The Notch Delta-4 ligand helps to maintain the quiescence and the short-term reconstitutive potential of haematopoietic progenitor cells through activation of a key gene network

• The Notch/Delta-4 pathway maintains a proportion of HPCs out of the cell cycle.
• The Notch/Delta-4 pathway limits in vivo the loss of HPCs primitive potential.
• PUMILIO-1 and -2 are new downstream factors of the Notch/Delta-4 pathway.

Understanding the role of Notch and its ligands within the different bone marrow niches could shed light on the mechanisms regulating haematopoietic progenitor cells (HPCs) maintenance and self-renewal. Here, we report that murine bone marrow HPCs activation by the vascular Notch Delta-4 ligand maintains a significant proportion of cells specifically in the G0 state. Furthermore, Delta-4/Notch pathway limits significantly the loss of the in vivo short-term reconstitutive potential upon transplantation of Delta-4 activated HPCs into lethally irradiated recipient mice. Both effects are directly correlated with the decrease of cell cycle genes transcription such as CYCLIN-D1, -D2, and -D3, and the upregulation of stemness related genes transcription such as BMI1, GATA2, HOXB4 and C-MYC. In addition, the transcriptional screening also highlights new downstream post-transcriptional factors, named PUMILIO1 and -2, as part of the stem signature associated with the Delta-4/Notch signalling pathway.