Research article

Silencing of directional migration in roundabout4 knockdown endothelial cells

Sukhbir Kaur^2* , Ganesh V Samant^1* , Kallal Pramanik¹ , Philip W Loscombe³ , Michael L Pendrak⁴ , David D Roberts⁴ and Ramani Ramchandran¹

¹  Department of Pediatrics, Children's Research Institute, Medical College of Wisconsin, Milwaukee, WI, USA

²  Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA

³  University of Scranton, Biology Department, Scranton, PN, USA

⁴  Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA

author email corresponding author email* Contributed equally

BMC Cell Biology 2008, 9:61doi:10.1186/1471-2121-9-61

Published:	3 November 2008

Abstract

Background

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 roundabout 4 (robo4), the predominant Robo in endothelial cells using small interfering RNA technology in vitro.

Results

Robo1 and Robo4 knockdown cells display distinct activity in endothelial cell migration assay. The knockdown of robo4 abrogated the chemotactic response of endothelial cells to serum but enhanced a chemokinetic response to Slit2, while robo1 knockdown cells do not display chemotactic response to serum or VEGF. Robo4 knockdown endothelial cells unexpectedly show up regulation of Rho GTPases. Zebrafish Robo4 rescues both Rho GTPase homeostasis and serum reduced chemotaxis in robo4 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.

Conclusion

This study identifies specific components of the Robo signaling apparatus that work together to guide directional migration of endothelial cells.