肥厚型心肌病致病基因复合突变剂量效应及其分子机制研究

Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiac diseases. The disease affects all age groups with marked clinical heterogeneity, ranging from a normal lifespan without symptoms to poor outcomes such as sudden cardiac death (SCD), advanced heart failure or stroke. Identification of patients with a poor prognosis has a great impact on improving clinical outcomes, including prevention of SCD. Several variables have been generally accepted as risk factors for SCD, including family history of SCD, unexplained syncope, non-sustained ventricular tachycardia, severe cardiac hypertrophy and abnormal blood pressure response to exercise. However, these factors have a low positive predictive value and are unable to predict the clinical outcomes of HCM-related heart failure and stroke. In our previous study, a total of 746 unrelated HCM patients were prospectively recruited. The 26 disease-causing genes of HCM were comprehensively screened by using multiplexing targeted sequencing. All coding exons and their adjacent 5 bp intronic sequences were enriched using a custom designed probe library and sequenced. Multiple mutations were identified in 17% of the study patients. The risk for cardiovascular death in patients with multiple mutations was higher than those without rare variant or those with single rare variant. Multivariate analysis revealed multiple rare variants were an independent risk factor for cardiovascular death (HR 3.74, 95% CI 1.84 to 7.58, P=0.0003), as well as sudden cardiac death (HR 3.57, 95% CI 1.23-10.35, P=0.019) and heart failure-related death (HR 4.62, 95% CI 1.67-12.76, P=0.003). These patients exhibit earlier and more severe clinical manifestations, suggesting the presence of a dosage effect of mutations on the severity of the phenotype. The presence of multiple mutations in related genes is an independent risk factor for poor outcomes in HCM, and may be appropriate to consider as a criterion in the risk stratification of HCM patients. In this project, we aim to investigate the molecular mechanisms of dosage-effect of multiple mutations in disease-causing genes on clinical manifestation of HCM patients using konck-in mouse models.

肥厚型心肌病(HCM)是导致年轻人猝死的最主要原因之一。我们在前期研究中用高通量测序技术对已收集的746例国人HCM患者的26个致病基因分析发现，携带2个以上致病基因突变的患者占比高达17%，且其临床表型比仅携带单个突变的患者显著加重，如发病早、猝死率高、心肌肥厚程度重等，这种基因突变的剂量效应(Dosage-effect)可能是影响前期报道的HCM患者基因型-临床表型关联变异较大的重要原因之一。本课题拟收集HCM患者至1000例（已收集746例）并进行高通量测序，建立较全面的国人HCM患者基因型-临床表型关联，从而初步实现对突变携带者进行危险分层，判断预后，实施临床早期预警和干预。同时利用基因敲入(Knock-In)小鼠模型研究剂量效应的分子机制，这不仅有助于更准确的建立HCM基因型-临床表型的关联，而且可以为治疗病理性心肌重塑提供可能的新靶点和新思路。

肥厚型心肌病（HCM）是导致年轻人心源性猝死的最主要原因之一，既往研究表明带 2 个以上致病基因突变的患者的临床表型比仅携带单个突变的患者显著加重，如发病早、猝死率高、心肌肥厚程度重等，这种基因突变的剂量效应可能是影响前期报道的 HCM 患者基因型-临床表型关联变异较大的重要原因之一。通过收集肥厚型心肌病患者样本并进行高通量测序分析，对致病基因MYH7和MYBPC3的突变筛查我们发现携带多个突变的患者的心血管死亡和全因死亡风险显著增加，表明突变剂量是影响患者临床表型的重要因素。构建TNNT2基因R92W点突变小鼠模型，发现相较于杂合突变，纯合突变的小鼠心肌肥厚更为明显，心肌纤维化程度更深，出生后的生存率更低，这也表明致病基因突变的剂量效应是影响动物表型的重要因素。这些对于将来检测到携带有突变的HCM 患者的危险分层、预后判断及早期干预将有极重要的临床应用价值。