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Teresa Puthussery, Kimberley Lerner, Jacqueline Gayet; Cell-type specific expression of Kv2 potassium channels in mouse and macaque inner retina. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1853.
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Differences in patterns of ion channel expression are important for shaping neural responses in parallel retinal circuits. Kv2 channels are delayed-rectifier voltage-gated potassium (Kv) channels comprised of two subunits, Kv2.1 and Kv2.2. These channels are widely expressed in the brain, but their retinal localization is not well understood. The goal of this study was to determine the cellular and circuit localization of Kv2.1 and Kv2.2 in mouse and primate inner retina.
We performed immunohistochemistry on vertical and horizontal sections of mouse and macaque retina. We used antibodies for Kv2.1 and Kv2.2 (Neuromab/UC Davis) together with a variety of antibodies that label select populations of bipolar, amacrine and ganglion cells. Confocal images were analyzed using Image J. All data are mean ± s.d.
Subsets of bipolar, amacrine and ganglion cells expressed Kv2.1 and Kv2.2. In macaque retina, Kv2.1 was concentrated in the distal axon of bipolar cells that provide input to parasol ganglion cells (DB3a and DB4 cells), as well as in rod bipolar cells. Kv2.2 was also present in DB3a and DB4 cells, but the staining was uniformly distributed in the somatodendritic and axonal membranes. Both Kv2 subunits were absent from midget bipolar cells. Kv2 channels formed giant clusters in ganglion cell membranes. Of the RBPMS+ ganglion cells in macaque retina, 22.3 ± 3.9% contained Kv2.1 (2,342 cells, 4 animals) and 98.4 ± 0.68% contained Kv2.2 (2,676 cells, 4 animals). Parasol ganglion cells expressed both Kv2 subunits whereas midget ganglion cells only contained Kv2.2. The proportions of Kv2.1+ and Kv2.2+ ganglion cells differed in mouse retina with ~100% containing Kv2.1 and 64.0 ± 2.3% containing Kv2.2 (3,495 cells, 4 mice). Of the GABA+ displaced amacrine cells in macaque retina, 55.1 ± 11% (908 cells, 4 animals) contained Kv2.1 and 61.4 ± 3% contained Kv2.2 (970 cells from 4 animals).
Kv2 channels are expressed in specific populations of inner retinal neurons. Both Kv2 subunits are expressed in bipolar cells that drive parasol, but not midget, ganglion cells. Midget and parasol ganglion cells differ in their inventory of Kv2 subunits - both cell types contain Kv2.2 but only parasol cells express Kv2.1. Our results suggest that differences in Kv2 channel expression may contribute to the distinct response properties of parallel retinal circuits.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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