Single-cell RNA sequencing for progeny tracking of native haematopoietic stem cells and progenitors

Results in the study of haematopoietic stem cells and progenitors were mainly achieved through the historically successful transplantation assay. Still, the invasive procedure raise the issue of whether transplantation conditions adequately resemble steady-state haematopoiesis. In the last few years, single-cell marking and transposon progeny tracking experiments shed new light on blood cell lineages, highlighting the differences between post-irradiation bone marrow repopulation and unperturbed haematopoiesis. With the use of single-cell sequencing, clustering and live imaging, researchers were able to further characterize both cell types and bone marrow niches. In particular, recent results argue for a slightly different haematopoietic tree, where erythrocytes are tightly related to granulocytes and monocytes, while megakaryocytes derive from an independent lineage. Clonal expansion of long-term haematopoietic stem cells appeared to be less significant than in transplant conditions, while progenitors role was re-evaluated. Lastly, bone remodelling fronts were found to influence stem cells niches localization and haematopoietic cells activation.