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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.

Original publication

DOI

10.1042/bst0371214

Type

Journal article

Journal

Biochemical Society transactions

Publication Date

12/2009

Volume

37

Pages

1214 - 1217

Addresses

Institute for Biomedical Research, Birmingham University Medical School, Vincent Drive, Birmingham B15 2TT, UK.

Keywords

Endothelial Cells, Animals, Humans, Membrane Proteins, Receptors, Cell Surface, Receptors, Immunologic, Nerve Tissue Proteins, RNA, Small Interfering, Signal Transduction, Cell Movement, Neovascularization, Physiologic, Databases, Genetic, Wiskott-Aldrich Syndrome Protein