OligochaetaLeechesCell LineageCell DifferentiationStem CellsPhylogenyGene Expression Regulation, DevelopmentalMice, TransgenicTranscription FactorsHematopoietic Stem CellsMolecular Sequence DataEvolution, MolecularHomeodomain ProteinsMice, Inbred C57BLEmbryonic Stem CellsThymus GlandBase SequenceCells, CulturedMesodermGerm CellsEmbryo, MammalianPhenotypeBasic Helix-Loop-Helix Transcription FactorsBiological EvolutionSignal TransductionMice, KnockoutHematopoiesisChimeraEmbryo, NonmammalianMultipotent Stem CellsEndodermEctodermMorphogenesisB-LymphocytesBone Marrow CellsFlow CytometrySequence Analysis, DNALymphopoiesisDNA-Binding ProteinsGene Expression Regulation