Potts, K.S.Sargeant, T.J.Markham, J.F.Shi, W.Biben, C.Josefsson, E.C.Whitehead, L.W.Rogers, K.L.Liakhovitskaia, A.Smyth, G.K.Kile, B.T.Medvinsky, A.Alexander, W.S.Hilton, D.J.Taoudi, S.2019-11-142019-11-142014Blood, 2014; 124(17):2725-27290006-49711528-0020http://hdl.handle.net/2440/121904In this study, we test the assumption that the hematopoietic progenitor/colony-forming cells of the embryonic yolk sac (YS), which are endowed with megakaryocytic potential, differentiate into the first platelet-forming cells in vivo. We demonstrate that from embryonic day (E) 8.5 all megakaryocyte (MK) colony-forming cells belong to the conventional hematopoietic progenitor cell (HPC) compartment. Although these cells are indeed capable of generating polyploid MKs, they are not the source of the first platelet-forming cells. We show that proplatelet formation first occurs in a unique and previously unrecognized lineage of diploid platelet-forming cells, which develop within the YS in parallel to HPCs but can be specified in the E8.5 Runx1-null embryo despite the absence of the progenitor cell lineage.en© 2014 by The American Society of Hematology.MegakaryocytesJournal article100000183410.1182/blood-2014-02-5594680003474575000182-s2.0-84908242967500212Kile, B.T. [0000-0002-8836-8947]