 There are two forms of the PDGF-R, alpha and beta each encoded by a different gene.Depending on which growth factor is bound, PDGF-R homo- or heterodimerizes.The PDGF family consists of PDGF-A, -B, -C and -D, which form either homo- or heterodimers (PDGF-AA, -AB, -BB, -CC, -DD).