HemangioblastsHematopoiesisYolk SacHematopoietic Stem CellsMesonephrosVascular Endothelial Growth Factor Receptor-2Smad1 ProteinEmbryonic Stem CellsCell LineageCell DifferentiationBlood CellsMesodermGene Expression Regulation, DevelopmentalBasic Helix-Loop-Helix Transcription FactorsEndothelial CellsEmbryo, MammalianZebrafishStem CellsProto-Oncogene ProteinsTranscription FactorsCells, CulturedVascular Endothelial Growth Factor AEndothelium, VascularDNA-Binding ProteinsModels, BiologicalSignal Transduction