by MDE-MRI. Magnetic resonance imaging findings had an excellent correlation with histopathology and predicted inducible VT on programmed electrical stimulation, suggesting a possible role in evaluation and diagnosis of patients with suspected ARVD/C.     

Mechanisms of disease: molecular genetics of arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy is an inherited cardiomyopathy estimated to affect approximately 1 in 5,000 individuals. Cardinal manifestations include right ventricular enlargement and dysfunction, fibrofatty replacement of myocytes in the right ventricle, characteristic electrocardiographic abnormalities, and ventricular arrhythmia most commonly arising from the right ventricle. The disease is frequently familial and typically involves autosomal dominant transmission with low penetrance and variable expressivity. Approximately 50% of symptomatic individuals harbor a mutation in one of the five major components of the cardiac desmosome. Nevertheless, other genetic modifiers and environmental factors complicate the clinical management of mutation carriers as well as counseling of their relatives. This Review summarizes the known genetic mutations associated with arrhythmogenic right ventricular dysplasia/cardiomyopathy, describes possible origins of recurrent mutations, presents theories on the pathogenesis of disease following a mutation, and discusses the current issues surrounding clinical use of genetic analysis in the assessment of individuals with this condition.     

A novel missense mutation in the myosin binding protein-C gene is responsible for hypertrophic cardiomyopathy with left ventricular dysfunction and dilation in elderly patients

OBJECTIVES: We studied the clinical features of hypertrophic cardiomyopathy (HCM) caused by a novel mutation in the myosin binding protein-C (MyBP-C) gene in patients and family members of Japanese descent. BACKGROUND: Previous reports have demonstrated that the clinical features of HCM associated with mutations in the MyBP-C gene include late onset and a favorable clinical course. Recently, some mutations in genes encoding sarcomeric proteins have been reported to be a cause of dilated cardiomyopathy (DCM), as well as HCM. However, mutations of the MyBP-C gene have not been reported as a cause of DCM up to now. METHODS: We analyzed MyBP-C gene mutations in 250 unrelated probands with HCM and in 90 with DCM. We used electrocardiography (ECG) and echocardiography to determine clinical phenotypes. RESULTS: We identified 17 individuals in 8 families (7 HCM, 1 DCM) with an Arg820Gln mutation in the MyBP-C gene. Overall, 2 (40%) of 5 carriers age >70 years displayed "burnt-out" phase HCM, and one of them had been diagnosed as having DCM before genetic identification. The disease penetrance in subjects age >50 years was 70% by echocardiography and 100% by ECG, and that in those age <50 years was 40% and 50%, respectively. CONCLUSIONS: Elderly patients with Arg820Gln mutation may show "burnt-out" phase HCM, and patients with this mutation may be included among those diagnosed as having DCM. Screening of patients with DCM, as well as HCM, for this mutation is of significant importance because patients with this mutation may be diagnosed clinically as having DCM.     

Molecular genetics of arrhythmogenic right ventricular cardiomyopathy: emerging horizon?

PURPOSE OF REVIEW: Recent developments in the elucidation of genes underlying arrhythmogenic right ventricular cardiomyopathy and possible pathogenic mechanisms will be highlighted. RECENT FINDINGS: The cardiac desmosome is a multiprotein structure involved in cell-cell interactions. Mutations in genes encoding desmosomal proteins such as PKP2, DSP, JUP, DSC2 and DSG2 underlie arrhythmogenic right ventricular cardiomyopathy, which can therefore be considered a desmosome cardiomyopathy. Mutations in the plakophilin-2 gene are most prevalent. Current pathophysiological insights suggest a final common pathway in which plakoglobin release from the desmosome, independent of the primarily affected desmosomal protein, results in desmosome impairment, intercalated disc remodeling and Wnt/beta-catenin pathway signaling defects. The recognition of left ventricular involvement associated with mutations in desmosomal protein genes and low penetrance suggests that formal criteria should not be followed too closely in selecting patients for DNA analysis, because finding a mutation may have important implications for clinical practice. SUMMARY: Recent developments have demonstrated that arrhythmogenic right ventricular cardiomyopathy can be considered a desmosome cardiomyopathy. Left ventricular involvement is not uncommon in this type of cardiomyopathy. Such findings are important for diagnostics and family screening and form a starting-point for the elucidation of other (non)-genetic factors influencing disease progression and outcome.     

