The cooperative effect of growth and differentiation factor-9 and bone morphogenetic protein (BMP)-15 on granulosa cell function is modulated primarily through BMP receptor II

Growth and differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15, GDF9B) are oocyte-derived proteins essential for the growth and function of ovarian follicles. Moreover, ovine (o) GDF9 and oBW15 cooperate to increase both H-3-thymidine incorporation and a-inhibin production and to inhibit progesterone production by rat or ovine granulosa cells. Although the receptors through which these proteins act individually have been determined, the receptor(s) involved in mediating the cooperative effects of GDF9 and BMP15 is (are) unknown. In this study, the effects of the extracellular domains of the types I and II TGF beta receptors on H-3-thymidine incorporation by rat granulosa cells stimulated by oGDF9 and oBMP15 were investigated. Stimulation of H-3-thymidine incorporation was completely blocked by the BMP receptor II (BMPRII) extracellular domain but unaffected by any other type II or any type I receptor. These results suggest that the initial interaction of oGDF9 and oBMIP15 is with BMPRII and that a type I receptor is either recruited or already associated with BMPRII to mediate the cooperative effects of these growth factors.