UC San Diego

With congenital heart disease as the most common birth defect in the world, investigating the genetic basis of heart development is an important endeavor that can be greatly advanced by studying the model organism Drosophila melanogaster. At the end of embryonic fly heart development, there are three types of pericardial cells (PCs) that are distinguished by their gene expression profiles. Among these PCs, those that specifically express the cardiac master regulator tinman (tin) are not well characterized (Tin-PCs). In this study, we use single-cell RNA sequencing, fluorescent staining, and mutational analysis to characterize the role of Tin-PCs in embryonic fly heart development. We have identified and confirmed the expression of several genes—CrzR, Neurotactin, Lachesin, coracle, sinuous, Wnt4, and cut—that were either distinctly expressed or highly enriched in Tin-PCs, but not in other types of PCs. Here, we present that knockdown of sinuous delayed dorsal closure of the heart and epidermis, knockdown of tin reduced expression of the cell adhesion protein Neurotactin, and loss of cut caused abnormal closure of Tin-PCs while ectopic Cut expression in cardioblasts reduced expression of the PC marker even-skipped. From these findings, we conclude that Tin-PCs play some role in dorsal closure, cardiac cell adhesion, and even-skipped expression in PCs of the Drosophila embryo. By elucidating the role of Tin-PCs in Drosophila embryogenesis, we hope to highlight the great potential of single-cell RNA sequencing in identifying novel cell types and provide further understanding of the cellular and genetic mechanisms that underlie Drosophila heart development.