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 angiog enesis but its target genes and function in blood vessel formation are stil l unknown. We have over-expressed Ets1 as a tagged protein in brain capilla ry endothelial cells and in 3T3 fibroblasts using a retroviral vector. Over -expression of Ets1 reduced by nearly half cell density at confluence of en dothelials but not of fibroblasts, As density at confluence is controlled i n part by cadherins, this growth arrest could be due to the up-regulation o f these cell contact molecules. Indeed, Ets1 increased the expression of th e endothelial-specific VE-cadherin without affecting N-cadherin expression levels. In parallel, both dominant negative mutant of Ets members and an Et s1 anti-sense oligonucleotide inhibited VE-cadherin expression in endotheli al cells, Ets1 bound to two Ets-binding sites located in the proximal regio n of the VE-cadherin promoter. Mutation of these sites abolished Ets1-induc ed transactivation of the promoter. The present work is the first demonstra tion of a function of Ets1 in the regulation of a specific endothelial mark er based on its endogenous gene and protein expression.