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Ephrin‐as are required for the topographic mapping but not laminar choice of physiologically distinct RGC types
Author(s) -
Sweeney Neal T.,
James Kiely N.,
Sales Emily C.,
Feldheim David A.
Publication year - 2015
Publication title -
developmental neurobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.716
H-Index - 129
eISSN - 1932-846X
pISSN - 1932-8451
DOI - 10.1002/dneu.22265
Subject(s) - superior colliculus , neuroscience , biology , laminar organization , ephrin , anatomy , axon , visual system , projection (relational algebra) , lamina , topographic map (neuroanatomy) , axon guidance , retina , cartography , sensory system , genetics , computer science , geography , receptor , algorithm
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 superior colliculus (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 two‐dimensional topographic maps that originate from specific types of RGCs, require ephrin‐A signaling, and form independently of the other maps. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 75: 584–593, 2015