BCR-ABL promotes hematopoietic stem and progenitor cell formation in embryonic stem cells

Generating Hematopoietic Stem Cells (HSCs) from Pluripotent Stem Cells (PSCs) has been a long-lasting quest in the field of hematopoiesis. Previous studies suggested that enforced expression of BCR-ABL, the unique oncogenic driver of Chronic Myelogeneous Leukemia (CML), in Embryonic Stem Cells (ESCs)-derived hematopoietic cells is sufficient to confer long-term in vivo repopulating potential. To precisely uncover the molecular events regulated by the Tyrosine-kinase activity of BCR-ABL1 (p210) during the course of hematopoietic differentiation, we engineered a Tet-ON inducible system to modulate its expression in murine ESC. We showed in unique site-directed knock-in ESC model, that BCR-ABL expression tightly regulated by doxycycline (dox) controls the formation and the maintenance of immature hematopoietic progenitors. Interestingly, these progenitors can be expanded in vitro for several passages in the presence of dox. Our analysis of cell surface markers and transcriptome compared to wild-type fetal and adult HSCs unraveled a similar molecular signature. LTC-IC assay confirmed their self-renewal capacities albeit with a differentiation bias towards erythroid and myeloid cells. Collectively, our novel Tet-ON system represents a unique in vitro model to shed lights on ESC-derived hematopoiesis, CML initiation and maintenance. KEY POINTS ### Competing Interest Statement The authors have declared no competing interest.