ETS1 lowers capillary endothelial cell density at confluence and induces the expression of VE-cadherin.

Ets1 is a transcription factor expressed in endothelial cells during angiogenesis but its target genes and function in blood vessel formation are still unknown. We have over-expressed Ets1 as a tagged protein in brain capillary endothelial cells and in 3T3 fibroblasts using a retroviral vector. Over-expression of Ets1 reduced by nearly half cell density at confluence of endothelials but not of fibroblasts. As density at confluence is controlled in part by cadherins, this growth arrest could be due to the up-regulation of these cell contact molecules. Indeed, Ets1 increased the expression of the endothelial-specific VE-cadherin without affecting N-cadherin expression levels. In parallel, both a dominant negative mutant of Ets members and an Ets1 anti-sense oligonucleotide inhibited VE-cadherin expression in endothelial cells. Ets1 bound to two Ets-binding sites located in the proximal region of the VE-cadherin promoter. Mutation of these sites abolished Ets1-induced transactivation of the promoter. The present work is the first demonstration of a function of Ets1 in the regulation of a specific endothelial marker based on its endogenous gene and protein expression.