Integrative Approach to Divergent Remodeling in Thin Filament Cardiomyopathies

描述(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人。临床范围很广，从正常的心功能和寿命到侵袭性心肌病重构和早期心脏性猝死。自1990年第一次遗传连锁研究以来，所有已知的肌瘤蛋白的突变都被认为是该病的原因，家族性疾病(FHC)被认为占所有病例的50%以上。长期以来，人们一直注意到，由细丝蛋白突变引起的疾病亚型特别复杂，许多患者不会发展为典型的左心室肥厚，而是经历激进的心室重塑，并经历相当频繁的心脏性猝死。最近，携带调控细丝原肌球蛋白(TM)中央“把关蛋白”突变(Asp230Asn)的患者被证明发展为复杂的双峰临床综合征，导致婴儿急性心力衰竭和成人晚期收缩功能障碍。这一独特的临床表现突出了关于FHC发病机制的重要问题，仍未得到解答，特别是，在复合体水平上细丝调节的主要生物物理缺陷是什么，以及是什么调节了随着时间的推移而改变的心室重构模式？在这笔赠款的最后一个资助期，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，对体外运动试验的修改，以及 独特的小鼠模型，使我们能够开发一个集成的硅胶-体外-体内系统，从原子到全心脏水平研究细丝突变的影响。我们将这种方法应用于心肌肌钙蛋白突变的一个子集，并发现单个突变的影响可以通过突变蛋白来“传播”，从而全面影响细丝调节，并导致进行性心血管重塑。我们现在将注意力转向TM和cTnT，并通过两个特定的目的来关注可能参与心肌病重构最早发展的两个独特的疾病机制：1)确定TNT1-TM头尾重叠区域已知突变导致差异性心室重构的机制(S)，并在体内通过cTnT亚型转换调节DCM表型；2)确定高度保守的TNT1 C末端“非结构化”结构域的功能作用，并确定该区域突变导致严重、进行性心肌病的致病机制。这种对早期疾病机制的新关注尤其重要，因为确定治疗干预点的可能性很高，以在患者发展为终末期疾病之前改变这种复杂心肌病的自然病史。

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.