Flt-1 lacking the tyrosine kinase domain is sufficient for normal development and angiogenesis in mice.
Receptor tyrosine kinases Flt-1 and Flk-1/KDR, and their ligand, the vascular endothelial growth factor (VEGF), were shown to be essential for angiogenesis in the mouse embryo by gene targeting. Flk-1/KDR null mutant mice exhibited impaired endothelial and hematopoietic cell development. On the other hand, Flt-1 null mutation resulted in early embryonic death at embryonic day 8.5, showing disorganization of blood vessels, such as overgrowth of endothelial cells. Flt-1 differs from Flk-1 in that it displays a higher affinity for VEGF but lower kinase activity, suggesting the importance of its extracellular domain. To examine the biological role of Flt-1 in embryonic development and vascular formation, we deleted the kinase domain without affecting the ligand binding region. Flt-1 tyrosine kinase-deficient homozygous mice (flt-1(TK-/-)) developed normal vessels and survived. However, VEGF-induced macrophage migration was strongly suppressed in flt-1(TK-/-) mice. These results indicate that Flt-1 without tyrosine kinase domain is sufficient to allow embryonic development with normal angiogenesis, and that a receptor tyrosine kinase plays a main biological role as a ligand-binding molecule.
Department of Genetics, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
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S
Hiratsuka
O
O
Minowa
J
J
Kuno
T
T
Noda
M
M
Shibuya
D000818:Animals; D001483:Base Sequence; D002199:Capillary Permeability / Q000235:genetics; D002478:Cells, Cultured; D017931:DNA Primers; D005314:Embryonic and Fetal Development / Q000502:physiology*; D016228:Endothelial Growth Factors / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D018390:Gene Targeting; D008222:Lymphokines / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018919:Neovascularization, Physiologic / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1; D042442:Vascular Endothelial Growth Factors
D017931:DNA Primers; D016228:Endothelial Growth Factors; D008222:Lymphokines; D011518:Proto-Oncogene Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020794:Receptor Protein-Tyrosine Kinases; D040281:Vascular Endothelial Growth Factor Receptor-1