MYH7B基因导致肥厚型心肌病的分子机制

Hypertrophic cardiomyopathy (HCM) is the most common monogenic cardiovascular diesease.The genetic causes of 30-40% HCM patients are still unclear. In previous study, we found mutation in MYH7B gene was cosegregated with disease in one HCM family, indicating MYH7B is a novel disease-causing gene of HCM. MYH7B belongs to myosin family and is high homologous to MYH7 which is one of the most important disease genes of HCM. Previous studies found that MYH7B was highly expressed in heart, however little was known aoubt its biological function. In present project, we will search the interacting partners of MYH7B protein firstly by using yeast two hybrid, followed by co-immunoprecipitation and fluorescent-immunohistochemistry. This will not only provide the basis to further understand the molecular mechanism of cardiac abnormalities induced by MYH7B mutation, but also help to get insigh to the role of MYH7B in regulaton of cardiac function. The effect of mutation in MYH7B on protein interacting will be investigated then by co-immunoprecipitation and immunohistochemistry. The abnormalities induced by mutation in MYH7B will also be studied in cultured neonatal rat cardiomyocytes. Wild and mutated MYH7B will be expressed in cultured cardiomyocytes by using adenovirus. The localization of MYH7B, co-localization of MYH7B and its interacting partners, ultra-structure as well as the phenotype and function of cardiomyocyte will be measured subsequently. Cardiac-specific transgenic mouse overexpressing wide-type and mutated MYH7B will be constructed, respectively. The cardiac structure and function will be measure, and the histological and ultrastructure changes will be observed. Through this study, we expecte to ultimately get deep insight on the molecular and pathological mechanism of HCM induced by mutation in MYH7B gene, and the biological roles of MYH7B gene in cardiomyocyte.

肥厚型心肌病（HCM）是最常见的单基因遗传心血管疾病，仍有30%-40%患者的致病基因不明。我们前期发现MYH7B是HCM的新致病基因。该基因心肌特异表达，与MYH7高度同源，但功能未知。本课题将1）在分子水平寻找MYH7B相互作用蛋白，揭示MYH7B的生物学功能，并研究MYH7B突变对其蛋白结合能力的影响；2）在体外培养的心肌细胞中，研究MYH7B突变对心肌细胞亚结构、功能、蛋白定位与共定位的影响；3）建立表达MYH7B突变的基因敲入小鼠模型，观察MYH7B突变对小鼠心脏结构、功能及生存能力的影响，研究MYH7B突变诱发的心肌病理组织改变、细胞间结构和细胞内超微结构异常。我们期望通过分子、细胞和动物水平的系统研究，阐释MYH7B突变导致HCM的分子病理机制，明确MYH7B在心肌中的生物学功能，进一步加深对HCM的认知。

通过本项目的资助，我们对 MYH7B 基因突变与肥厚型心肌病（HCM）的关系进行了研究。首先，我们发现了2名HCM先证者携带同一MYH7B基因突变p.M1913_Q1914delinsIX，并对其中一个先证者进行家系分析发现该突变与疾病共分离，提示MYH7B是HCM的新致病基因。对患者的临床特点进行总结发现该突变携带者的发病年龄均较大，室壁增厚程度较轻。在此基础上，我们构建了该突变的基因敲入大鼠模型，在不同的年龄阶段观察该突变对大鼠心脏结构与功能的影响。基线状态下，各年龄段大鼠均未观察到明显的HCM表型。运动训练是诱导生理性心肌肥厚的常用方法，给予大鼠运动刺激后也未能观察到明显的HCM表型。我们推测该可能是由于突变所致HCM患者的表现比较轻，以及物种间差异，导致基因敲入大鼠未出现明显的HCM表型。.结论：我们在患者中通过家系分析发现MYH7B是HCM的新致病基因，然而在基因敲入大鼠模型中未能重复出该发现，推测可能是由于该基因突变所致的HCM表现较轻，以及物种差异所致。后续研究可以尝试在其他物种中验证MYH7B基因的致病性。