Whole-transcriptome analysis of endothelial to hematopoietic stem cell transition reveals a requirement for Gpr56 in HSC generation
Parham Solaimani Kartalaei (Erasmus MC)
Tomoko Yamada-Inagawa (Erasmus MC)
Chris S. Vink (Erasmus MC)
Emma de Pater (Erasmus MC)
Reinier van der Linden (Erasmus MC)
Jonathon Marks-Bluth (University of New South Wales)
Anthon van der Sloot (Erasmus MC)
Mirjam van den Hout (Erasmus MC)
Tomomasa Yokomizo (National University of Singapore)
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Abstract
Hematopoietic stem cells (HSCs) are generated via a natural transdifferentiation process known as endothelial to hematopoietic cell transition (EHT). Because of small numbers of embryonal arterial cells undergoing EHT and the paucity of markers to enrich for hemogenic endothelial cells (ECs [HECs]), the genetic program driving HSC emergence is largely unknown. Here, we use a highly sensitive RNAseq method to examine the whole transcriptome of small numbers of enriched aortic HSCs, HECs, and ECs. Gpr56, a G-coupled protein receptor, is one of the most highly up-regulated of the 530 differentially expressed genes. Also, highly up-regulated are hematopoietic transcription factors, including the "heptad" complex of factors. We show that Gpr56 (mouse and human) is a target of the heptad complex and is required for hematopoietic cluster formation during EHT. Our results identify the processes and regulators involved in EHT and reveal the surprising requirement for Gpr56 in generating the first HSCs.