PTPN21作为全新的先天性心脏病候选基因的功能和作用机制研究

Congenital heart diseases (CHDs) rank the first in the prevalence list of birth defects in China. The interaction of genetic and environmental factors contributes to the pathogenesis of CHD. Therefore, the researches integrating clinical samples, animal models, and ill pedigrees together can supply more solid theory basis for clinical diagnosis and treatment of CHD. In previous cohort of CHD supported by National Program on Key Basic Research Project (973 Program), we found a family suffering from atrial septal defects with pulmonary valve stenosis. The results of whole exome sequencing suggested PTPN21 as a novel candidate pathogenic gene of human CHD. Innovatively, we postulated that the frameshift mutation in PTPN21 gene was one of the genetic etiology of secundum atrial septal defect combined with pulmonary valve stenosis. The mutant PTPN21 could function by affecting the phosphorylation of β-Catenin and/or Src/FAK, which led to abnormal cell adhesion and proliferation and finally caused atrial septal defect combined with pulmonary valve stenosis. In this study, we will elucidate the function of PTPN21 in heart development and the pathogenic mechanism from three levels including population study, animal model, and cell research. The results from this study will increase the knowledge of genetic mechanism of CHD and provide new candidate targets for screen, genetic counseling, and clinical diagnosis and treatment of CHD.

先天性心脏病位列我国出生缺陷发生的第一顺位，其发生是由于遗传和环境综合作用的结果，其中基因突变在先心病的发生中占据重要地位。本课题组在前期国家“973”项目研究中发现了一个临床表型一致的房间隔缺损伴肺动脉瓣狭窄家系，经全基因组外显子扫描测序和前期细胞预实验提示PTPN21可能是一个全新的人类先心病致病候选基因，PTPN21的移框突变可能是导致继发孔房间隔缺损合并肺动脉瓣狭窄发生的遗传学病因之一，PTPN21突变体可能通过调控β-Catenin/Wnt和/或Src/FAK通路调节在房间隔缺损伴肺动脉瓣狭窄形成中有关键作用的内皮细胞的黏附和增殖参与了先心病的发生过程。该项目从家系研究结果为出发点，通过人群、动物模型和细胞三个层面深入研究PTPN21基因突变在心脏发育中的作用及发病机制。研究结果将很好地丰富先天性心脏病的遗传学发病机制研究，同时还可以为先心病的筛查、遗传咨询及诊疗提供候选靶点。

先天性心脏病是指胚胎在发育过程中，由于心血管系统发育异常所导致的心血管畸形。鉴于该病的类型繁多且遗传方式不尽相同，仍有80%的病例遗传机制不明。了解先天性心脏病的遗传机制，可能为临床上对该病的产前诊断、早期干预，乃至基因治疗提供重要靶点。本课题前期纳入一继发孔型房间隔缺损合并肺动脉瓣狭窄的家系，通过全外显子测序发现全新的致病候选基因PTPN21。本课题从群体层面、细胞层面、动物层面探讨PTPN21与心脏发育或与先天性心脏病发生的关系。本课题得出以下主要结果和结论：1、PTPN21在房间隔缺损合并肺动脉瓣狭窄患儿群体中的突变频率为5%，为PTPN21成为临床上先天性心脏病筛查、遗传咨询及诊疗的新候选基因或靶点提供进一步依据；2、靶向沉默PTPN21能促进内皮细胞的增殖并抑制其迁移，且引起SMAD4、BMPR2、WNT11等与心脏发育相关的基因表达水平发生变化。PTPN21引起的内皮细胞增殖、迁移紊乱，可能是导致继发孔型房间隔缺损和肺动脉瓣狭窄的病理基础；3、通过CRISPR/Cas9构建PTPN21突变敲入小鼠后发现，突变小鼠摄氧率较野生型小鼠下降，提示PTPN21突变对小鼠心肺功能产生影响。