限制性心肌病cTnIR193H突变介导组蛋白修饰PDEs低表达致心肌高钙敏性研究

Cardiac myofibril hypersensitivity to Ca2+ is a major factor that causes impaired relaxation of myocardial cells in cTnI mutation induced restrictive cardiomyopathy (RCM), however, the underlying mechanisms are still not clear. PDEs expression levels are strongly associated with Ca2+ sensitivity, and our preliminary data showed that PDE2A and PDE3A reduced in cTnI R193H mutation model, that may be caused by reduced binding levels of HDAC1. Meanwhile, we also found that cTnI protein may bind with histone modification enzymes HDAC1 and Smyd1. Therefore, the hypothesis of our proposal is that cTnI plays a crucial role in histone modification regulated PDEs decrease in RCM model. In order to confirm the hypothesis, we are planning to use our cTnI R193H mutation mouse models to investigate the following specific aims: 1) to determine cTnI may involve in the regulation of PDEs transcription; 2) to demonstrate the key role of cTnI in PDEs decrease by using cTnI knock out model; 3) to explore the effect of cTnI mutation in the pathological process. The data from this study will provide us with novel scientific evidence on the roles of cTnI as a transcription factor, and epigenetic regulation on the development of Ca2+ hypersensitivity, which may be potential intervention targets for the prevention and treatment of certain cardiovascular diseases.

肌钙蛋白I（cTnI）R193H基因突变可致限制性心肌病（RCM），心肌细胞钙敏性增高是RCM心肌主动舒张功能障碍的关键因素，但其机理不明。PDEs是调控心肌细胞钙敏性的重要因子，预实验利用人源突变位点RCM小鼠模型发现cTnI R193H突变小鼠心肌PDEs低表达，且组蛋白修饰酶HDAC1可能参与PDEs表达调控，而cTnI蛋白能与HDAC1等核蛋白结合。因此提出科学假设：cTnI R193H突变介导组蛋白修饰调控PDEs低表达致心肌细胞钙敏性增高。我们将采用双荧光素酶报告技术及cTnI敲低模型证明cTnI参与PDEs转录调控；CoIP及ChIP等方法阐明cTnI R193H突变蛋白募集组蛋白修饰酶介导PDEs低表达的表观遗传调控机制。以期探讨cTnI调控钙离子敏感性的作用机理，有望为改善RCM的舒张功能障碍提供潜在干预靶点，并为其他基因突变致心血管疾病的研究提供新思路。

限制性心肌病临床治疗棘手、病情重、预后差，是危害儿童健康的重要医学问题。cTnI基因点突变是原发性心肌病的重要病因，既往研究提示心肌细胞钙敏性增高是导致病理表型的重要原因，但基因突变如何导致心肌细胞钙敏性升高，这一问题始终无明确答案。项目利用cTnI R193H点突变致限制性心肌病的特有模式动物，提出“cTnI R193H突变介导组蛋白修饰调控PDEs低表达致心肌细胞钙敏性增高”的科学假说，开展了以下三方面研究内容。首先明确了cTnI参与PDEs基因转录表达调控；第二阐明了cTnI突变致限制性心肌病心肌细胞钙敏感性失衡的分子机制，即突变蛋白通过与组蛋白乙酰化酶HDAC1结合而抑制PDEs表达，进而影响心肌细胞钙敏感性；第三，我们在生理情况下，发现cTnI存在于胞核内，其可能通过于YY1结合而调控Atp2a2表达，进而调控心肌细胞舒缩功能，此对课题进行了延展。项目在生理和病理情况下对cTnI入核后如何调控心肌细胞舒缩功能进行了阐释。打破了对cTnI仅作为胞浆结构功能蛋白的传统认识。为心血管生理及病理研究提供新的理论思考角度，丰富了限制性心肌病发病机理，为其治疗提供潜在转化医学靶点。项目共培养研究生三名，三次参加国际会议，研究成果得到参会同仁的高度认可。数据已发表SCI论文3篇，另有一篇SCI论文正在审稿中。