A Cellular Atlas of Pitx2-Dependent Cardiac Development

The Pitx2 gene encodes a homeobox transcription factor that is required for mammalian development. Disruption of PITX2 expression in humans causes congenital heart diseases and is associated with atrial fibrillation (AF), however, the cellular and molecular processes dictated by Pitx2 during cardiac ontogeny remain unclear. To characterize the role of Pitx2 during murine heart development we sequenced over 75,000 single cardiac cell transcriptomes between two key developmental timepoints in control and Pitx2-null embryos. We uncovered that cardiac cell composition was dramatically altered in mutants at both E10.5 and E13.5. Interestingly, the differentiation dynamics of both anterior and posterior second heart field derived progenitor cells were disrupted in Pitx2 mutants. We also uncovered evidence for defects in left-right asymmetry within atrial cardiomyocyte populations. Furthermore, we were able to detail defects in cardiac outflow tract and valve development associated with Pitx2. Our findings offer insight into Pitx2 biology and provide a compilation of gene expression signatures for further detailing the complexities of heart development that will serve as the foundation for future studies of cardiac morphogenesis, congenital heart disease, and arrhythmogenesis. Here, we used single cell transcriptomics to inspect Pitx2 function in cardiac development and left-right cellular specification. Deployment of a high-throughput scRNA-seq platform on cardiac tissue dissected from both control and Pitx2-null embryos at E10.5 and E13.5 was carried out to characterize all deviations in cell composition, cellular state, and differentiation trajectories.Pitx2基因编码同源盒转录因子（homeobox transcription factor），是哺乳动物发育所必需的调控因子。人类体内PITX2表达异常可引发先天性心脏病，且与心房颤动（atrial fibrillation, AF）密切相关，但Pitx2在心脏发生（cardiac ontogeny）过程中所介导的细胞与分子机制仍不明晰。为解析Pitx2在小鼠心脏发育中的功能，本研究对对照组与Pitx2纯合敲除（Pitx2-null）胚胎的两个关键发育时间点的逾75000个单个心脏细胞转录组进行了测序。研究发现，在E10.5与E13.5两个时间点，突变体小鼠的心脏细胞组成均发生了显著改变。有趣的是，前、后第二心区（second heart field）来源的祖细胞的分化动态在Pitx2突变体中均遭到破坏。我们还观察到心房心肌细胞群体存在左右不对称发育缺陷。此外，本研究详细阐明了与Pitx2相关的心脏流出道（outflow tract）与瓣膜发育异常。本研究结果为Pitx2的生物学功能提供了新的认知，并整理了一套基因表达特征数据集，用于进一步解析心脏发育的复杂机制，该数据集将作为未来心脏形态发生（cardiac morphogenesis）、先天性心脏病及心律失常发生（arrhythmogenesis）领域研究的重要基础。本研究借助单细胞转录组学技术，探究了Pitx2在心脏发育及左右细胞特化中的功能。我们通过高通量单细胞RNA测序（single cell RNA-seq, scRNA-seq）平台，对E10.5与E13.5时期对照组及Pitx2-null胚胎的解离心脏组织进行测序，以全面表征细胞组成、细胞状态及分化轨迹的所有异常变化。