Abstract
Most cell fate trajectories during development follow a diverging, tree-like branching pattern, but the opposite can occur when distinct progenitors contribute to the same cell type. During this convergent differentiation, it is unknown if cells “remember” their origins transcriptionally or whether this influences cell behavior. Most coronary blood vessels of the heart develop from two different progenitor sources—the endocardium (Endo) and sinus venosus (SV)—but whether transcriptional or functional differences related to origin are retained is unknown. We addressed this by combining lineage tracing with single-cell RNA sequencing (scRNAseq) in embryonic and adult mouse hearts. Shortly after coronary development begins, capillary ECs transcriptionally segregated into two states that retained progenitor-specific gene expression. Later in development, when the coronary vasculature is well-established but still remodeling, capillary Ecs again segregated into two populations, but transcriptional differences were primarily related to tissue localization rather than lineage. Specifically, ECs in the heart septum expressed genes indicative of increased local hypoxia and decreased blood flow. Adult capillary ECs were more homogeneous with respect to both lineage and location. In agreement, SV- and Endo-derived ECs in adult hearts displayed similar responses to injury. Finally, scRNAseq of developing human coronary vessels indicated that the human heart followed similar principles. Thus, over the course of development, transcriptional heterogeneity in coronary ECs is first influenced by lineage, then by location, until heterogeneity declines in the homeostatic adult heart. These results highlight the plasticity of ECs during development, and the validity of the mouse as a model for human coronary development.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
This study reveals the transcriptional and functional convergence of coronary endothelial cells (ECs) from two separate lineages, the endocardium (Endo) and the sinus venosus (SV), as well as an association between location and gene expression, which is specific to development. It further uncovers key similarities between mouse and human development that cement the relevance of prior and future mouse studies to the clinical goal of regenerating human arteries. The major experiments and analyses added to the manuscript based on input from reviewers are: - A deeper analysis of differential gene expression in e17.5 capillaries, providing additional evidence that EC heterogeneity at this stage is predominantly related to location, rather than lineage - Validation of location-based heterogeneity among human fetal heart ECs, matching the spatial patterns we identified in mice - Generation and analysis of a new and larger scRNAseq dataset of lineage-specific adult mouse coronary ECs, confirming the finding that there is no transcriptional difference between ECs from distinct lineages
