The earliest blood vessels in the mammalian embryo are formed when endothelial cells (ECs) differentiate from angioblasts and coalesce into tubular networks. Thereafter, the en-dothelium is thought to expand solely by proliferation of pre-existing ECs. Here we show that the earliest precursors of erythrocytes, megakaryocytes and macrophages, the yolk sac-derived erythro-myeloid progenitors (EMPs), provide a complementary source of ECs that are recruited into pre-existing vasculature. Whereas a first wave of yolk sac-resident EMPs contributes ECs to the yolk sac endothelium, a second wave of EMPs colonises the embryo and contributes ECs to intraembryonic endothelium in multiple organs, where they persist into adulthood. By demonstrating that EMPs constitute a hitherto unrecognised source of ECs, we reveal that embryonic blood vascular endothelium expands in a dual mechanism that involves both the proliferation of pre-existing ECs and the incorporation of ECs derived from hematopoietic precursors. SOURCE: Alessandro Fantin (a.fantin@ucl.ac.uk) -  University College London

Pluto Bioinformatics

GSE117978: Erythro-myeloid progenitors contribute endothelial cells to developing blood vessels