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12 Cards in this Set
- Front
- Back
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Growth cone |
- Dynamic & specialized endings of axons, guiding them through chemical environment - At tip: lamellipodia & filopodia - Δ environment -> Δ F-actin -> Δ growth => become presynaptic termini |
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Guidepost cells |
~ kiosks at critical decision points, guiding axon growth cones via diffusible & direct interactions -ex.: glia, microglia, Cajal-Retzius cells (reelin), etc. - often also act as pioneer neurons |
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Pioneer neurons |
- first migrate to non-colonized areas of neural development, glia-independent - growth cones have many active filopodia - ex.: Rohon-Beard neurons (1° sensory n's): first sensory n's, then apoptosis (replaced by DRG's) - development of hippocampus & cortex (marginal zone = layer I) |
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Chemoattractants & chemorepellants |
- secreted or tethered (to membranes/ECM) - guide axonal growth (route & destination) by gradients - attracting/repelling response can change dynamically Trophic - support growth & survival Tropic - guide |
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Interneurons |
- use GABA (inh.) - do not migrate on glia scaffolds - migrate tangentially from primordial bumps (lateral & medial ganglionic eminence, LGE/MGE) |
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ECM-guiding mollecules |
laminin, collagen, fibronectin (ECM) -> integrins (axons) -> guidance & growth |
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Cell adhesion molecules (CAMs) & cadherins |
Expressed by pioneer & follower axons, substrate cells Bind homophilically & heterophilically: - same -> fasciculate - different -> mutual inhibition |
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Retinal ganglion cell (RGC) connectivity |
- identify correct regional postsynaptic partners according to multiple (anti-parallel) overlapping gradients of ephrin (soluble factors) & eph (R's) signaling |
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Major decussations (contralateral crossings) in the CNS |
Anterior & posterior comissure Corpus callosum Hippocampal commisure Habenular commisure Decussation of the superior cerebellar peduncle Anterior commissure (spinal cord) Other: optic n (chiasm), auditory pwy's |
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Decussation signaling |
Robo/Slit vs Netrin/DCC |
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Defects in axonal guidance signaling disrupt & cause |
--| Neuronal migration, axonal pathfinding, synaptic plasticity -> autism, neurodegenerative diseases (ALS, PD, AD, dyslexia, epilepsy) |
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Genetic defects in axon guidance |
Congenital mirror movements Kallman's syndrome (GnRH -> arrested puberty) Hirschspring's disease (congenital megacolon) Horizontal gaze palsy w/ progressive scoliosis (HGPSS) |
