title: Functionally defining the endothelial transcriptome, from Robo4 to ECSCR.
abstract: We have applied search algorithms to expression databases to identify genes whose expression is restricted to the endothelial cell. Such genes frequently play a critical role in endothelial biology and angiogenesis. Two such genes are the roundabout receptor Robo4 and the ECSCR (endothelial-cell-specific chemotaxis regulator). Endothelial cells express both Robo1 and Robo4, which we have knocked down using siRNA (small interfering RNA) and then studied the effect in a variety of in vitro assays. Both Robo4 and Robo1 knockdown inhibited in vitro tube formation on Matrigel. Transfection of Robo4 into endothelial cells increased the number of filopodial extensions from the cell, but failed to do so in Robo1-knockdown cells. Separate immunoprecipitation studies showed that Robo1 and Robo4 heterodimerize. We conclude from this and other work that a heteroduplex of Robo1 and Robo4 signals through WASP (Wiskott-Aldrich syndrome protein) and other actin nucleation-promoting factors to increase the number of filopodia and cell migration. Knockdown of the transmembrane ECSCR protein in endothelial cells also reduced chemotaxis and impaired tube formation on Matrigel. Yeast two-hybrid analysis and immunoprecipitation studies showed that, in contrast with the roundabouts, ECSCR binds to the actin-modulatory filamin A. We conclude that all three of these genes are critical for effective endothelial cell migration and, in turn, angiogenesis.
authors.affiliation: Institute for Biomedical Research, Birmingham University Medical School, Vincent Drive, Birmingham B15 2TT, UK.
authors.forename: Ana Raquel
authors.initials: AR
authors.lastname: Verissimo
authors.forename: John M J
authors.initials: JM
authors.lastname: Herbert
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Heath
authors.forename: John A
authors.initials: JA
authors.lastname: Legg
authors.forename: Helen
authors.initials: H
authors.lastname: Sheldon
authors.forename: Maud
authors.initials: M
authors.lastname: Andre
authors.forename: Rajeeb Kumar
authors.initials: RK
authors.lastname: Swain
authors.forename: Roy
authors.initials: R
authors.lastname: Bicknell
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D002465:Cell Movement / Q000502:physiology; D030541:Databases, Genetic; D042783:Endothelial Cells / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018919:Neovascularization, Physiologic; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051316:Wiskott-Aldrich Syndrome Protein / Q000235:genetics / Q000378:metabolism; D000097905:Roundabout Proteins
chemical_list: D051017:Apoptosis Regulatory Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D051316:Wiskott-Aldrich Syndrome Protein; D000097905:Roundabout Proteins; C531407:ECSCR protein, human; C462951:ROBO4 protein, human