An interactive resource of molecular signalling in the developing human haematopoietic stem cell (HSC) niche [LCM-Seq]

The emergence of definitive human haematopoietic stem cells (HSCs) during Carnegie Stages (CS) 14-17 in the aorta-gonad-mesonephros (AGM) region is a complex and tightly regulated process. In a previous study we conducted spatial transcriptomic analysis of the human AGM region at the end of this period (CS16/17) and identified secreted factors involved in HSC development. Here, we extend our analysis to investigate the progression of dorso-ventral polarized signalling around the dorsal aorta over the entire period of HSC emergence. Our results reveal a dramatic increase in signalling complexity from the CS13 to CS14 transition, coinciding with the activation of endothelial-to-haematopoietic transition (EHT) in the ventral domain of the dorsal aorta. We further observe stage-specific changes in signalling complexity up to CS17. Signalling progression described here may underpin step-wise maturation of HSCs described in the mouse model. A data-rich bioinformatics resource presented here along with an interactive online interface enables in silico analysis of molecular interactions between spatially defined domains of the AGM region. This resource will be of particular interest for researchers studying mechanisms underlying human HSC development as well as those developing in vitro methods for the generation of clinically relevant HSCs from pluripotent stem cells. Overall design: Laser capture microdissection of spatial domains around the carnegie stage (CS) 13 and 14 dorsal aorta in the developing human embryo with RNA-Seq libraries prepared from each region. N = 2 for each embryo and 6 spatial domains were taken for each stage.