Contents -- Preface -- 1 The Role of Maternal Factors in Early Zebrafish Development Francisco Pelegri -- 1. Maternal-Effect Genes -- 1.1. Definition -- 1.2. Classification of Maternal Effect Genes -- 1.2.1. Strictly maternal-effect genes -- 1.2.2. Maternal-zygotic genes -- 1.3. Underlying Basis for Strictly Maternal and Maternal-Zygotic Genetic Effects -- 2. Tools to Identify and Study Maternal-Effect Genes -- 2.1. Forward Screens -- 2.2. Testing for the Maternal Contribution of Known Zygotic Genes -- 2.2.1. Viable or semi-viable mutations -- 2.2.2. Non-viable mutations with a phenotype that can be rescued experimentally -- 2.2.3. Non-viable mutations using germ line chimeras -- 2.3. Reverse Genetic Approaches -- 2.3.1. Morpholino-mediated functional knockdown -- 2.3.2. RNA interference -- 2.3.3. Target selected inactivation -- 3. Maternal Products during Egg Activation and Early Embryogenesis -- 3.1. Redistribution of Maternal mRNAs during Egg Activation -- 3.1.1. mRNAs evenly distributed in the mature oocyte -- 3.1.2. mRNAs localized to the animal pole of the oocyte during oogenesis -- 3.1.3. mRNAs localized to the vegetal pole of the oocyte -- 3.1.4. The mRNA for the gene vasa -- 3.2. Redistribution of Components of the Germ Plasm during the Early Cleavage Stages -- 3.3. Redistribution of Dorsal Determinant Signal during the Early Cleavage Stages -- 3.4. The Yolk Cell and Maternal Determinants -- 4. Maternal Genes with a Function in Early Development -- 4.1. General Functions -- 4.2. Induction of Cell Fates along the Dorsoventral Axis -- 4.2.1. Local activation of Wnt/ -catenin signaling: induction of the dorsal organizer -- 4.2.2. Wnt/calcium signaling: downregulation of the dorsal organizer -- 4.2.3. Bmp signaling: promotion of ventral cell fates -- 4.2.4. Integration of pathways regulating dorsoventral patterning.

4.3. Induction of Cell Fates along the Anteroposterior Axis -- 4.4. Induction of the Mesendodermal Layer -- 5. Determination of the Maternal-Zygotic Transition -- 6. Conclusions -- Acknowledgements -- References -- 2 Gastrulation in Zebrafish Florian Ulrich and Carl-Philipp Heisenberg -- Introduction -- I. Cellular Mechanisms -- Epiboly -- Internalization -- Convergence and Extension -- Future Directions -- II. Molecular Mechanisms -- Wnt/PCP Pathway -- Cell Adhesion Molecules -- Nodal/TGF Signaling -- PDGF/PI3K Pathway -- Other Pathways -- III. Future Prospects -- 'New' Methods -- Remaining and Arising Questions -- Acknowledgments -- References -- 3 Development of the Zebrafish Organizer and Notochord Kevin A. Thomas and Derek L. Stemple -- 1. Organizer -- 1.1. Introduction -- 1.2. Specification of the Organizer -- Dorsal specification -- Mesendoderm induction -- 1.3. Structure and Patterning of the Organizer -- 1.4. Organizer Activities -- 2. Notochord -- 2.1. Introduction -- 2.2. Differentiation of the Notochord -- 2.3. Patterning of Surrounding Tissues by the Notochord -- 2.4. Mechanics of Notochord Structure and Development -- Acknowledgments -- References -- 4 Formation and Functions of the Floor Plate Jing Tian and Karuna Sampath -- 1. Introduction -- 2. Overview of the Neural Tube -- 2.1. Formation of the Neural Tube: Neurulation -- 2.2. The Floor Plate: A Transient Structure in the CNS Which Forms during Neurulation -- 2.3. Signals Involved in Polarization within the Neural Tube -- 2.3.1. Shh, a major signaling molecule in ventral neural tube patterning -- 2.3.2. BMPs: key signaling factors in patterning the dorsal neural tube -- 3. The Roles of the Floor Plate in the Central Nervous System -- 3.1. Axon Guidance -- 3.1.1. Overview of axon projections which are influenced by the floor plate -- 3.1.2. Chemoattraction by the floor plate.

3.1.3. Chemorepulsion by the floor plate -- 3.1.4. Guidance at the midline by the floor plate -- 3.1.5. Molecular mechanisms of axon guidance by the floor plate -- 3.2. Floor Plate in Neuronal Differentiation -- 3.2.1. Ventral neural cell type differentiation -- 3.2.2. Motor neuron differentiation by the floor plate -- 3.2.3. Ventral neural tube patterning by Shh secreted by the floor plate and notochord -- 4. The Origin of the Floor Plate -- 4.1. Model One: Shh-Mediated Induction of Floor Plate by the Notochord -- 4.1.1. Vertical induction of floor plate by Shh secreted from notochord -- 4.1.2. Homeogenetic induction of the floor plate -- 4.2. Model Two: Floor Plate Induction Occurs Independent of the Notochord -- 4.2.1. Node/organizer: the common source of floor plate and notochord cells -- 4.2.2. When is the floor plate induced? -- 4.2.3. Where are the floor plate cells induced: functional domains within Hensen's node -- 4.2.4. The different origins of medial floor plate and lateral floor plate -- 5. Concluding Remarks -- The origin of the floor plate: reconciling planar, vertical and homeogenetic induction -- Acknowledgments -- References -- 5 Form and Function in the Zebrafish Nervous System Michael Hendricks and Suresh Jesuthasan -- Introduction -- Development of the Nervous System: Axon Guidance -- Function of the Nervous System: Sensory Perception -- Mechanotransduction -- Odor Perception -- Network Function -- The Visual System -- The Touch Response -- Concluding Remarks -- References -- 6 Development of the Primary Nervous System of the Zebrafish Embryo Uwe Strahle and Vladimir Korzh -- Introduction -- Different Classes of Primary Neurons Occupy Characteristic Positions in the Embryonic Nervous System -- Primary Neurons Form Distinct Domains in the Neural Plate -- External Signals in the Spatial Control of Neurogenesis.

