Article

Architecture and activity-mediated refinement of axonal projections from a mosaic of genetically identified retinal ganglion cells.

Department of Neurobiology, Fairchild Science Building D235, Stanford University School of Medicine, Palo Alto, CA 94305, USA.
Neuron (Impact Factor: 15.77). 09/2008; 59(3):425-38. DOI: 10.1016/j.neuron.2008.07.018
Source: PubMed

ABSTRACT Our understanding of how mammalian sensory circuits are organized and develop has long been hindered by the lack of genetic markers of neurons with discrete functions. Here, we report a transgenic mouse selectively expressing GFP in a complete mosaic of transient OFF-alpha retinal ganglion cells (tOFF-alphaRGCs). This enabled us to relate the mosaic spacing, dendritic anatomy, and electrophysiology of these RGCs to their complete map of projections in the brain. We find that tOFF-alphaRGCs project exclusively to the superior colliculus (SC) and dorsal lateral geniculate nucleus and are restricted to a specific laminar depth within each of these targets. The axons of tOFF-alphaRGC are also organized into columns in the SC. Both laminar and columnar specificity develop through axon refinement. Disruption of cholinergic retinal waves prevents the emergence of columnar- but not laminar-specific tOFF-alphaRGC connections. Our findings reveal that in a genetically identified sensory map, spontaneous activity promotes synaptic specificity by segregating axons arising from RGCs of the same subtype.

0 Bookmarks
 · 
140 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the retinocollicular projection, the axons from functionally distinct retinal ganglion cell (RGC) types form synapses in a stereotypical manner along the superficial to deep axis of the SC. Each lamina contains an orderly topographic map of the visual scene but different laminae receive inputs from distinct sets of RGCs, and inputs to each lamina are aligned with the others to integrate parallel streams of visual information. To determine the relationship between laminar organization and topography of physiologically defined RGC types, we used genetic and anatomical axon tracing techniques in wild type and ephrin-A mutant mice. We find that adjacent RGCs of the same physiological type can send axons to both ectopic and normal topographic locations, supporting a penetrance model for ephrin-A independent mapping cues. While the overall laminar organization in the SC is unaffected in ephrin-A2/A5 double mutant mice, analysis of the laminar locations of ectopic terminations shows that the topographic maps of different RGC types are misaligned. These data lend support to the hypothesis that the retinocollicular projection is a superimposition of a number of individual 2-D topographic maps that originate from specific types of RGCs, require ephrin-A signaling, and form independently of the other maps. This article is protected by copyright. All rights reserved.
    Developmental Neurobiology 02/2015; DOI:10.1002/dneu.22265 · 4.42 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The zebrafish retinotectal projection provides an attractive model system for studying many aspects of topographic map formation and maintenance. Visual connections initially start to form between three and five days post fertilization, and remain plastic throughout the life of the fish. Zebrafish are easily manipulated surgically, genetically and chemically, and a variety of molecular tools exist to enable visualization and control of various aspects of map development. Here we review zebrafish retinotectal map formation, focusing particularly on the detailed structure and dynamics of the connections, the molecules that are important in map creation, and how activity regulates the maintenance of the map. This article is protected by copyright. All rights reserved. Copyright © 2014 Wiley Periodicals, Inc., a Wiley company.
    Developmental Neurobiology 12/2014; DOI:10.1002/dneu.22256 · 4.42 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A recent study has shown that the zebrafish tectum processes inputs from the retina tuned to ethologically relevant size classes, suggesting a role for the tectum in selecting approach or avoidance behaviours based on size-based categorization of visual targets. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Current Biology 11/2014; 24(21):R1048-R1050. DOI:10.1016/j.cub.2014.09.043 · 9.92 Impact Factor

Full-text (2 Sources)

Download
48 Downloads
Available from
May 31, 2014