[Transcriptional regulation of the endothelial cell-specific receptor, Robo4]

Roundabout4 (Robo4) is a transmembrane receptor that belongs to the Robo family of neural cell adhesion molecules. Robo4 has been shown to play a role in endothelial cell (EC) migration, proliferation, angiogenesis, and stabilizing the vasculature. Robo4 is expressed specifically in ECs in the developing embryo, placenta, tumors, and normal tissues. The goal of our study is to understand the mechanism for Robo4 gene expression. In the previous study we demonstrated that EC-specific Robo4 gene expression was regulated by the 3-kb Robo4 promoter in the 5'-flanking region of the human Robo4 gene. In vitro studies demonstrated that the Robo4 promoter is activated by the transcription factors GA-binding protein (GABP) and SP1 through the ETS binding site at -119 and the 2 SP1 binding sites at -42 and -153, respectively. The functional relevance of these sites was confirmed by in vivo reporter gene assays using Hprt locus knock in mice. In addition to the regulation mechanism by transcription factors, our recent study implicated that epigenetic modification of the promoter contributes to the Robo4 gene expression. Here I will discuss the regulation mechanism of Robo4 gene expression by transcription factors and epigenetic control.