Autophagy regulates the maturation of hematopoietic precursors in the embryo

Abstract The ability to generate hematopoietic stem cells(HSC) in vitro is advancing as a powerful resource for the treatment of blood diseases. An understanding of the mechanisms regulating HSC development in the embryo would facilitate the achievement of this goal. The aorta-gonad-mesonephros(AGM) region is the site of HSC production in the embryo. As these cells are formed from hemogenic endothelial cells(HEC) and appear as hematopoietic clusters on the lumenal side of the aorta. While several distinct regulators are known to be involved in this process, it is not yet known whether macroautophagy(autophagy) plays a role in hematopoietic development in the pre-liver stage of embryo development. Here, by using the LC3-RFP-EGFP autophagy reporter mouse model, we show that different states of autophagy exist in hematopoietic precursors, and correlate with hematopoietic potential. Deficiency of the autophagy-related gene(Atg) 5 specifically in endothelial cells disrupted endothelial cell to hematopoietic transition(EHT), by blocking the fusion between autophagosome and lysosome. Using combined approaches, including single-cell RNA-sequencing(scRNA-seq), we confirmed that Atg5 deletion interrupted the developmental temporal order of EHT to further affect the pre-HSC I maturation. The rescue experiments with in vivo analyses suggest that autophagy influenced the hemogenic potential of HEC and the formation of pre-HSC I likely via the nucleolin pathway. These findings demonstrate a vital role for autophagy in the formation/maturation of hematopoietic precursors derived from HECs.