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Recent genome-wide association studies newly identified the human KIAA1462 gene as a new locus for coronary artery disease. However, the function of the gene product, named JCAD (junctional protein associated with coronary artery disease), is unknown. Because JCAD is expressed at cell–cell junctions in endothelial cells, we hypothesized and tested whether JCAD regulates angiogenic processes in vitro and in vivo.Cell culture experiments revealed impaired angiogenic ability (proliferation, migration, and cord formation) by the knockdown of JCAD with siRNA (P<0.05 versus control siRNA). We have generated mice lacking JCAD (mKIAA1462−/−) by gene-targeted deletion of JCAD to address in vivo angiogenic function. mKIAA1462−/− mice did not show morphological differences in development of retinal vasculature. Ex vivo aortic ring model demonstrated impaired neovascularization in aorta from mKIAA1462−/− mice than control wild-type mice (P<0.05). Tumor growth was assessed by monitoring tumor volume after the subcutaneous injection of melanoma, LLC (Lewis lung carcinoma), and E0771 cells into the mice. mKIAA1462−/− mice exhibited significantly smaller tumor volume compared with wild-type mice (P<0.001). Histological assessment of the tumor exhibited less smooth muscle actin–positive neovascularization determined by CD31-positive vascular structure in tumor of mKIAA1462−/− mice than wild-type mice, indicating that knockdown of JCAD inhibited the vascular maturation in pathological angiogenic process.These in vitro and in vivo studies suggest that JCAD has a redundant functional role in physiological angiogenesis but serves a pivotal role in pathological angiogenic process after birth.