The function of COL18A1 (collagen type XVIII alpha 1 chain, ENSG00000182871) is as follows. Probably plays a major role in determining the retinal structure as well as in the closure of the neural tube. . [Non-collagenous domain 1]: May regulate extracellular matrix-dependent motility and morphogenesis of endothelial and non- endothelial cells; the function requires homotrimerization and implicates MAPK signaling. . [Endostatin]: Potently inhibits endothelial cell proliferation and angiogenesis (PubMed:9459295). May inhibit angiogenesis by binding to the heparan sulfate proteoglycans involved in growth factor signaling (By similarity). Inhibits VEGFA-induced endothelial cell proliferation and migration. Seems to inhibit VEGFA- mediated signaling by blocking the interaction of VEGFA to its receptor KDR/VEGFR2. Modulates endothelial cell migration in an integrin- dependent manner implicating integrin ITGA5:ITGB1 and to a lesser extent ITGAV:ITGB3 and ITGAV:ITGB5 (By similarity). May negatively regulate the activity of homotrimeric non-collagenous domain 1 (PubMed:11257123). {ECO:0000250|UniProtKB:P39061, ECO:0000269|PubMed:11257123, ECO:0000269|PubMed:9459295}.