Cardiac outflow tract (OFT) is a major hotspot for congenital heart diseases. A thorough understanding of the cellular diversity, transitions, and regulatory networks of normal OFT development is essential to decipher the etiology of OFT malformations. We performed single-cell transcriptomic sequencing of 55,611 mouse OFT cells from three developmental stages that generally correspond to the early, middle, and late stages of OFT remodeling and septation. Known cellular transitions, such as endothelial-to-mesenchymal transition, have been recapitulated. In particular, we identified convergent development of the vascular smooth muscle cell (VSMC) lineage where intermediate cell subpopulations were found to be involved in either myocardial-to-VSMC trans-differentiation or mesenchymal-to-VSMC transition. Finally, we uncovered transcriptional regulators potentially governing cellular transitions. Our study provides a single-cell reference map of cell states for normal OFT development and paves the way for further studies of the etiology of OFT malformations at the single-cell level.

心脏流出道（OFT）是先天性心脏病的主要热点。对正常OFT发育的细胞多样性，转变和调控网络的透彻了解对于破译OFT畸形的病因至关重要。我们从三个发展阶段进行了55,511个小鼠OFT细胞的单细胞转录组测序，这三个阶段通常对应于OFT重塑和分离的早期，中期和后期。概括了已知的细胞过渡，例如内皮细胞向间充质的过渡。特别是，我们确定了血管平滑肌细胞（VSMC）谱系的趋同发展，其中发现中间细胞亚群参与了心肌到VSMC的转分化或间充质到VSMC的转变。最后，我们发现了潜在调控细胞过渡的转录调控因子。我们的研究为正常OFT的发展提供了细胞状态的单细胞参考图，并为进一步研究单细胞水平上的OFT畸形的病因铺平了道路。