Activin Receptors, Type IIActivin ReceptorsActivinsInhibin-beta SubunitsActivin Receptors, Type IInhibinsFollistatinReceptors, Growth FactorMyostatinReceptors, Transforming Growth Factor betaSmad2 ProteinBone Morphogenetic Protein Receptors, Type IBone Morphogenetic ProteinsTransforming Growth Factor betaSignal TransductionProtein-Serine-Threonine KinasesTrans-ActivatorsMolecular Sequence DataDNA-Binding ProteinsAmino Acid SequenceNodal ProteinFollicle Stimulating Hormone, beta SubunitGoosecoid ProteinFollistatin-Related ProteinsSmad3 ProteinSmad ProteinsGonadotrophsXenopus ProteinsGrowth SubstancesMesodermFollicle Stimulating HormoneEmbryonic InductionSmad4 ProteinRNA, MessengerDioxolesBone Morphogenetic Protein 4Cell DifferentiationXenopusGlycoproteinsSmad7 ProteinFetal ProteinsGene Expression Regulation, DevelopmentalCells, Cultured