Integrative Approach to Divergent Remodeling in Thin Filament Cardiomyopathies

描述（由申请人提供）：肥厚性心肌病（HCM）是一种相对常见的疾病，影响1/500的个体。临床谱是巨大的，从正常的心脏功能和寿命到侵袭性心肌病性重塑和早期心脏性猝死。自1990年第一次遗传连锁研究以来，所有已知的肌节蛋白中的突变都被认为是该疾病的病因，并且家族性疾病（FHC）被认为占所有病例的50%以上。长期以来，人们注意到由细丝蛋白突变引起的疾病亚组特别复杂，许多患者没有发展为“经典”左心室肥大，而是经历了积极的心室重塑，并经历了显着的心脏性猝死频率。最近，在调节细丝原肌球蛋白（TM）的中心“看门人”蛋白中携带突变（Asp 230 Asn）的患者已显示出发展复杂的双峰临床综合征，导致婴儿的急性心力衰竭和成人的收缩功能障碍的晚期发展。这种独特的临床表现突出了关于FHC发病机制的重要问题，这些问题仍未得到解答，特别是，在复合物水平上，细丝调节的主要生物物理缺陷是什么，以及随着时间的推移，是什么调节了心室重塑的变化模式？在该资助的最后一个资助期内，我们开发了一系列多方面的方法学方法，包括一种新的细丝计算模型，体外运动试验的修改， 独特的小鼠模型，使我们能够开发一个集成的计算机-体外-体内系统，用于研究从原子到整个心脏水平的细丝突变的影响。我们将这种方法应用于心肌肌钙蛋白突变的一个子集，发现单个突变的影响可以通过突变蛋白“传播”，从而全面影响细丝调节并导致进行性心血管重塑。我们现在将我们的注意力转向TM和cTnT，并通过两个特定的目的关注可能参与心肌病性重构的早期发展的两种独特的疾病机制：1）确定由TNT 1-TM头-尾重叠结构域中的已知突变引起的差异心室重构的潜在机制，并通过体内cTnT同种型转换调节DCM表型; 2）确定高度保守的TNT 1 C末端“非结构化”结构域的功能作用，并确定该区域突变引起的严重进行性心肌病的致病机制。这种对早期疾病机制的新关注特别重要，因为在患者发展为终末期疾病之前，确定治疗干预点以改变这种复杂心肌病的自然史的潜力很大。

DESCRIPTION (provided by applicant): Hypertrophic Cardiomyopathy (HCM) is a relatively common disorder, affecting 1/500 individuals. The clinical spectrum is vast, ranging from normal cardiac function and lifespan to aggressive cardiomyopathic remodeling and early sudden cardiac death. Since the first genetic linkage study in 1990, mutations in all of the known sarcomeric proteins have been implicated as causal for the disease and the familial form of the disorder (FHC) is thought to comprise over 50% of all cases. It has long been noted that the subset of the disease caused by mutations in the thin filament proteins is particularly complex, whereby many patients do not develop the "classic" left ventricular hypertrophy, but instead undergo aggressive ventricular remodeling and experience a significant frequency of sudden cardiac death. More recently, patients carrying a mutation (Asp230Asn) in the central "gatekeeper' protein of the regulatory thin filament, tropomyosin (TM) have been shown to develop a complex bimodal clinical syndrome, resulting in acute cardiac failure in infants and a late development of systolic dysfunction in adults. This unique clinical presentation highlights important questions regarding the pathogenesis of FHC that remain unanswered, in particular, what is the primary biophysical defect in thin filament regulation at the level of the complex and what regulates the changing patterns of ventricular remodeling over time? In the last funding period of this grant we developed a series of multifaceted methodological approaches including a novel computational model of the thin filament, a modification of the in vitro motility assay and unique mouse models that enabled us to develop an integrated in silico - in vitro - in vivo system for studying the effects of thin filament mutations from the atomic to whole-heart levels. We applied this approach to a subset of cardiac troponin mutations and found that the effects of single mutations can be "propagated" through the mutant proteins to globally affect thin filament regulation and cause progressive cardiovascular remodeling. We now turn our attention to both TM and cTnT and focus on two unique disease mechanisms that are likely to be involved in the earliest development of cardiomyopathic remodeling via two Specific Aims: 1) To determine the mechanism(s) underlying the differential ventricular remodeling caused by known mutations in the TNT1-TM head-to-tail overlap domain and to modulate the DCM phenotype via cTnT isoform-switching in vivo; 2) To define the functional role of the highly conserved TNT1 C- terminal "unstructured" domain and determine the pathogenic mechanism underlying the severe, progressive cardiomyopathies caused by mutations in this region. This new focus on early disease mechanisms is particularly important given the high potential for identifying points of therapeutic intervention to change the natural history of this complex cardiomyopathy in patients before they develop end-stage disease.