title: Corticothalamic Axons Are Essential for Retinal Ganglion Cell Axon Targeting to the Mouse Dorsal Lateral Geniculate Nucleus.
abstract: Retinal ganglion cells (RGCs) relay information about the outside world to multiple subcortical targets within the brain. This information is either used to dictate reflexive behaviors or relayed to the visual cortex for further processing. Many subcortical visual nuclei also receive descending inputs from projection neurons in the visual cortex. Most areas receive inputs from layer 5 cortical neurons in the visual cortex but one exception is the dorsal lateral geniculate nucleus (dLGN), which receives layer 6 inputs and is also the only RGC target that sends direct projections to the cortex. Here we ask how visual system development and function changes in mice that develop without a cortex. We find that the development of a cortex is essential for RGC axons to terminate in the dLGN, but is not required for targeting RGC axons to other subcortical nuclei. RGC axons also fail to target to the dLGN in mice that specifically lack cortical layer 6 projections to the dLGN. Finally, we show that when mice develop without a cortex they can still perform a number of vision-dependent tasks.
  
  
  
  The dorsal lateral geniculate nucleus (dLGN) is a sensory thalamic relay area that receives feedforward inputs from retinal ganglion cells (RGCs) in the retina, and feed back inputs from layer 6 neurons in the visual cortex. In this study we examined genetically manipulated mice that develop without a cortex or without cortical layer 6 axonal projections, and find that RGC axons fail to project to the dLGN. Other RGC recipient areas, such as the superior colliculus and suprachiasmatic nucleus, are targeted normally. These results provide support for a new mechanism of target selection that may be specific to the thalamus, whereby descending cortical axons provide an activity that promotes feedforward targeting of RGC axons to the dLGN.
authors.affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064.
authors.forename: James A
authors.initials: JA
authors.lastname: Shanks
authors.affiliation: Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California 95064, and.
authors.forename: Shinya
authors.initials: S
authors.lastname: Ito
authors.affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064, Department of Biology, Trinity College, Hartford, Connecticut 06106.
authors.forename: Laura
authors.initials: L
authors.lastname: Schaevitz
authors.affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064.
authors.forename: Jena
authors.initials: J
authors.lastname: Yamada
authors.affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064.
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.affiliation: Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, Santa Cruz, California 95064, and.
authors.forename: Alan
authors.identifier: 0000-0003-3973-3642
authors.initials: A
authors.lastname: Litke
authors.affiliation: Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064, feldheim@biology.ucsc.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Feldheim
mesh_terms: D000818:Animals; D000071437:Axon Guidance; D005260:Female; D005829:Geniculate Bodies / Q000166:cytology / Q000254:growth & development* / Q000502:physiology; D008297:Male; D051379:Mice; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology / Q000254:growth & development* / Q000502:physiology
keywords: axon-targeting; cortex; dLGN; retina; target selection; visual system