title: SCL/tal-1-dependent process determines a competence to select the definitive hematopoietic lineage prior to endothelial differentiation.
abstract: Hematopoiesis in most vertebrate species occurs in two distinct phases, primitive and definitive, which diverge from FLK1(+)VE-cadherin(-) mesoderm and FLK1(+)VE-cadherin(+) endothelial cells (EC), respectively. This study aimed at determining the stage at which hematopoietic lineage fate is determined by manipulating the SCL/tal-1 expression that is known to be essential for the early development of the primitive and definitive hematopoietic systems. We established SCL-null ES cell lines in which SCL expression is rescued by tamoxifen-inducible Cre recombinase-loxP site-mediated recombination. While no hematopoietic cells (HPC) were detected in SCL-null ES cell differentiation cultures, SCL gene reactivation from day 2 to day 4 after initiation of differentiation could rescue both primitive and definitive hematopoiesis. SCL reactivation at later phases was ineffective. Moreover, generation of VE-cadherin(+) EC that can give rise to definitive HPC required SCL reactivation prior to VE-cadherin expression. These results indicated that the competence to become HPC is acquired at the mesodermal stage by a SCL-dependent process that takes place independently of determination of endothelial fate.
authors.affiliation: Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto, 606-8057, Japan. mendoh@virus.kyoto-u.ac.jp
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Endoh
authors.forename: Minetaro
authors.initials: M
authors.lastname: Ogawa
authors.forename: Stuart
authors.initials: S
authors.lastname: Orkin
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Nishikawa
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D015152:Blotting, Northern; D002454:Cell Differentiation; D002460:Cell Line; D019070:Cell Lineage; D002469:Cell Separation; D002645:Chickens; D004268:DNA-Binding Proteins / Q000502:physiology*; D018274:Electroporation; D004622:Embryo, Mammalian / Q000166:cytology; D004625:Embryo, Nonmammalian; D004727:Endothelium / Q000196:embryology* / Q000502:physiology; D005434:Flow Cytometry; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells; D007700:Kinetics; D008648:Mesoderm / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D013997:Time Factors; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors; C489366:Tal1 protein, mouse