Growth factor that binds to EGFR, ERBB4 and other EGF receptor family members. Potent mitogen for retinal pigment epithelial cells and vascular smooth muscle cells. Monomer. Interacts with EGFR and ERBB4. Found in several mouse tissues including kidney, uterus and liver, as well as in beta tumor cell line and MCF-7 cells. It is not detected in the brain.