Promotes angiogenesis and the proliferation of endothelial cells. Able to bind to endothelial cells and promote cell proliferation, suggesting that it may act in an autocrine fashion. Interacts with the secreted angiogenic factor TNFSF12. Cytoplasmic in microvascular endothelial cells. Upon angiogenesis, when endothelial cell tube formation is initiated, it is secreted. Widely expressed. Expressed in endothelial cells, vascular smooth muscle cells and osteoblasts. Expressed in umbilical vein endothelial cells and microvascular endothelial cells. The disease is caused by variants affecting the gene represented in this entry. Truncated C-terminus.