BIOL 1111 Lecture Notes - Neurogenesis, Commissure, Bone Morphogenetic Protein 4
1 Feb 2013
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Development ii: neural induction: the notochord plays a key role, quick review. During gastrulation, dorsal tissue migrates through blastopore lip to become mesoderm. Notochord forms from mesoderm, and induces ectodermal neural plate formation: neural induction. Default fate of ectodermal cells is neuronal; bmp4 induces epidermal fate. Notochord produces noggin, chordin to inhibit bmp4, thereby inducing neural diffn. Notochord produces shh a ventralizing morphogen that acts in a graded manner: high shh (most ventral) induces motoneurons, intermediate induces interneurons, low produces commissural neurons. Roof plate produces bmp2, a dorsalizing morphogen. Neurons are produced by lateral walls of neural tube, not the roof or floor plate. Asymmetric divisions (parallel to base) give rise to neurons, whereas symmetric divisions (perpendicular to base) do not. Neurons are generated early and glial cells are generated later. Neuroblasts divide only 1-2 times before diffn into neurons. Glioblasts divide many times before diffn, \ fewer glioblasts needed than neuroblasts.
