title: Fundamental properties of unperturbed haematopoiesis from stem cells in vivo.
abstract: Haematopoietic stem cells (HSCs) are widely studied by HSC transplantation into immune- and blood-cell-depleted recipients. Single HSCs can rebuild the system after transplantation. Chromosomal marking, viral integration and barcoding of transplanted HSCs suggest that very low numbers of HSCs perpetuate a continuous stream of differentiating cells. However, the numbers of productive HSCs during normal haematopoiesis, and the flux of differentiating progeny remain unknown. Here we devise a mouse model allowing inducible genetic labelling of the most primitive Tie2(+) HSCs in bone marrow, and quantify label progression along haematopoietic development by limiting dilution analysis and data-driven modelling. During maintenance of the haematopoietic system, at least 30% or ∼5,000 HSCs are productive in the adult mouse after label induction. However, the time to approach equilibrium between labelled HSCs and their progeny is surprisingly long, a time scale that would exceed the mouse's life. Indeed, we find that adult haematopoiesis is largely sustained by previously designated 'short-term' stem cells downstream of HSCs that nearly fully self-renew, and receive rare but polyclonal HSC input. By contrast, in fetal and early postnatal life, HSCs are rapidly used to establish the immune and blood system. In the adult mouse, 5-fluoruracil-induced leukopenia enhances the output of HSCs and of downstream compartments, thus accelerating haematopoietic flux. Label tracing also identifies a strong lineage bias in adult mice, with several-hundred-fold larger myeloid than lymphoid output, which is only marginally accentuated with age. Finally, we show that transplantation imposes severe constraints on HSC engraftment, consistent with the previously observed oligoclonal HSC activity under these conditions. Thus, we uncover fundamental differences between the normal maintenance of the haematopoietic system, its regulation by challenge, and its re-establishment after transplantation. HSC fate mapping and its linked modelling provide a quantitative framework for studying in situ the regulation of haematopoiesis in health and disease.
authors: Division of Cellular Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Katrin
authors: K
authors: Busch
authors: Division of Cellular Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Kay
authors: K
authors: Klapproth
authors: Division of Theoretical Systems Biology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Melania
authors: M
authors: Barile
authors: Division of Theoretical Systems Biology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Michael
authors: M
authors: Flossdorf
authors: Division of Biostatistics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Tim
authors: T
authors: Holland-Letz
authors: 1] Department of Microbiology and Immunology, University of Leuven, B-3000 Leuven, Belgium [2] Autoimmune Genetics Laboratory, VIB, B-3000 Leuven, Belgium.
authors: Susan M
authors: SM
authors: Schlenner
authors: 1] BIOSS, Centre For Biological Signaling Studies, University of Freiburg, Schänzlestraße 18, D-79104 Freiburg, Germany [2] Department of Molecular Immunology, BioIII, Faculty of Biology, University of Freiburg, and Max-Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, D-79108 Freiburg, Germany.
authors: Michael
authors: M
authors: Reth
authors: Division of Theoretical Systems Biology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Thomas
authors: T
authors: Höfer
authors: Division of Cellular Immunology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
authors: Hans-Reimer
authors: HR
authors: Rodewald
mesh_terms: D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D016026:Bone Marrow Transplantation; D019070:Cell Lineage / Q000502:physiology*; D049109:Cell Proliferation; D058948:Cell Tracking; D005260:Female; D005333:Fetus / Q000166:cytology / Q000196:embryology; D005472:Fluorouracil; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism; D008297:Male; D051379:Mice; D042787:Receptor, TIE-2 / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism
chemical_list: D042787:Receptor, TIE-2; C079086:Tek protein, mouse; D005472:Fluorouracil