The M6 cell: A small-field bistratified photosensitive retinal ganglion cell |
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Authors: | Lauren E Quattrochi Maureen E Stabio Inkyu Kim Marissa C Ilardi P Michelle Fogerson Megan L Leyrer David M Berson |
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Institution: | 1. Department of Neuroscience and Carney Institute for Brain Science, Brown University, Providence, Rhode Island;2. Department of Cell & Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado |
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Abstract: | We have identified a novel, sixth type of intrinsically photosensitive retinal ganglion cell (ipRGC) in the mouse—the M6 cell. Its spiny, highly branched dendritic arbor is bistratified, with dendrites restricted to the inner and outer margins of the inner plexiform layer, co-stratifying with the processes of other ipRGC types. We show that M6 cells are by far the most abundant ganglion cell type labeled in adult pigmented Cdh3-GFP BAC transgenic mice. A few M5 ipRGCs are also labeled, but no other RGC types were encountered. Several distinct subnuclei in the geniculate complex and the pretectum contain labeled retinofugal axons in the Cdh3-GFP mouse. These are presumably the principle central targets of M6 cells (as well as M5 cells). Projections from M6 cells to the dorsal lateral geniculate nucleus were confirmed by retrograde tracing, suggesting they contribute to pattern vision. M6 cells have low levels of melanopsin expression and relatively weak melanopsin-dependent light responses. They also exhibit strong synaptically driven light responses. Their dendritic fields are the smallest and most abundantly branched of all ipRGCs. They have small receptive fields and strong antagonistic surrounds. Despite deploying dendrites partly in the OFF sublamina, M6 cells appear to be driven exclusively by the ON pathway, suggesting that their OFF arbor, like those of certain other ipRGCs, may receive ectopic input from passing ON bipolar cells axons in the OFF sublayer. |
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Keywords: | cadherin ganglion cell photoreceptors intrinsically photosensitive lateral geniculate nucleus melanopsin retinal ganglion cells RRID: AB_11214110 RRID: AB_2079751 RRID: AB_1608077 RRID: AB_221570 RRID: AB_2536190 RRID: AB_2534105 RRID: AB_142540 RRID: AB_141844 RRID: AB_2535792 RRID: AB_141637 RRID: AB_143165 RRID: AB_141359 RRID: AB_141930 RRID: AB_2716806 |
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