Functional screening in HUVECs of human genes contributing to angiogenesis. (A) Expression of ARHGEF15, CSGALNACT1, SHE, PLVAP, TMEM204, GPR182, GCOM1, and GPR116 in HUVECs. KDR, PECAM1, VE-CADHERIN, and CD34 are endothelial markers. (B) Knockdown of ARHGEF15 mRNA inhibits tube formation in HUVECs. A control siRNA oligonucleotide did not affect VEGF-dependent tube formation of HUVECs; however, siRNA for ARHGEF15 reduced the ability to form a vascular network. (C) Quantification of relative tube length, branch points, and vessel area in control and knockdown HUVECs. Images (B) were captured with a Keyence BioRevo microscope (Plan Fluor 10×/0.30 NA lens) and with BZ-II Viewer.