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Rana El-Danaf, Andrew Huberman; Distinct retinal ganglion cell subtypes exhibit diverse topographic characteristics across the mouse retina. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2585.
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© ARVO (1962-2015); The Authors (2016-present)
As the sole output neurons of the retina, retinal ganglion cells (RGCs) possess an essential role for visual signal processing. Their loss is detrimental, as in neurodegenerative disorders like glaucoma- a leading cause of blindness. In recent years, the mouse has emerged as a premiere model for probing visual system disease, structure, and function. The general belief is that mice possess a relatively even topographic distribution of RGCs contrary to other species. Knowing that in mouse there are ~30 subtypes of RGCs each responding best to a specific feature in the visual scene, do different RGC subtypes possess topographic variations across the retina?
Different transgenic mouse lines were used to target five genetically-tagged RGC subtypes. These include: transient Off- alpha (tOff-α) RGCs labeled in the CB2-GFP transgenic mouse line (Huberman et al., 2008); posterior tuned On-Off direction selective RGCs (pOn-Off DSGCs) labeled in the TRHR-GFP transgenic mouse line (Rivlin-Etzion et al., 2011); Non-image forming “On” (NIF-On) and Non-image forming “diving” (NIF-diving) RGCs labeled in the Cdh3-GFP transgenic mouse line (Osterhout et al., 2011); and the W3-RGCs labeled in the TYW3 transgenic mouse line (Kim et al., 2010; Zhang et al., 2012). Using sharp electrodes, we injected fluorescent dyes intracellularly to fill individual RGCs at specific locations from across the retinal surface. We then evaluated their soma size and dendritic arbor extent according to their specific location using FIJI software.
A total of 418 intracellularly labeled RGCs were analyzed. We discovered that 3/5 RGC subtypes exhibited dramatic topographic variations in arbor size. Each pattern of variation was distinct according to RGC subtype: pOn-Off RGCs displayed smaller dendritic fields in the ventral retina (r2 = 0.5648), while smaller NIF-On RGCs were present in the nasal retina (r2 = 0.5822) and W3-RGCs showed eccentricity related changes (r2 = 0.5356).
Our results provide increasing evidence of the presence of topographic variations of RGC subtypes in the mouse retina; and that visual space is encoded in a region-specific manner such that certain visual features are sampled far more densely at some locations than others. A clearer understanding of how these different RGC subtypes are organized leads to insights into their role in visual processing, behavior and disease.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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