Neuronal Development

Studies of simple and emerging systems have been undertaken to un­ derstand the processes by which a developing system unfolds, and to understand more completely the basis of the complexity of the fully formed structures. The nervous system has long been particularly in­ triguing for such studies, because of the early recognition of a multitude of distinctly differentiated states exhibited by nerve cells with different morphologies. Anatomical studies suggest that one liver cell may be very like another, but indicate that neurons come in a remarkable di­ versity of forms. This diversity at the anatomical level has parallels at the physiological and biochemical levels. It is becoming increasingly easy to characterize the different cellular phenotypes of neurons. The repeatability with which these phenotypes are expressed may account in part for the specificity and reliability with which neurons form con­ nections, and it has allowed precise description of the first appearance and further development of the differentiated characteristics of individ­ ual neurons from relatively undifferentiated precursor cells. This rep­ resents a major advance over our knowledge of development at the level of tissues, and makes it feasible to define and address questions about the underlying molecular mechanisms involved. Central to these advances has been the clear recognition that there is no single best preparation for the study of neuronal development. Furthermore, it has become evident that no single technique can tell us all we want to know.

Contenu

1. Cell Lineage in the Development of the Leech Nervous System.- 1. Introduction.- 1.1. Developmental Cell Lineages.- 1.2. The Leech Nervous System.- 2. Leech Embryogenesis.- 2.1. Two Experimentally Favorable Leech Species.- 2.2. A Developmental Staging System.- 3. A Novel Cell Lineage Tracing Method.- 3.1. Horseradish Peroxidase Tracer.- 3.2. Fluorescent Tracer.- 4. Development of Germinal Bands.- 4.1. Ectodermal Stem Cell Bandlets.- 4.2. Mesodermal Stem Cell Bandlets.- 5. Origin of the Segmental Ganglia.- 5.1. Ectoteloblast Contribution.- 5.2. Distribution Pattern of Four Neuronal Kinship Groups.- 5.3. Number of Ganglion Founder Cells.- 5.4. Mesoteloblast Contribution.- 5.5. Origin of the Supraesophageal Ganglion.- 6. Cell-Specific Ablation.- 6.1. Role of Mesoderm in Ectodermal Development.- 6.2. Role of Ectoderm in Mesodermal Development.- 6.3. Morphogenetic Interactions within the Ectoderm.- 7. Conclusion.- 7.1. Governance of Cell Fate by Cell Lineage.- 7.2. Neuronal Kinship Groups.- 7.3. Segmentation.- 8. References.- 2. Origins of the Nervous System in Amphibians.- 1. Introduction.- 2. The Theory of Compartmentation.- 3. Predictions Made from the Theory and Their Experimental Verification.- 3.1. Deployment of Labeled Clones after HRP Injection into Ancestral Cells at Various Stages.- 3.2. Origins of Compartment-Specific Properties.- 3.3. Relation of Compartment Founder Cell Groups to Differentiated Cell Types.- 4. Critique of the Theory of the Organizer.- 4.1. Preliminary Considerations.- 4.2. Early Experimental Tests.- 4.3. Recent Experimental Tests with HRP Label.- 5. Compartment vs. Organizer Theories.- 5.1. The Case for the Compartment Theory.- 5.2. Difficulties with the Organizer Theory.- 6. References.- 3. Monoclonal Antibodies to Embryonic Neurons: Cell-Specific Markers for Chick Ciliary Ganglion.- 1. Introduction.- 1.1. Formation of Complex Connections in the Nervous System.- 1.2. Antibodies as Cytochemical Markers of Neuronal Cells.- 1.3. The Ciliary Ganglion, a Model of Neuronal Development in Vertebrates.- 2. Materials and Methods.- 2.1. Dissociated Cell Cultures.- 2.2. Immunological Procedures.- 2.3. Reagents.- 3. Results.- 3.1. Initial Selection and Cloning of Antibody-Producing Hybrids.- 3.2. Monoclonal Antibodies Specific for CG Neurons.- 3.3. Staining of Cranial Neural Crest Cells in Vitro.- 3.4. Cytotoxicity of CG-1.- 3.5. Other Monoclonal Antibodies.