Desmoplakinopathies: Integrated Pathophysiology and Therapeutics

项目摘要 致心律失常性心肌病（ACM）是一种遗传性疾病，其弥合了心律失常与心肌梗死之间的差距。 心肌病和遗传性心律失常综合征。在其早期的“隐蔽”阶段，ACM促进 在没有明显结构或机械重塑的情况下发生室性心律失常。随着疾病 进展时，出现肌细胞损失、炎症和纤维脂肪浸润，最终导致双心室衰竭， 心源性猝死（SCD）的风险。强调了该病的病理生理学意义 ACM是< 35岁的年轻人SCD的主要原因。桥粒突变 蛋白质占大多数（大约。60%）的ACM病例，在这个项目中，我们专注于一种形式的ACM 称为桥粒斑蛋白（DSP）心肌病（DSP-CM）。DSP-CM最近已成为一种独特的临床 导致严重的左优势型疾病的实体。DSP-CM现在被公认为是 一种以常染色体显性模式传播的遗传性疾病，尽管具有不完全和高度可变的 外显率事实上，该领域的一个主要挑战是缺乏区分谁是 致病性DSP变异的携带者确实有SCD的风险，他们将继续健康地生活， 自由的生活鉴于DSP-CM中SCD的预防策略是运动， 限制，对于年轻健康的人，通常是运动员，这是一项相当严厉的措施。高度可变的 与DSP-CM相关的心律失常以及这些患者表现出的典型SCD模式突出了 基因-环境相互作用在揭示疾病致病性中的重要性。我们最近的工作 发现钙蛋白酶介导的桥粒斑蛋白降解是连接DSP突变与发育的关键因素， ACM及其运动加重。我们的中心假设是：1）钙蛋白酶介导的心肌细胞损失 DSP蛋白是运动和β-肾上腺素能刺激揭示的关键分子事件，2） 椎间盘（ID）DSP降解的致病作用因异常牵张相关的 导致心律失常和心力衰竭的机械传导。我们将使用一个多- 规模方法，包括人类工程心脏组织（hEHT）的补充研究， 创新的遗传和外科小鼠模型，旨在解决 DSP表现中的外部应激源（前负荷增加）和遗传易感性（DSP突变）- 厘米我们的研究将使我们能够梳理出耐力运动的各个方面对肌细胞的贡献， 功能障碍和暴露的病理生理机制，其中钙蛋白酶的脆弱性是由外部 应激刺激促进早发性心律失常和心力衰竭进展。最后，我们将测试新的基因， 基于小分子的方法来抑制运动相关的钙蛋白酶脆弱性，同时避免毒性。

PROJECT SUMMARY Arrhythmogenic Cardiomyopathy (ACM) is a heritable disease that bridges the gap between the cardiomyopathies and the inherited arrhythmia syndromes. In its early “concealed” phase, ACM promotes the incidence of ventricular arrhythmias in the absence of overt structural or mechanical remodeling. As the disease progresses, myocyte loss, inflammation, and fibrofatty infiltration emerge, culminating in biventricular failure and further risk of sudden cardiac death (SCD). The pathophysiological significance of the disease is underscored by the fact that ACM is a leading cause of SCD in young individuals < 35 years of age. Mutations in desmosomal proteins account for the majority (approx. 60%) of ACM cases, and in this project we focus on a form of ACM known as Desmoplakin (DSP) cardiomyopathy (DSP-CM). DSP-CM has recently emerged as a unique clinical entity that engenders a severe left-dominant form of the disease. DSP-CM is now well recognized to be a heritable disease that is transmitted in an autosomal dominant pattern, albeit with incomplete and highly variable penetrance. Indeed, a major challenge in the field has been the lack of ability to distinguish whom amongst carriers of pathogenic DSP variants are truly at risk of SCD and whom will go on to live healthy and symptom- free lives. This issue takes on added urgency given that the prevention strategy for SCD in DSP-CM is exercise restriction, a rather draconian measure for young healthy individuals, often athletes. The highly variable penetrance associated with DSP-CM as well as the typical mode of SCD that these patients exhibit highlight the importance of gene-environment interactions in unmasking disease pathogenicity. Our own recent work has identified calpain-mediated desmoplakin degradation as a key factor linking DSP mutations with the development of ACM and its exacerbation by exercise. Our central hypothesis is that: 1) calpain-mediated loss of myocyte DSP protein is a key molecular event that is unmasked by exercise and β-adrenergic stimulation, and 2) the pathogenic effects of DSP degradation at the intercalated disc (ID) are exacerbated by abnormal stretch-related mechanotransduction leading to arrhythmias and heart failure. We will address this dual hypothesis using a multi- scale approach encompassing complementary studies in human engineered heart tissues (hEHT) and innovative genetic and surgical mouse models that are designed to address the complex interactions between external stressors (increased preload) and genetic predisposition (DSP mutations) in the manifestation of DSP- CM. Our studies will enable us to tease out contributions of separate aspects of endurance exercise to myocyte dysfunction and expose pathophysiological mechanisms by which calpain vulnerability is unmasked by external stressors to promote early onset arrhythmias and heart failure progression. Finally, we will test novel gene and small molecule-based approaches to inhibit exercise-related calpain vulnerability while avoiding toxicity.