Pre-Pattern Genes in the Neural Plate -- Primary Neurons are Selected from Pools of Precursors by Lateral Inhibition -- bHLH Genes as Regulators of Neuronal Subtype -- The Regulatory Elements Controlling Gene Expression in Primary Neurons are Conserved among Vertebrates -- Acknowledgments -- References -- 7 Making Scents: Development and Function of the Olfactory Sensory System Kathleen E. Whitlock -- 1. Amazing Conservation: Organization of Olfactory Sensory Systems -- 1.1. Fish as a Model System -- 1.2. Sensory Epithelium -- 1.3. Olfactory Bulb -- 1.4. Terminal Nerve -- 2. The Olfactory Placode Arises from the Edge of the Developing Neural Plate -- 2.1. Origin -- 2.2. Gene Expression in the Olfactory Field of the Anterior Neural Plate -- 2.3. Induction -- 2.4. The Differentiating Olfactory Organ -- 2.5. Mutations Disrupting Olfactory Placode Development -- 2.6. Structural Elements of the Olfactory System Arise from Cranial Neural Crest -- 3. The Olfactory Bulb Arises from the Anterior Neural Plate -- 3.1. Gene Expression in the Developing Olfactory Bulb -- 3.2. Axonal Input and Olfactory Bulb Development -- 4. Axon Guidance: The Connection of the Olfactory Sensory Axons with the Developing Olfactory Bulb -- 4.1. Guidance Cues -- 4.2. Cell Surface Molecules -- 4.3. Olfactory Receptors -- 4.4. Pioneer Neurons -- 5. Olfactory Receptors: The Interface with the Outside World -- 5.1. Main Olfactory Epithelium -- 5.2. Onset of Olfactory Receptor Expression during Development -- 5.3. Do Fish Have a Vomeronasal System? -- 5.4. Development -- 6. Other Derivatives of the Olfactory Placode: Neuroendocrine Cells -- 6.1. The Terminal Nerve -- 6.2. Cells Appear to Exit the Olfactory Placode -- 6.3. The Neural Crest -- 6.4. The Adenohypophysis -- 7. Olfactory Physiology and Behavior: The Key to Survival and Reproduction -- 7.1. Fishy Smells.

8. Evolution of the Olfactory Sensory System -- 8.1. Is there a Unifying Placode Theme? -- 8.2. Olfactory and Adenohypophysis -- 8.3. Olfactory Placode Field and Neural Crest -- A World of Questions Remain -- Acknowledgments -- References -- 8 Somite Segmentation: A View from Fish Hiroyuki Takeda and Yumiko Saga -- 1. Introduction -- 1.1. General View of Vertebrate Somite Segmentation -- 1.2. Zebrafish Somite Formation and Mutants -- 2. Gene Expression and Segmental Property in the PMS -- 3. A Molecular Clock Functions in the PSM -- 4. Molecular Circuit in the Clock -- 5. Wavefront -- 5.1. Fused Somites/Tbx24 Regulate the Wavefront Activity -- 5.2. Positioning the Wavefront in the Anterior PSM -- 6. Establishment of Rostrocaudal Polarity -- 6.1. Gene Network Centered on Mesp Gene -- 6.2. Rostrocaudal Patterning and Clock Mechanism -- 7. Formation of Morphologically Distinct Somite Boundary -- 8. Unanswered Questions -- Acknowledgment -- References -- 9 Vertebrate Somite Development, Notch Signaling and Others Yun-Jin Jiang -- 1. Introduction -- 2. The Way to a Segmentation Clock -- 2.1. Heat-Shock Experiment -- 2.2. Cell Cycle -- 2.3 Previous Models -- 3. Molecular Era - Oscillation and Clock -- 3.1. Cyclic Genes - Expression Level Changing with Time and Space -- 3.2. Notch Signaling and Mutants -- 3.3. The Clockwork of the Segmentation Clock -- 3.3.1. Autoinhibitory loops - the essence of the segmentation clock -- 3.3.2 Two transcription factors drive interconnected loops of segmentation clock -- 3.3.3. Dual role of Notch signaling in somite segmentation -- 3.3.4. Post-translational regulation in Notch signaling and others -- 4. Molecular Era - Gradients and Clock Output -- 4.1. FGF Signaling - A Gradient Positioning the Boundary -- 4.2. WNT Signaling - A Gradient Harmonizing Tail Growth with Segmentation and, Therefore, the Cellular Oscillator.

4.3. Hox Genes are Clock-Controlled.