Developmental Neurobiology BIPN 144
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This 3 page Class Notes was uploaded by Mrs. Katlyn Hodkiewicz on Thursday October 22, 2015. The Class Notes belongs to BIPN 144 at University of California - San Diego taught by Staff in Fall. Since its upload, it has received 15 views. For similar materials see /class/226772/bipn-144-university-of-california-san-diego in Biology at University of California - San Diego.
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Date Created: 10/22/15
Lecture 10 Neuronal Differentiation gt Cell Movement and Migration 1 Neuronal Differentiation General Cells stop dividing Axonal outgrowth begins Cells become electrically excitable axon first then soma Axons contact target area Axons chose specific site to synapse Synapse formation Modulation of synapse strength experience controlled Vertebrate brain Neuronal precursors crudely defined at ventricular zone Indeterminate lineage divisions give rise to variable progeny Neurons migrate out radial glia Late dividing cells migrate past early dividing cells quotinsideoutquot pattern Plasticity of transmitter choice in sympathetic ganglion cells Normally become adrenergic Plus heart conditioned medium become cholinergic Intermediates express both transmitters Intrinsic neuron branching pattern tendencies Sensory unipolar Motor neurons multipolar pyramidal cells triangular cell bodies apical and basal dendrites 2 Cell Migration Postmitotic neurons recap basic features including migration and axon outgrowth Cell migration Neurons move from one location to another Axonogenesis Neurons send out processes dendrites and axons San Diego to LA on I5 analogy General processes Intrinsic initial cell polarity recently divided fibroblasts grasshopper limb sensory neurons Intrinsic neuron branching pattern tendencies Sensory unipolar Motor neurons multipolar pyramidal cells triangular cell bodies apical and basal dendrites Chemoattractants chemotaxis Cell surface and cell matrix guidance cuesAdhesion molecules Dissociationreaggregation experiments Expression and function of various cadherins N and E in neural tube Mechanism of directional movement Cells typically follow several redundant cues eg Iaminin fibronectin collagen etc Cell culture experiments on ECM need to block with antibodies to several cues to block migration Neural Crest Between neural tube and somites gt track along fibronectin path In vitro block with single NC migration with single antiFibronectin Ab In vivo block migration with antiFibronectin Ab injection Control side fine LECTURE 11 CNS Pathfinding in Vertebrates and Invertebrates Introduction Path nding is a central unsolved problem in developmental neurobiology The Limb Bud The Grasshopper Limb System Bentley Diagram of limb Ti1 cells emerge from the neuroepithelium Growth cone orientation toward CNS is intrinsic Path nd along guideposts Fe1 Tr1 CX1 Later sensory nerves follow the TH pathway Pioneers and guideposts die after establishing pathway Til O Fe1 CX1 Trl CNS Experimental Questions Do Fe1 need Ti1 pioneers No ablations of TM 5 Do pioneers need guideposts Yes to an extent kill CX1 Ti1 stuck at TrCX boundary Kill Fe1 or Tr1 Ti1 slows down but ultimately nds its way Axons react to guideposts make close contact dye couple Single filopodia touch a guidepost CX1 reorient whole growth cone Remove lopodia with cytochalasin Ti1s get lost Filleted limb prep What do Ti1 axons follow between TH and TH Not signal from CNS lleted limb separated from CNS Not signal on mesoderm can dissect it off Not signal on ECM can digest it away Signal must be on remaining epithelium CNS pathways first seven axons MP1 dMP2 vMP2 pCC aCC U1 U2 make first three longitudinal fascicles dMP2MP1 and pCC interactfasciculate aCC followsfasciculates on U s ablate Us aCC gets lost Motor axon pathfinding SNa versus SNb axon projections to ventral muscles What molecules are involved The search for Fasciclins with mAbs Fasl novel membrane protein Fasl on aCC not pCC Fasll lg superfamily homolog to NCAM Fasll on MP1 vMP2 axons Faslll and Neuroglian also lg family members Neuroglian homolog of L1 Netrin worm unc6 and Netrin receptors attractive receptor human DCC deleted in colorectal cancer y Frazzled worm unc40 repulsive receptor worm unc5 Roundabout RoboSlit and Commisureless Comm Axonin See Figure 7a Midline Axon Guidance Netrin midline attractant for most axons and repellent for others Attraction mediated by DCC Frz Unc40 gt lchMP Repulsion mediated by unc5 gt UcAMP Robo receptor for repulsive Slit ligand expressed in midline cells Comm expressed in midline gt U Robo robo comm double mutants robo don t need to downregulate Robo if it isn t there Moderate overexpression of comm robo phenotype Strong overexpression of comm slit phenotype gt all axons collapse onto midline reason that slit mutant is stronger than robo due to existence of multiple Robos Robo Rob02 and Robo3 lnner track axons express only robo Intermediate track axons express robo and robo2 Outer track axons express robo robo2 and robo3 Trobo genes expressed eg T levels gt axon tracks further from midline See Figure 7a RoboSlit also mediate repulsion for migrating fly muscle cells and for vertebrate leukocytes gt similar mechanisms underlie migration and path nding
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