- 3.6. Blocking Studies.- 4. Discussion.- 4.1. The Specificity of These Monoclonal Antibodies.- 4.2. Possible Identification of CG Neuron Precursors.- 4.3. Independence and Identity of the Antigenic Determinants.- 4.4. Potential Heterogeneity of CG Neurons.- 5. References.- 4. Genetic Manipulation of Sensory Pathways in Drosophila.- 1. Introduction.- 1.1. Levels of Analysis.- 1.2. Advantages of Different Organisms.- 1.3. What Understanding Can We Gain from Genetic Manipulation?.- 2. The Experimental Material.- 2.1. Mutants.- 2.2. Mosaics.- 3. A Theoretical Framework.- 3.1. Binary Decisions.- 3.2. The Bithorax Complex.- 3.3. The Antennapedia Complex.- 3.4. Compartments.- 3.5. Evaluation.- 3.6. Working Hypotheses and Questions for Neurobiologists.- 4. Compartments Boundaries and Peripheral Nerves.- 4.1. General Neuroanatomy of Drosophila.- 4.2. Neuroanatomy of the Wing.- 4.3. The Behavior of Axons at the A-P Compartment Border.- 4.4. Evidence That the Compartment Border Is Intact.- 4.5. The Next Hypothesis-Pupal Nerves Guide Adult Axons.- 4.6. Evaluation.- 5. Central Projections in Mutants of the Antennapedia Complex.- 5.1. Antennapedia.- 5.2. Proboscipedia.- 5.3. Interpretation.- 6. Central Projections in Mutants of the Bithorax Complex.- 6.1. Different Classes of Receptors Form Different Projections.- 6.2. The Projection of Single Axons Is Not Always Precisely Specified.- 6.3. Axons from the Normal Wings of Mutant Flies Branch More.- 6.4. Some Axons from Homeotic Wings Follow Normal Wing Tracts.- 6.5. Some Axons from Homeotic Wings Follow Haltere Tracts.- 6.6. Some Axons from Homeotic Wings Find an Adequate Home in the Metathorax.- 6.7. Is The CNS Directly Affected by BX-C Mutations?.- 7. Analysis.- 7.1. Transplantation by Mutation.- 7.2. Special Contributions of Genetic Studies.- 7.3. The Strengths and Limitations of Mosaic Studies.- 7.4. The Role of Compartments.- 7.5. Evaluation and Prognosis.- 8. References.- 5. Embryonic Development of Identified Neurons in the Grasshopper.- 1. Introduction.- 2. The Grasshopper Nervous System.- 3. Grasshopper Embryology.- 4. Neuronal Precursor Cells.- 5. Early Axonal Pathways.- 6. Cell Lineage of the Median Neuroblast.- 7. Cell Lineage of Midline Precursor 3.- 8. Properties of the Progeny of a Single Precursor.- 8.1. Biochemistry.- 8.2. Physiology.- 8.3. Morphology.- 9. Morphological Differentiation.- 9.1. DUM 5.- 9.2. The H Cell.- 10. Physiological Differentiation.- 10.1. Chemosensitivity.- 10.2. Electrical Excitability.- 10.3. Electrical and Dye Coupling.- 11. Biochemical Differentiation.- 12. Temporal Sequence of Development.- 13. Segment-Specific Cell Death.- 14. Segment-Specific Differentiation.- 15. Limb Bud Removal Experiments.- 16. Conclusions and Questions.- 17. References.- 6. Nerve Fiber Growth and Its Regulation by Extrinsic Factors.- 1. Introduction.- 2. Behavior of the Growing Nerve Fiber Tip.- 2.1. Protrusion and Regression.- 2.2. Contacts of the Nerve Fiber Tip.- 2.3. Cell-Substratum Adhesion and Neurite Growth.- 3. Structure of the Growing Nerve Fiber.- 3.1. The Neurite.- 3.2. The Nerve Fiber Tip.- 4. Mechanism of Nerve Fiber Growth.- 4.1. Expansion of the Neurite Membrane.- 4.2. Growth of the Cytoskeleton.- 4.3. Protrusion, Adhesion, and Actomyosin Action.- 4.4. Force Exertion in the Growth Cone Margin; How the Neurite Grows.- 5. Regulation of Nerve Fiber Growth by Environmental Factors.- 5.1. Regulation by Cell-Substratum Adhesion.- 5.2. Regulation by Spatial Variations in Adhesivity.- 6. Regulation of Nerve Fiber Growth by Chemotaxis.- 6.1. NGF as a Chemoattractant.- 6.2. Behavioral Responses of Growth Cones That Indicate a Chemotactic Response to NGF.- 6.3. Mechanisms of Chemotactic Response to NGF.- 6.4. NGF Receptors and Electrical Currents.- 7. Future Prospects.- 7.1. Regulation of Actin Structure and Function.- 7.2. Intrinsic Regulation of Neuronal Morphogenesis.- 7.3. Interactions of Neurites with Other Cells and in Vivo Surfaces.- 8. Conclusions.- 9. References.- 7. Pi…