14-Target_selection - Target Selection Axon Targeting Axon...

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Target Selection
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Axon Targeting Axon reaches a target area, slow down, send out filopodia, find a right partner, form synapses.
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Axon slows down in target zones and branches to make synapses. Tectum has low level of FGF-2, forming a gradient drop. Abnormally high FGF2 level in tectum will diminish the gradient and not a suitable target for retinal axon, so it keeps on going. FGF-2 low Growth Cones Change in Target Zones
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Axons are fasciculated because integral membrane protein beat-1c binds the beat receptor. In target area, soluble beat-1a protein binds the beat receptor, breaking the adhesion, the axons defasciculate. Defasciculation Is Regulated by Beat Proteins Axon Defasiculate in the region of its target No defasciculation
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NT3 Guides SCG Axon to External Ear SCG: superior cervical ganglion NT3, a neurotrophin, is important for SCG neurons to innervate the target pinna.
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B. In BDNF, NT-3 or TrkB, TrkC double mutants, the inner ear remains uninnervated. C. In transgenic mice in which BDNF has been knocked into the NT-3 coding region, the cochlear region becomes innervated by the vestibular part of the ganglion. Innervation of the Inner Ear is Regulated by BDNF and NT-3 vestibulo-cochlear ganglion TrkB/TrkC
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Secondary Targets: Visual and Auditory Targets Share Similar Cues Under experimental condition, visual signal can be sent to auditory cortex, so that you may “hear” a beautiful photo! LGN ablated EphrinA2/EphrinA5 define the border between LGN and MGN
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SCG: superior cervical ganglion Target Specific Regeneration Different SCG neurons may secret specific signals to attract T1 or T4 axons to re-innervate the right target after cut.
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This note was uploaded on 08/26/2011 for the course BIOL 426 taught by Professor Profgongchen during the Spring '08 term at Pennsylvania State University, University Park.

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14-Target_selection - Target Selection Axon Targeting Axon...

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