The morphological characterization of orientation‐biased displaced large‐field ganglion cells in the central part of goldfish retina

Abstract

The vertebrate retina has about 30 subtypes of ganglion cells. Each ganglion cell receives synaptic inputs from specific types of bipolar and amacrine cells ramifying at the same depth of the inner plexiform layer (IPL), each of which is thought to process a specific aspect of visual information. Here, we identified one type of displaced ganglion cell in the goldfish retina which had a large and elongated dendritic field. As a population, all of these ganglion cells were oriented in the horizontal axis and perpendicular to the dorsal-ventral axis of the goldfish eye in the central part of retina. This ganglion cell has previously been classified as Type 1.2. However, the circuit elements which synapse with this ganglion cell are not yet characterized. We found that this displaced ganglion cell was directly tracer-coupled only with homologous ganglion cells at sites containing Cx35/36 puncta. We further illustrated that the processes of dopaminergic neurons often terminated next to intersections between processes of ganglion cells, close to where dopamine D1 receptors were localized. Finally, we showed that Mb1 ON bipolar cells had ribbon synapses in the axonal processes passing through the IPL and made ectopic synapses with this displaced ganglion cell that stratified into stratum 1 of the IPL. These results suggest that the displaced ganglion cell may synapse with both Mb1 cells using ectopic ribbon synapses and OFF cone bipolar cells with regular ribbon synapses in the IPL to function in both scotopic and photopic light conditions.

Spatial distribution and functional integration of displaced ipRGCs

“…Displaced ganglion cells have been shown to exist in various vertebrate species, such as fish, birds, and mammals including human retina (e.g. (Bunt and Minckler, 1977;Chandra et al, 2019;Dacey et al, 2005;Dräger and Olsen, 1981;Hoshi and Sato, 2018;Mey and Johann, 2001;Nadal-Nicolás et al, 2014;Robson and Holländer, 1984;Salinas-Navarro et al, 2009b, 2009aStell and Witkovsky, 1973;Tachibana, 1978) . However, it remained unclear whether displaced RGCs represent independent cell types, an odd part of the population of regular types, or just futile remnants of disordered neuronal development.…”

Embryonic Hyperglycemia Delays the Development of Retinal Synapses in a Zebrafish Model

“…All IHC analysis was performed on zebrafish larvae exposed to high glucose on alternating days. We used antibodies specific for the CtBP domain that primarily binds to ribeye a and b proteins [ 24 , 25 ] to reveal the morphology and maturity of synaptic ribbons in 5 dpf control and hyperglycemic larvae. CtBP2 proteins were primarily expressed in the OPL of both control and hyperglycemic larvae ( Figure 2 B).…”