title: Hoxb4-YFP reporter mouse model: a novel tool for tracking HSC development and studying the role of Hoxb4 in hematopoiesis.
abstract: Hoxb4 overexpression promotes dramatic expansion of bone marrow (BM) hematopoietic stem cells (HSCs) without leukemic transformation and induces development of definitive HSCs from early embryonic yolk sac and differentiating embryonic stem cells. Knockout studies of Hoxb4 showed little effect on hematopoiesis, but interpretation of these results is obscured by the lack of direct evidence that Hoxb4 is expressed in HSCs and possible compensatory effects of other (Hox) genes. To evaluate accurately the pattern of Hoxb4 expression and to gain a better understanding of the physiologic role of Hoxb4 in the hemato-poietic system, we generated a knock-in Hoxb4-yellow fluorescent protein (YFP) reporter mouse model. We show that BM Lin(-)Sca1(+)c-Kit(+) cells express Hoxb4-YFP and demonstrate functionally in the long-term repopulation assay that definitive HSCs express Hoxb4. Similarly, aorta-gonad-mesonephrous-derived CD45(+)CD144(+) cells, enriched for HSCs, express Hoxb4. Furthermore, yolk sac and placental HSC populations express Hoxb4. Unexpectedly, Hoxb4 expression in the fetal liver HSCs is lower than in the BM, reaching negligible levels in some HSCs, suggesting an insignificant role of Hoxb4 in expansion of fetal liver HSCs. Hoxb4 expression therefore would not appear to correlate with the cycling status of fetal liver HSCs, although highly proliferative HSCs from young BM show strong Hoxb4 expression.
authors.affiliation: Ontogeny of Haematopoietic Stem Cells Group, Medical Research Council/Juvenile Diabetes Research Foundation Centre for Development in Stem Cell Biology, Institute for Stem Cell Research, University of Edinburgh, West Mains Road, Edinburgh, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Hills
authors.forename: Ruby
authors.initials: R
authors.lastname: Gribi
authors.forename: Jan
authors.initials: J
authors.lastname: Ure
authors.forename: Natalija
authors.initials: N
authors.lastname: Buza-Vidas
authors.forename: Sidinh
authors.initials: S
authors.lastname: Luc
authors.forename: Sten Eirik W
authors.initials: SE
authors.lastname: Jacobsen
authors.forename: Alexander
authors.initials: A
authors.lastname: Medvinsky
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D058948:Cell Tracking / Q000379:methods*; D004622:Embryo, Mammalian; D005260:Female; D017930:Genes, Reporter / Q000502:physiology; D006410:Hematopoiesis / Q000235:genetics* / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D023421:Models, Animal; D008954:Models, Biological; D011247:Pregnancy; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D018398:Homeodomain Proteins; C513262:Hoxb4 protein, mouse; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C054562:yellow fluorescent protein, Bacteria