Organizers, EmbryonicNucleolus Organizer RegionEmbryonic DevelopmentGoosecoid ProteinGene Expression Regulation, DevelopmentalBody PatterningEmbryo, NonmammalianGastrulaEmbryonic InductionXenopus ProteinsZebrafish ProteinsSilver StainingEmbryologyHomeodomain ProteinsZebrafishMesodermIn Situ HybridizationEmbryonic and Fetal DevelopmentXenopusEmbryo, MammalianOtx Transcription FactorsMorphogenesisBlastocystNervous SystemWnt ProteinsFibroblast Growth Factor 8RhombencephalonEctodermXenopus laevisNotochordTranscription FactorsNodal ProteinBone Morphogenetic ProteinsChick EmbryoMolecular Sequence DataSignal TransductionIntercellular Signaling Peptides and ProteinsMesencephalonHeadNodal Signaling LigandsGenes, HomeoboxHydraEndodermAxisTissue TransplantationLIM-Homeodomain ProteinsBlastulaAmino Acid SequenceCell DifferentiationEmbryo LossZygoteCell NucleolusRNA, MessengerBase SequenceFetal ProteinsWnt1 ProteinActivinsSilverProteinsT-Box Domain ProteinsOocytesHedgehog ProteinsFibroblast Growth FactorsPregnancyDNA-Binding ProteinsBlastodermPhenotypeRepressor ProteinsMutationbeta CateninDevelopmental BiologyTrans-ActivatorsDrosophila ProteinsCentral Nervous SystemDrosophilaLeft-Right Determination FactorsSequence Homology, Amino AcidBone Morphogenetic Protein 4Mice, KnockoutGlycoproteinsTransforming Growth Factor betaSomitesBlastomeresCell LineageNeural TubeAnimals, Genetically ModifiedMetencephalonMicroinjectionsOrganogenesisNerve Tissue ProteinsModels, BiologicalGenes, DevelopmentalCloning, MolecularTime FactorsImmunohistochemistryAmphibiansGastrulationDNA, ComplementaryCarrier ProteinsTwins, Conjoined