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4-1 4. Dr. Taube P. Rothman P&S 12-520 [email protected] 212-305-7930 Recommended Reading: Larsen Human Embryology, 3rd Edition, pp. 85-102, 126-130 Summary: In this lecture, we will first consider the induction of the neural plate and the formation of the neural tube, the rudiment of the central nervous system (CNS). The anterior portion of the neural tube gives rise to the brain, the more caudal portion gives rise to the spinal cord. We will see how the requisite numbers of neural progenitors are generated in the CNS and when these cells become post mitotic. The molecular signals required for their survival and further development will also be discussed. We will then turn our attention to the neural crest, a transient structure that develops at the site where the neural tube and future epidermis meet. After delaminating from the neuraxis, the crest cells migrate via specific pathways to distant targets in an embryo where they express appropriate target-related phenotypes. The progressive restriction of the developmental potential of crest-derived cells will then be considered. Additional topics include formation of the fundamental subdivisions of the CNS and PNS, as well as molecular factors that regulate neural induction and regional distinctions in the nervous system. Learning Objectives: At the conclusion of the lecture you should be able to: 1. Discuss the tissue, cellular, and molecular basis for neural induction and neural tube formation. Be able to provide some examples of neural tube defects caused by perturbation of neural tube closure. 2. Explain how neuronal precursors are generated in the CNS. 3. Describe the early changes in neural tube shape and the formation of the primary brain vesicles. 4. Discuss the ways in which two important signaling molecules, Sonic hedgehog (Shh) and bone morphogenic protein (BMP-4), regulate expression of regional distinctions in the nervous system. 5. Discuss where and how the neural crest forms, the origin of the migratory pathways that lead crest- derived cells to specific targets, and the effect of the genetic and environmental cues they encounter as they migrate and differentiate. ECTODERM: NEURULATION, NEURAL TUBE, NEURAL CREST
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