利用单细胞转录组研究视黄酸信号在大动脉转位发生、发展中的作用机制

大动脉转位是一种常见的先心病，其发病比例高、手术难度大、致死率高。目前对大动脉转位疾病的发生、发展机制很大程度上依旧未知。利用单细胞转录组数据构建正常发育与疾病状态下的流出道单细胞转录图谱不仅能够系统地理解正常发育过程，而且能为流出道畸形的致病机制研究提供强有力的参考基础。前期研究发现心肌细胞向血管平滑肌细胞转分化的现象，还有一群间充质细胞亚群特异性高表达视黄酸信号转导的两个重要因子Crabp1/2（细胞视黄酸结合蛋白），这可能是流出道疾病发生的关键。在此基础之上，在本项目计划通过建立高视黄酸诱导的大动脉转位小鼠模型，通过单细胞转录组比较研究疾病发生过程中流出道细胞转录状态的变化、对心肌细胞向血管平滑肌细胞转分化的影响、视黄酸信号响应亚群（Crabp1+）中视黄酸信号转导及对其它重要发育相关信号通路的影响及调控，以期在单细胞水平上对大动脉转位发生的细胞与分子机制进行更深入的研究。

Transposition of the great arteries (TGA) is a common outflow tract malformation. TGA is one of the most serious congenital heart diseases with high incidence, high mortality and more difficulties in operation. However, the pathogenesis and development mechanism of TGA remain largely unknown. The construction of single-cell transcriptional atlas of outflow tract cells under normal and disease states cannot only help understand the normal biological development process, but also provides a strong reference basis for the study of the pathogenic mechanism of outflow tract malformation. In our previous single-cell transcriptome study of normal outflow tract development, we found that cardiomyocytes could transdifferentiate into vascular smooth muscle cells at the base of the aorta, but whether this process will lead to outflow tract malformations was unknown. Retinoic acid signaling plays an important role in normal heart development. Too high or too low retinoic acid signal can cause abnormal cardiac development. In the single-cell transcriptome study of cardiac neural crest cells(CNCC) derivatives, we found that Crabp1 and Crabp2 (cellular retinoic acid binding protein), two important regulators of retinoic acid signal transduction, were highly expressed in key mesenchymal cell subpopulations related to outflow tract development. The response mechanism of this subpopulation to retinoic acid signal and how to regulate the normal development of outflow tract is the key to study the process of outflow tract remodeling. On these basis, we plan to establish a mouse model of TGA and compare the changes of the transcriptional status of outflow tract cells in the mouse model of TGA induced by high concentration of retinoic acid, the effect on the trans-differentiation of cardiomyocytes to vascular smooth muscle cells, retinoic acid signal transduction in retinoic acid signal response subsets (Crabp1+) and other important development-related signal pathways and their regulation. The ultimate purpose of this project is to reveal the cellular and molecular mechanism of TGA at the single cell resolution.