Silencing of directional migration in roundabout4 knockdown endothelial cells

<p>Abstract</p> <p>Background</p> <p>Roundabouts are axon guidance molecules that have recently been identified to play a role in vascular guidance as well. In this study, we have investigated gene knockdown analysis of endothelial Robos, in particular <it>roundabout 4 </it>(<it>robo4</it>), the predominant Robo in endothelial cells using small interfering RNA technology <it>in vitro</it>.</p> <p>Results</p> <p><it>Robo1 and Robo4 </it>knockdown cells display distinct activity in endothelial cell migration assay. The knockdown of <it>robo4 </it>abrogated the chemotactic response of endothelial cells to serum but enhanced a chemokinetic response to Slit2, while <it>robo1 </it>knockdown cells do not display chemotactic response to serum or VEGF. <it>Robo4 </it>knockdown endothelial cells unexpectedly show up regulation of Rho GTPases. Zebrafish Robo4 rescues both Rho GTPase homeostasis and serum reduced chemotaxis in <it>robo4 </it>knockdown cells. Robo1 and Robo4 interact and share molecules such as Slit2, Mena and Vilse, a Cdc42-GAP. In addition, this study mechanistically implicates IRSp53 in the signaling nexus between activated Cdc42 and Mena, both of which have previously been shown to be involved with Robo4 signaling in endothelial cells.</p> <p>Conclusion</p> <p>This study identifies specific components of the Robo signaling apparatus that work together to guide directional migration of endothelial cells.</p