Origins and Development of the Embryonic Vascular System in Xenopus
Each step of vascular development needs to be carefully regulated; endothelial precursors must be specified, these cells then proliferate and coalesce to form vascular cords, and finally they lumenate, undergo angiogenic branching and remodeling, and recruit smooth muscle cells to establish a mature vessel. An aberration at any of these steps during embryonic development is incompatible with life, and vascular pathologies in the adult are associated with numerous diseases including stroke, arteriosclerosis, diabetic retinopathies and cancer progression. My work has aimed to understand how endothelial precursors are specified, and more precisely the cell-signaling pathways and transcriptional networks that guide their fate. This work leads us to conclude the following: (1) blood island precursor cells in the Xenopus embryo can give rise to either blood or endothelial cells, and it is BMP-mediated activation of the erythroid transcriptional program that regulates cell fate, (2) endothelial specification requires the Ets transcription factor Etv2. Persistence of Etv2 expression in blood/endothelial cell precursors allows these cells to develop into endothelium, and overexpression of Etv2 in any of the three germ layers causes activation of every endothelial marker examined. Along the way we have characterized a number of small-molecule inhibitors that should be useful to the Xenopus community and applicable to other model systems.
hemangioblast, vasculogenesis, Molecular & Cellular Biology, endothelium
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