Résumé
During embryogenesis of all vertebrates, haematopoietic stem/progenitor cells 16 (HSPCs) extrude from the aorta by a complex process named Endothelial-to-17 Haematopoietic Transition (EHT). HSPCs will then colonize haematopoietic organs 18 allowing haematopoiesis throughout adult life. The mechanism underlying EHT 19 including the role of each aortic endothelial cell within the global aorta dynamics 20 remains unknown. In the present study, we show for the first time that EHT involves the 21 remodelling of individual cells within a collective migration of endothelial cells which is 22 tightly orchestrated, resulting in HSPCs extrusion in the sub-aortic space without 23 compromising aorta integrity. By performing a cross-disciplinary study which combines 24 high resolution 4D imaging and theoretical analysis based on the concepts of classical 25 mechanics, we propose that this complex developmental process is dependent on 26 mechanical instabilities of the aorta preparing and facilitating the extrusion of HSPCs. 27 28 29 We dedicate this work to the memory of our friend and colleague, V. Lorman. 30 31 All rights reserved. No reuse allowed without permission. (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.