Mice, KnockoutPhenotypeIntegrasesGene Knockout TechniquesGene DeletionMice, TransgenicMice, Inbred C57BLProsencephalonGene TargetingEmbryo, MammalianSignal TransductionDisease Models, AnimalGene Expression Regulation, DevelopmentalCell DifferentiationCell ProliferationCells, CulturedReverse Transcriptase Polymerase Chain ReactionNeuronsOrgan SpecificityHomeostasisNerve Tissue ProteinsGene Expression RegulationImmunohistochemistryBlotting, WesternHomeodomain ProteinsApoptosisTranscription FactorsMutationGenotypeBrainCell SurvivalTime FactorsLiverMice, 129 StrainEmbryo LossAnimals, NewbornRNA, MessengerBehavior, AnimalHomozygoteNeurogenesisMembrane ProteinsHeterozygoteEmbryonic DevelopmentRibonuclease IIIFertilityHippocampusAllelesCyclin-Dependent Kinase 5Motor ActivityDEAD-box RNA HelicasesLIM-Homeodomain ProteinsReceptors, Transforming Growth Factor betaGenes, LethalGene ExpressionBasic Helix-Loop-Helix Transcription FactorsSertoli CellsDNA PrimersDNA-Binding ProteinsMammary Glands, AnimalStem Cells