EndodermSOXF Transcription FactorsMesodermGene Expression Regulation, DevelopmentalGastrulaGerm LayersEmbryonic InductionVisceraGATA6 Transcription FactorBody PatterningEctodermGATA5 Transcription FactorNodal ProteinHepatocyte Nuclear Factor 3-betaSOX Transcription FactorsDigestive SystemCell DifferentiationYolk SacEmbryo, NonmammalianIn Situ HybridizationEmbryonic Stem CellsHomeodomain ProteinsMorphogenesis