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Neural Crest Cells and Axonal Specificity

Neural Crest Cells and Axonal Specificity

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Neural Crest Cells and Axonal Specificity

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  1. Neural Crest Cells and Axonal Specificity

  2. Neural Crest • Where is the neural crest located and why is this region so important?

  3. Neural Crest • What factors are important in the specification of neural crest?

  4. Neural Crest • What are the four domains and their derivatives? • cranial • cartilage, bone, cranial neurons, glia, connective tissue of face • trunk • dorsal root ganglia – sensory neurons, sympathetic ganglia, adrenal medulla, nerves around aorta, melanocytes

  5. Neural Crest • What are the four domains and their derivatives? • vagal and sacral • parasympathetic ganglia of gut • cardiac • melanocytes, neurons, cartilage, connective tissue, wall of large arteries, septum between aorta & pulmonary artery

  6. Neural Crest

  7. Trunk Neural Crest • What are the two migration pathways of trunk neural crest cells?

  8. Trunk Neural Crest • What initiates the migration of these cells? • transformed from epithelial to mesenchymal cells • presence of Wnt, FGF, and BMP’s induces formation of Slug and Rho B proteins • slug – dissociation of tight junctions, loss of N-cadherin • Rho B – promotes actin polymerization into microfilaments

  9. Trunk Neural Crest • How do migratory cells know the route to travel? • proteins that promote or impede migration found in extracellular matrix • promote – fibronectin, laminin, tenascin • thrombospondin – found in anterior part of sclerotome • impede – ephrin proteins • found in posterior part of sclerotome • stem cell factor promotes proliferation of neural crest that enter skin

  10. Trunk Neural Crest • What is meant by the pluripotency of these cells? • What determines how a specific cell will differentiate? • Are all neural crest pluripotent?

  11. Cranial Neural Crest • What is a major distinction between cranial and trunk neural crest? • cranial can form bone and cartilage in addition to neurons, melanocytes and glial cells

  12. Cranial Neural Crest • cranial neural crest migrate ventrally from rhombomeres of hindbrain

  13. Cranial Neural Crest • What is involved in intramembranous ossification?

  14. Cranial Neural Crest • What are the cranial placodes?

  15. Cranial Neural Crest • Placodes are induced to form by neighboring tissue

  16. Cranial Neural Crest • What happens during the “second wave” of migration? • crest cells migrate dorsally to form glial cells • glial cells provide tracks to guide neurons from placodes to hindbrain

  17. Cardiac Neural Crest

  18. Neuronal Specification • First decision • neuron or epidermis • Second decision • type of neuron • sensory • motor • interneurons • Third decision • target of neuron

  19. Neuronal Specification • What determines the specification of the type of neuron? • position of neuronal precursor within neural tube • when it forms (birthday)

  20. Neuronal Specification • What determines target of motor neuron? • a-p specification • hox genes from hindbrain through spinal cord and head genes (Otx) in brain regulate • in a given region – cell layer • age of cell – last division • Lim genes – transcription factors • Targets are specified before axons extend into periphery

  21. Neuronal Specification

  22. Pattern Generation • How does a neuronal axon “know” how to travel to a given area and make specific connections? • Appears to involve three steps: • pathway selection • target selection • address selection

  23. Pattern Generation • What role does the substrate play in directing the pathway of axons?

  24. Pattern Generation • Are there other molecules known to direct the migration of axons?

  25. Pattern Generation • What is the function of neurotrophins?

  26. Pattern Generation • What is involved in the formation of a synapse?

  27. Pattern Generation • What is the role of neurotropic factors in the survival of neurons?

  28. Pattern Generation • What is known about the migration of retinal ganglion axons?

  29. Pattern Generation • How do axons distinguish between different regions of optic tectum?