Etiopathogenesis of arrhythmogenic right ventricular dysplasia

Arhythmogenic right ventricular dysplasia (ARVD) is a genetically determined cardiomyopathy with a dominant transmission mode and variable penetrance. Transdifferenciation of cardiomyocytes into adipocytes is likely to explain massive replacement of right ventricular and to a lesser extent left ventricular myocardium by adipose tissue. This phenomenon starts in the mediomural layers and extends into the epicardium. It can occur in the fetus, however youth and young adults are more frequently involved. Apoptosis defined as a programmed cell death, is likely to enhance adipogenesis and tiny fibrosis production. Inflammation can be superimposed on the genetically determined substrate and usually involves both ventricles. Myocarditis can be acute or chronic with interstitial or scar fibrosis, or active chronic. In some cases, left ventricular involvement can be as important as right ventricle, characterizing biventricular dysplasia. In Naxos disease, ARVD is associated with an ectodermic dysplasia. The transmission mode is recessive.     

The detection of cardiotropic viruses in the myocardium of patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy

OBJECTIVES: We sought to investigate the role of cardiotropic viruses, including adenovirus, cytomegalovirus (CMV), enterovirus and parvovirus, in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy is characterized by a gradual loss of myocytes, inflammatory infiltrates and replacement by fatty and fibrous tissue. It has been speculated that ARVD/C is a sequela of viral myocarditis in some patients, and the role of the coxsackievirus B3 has been debated. METHODS: Myocardial samples from 12 patients with ARVD/C were analyzed by polymerase chain reaction for the presence of cardiotropic viruses. RESULTS: Enteroviral sequences were detected in seven patients and adenovirus type 5 in another two patients. During the same period, 215 control samples were analyzed in which only CMV (n = 2) and enterovirus (n = 1) were detected. This suggests a link between ARVD/C and the presence of viral genome (enterovirus or adenovirus) in the myocardium. CONCLUSIONS: We report that cardiotropic viruses are more frequently identified in patients with ARVD/C than in control subjects. However, the role of these viruses in ARVD/C pathogenesis remains unknown.     

Arrhythmogenic right ventricular dysplasia/ cardiomyopathy

Optional statement Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a genetic cardiomyopathy characterized by ventricular arrhythmias and structural abnormalities of the right ventricle (RV). The most important aspect in the treatment of ARVD/C is establishing a correct diagnosis based on the International Task Force criteria. In our experience, cardiologists are not aware of these diagnostic criteria for ARVD/C and place too much importance on the results of magnetic resonance imaging of the RV. Patients with ARVD/C generally all have an abnormal 12-lead electrocardiogram, abnormal echocardiogram, and ventricular arrhythmias with a left bundle branch block morphology. If noninvasive testing suggests ARVD, invasive testing with an RV angiogram, RV biopsy, and electrophysiology study are recommended. We encourage patients to participate in the National Institutes of Health-sponsored multicenter clinical trial of ARVD/C (http://www.ARVD.com or http://www.ARVD.org). Once a diagnosis of ARVD/C is established, the main treatment decision involves whether to implant an implantable cardioverter-defibrillator (ICD). ICDs are recommended for patients who have experienced syncope, sudden death, or a sustained ventricular arrhythmia, and also for patients with overt evidence of ARVD, particularly if the electrophysiology study is abnormal or there is a family history of sudden death. We also recommend treatment of patients with ARVD/C with β blockers and angiotensin-converting enzyme inhibitors, and that all patients with ARVD/C be screened for a mutation in the gene for plakophilin-2, because this is present in more than one third of patients with ARVD/C and may be helpful in the management of firstdegree relatives.     

