Lecture+2++Compatibility+Mode+

Lecture+2++Compatibility+Mode+ - 11/1/2011 TargetSelection...

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11/1/2011 1 November 3, 2011 Target Selection Chapter 6 Dev of the Nervous System Susana Cohen-Cory, Ph.D. Neurobiology and Behavior Office: 1230 McGaugh Hall X 48188 e-mail: scohenco@uci.edu Dev. of the Nervous System Sanes, Reh & Harris Peripheral nerve grafts support central neuron axon regrowth Adult astrocytes and oligodendrocytes that form a glial scar inhibit axon regrowth
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11/1/2011 2 NgR – Nogo receptor, also acts as a receptor for MAG and OMpg together with other co receptors Nogo, MAG (myelin associated glycoprotein) and OMgp (oligodendrocyte myelin glycoprotein) are proteins that inhibit axon growth MAG and OMpg, together with other co receptors. A decrease in cAMP is responsible for inhibiting axon growth in the adult. Lack of neurotrophic signals that normally increase cAMP levels is also responsible for axons in the adult not to be able to regnerate Conceptual stages of targeting. From top to bottom: An axon defasciculate in the region Axon targeting An axon defasciculates in the region of the target. It enters the target and begins to branch, and is prevented from exiting by a repulsive border. The axon responds to a topographic gradient that promotes branching at the correct location. It then selects a particular layer and finally homes in on particular target cells.
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11/1/2011 3 Defasciculation Axons need to exit from a tight bundle of nerves Axons often travel past a variety of potential targets As they do, specific axons or groups of axons peel off of these common pathways N CAM and its homologs can cause similar axons to fasciculate (group) N CAM and its homologs can cause similar axons to fasciculate (group) together into nerves or tracts How do axons leave these tracts and nerves? Example below: Some proteins are required for selective defasciculation at specific points (Beat 1a is an anti adhesion factor for Drosophila motor axons). Other repulsive cues (i.e. semaphorin) can also promote defasciculation Axon targeting
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11/1/2011 4 Axon Targeting Target recognition Targets can be internal organs, sensory cells, muscles or other neuronal nuclei in the CNS or PNS.
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Lecture+2++Compatibility+Mode+ - 11/1/2011 TargetSelection...

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