[Progress in single-cell analysis of hematopoiesis]

The mechanism underlying production of various types of blood cells from hematopoietic stem and progenitor cells has been a central theme in hematology. Conventionally, hematopoietic cell populations are analyzed by cell surface markers to judge cell types and differentiation stages, and by transplantation assays to assess differentiation potential. Recently, however, next-generation sequencing technology has enabled single-cell transcriptome and epigenome analyses and cell barcoding-based lineage tracing during unperturbed hematopoiesis. These innovative assays revealed that each cell population is extensively heterogenous. Many cells within hematopoietic stem cell populations may not be multipotent, and conversely, hematopoietic progenitor cells often display self-renewal capacity. Moreover, cells tend to make their lineage choice much earlier than previously thought. Altogether, these results challenge the current hierarchical differentiation models and propose new continuous models. Single-cell analyses are expected to greatly contribute to our understanding of normal and abnormal hematopoiesis and to the development of new therapies for blood disorders.