Biological Characteristics and Regulation of Early Megakaryocytopoiesis.

For decades, megakaryocytopoiesis is believed to occur following a classical binary hierarchical developmental model. This model is based on an analysis of predefined flow-sorted cell populations by using cell surface markers. However, this classical model has been challenged by increasing evidences obtained with new techniques which integrating flow cytometric, transcriptomic and functional data at single-cell level and with lineage tracing technique. These recent advances in megakaryocytopoiesis proposed that commitment of haematopoietic stem cells (HSCs) towards megakaryocytic lineage occurs in much earlier stage than that postulated in the classical model. There may exist multipotent but megakaryocyte (MK)/platelet-biased HSCs within HSC compartment and even HSCs can directly differentiate into MKs in steady state or in response to stress. In this review, we focus on recent findings about differentiation from commitment of HSCs to MK and its regulation, and discuss future directions in this research field.