Betacellulin (BTC) is a member of the EGF (epidermal growth factor) family. The transmembrane BTC precursor undergoes proteolytic cleavage, releasing the BTC ligand. It binds to both EGFR/ErbB-1 and ErbB-4 receptor tyrosine kinases. Betacellulin has been found to affect influence various cell types, such as neural stem cells (NSCs), mesenchymal stem cells (MSCs), pancreatic beta cells, retinal pigment epithelial cells and smooth muscle cells.