Fig. 7. Oocyte-paracrine factors signal through the TGFß/activin intracellular pathway, and not through the BMP pathway. Mural GCs were transiently transfected during culture with either a SMAD3-responsive CAGA-luciferase plasmid (A) or a SMAD1-responsive BRE-luciferase reporter plasmid (B), then treated with various TGFß superfamily growth factors or were co-cultured with 60 oocytes/250-µl well. GDF9 was used at 40 ng/ml. TGFß1 (0.5 ng/ml) is a positive control for CAGA (and negative control for BRE), and BMP6 (50 ng/ml) is a positive control for BRE (and negative controls for CAGA). 293H is the GDF9 negative control: an equivalent v/v of conditioned medium from untransfected 293H cells. Columns represent means ± s.e.m. from four replicate experiments. Oocytes significantly (P<0.01) increased mural GC CAGA-luciferase, but not BRE-luciferase activity (P>0.05); asterisks indicate significantly different to control (P<0.01).