Canonical Wnt Signaling in Pathogenesis and Rescue of ARVC Phenotype

描述(申请人提供)：总体目标是描述致心律失常性右室心肌病(ARVC)的分子发病机制，以预防、减轻和逆转其演变表型。ARVC是一种罕见的遗传病，由至少五种桥粒蛋白突变引起。ARVC患者通常表现为心律失常、心脏性猝死(SCD)，并处于全球心力衰竭的进展期。在大约25%的病例中，SCD是该病的首发症状。ARVC的表型特征是心肌纤维脂肪细胞的浸润，并伴随着心肌细胞的凋亡。ARVC的分子发病机制和纤维肥胖症的细胞起源尚不清楚。ARVC作为一种突变型桥粒蛋白疾病，其遗传学基础的阐明为阐明其表型的发病机制提供了机会。斑点蛋白(PG)是一种桥粒蛋白，它是一种桥粒蛋白，也是一种螳螂家族成员，其结构和功能与经典Wnt信号转导蛋白2-catenin的结构和功能相似，我们推测PG(又名3-catenin)和2-catenin之间的竞争性相互作用抑制了典型的Wnt信号，导致心肌细胞凋亡和促进脂肪生成。为了验证这一假设，我们建立了心脏受限的桥粒蛋白(DP)缺陷小鼠和siRNA介导的DP缺陷的心房肌细胞。我们发现，DP缺乏导致PG核移位、Wnt信号受抑制、心肌细胞凋亡、纤维化和脂肪生成。我们建议鉴定心脏中过剩脂肪细胞的细胞来源，描述被抑制的典型Wnt信号的分子基础，并通过激活典型的Wnt信号来防止表型。其目的是：1.通过体内遗传命运定位和共培养研究确定ARVC中过度脂肪细胞的细胞来源；2.通过在转基因小鼠心脏中表达可滴定水平的突变桥粒蛋白，确定抑制规范的Wnt信号是否是ARVC发病的共同机制；3.通过研究蛋白质-蛋白质相互作用和PG对Wnt核心蛋白复合体的有效组装的影响，阐明核PG抑制规范的Wnt信号的机制；4.通过有条件地激活抗降解的2-连环蛋白和药物激活来激活规范的Wnt信号，从而挽救体内和体内的ARVC表型，从而满足Koch的因果关系假设。在转基因小鼠、转导的心肌细胞和肌成纤维细胞上的研究旨在描绘每个目标的组成部分。本研究结果有助于阐明桥粒ARVC的分子发病机制，为人类ARVC的治疗和预防提供新的分子诊断标记和新的药理靶点。项目简介我们建议研究人类心肌疾病ARVC的分子基础，并防止其在转基因小鼠模型中的发展。ARVC是导致年轻人猝死的重要原因。目前，对ARVC尚无特效治疗或预防措施。

DESCRIPTION (provided by applicant): The overall objective is to delineate the molecular pathogenesis of arrhythmogenic right ventricular cardiomyopathy (ARVC) in order to prevent, attenuate and reverse its evolving phenotype. ARVC is an uncommon genetic disease caused by mutations in at least five desmosomal proteins. Patients with ARVC typically present with cardiac arrhythmias, sudden cardiac death (SCD) and in advances stages with global heart failure. SCD is the first manifestation of the disease in approximately 25% of the cases. The phenotypic hallmark of ARVC is fibro-adipocytic infiltration of the myocardium that occurs in conjunction with myocyte apoptosis. The molecular pathogenesis of ARVC and the cellular origin of fibro-adiposis are unknown. Elucidation of the genetic basis of ARVC, as a disease of mutant desmosomal proteins, has provided the opportunity to delineate the pathogenesis of its phenotype. Based on structural and functional similarities between plakoglobin (PG), a desmosomal protein and a member armadillo family, and 2-catenin, the signal transducer of the canonical Wnt signaling and also an armadillo protein, we posit competitive interactions between PG (aka 3-catenin) and 2-catenin suppresses the canonical Wnt signaling, leads to myocyte apoptosis and enhanced adipogenesis. To test the hypothesis, we generated cardiac-restricted desmoplakin (DP) deficient mice and siRNA-mediated DP-deficient atrial myocytes. We showed DP-deficiency led to nuclear translocation of PG, suppression of the canonical Wnt signaling, myocyte apoptosis, fibrosis and adipogenesis. We propose to identify the cellular origin of excess adipocytes in the heart, delineate the molecular basis of suppressed canonical Wnt signaling and prevent the phenotype by activating the canonical Wnt signaling. The aims are: 1. To identify the cellular origin of excess adipocytes in ARVC through in vivo genetic fate-mapping and co-culture studies; 2. To determine whether suppressed canonical Wnt signaling is a common mechanism for the pathogenesis of ARVC by expression of titratable levels of mutant desmosomal proteins in transgenic mice hearts; 3. To delineate the mechanism by which nuclear PG suppresses the canonical Wnt signaling by studying protein-protein interactions and the effects of PG on effective assembly of Wnt core proteins complex; 4. To rescue the ARVC phenotype in vivo and in vivo by activating the canonical Wnt signaling through conditional activation of degradation-resistant 2-catenin and pharmacological activation and hence, to fulfill the Koch's postulates of causality. Studies in genetically modified mice, transduced cardiac myocytes and myofibroblasts are designed to delineate the components of each aim. The results could elucidate the molecular pathogenesis of desmosomal ARVC and lead to identification of new molecular diagnostic markers and novel pharmacological targets for the treatment and prevention of ARVC in humans. Project Narrative we propose to study the molecular basis of human heart muscle disease ARVC and to prevent its development in genetically modified mouse models. ARVC is an important cause of sudden death in the young. Currently, there is no specific treatment or prevention for ARVC.