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Blood, 1 June 2006, Vol. 107, No. 11, pp. 4317-4325. Prepublished online as a Blood First Edition Paper on February 2, 2006; DOI 10.1182/blood-2005-09-3747.
HEMATOPOIESIS Genetic marking of hematopoietic stem and endothelial cells: identification of the Tmtsp gene encoding a novel cell surface protein with the thrombospondin-1 domainFrom the Laboratory of Stem Cell Therapy and Division of Gene Expression and Regulation, the Center for Experimental Medicine, and the Department of Cancer Research Division of Pathology, Institute of Medical Science, University of Tokyo; the Cell Engineering Division, RIKEN BioResource Center, Ibaraki; the Department of Tissue and Organ Development, Regeneration and Advanced Medical Science, Gifu University Graduate School of Medicine, Gifu; the Department of Molecular Neurobiology, Institute of Basic Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki; the Department of Cell Differentiation, the Sakaguchi Laboratory, School of Medicine, Keio University, Tokyo; and the Department of Cellular and Molecular Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan.
Using an in silico database search, we identified a novel gene encoding a cell surface molecule with a thrombospondin domain, and designated the gene as transmembrane molecule with thrombospondin module (Tmtsp). Expression profiling of Tmtsp using specific monoclonal antibodies and Venus, a variant of yellow fluorescent protein knock-in mice in the Tmtsp locus, demonstrated its specific expression in hematopoietic and endothelial cells. In lymphohematopoietic cells, Tmtsp was predominantly expressed in hematopoietic stem and progenitor cells, and the level of expression gradually declined as the cells differentiated. Venus expression faithfully traced the expression of Tmtsp, and the level of Venus expression correlated well to the in vitro hematopoietic activity as well as the in vivo bone marrow repopulating capacity. Notably, Venus expression marked the development of definitive hematopoiesis in both the extraembryonic yolk sac and the intraembryonic aorta-gonadmesonephros (AGM) region and, in combination with CD41, strikingly promoted the enrichment of developing progenitors in the CD41+Venushigh fraction at embryonic day 10.5 (E10.5). In this context, Tmtsp is a novel marker gene for primitive hematopoietic cells and endothelial cells, and TmtspVenus/+ mice would serve as a valuable mouse model for the analysis of both embryonic and adult hematopoiesis, as well as for vascular biology.
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