Organizers, EmbryonicNucleolus Organizer RegionEmbryonic DevelopmentGoosecoid ProteinGene Expression Regulation, DevelopmentalBody PatterningGastrulaEmbryonic InductionEmbryo, NonmammalianXenopus ProteinsSilver StainingZebrafish ProteinsEmbryologyHomeodomain ProteinsMesodermZebrafishIn Situ HybridizationOtx Transcription FactorsXenopusEmbryonic and Fetal DevelopmentMorphogenesisEmbryo, MammalianFibroblast Growth Factor 8RhombencephalonWnt ProteinsNotochordNervous SystemNodal ProteinEctodermXenopus laevisBone Morphogenetic ProteinsTranscription FactorsBlastocystIntercellular Signaling Peptides and ProteinsSignal TransductionMesencephalonMolecular Sequence DataHeadHydraNodal Signaling LigandsChick EmbryoGenes, HomeoboxAxisTissue TransplantationLIM-Homeodomain ProteinsEndodermBlastulaAmino Acid SequenceCell NucleolusCell DifferentiationWnt1 ProteinSilverFetal ProteinsActivinsRNA, MessengerBase SequenceZygoteProteinsT-Box Domain ProteinsFibroblast Growth FactorsEmbryo LossLeft-Right Determination FactorsBlastodermHedgehog ProteinsRepressor ProteinsDNA-Binding ProteinsMutationPhenotypebeta CateninGlycoproteinsCentral Nervous SystemBone Morphogenetic Protein 4Drosophila ProteinsMetencephalonTrans-ActivatorsTransforming Growth Factor betaOocytesDrosophilaPregnancySequence Homology, Amino AcidDevelopmental BiologyMice, KnockoutBlastomeresModels, BiologicalCell LineageNerve Tissue ProteinsAnimals, Genetically ModifiedSomitesOrganogenesisMicroinjectionsTime FactorsTwins, ConjoinedNeural TubeAmphibiansGenes, DevelopmentalCloning, MolecularImmunohistochemistryTissue and Organ ProcurementOrgan TransplantationOrgan Specificity