Chasing the precursor of functional hematopoietic stem cells at the single cell levels in mouse embryos

BACKGROUND Adult hematopoietic stem cells (HSCs), the ideal system for regenerative research, were isolated at single cell levels decades ago, whereas studies on embryonic HSCs are much more difficult. METHODS Zhou et al identified a new pre-HSC cell surface marker, CD201, by which they isolated pre-HSCs at single cell levels for further analyses. RESULTS The novel expression pattern of HSC development is revealed, including the fundamental role of mammalian targets of rapamycin (mTOR) signaling pathway in HSCs emergence, and the repopulation potential of S/G2/M phase pre-HSCs. CONCLUSIONS Deeper understandings of the cellular origin and developmental regulatory network of HSCs are essential to develop new strategies of generating HSCs in vitro for clinical application.