GDF3 simultaneously antagonizes BMP signaling and activates TGFβ receptor signaling

Abstract: Growth differentiation factor 3 (Gdf3) is a relatively understudied member of the Tgfβ superfamily. GDF3 is highly expressed in stem cell populations and restricts cellular differentiation. Gdf3 expression levels decrease after development only to rise in states of obesity and inflammation. However, the function of GDF3 in adult mammalian biology is contentious. To understand the impact of GDF3 on cellular signaling we explored the cellular responses to either recombinant GDF3 or an inducible genetically-encoded Gdf3 in C2C12 myoblasts. In addition, we employ fluorescent reporters to simultaneously assay both BMP receptor signaling through a SMAD1/5/8 DNA-binding BMP-responsive element and TGFβ receptor signaling through a SMAD3 DNA-binding element. We find that GDF3 is capable of dose-dependent inhibition of multiple BMP proteins including BMP2, BMP7, BMP9, BMP10, and BMP15. We also find that GDF3 produces a bona fide activin-like ligand signaling through the TGFBR2 receptor. Expression profiling with RNA-seq reveals that BMP2-regulated genes are attenuated by the addition of GDF3. Together these results clarify the dual biological roles of Gdf3 in cultured myoblasts.