COUP-TFII plays a critical role in angiogenesis during development. It has also been shown to suppress Notch signaling pathway to confer vein identity. However, the downstream targets and the mechanism mediate COUP-TFII function to regulate these processes remain elusive. To identify the downstream targets and the mechanism by which COUP-TFII regulates agiogenesis and vein specification, we knocked down COUP-TFII in HUVEC cells using COUP-TFII specific siRNA and used microarray analysis to identify downstream targets. Interestingly, we found the expression of many genes in the cell cycle pathway and Notch signaling pathway are significantly altered in the COUP-TFII depleted cells.