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Vascular endothelial growth factor (VEGF) is an important signaling protein involved in both vasculogenesis (the de novo formation of the embryonic circulatory system) and angiogenesis (the growth of blood vessels from pre-existing vasculature). As its name implies, VEGF activity is restricted mainly to cells of the vascular endothelium, although it does have effects on a limited number of other cell types (e.g. stimulation monocyte/macrophage migration). In vitro, VEGF has been shown to stimulate endothelial cell mitogenesis and cell migration. VEGF also enhances microvascular permeability and is sometimes referred to as vascular permeability factor. VEGF has a number of splice variants which differ by the number of amino acids they contain (in humans: VEGF121, VEGF145, VEGF165, VEGF189, VEGF206). These proteins differ by the presence or absence of short C-terminal domains encoded by exons 6a, 6b and 7 of the VEGF gene. These domains have important functional consequences for the VEGF splice variants as they mediate interactions with heparan sulfate proteoglycans (HSPGs) and neuropilin co-receptors on the cell surface, enhancing their ability to bind and activate the VEGF signaling receptors (VEGFRs).
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