Splicing enhancers and recognition factors 56 Cell Signaling 79 Control of Gene Expression at the Level of Induction and competence 79 Translation 58 Cascades of induction: Reciprocal and sequential Differential mRNAlongevity 58 inductive events s0 elective inhibition of mRNa translation: Stored Instructive and permissive interactions 81 pithelial-mesenchymal interactions 82 microRNAs: Specific regulators of mRNA Paracrine Factors: The Inducer Molecules 84 translation and transcription 61 Signal transduction cascades: The response to m SIDELIGHTS SPECULatIoNs microRNAs in inducers 85 Transcriptional Gene Regulation 63 Fibroblast growth factors and the RTK pathway Control of rNA expression by cytoplasmic localization 64 The JAK-STAT pathway 88 Stored mRNAs in brain cells The Hedgehog family 90 Posttranslational regulation of gene expression 66 The Wnt family 92 The TGF-B superfamily 94 Other paracrine fa CHAPTER 3 I S/DELIGHTS SPECULATIONS Cell Death Pathways 96 Cell-Cell Communication in uxtacrine Signaling 98 Development 69 The Notch pathway: Juxtaposed ligands and receptors 98 Cell Adhesion 70 m SIDEU/GHTS SPECULATIONS Juxtacrine Signaling and Cell Patterning 99 Differential cell affinity 70 Maintaining the Differentiated State 101 The thermodynamic model of cell interactions 72 The Extracellular Matrix as a source of Cadherins and cell adhesion 73 Developmental Signals 102 L SIDELIGHTS SPECULATIONS Shape Change and Integrins: Receptors for extracellular matrix pithelial Morphogenesis: The Force Is Strong molecules 102 Epithelial-Mesenchymal Transition 105 Cell Migration 78 SPECIFICATION Introducing Cell Commitment PART and Early Embryonic Development 109 Levels of Commitment 109 Morphogen Gradients and Cell Specification 116 Autonomous Specification 110 Syncytial Specification 117 Conditional Specification 112 Summary 119 CHAPTER 4 External Fertilization in Sea Urchins 127 Fertilization: Beginning a New Sperm attraction: Action at a distance 128 The acrosome reaction 130 Organism 121 Recognition of the eggs extracellular coat 131 Fusion of the egg and sperm cell membranes 133 Structure of the Gametes 121 The fast block to polyspermy 135 Sperm 121 The slow block to polyspermy 136 The egg 125 Calcium as the initiator of the cortical granule Recognition of egg and sperm 127 actonSplicing enhancers and recognition factors 56 Control of Gene Expression at the Level of Translation 58 Differential mRNA longevity 58 Selective inhibition of mRN A translation: Stored oocyte mRNAs 58 microRNAs: Specific regulators of mRNA translation and transcription 61 • SIDELIGHTS & SPECULATIONS microRNAs in Transcriptional Gene Regulation 63 Control of RNA expression by cytoplasmic localization 64 Stored mRNAs in brain cells 65 Posttranslational regulation of gene expression 66 CHAPTER 3 Cell-Cell Communication in Development 69 Cell Adhesion 70 Differential cell affinity 70 The thermodynamic model of cell interactions 72 Cadherins and cell adhesion 73 • SIDELIGHTS & SPECULATIONS Shape Change and Epithelial Morphogenesis: "The Force Is Strong in You" 76 Cell Migration 78 Cell Signaling 79 Induction and competence 79 Cascades of induction: Reciprocal and sequential inductive events 80 Instructive and permissive interactions 81 Epithelial-mesenchymal interactions 82 Paracrine Factors: The Inducer Molecules 84 Signal transduction cascades: The response to inducers 85 Fibroblast growth factors and the RTK pathway 85 The JAK-STAT pathway 88 The Hedgehog family 90 The Wnt familv 92 The TGF-fi superfamily 94 Other paracrine factors 95 • SIDELIGHTS & SPECULATIONS Cell Death Pathways 96 Juxtacrine Signaling 98 The Notch pathway: Juxtaposed ligands and receptors 98 • SIDELIGHTS & SPECULATIONS Juxtacrine Signaling and Cell Patterning 99 Maintaining the Differentiated State 101 The Extracellular Matrix as a Source of Developmental Signals 102 Integrins: Receptors for extracellular matrix molecules 102 Epithelial-Mesenchymal Transition 105 PART SPECIFICATION Introducing Cell Commitment and Early Embryonic Development 109 Levels of Commitment 109 Autonomous Specification 110 Conditional Specification 112 CHAPTER 4 : Beginning a New Organism 121 Structure of the Gametes 121 Sperm 121 The egg 125 Recognition of egg and sperm 127 Morphogen Gradients and Cell Specification 116 Syncytial Specification 117 Summary 119 External Fertilization in Sea Urchins 127 Sperm attraction: Action at a distance 128 The acrosome reaction 130 Recognition of the egg's extracellular coat 131 Fusion of the egg and sperm cell membranes 133 The fast block to polyspermy 135 The slow block to polyspermy 136 Calcium as the initiator of the cortical granule reaction 137