Betacellulin, also known as BTC protein, is encoded by the BTC gene located on chromosome 4q13.3 in humans. The protein is a member of the epidermal growth factor (EGF) family. It is primarily synthesized as a transmembrane precursor and processed into a mature molecule through protein cleavage. This protein serves as a ligand for EGF receptors and binds to EGFR, ERBB4, and other members of the EGF receptor family. It is also an effective mitogen for retinal pigment epithelial cells and vascular smooth muscle cells. Data indicate that BTC can effectively promote angiogenesis through activation of EGF receptors in endothelial cells, activation of mitogen-activated protein kinases, and phosphatidylinositol 3-kinase/protein kinase pathways.