MOLECULAR BIOLOGY AND PATHOPHYSIOLOGY OF HYPERTROPHIC CARDIOMYOPATHY

肥厚型心肌病的分子生物学和病理生理学

• 批准号: 6290450
• 负责人: NEAL DAVID EPSTEIN
• 金额: --
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6290450
• 关键词: clinical research; disease /disorder model; gene mutation; genetic disorder; genetically modified animals; human subject; hypertrophic myocardiopathy; laboratory mouse; molecular pathology; muscle function; myocardium disorder; myosins; protein isoforms; protein structure function; stretch receptors

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac disease characterized by an increased left ventricular mass in the absence of another cause for hypertrophy. This disease provides a model to study the process of cardiac hypertrophy. In approximately 15% of affected families, the disease gene encodes a beta myosin heavy chain (BMHC) gene with a missense mutation. We have identified 32 distinct mutations in the BMHC gene and mapped them onto the 3D structure of the head of skeletal myosin. The mutations cluster in 4 regions, suggesting different types of interference in the actomyosin cross-bridge kinetics as a function of mutation location. We have studied the mechanical properties of extracted mutant myosins and muscle fibers expressing these myosins, to analyze the pathophysiology at a molecular level. One of the clusters of mutations led us to the discovery of mutations in the myosin light chains which cause a variant of HCM characterized by an obstruction in the middle of the left ventricle. Through a series of arguments, the association of the myosin light chain mutations with the rare subtype of HCM led us to hypothesize the importance of the stretch-activation response to the function of the normal heart. The stretch-activation response in Drosophila flight muscle has been previously shown to be distorted by a mutation in the regulatory myosin light chain (RLC), resulting in flightless flies whose wings do not beat properly. We have developed transgenic mice expressing the mutant myosin essential light chain (ELC), from a patient with cardiac hypertrophy. The hearts from these mice also do not beat properly. That is, there is a shift of the frequency of maximum power output to a rate beyond the physiologic range, with consequent loss of oscillatory power. We have cloned the human enzyme that phosphorylates the RLC and identified naturally occurring variations of the human phosphorylating enzyme in the African-American population that we will study in a hypertensive population. To study this effect in an animal model, we have overexpressed the enzyme in mice. Muscle fibers from these mice and others we have produced, are being used to study the basic biophysical response of muscle fibers to light chain phosphorylation. An antibody to the phosphorylated site has been produced and processed to provide a first approximation to a therapeutic intervention in isolated muscle fibers from these mice. We are also using these mice to study what we believe are cardiac muscle stem cells produced in these mice. - hypertrophic cardiomyopathy (HCM), beta myosin heavy chain (BMHC)gene - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only

肥厚性心肌病（HCM）是一种遗传性心脏病，其特征是在没有另一个肥大原因的情况下左心室肿块增加。该疾病提供了研究心脏肥大过程的模型。在大约15％的受影响家庭中，该疾病基因编码具有错义突变的β肌球蛋白重链（BMHC）基因。我们已经确定了BMHC基因中的32个不同的突变，并将其映射到骨骼肌球蛋白头部的3D结构上。突变簇在四个区域中，表明肌动菌素跨桥动力学中的不同类型的干扰是突变位置的函数。我们已经研究了表达这些肌球蛋白的提取的突变肌蛋白和肌肉纤维的机械性能，以分析分子水平的病理生理学。突变的簇之一使我们发现了肌球蛋白光链中突变的发现，这些突变引起了HCM的变体，其特征是左心室中间有阻塞。通过一系列参数，肌球蛋白轻链突变与HCM罕见的亚型的关联导致我们假设拉伸激活反应对正常心脏功能的重要性。果蝇飞行肌肉中的拉伸激活反应先前已被调节性肌球蛋白轻链（RLC）突变扭曲，从而导致无飞的苍蝇，其机翼无法正常跳动。我们已经从心脏肥大患者中开发出表达突变肌球蛋白必需轻链（ELC）的转基因小鼠。这些老鼠的心也无法正常跳动。也就是说，最大功率输出的频率转移到了生理范围之外的速率，随之而来的振荡能力损失。我们将人类酶磷酸化，该酶磷酸化RLC并确定了非裔美国人人群中人类磷酸化酶的自然变化，我们将在高血压人群中研究。为了在动物模型中研究这种作用，我们已经过表达了小鼠的酶。这些小鼠和我们生产的其他小鼠的肌肉纤维正在用于研究肌肉纤维对轻链磷酸化的基本生物物理反应。已经产生并处理了对磷酸化位点的抗体，以在这些小鼠的孤立肌肉纤维中提供对治疗干预的第一近似值。我们还使用这些小鼠研究这些小鼠中产生的心肌干细胞。 - 肥厚的心肌病（HCM），β肌球蛋白重链（BMHC）基因 - 人类受试者和人类受试者：访谈，问题或调查