Dermomyotome-derived endothelial cells migrate to the dorsal aorta to support hematopoietic stem cell emergence.

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Public Summary:
This study uncovers how certain cells from the dermomyotome, a region in developing embryos, migrate to the dorsal aorta and play a crucial role in forming blood cells. Researchers discovered that these specialized endothelial cells, emerging from the dermomyotome, integrate into the dorsal aorta and facilitate the creation of hematopoietic stem cells, vital for the formation of the blood system. Using zebrafish embryos, the study highlights a complex interplay between different cell types in the early stages of development, providing new insights into how our blood system forms during embryogenesis.
Scientific Abstract:
Development of the dorsal aorta is a key step in the establishment of the adult blood-forming system, since hematopoietic stem and progenitor cells (HSPCs) arise from ventral aortic endothelium in all vertebrate animals studied. Work in zebrafish has demonstrated that arterial and venous endothelial precursors arise from distinct subsets of lateral plate mesoderm. Here, we profile the transcriptome of the earliest detectable endothelial cells (ECs) during zebrafish embryogenesis to demonstrate that tissue-specific EC programs initiate much earlier than previously appreciated, by the end of gastrulation. Classic studies in the chick embryo showed that paraxial mesoderm generates a subset of somite-derived endothelial cells (SDECs) that incorporate into the dorsal aorta to replace HSPCs as they exit the aorta and enter circulation. We describe a conserved program in the zebrafish, where a rare population of endothelial precursors delaminates from the dermomyotome to incorporate exclusively into the developing dorsal aorta. Although SDECs lack hematopoietic potential, they act as a local niche to support the emergence of HSPCs from neighboring hemogenic endothelium. Thus, at least three subsets of ECs contribute to the developing dorsal aorta: vascular ECs, hemogenic ECs, and SDECs. Taken together, our findings indicate that the distinct spatial origins of endothelial precursors dictate different cellular potentials within the developing dorsal aorta.