Hoxb5 reprogrammes murine multipotent blood progenitors into haematopoietic stem cell‐like cells.

Objectives: The expression of transcription factor Hoxb5 specifically marks the functional haematopoietic stem cells (HSC) in mice. However, our recent work demonstrated that ectopic expression of Hoxb5 exerted little effect on HSC but could convert B‐cell progenitors into functional T cells in vivo. Thus, cell type‐ and development stage‐specific roles of Hoxb5 in haematopoietic hierarchy await more extensive exploration. In this study, we aim to investigate the effect of Hoxb5 expression in multipotent blood progenitor cells. Materials and Methods: A Mx1cre/RosaLSL‐Hoxb5‐EGFP/+ mouse model was used to evaluate the effect of Hoxb5 expression in blood multipotent progenitor cells (MPP). Golden standard serial transplantation experiments were used to test the long‐term haematopoiesis potential of Hoxb5‐expressing MPP. Single‐cell RNA‐seq analysis was used to characterize the gained molecular features of Hoxb5‐expressing MPP and to compare with the global transcriptome features of natural adult HSC and fetal liver HSC (FL HSC). Results: Here, with a mouse strain engineered with conditional expression of Hoxb5, we unveiled that induced expression of Hoxb5 in MPP led to the generation of a de novo Sca1+c‐kit+CD11b+CD48+ (CD11b+CD48+SK) cell type, which can repopulate long‐term multilineage haematopoiesis in serial transplantations. RNA‐seq analysis showed that CD11b+CD48+SK cells exhibited acquired features of DNA replication and cell division. Conclusions: Our current study uncovers that Hoxb5 can empower MPP with self‐renewal ability and indicates an alternative approach for generating HSC‐like cells in vivo from blood lineage cells. [ABSTRACT FROM AUTHOR]