Troponin-I elevation in a young man with arrhythmogenic right ventricular dysplasia/cardiomyopathy

Ventricular arrhythmias occur frequently in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) as well as those with ischemic heart disease. We present the case of a 29-year-old man with ARVD/C and multiple episodes of symptomatic ventricular tachycardia terminated by implantable cardioverter defibrillator (ICD) discharges. Phasic elevation of troponin-I prompted repeated coronary angiograms, all of which were normal. The patient was successfully treated with radiofrequency ablation. This case illustrates that ARVD/C may result in elevated cardiac enzymes in the absence of coronary artery disease.     

Desmosomal dysfunction due to mutations in desmoplakin causes arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is characterized by progressive degeneration of the right ventricular myocardium, ventricular arrhythmias, fibrous-fatty replacement, and increased risk of sudden death. Mutations in 6 genes, including 4 encoding desmosomal proteins (Junctional plakoglobin (JUP), Desmoplakin (DSP), Plakophilin 2, and Desmoglein 2), have been identified in patients with ARVD/C. Mutation analysis of 66 probands identified 4 variants in DSP; V30M, Q90R, W233X, and R2834H. To establish a cause and effect relationship between those DSP missense mutations and ARVD/C, we performed in vitro and in vivo analyses of the mutated proteins. Unlike wild-type (WT) DSP, the N-terminal mutants (V30M and Q90R) failed to localize to the cell membrane in desomosome-forming cell line and failed to bind to and coimmunoprecipitate JUP. Multiple attempts to generate N-terminal DSP (V30M and Q90R) cardiac-specific transgenes have failed: analysis of embryos revealed evidence of profound ventricular dilation, which likely resulted in embryonic lethality. We were able to develop transgenic (Tg) mice with cardiac-restricted overexpression of the C-terminal mutant (R2834H) or WT DSP. Whereas mice overexpressing WT DSP had no detectable histologic, morphological, or functional cardiac changes, the R2834H-Tg mice had increased cardiomyocyte apoptosis, cardiac fibrosis, and lipid accumulation, along with ventricular enlargement and cardiac dysfunction in both ventricles. These mice also displayed interruption of DSP-desmin interaction at intercalated discs (IDs) and marked ultra-structural changes of IDs. These data suggest DSP expression in cardiomyocytes is crucial for maintaining cardiac tissue integrity, and DSP abnormalities result in ARVD/C by cardiomyocyte death, changes in lipid metabolism, and defects in cardiac development.     

Molecular composition of the intercalated disc in a spontaneous canine animal model of arrhythmogenic right ventricular dysplasia/cardiomyopathy

BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is characterized by ventricular arrhythmias, sudden death, and fatty or fibrofatty replacement of right ventricular myocytes. Recent studies have noted an association between human ARVD/C and molecular remodeling of intercalated disc structures. However, progress has been constrained by limitations inherent to human studies. OBJECTIVE: We studied the molecular composition of the intercalated disc structure in a naturally occurring animal model of ARVD/C (Boxer dogs). METHODS: We studied hearts from 12 Boxers with confirmed ARVD/C and 2 controls. Ventricular sections from 4 animals were examined by immunofluorescent microscopy. Frozen tissue samples were used for Western blot analysis. Proteins investigated were N-cadherin, plakophilin 2, desmoplakin, plakoglobin, desmin, and connexin 43 (Cx43). RESULTS: In control dogs, all proteins tested by immunofluorescence analysis yielded intense localized signals at sites of end-to-end cell apposition. In contrast, myocardial tissues from ARVD/C-afflicted Boxers showed preservation of N-cadherin staining but loss of detectable signal for Cx43 at the intercalated disc location. Western blots indicated that the Cx43 protein was still present in the samples. Gene sequencing analysis showed no mutations in desmoplakin, plakoglobin, Cx43, or plakophilin 2. CONCLUSION: Mutation(s) responsible for ARVD/C in Boxers lead, directly or indirectly, to severe modifications of mechanical and electrical cell-cell interactions. Furthermore, significant reduction in gap junction formation may promote a substrate for malignant ventricular arrhythmias. This model may help to advance our understanding of the molecular basis, pathophysiology, and potential therapeutic approach to patients with ARVD/C.