Activin ReceptorsActivin Receptors, Type IActivinsActivin Receptors, Type IIInhibinsInhibin-beta SubunitsFollistatinReceptors, Growth FactorMyostatinSmad2 ProteinReceptors, Transforming Growth Factor betaTransforming Growth Factor betaNodal ProteinBone Morphogenetic ProteinsSignal TransductionSmad Proteins