PROCR and hereditary elliptocytosis: We leveraged our previously reported model utilizing AGM-derived endothelial cell stroma (AGM-EC), which provides an instructive niche for the generation of engrafting HSCs from clonal embryonic precursors as early as E927–29, to identify a cell surface phenotype (VE-Cadherin+CD61+EPCR+) enriching for HSC precursors across their developmental spectrum from HE.