PDGF Receptor alpha is a cell surface tyrosine kinase receptor for members of the platelet-derived growth factor family. These growth factors are mitogens for cells of mesenchymal origin. The identity of the growth factor bound to a receptor monomer determines whether the functional receptor is a homodimer or a heterodimer, composed of both platelet-derived growth factor receptor alpha and beta polypeptides. Studies in knockout mice, where homozygosity is lethal, indicate that the alpha form of the platelet-derived growth factor receptor is particularly important for kidney development. Mice heterozygous for the receptor exhibit defective kidney phenotypes. Moreover, the SH2 domain of Shf can bind to PDGF Receptor alpha at tyrosine 720 .