| Similar to the known BMP antagonist , gremlin , PRDC blocked ligand signaling induced by BMP 2 and BMP 4 but had minimal effects on reporter gene activation induced by GDF 9 , activin , or transforming growth factor beta . ^^^ Co precipitation assays further demonstrated the direct protein protein interactions between PRDC and BMP 2 or BMP 4 . ^^^ In addition , co treatment with PRDC antagonized the inhibitory effects of BMP 4 on the follicle stimulating hormone stimulation of progesterone production by cultured rat granulosa cells . ^^^ |