 The low affinity for ligands suggests that BMPR2 may differ from other type II TGF beta receptors in that the ligand may bind the type I receptor first.BMPR2 is expressed on both human and animal granulosa cells, and is a crucial receptor for bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF 9).These two protein signaling molecules and their BMPR2 mediated effects play an important role in follicle development in preparation for ovulation.