Abstract
Purpose: :
Arrestin domain-containing (ArrDC) proteins are early ancestors of the visual arrestins. Two of these, thioredoxin-interacting protein (TXNIP) and ArrDC3, have been shown to function in diverse systems in mammals - TXNIP in glucose metabolism and oxidative stress response, ArrDC3 in receptor downregulation. We previously showed retinal localization of both proteins. The purpose of this project is to determine circadian and light-dependent localization of TXNIP and ArrDC3 in the mammalian retina using immunohistochemistry.
Methods: :
In circadian experiments, adult C57BL/6J mice were dark-adapted overnight and sacrificed before, at and after subjective dawn while being retained in the dark. In light/dark experiments, adult C57BL/6J mice were dark-adapted overnight. They were then either sacrificed or light-adapted one hour and sacrificed. Retinal sections were obtained from these mice and probed with antibodies to TXNIP (mouse monoclonal, generated in our laboratory) or ArrDC3 (rabbit polyclonal, Abcam). Visualization was performed via spinning disc confocal fluorescence microscopy.
Results: :
The localization of TXNIP was found to change within the retina during the circadian cycle: before dawn, TXNIP was primarily localized in ganglion cell and inner plexiform layers; at dawn, its localization increased in the outer plexiform layer; by one hour after dawn, TXNIP localization predominated in the ganglion cell and inner plexiform layers. ArrDC3 may change its localization in the retina in a light-dependent manner. In dark-adapted retinas, it was distributed throughout the retina in inner and outer plexiform layers, as well as inner nuclear and ganglion cell layers; in light-adapted retinas, ArrDC3 immunoreactivity increased in the inner nuclear layer.
Conclusions: :
TXNIP localizes in the retina in a circadian manner - its broad increase in the inner retina after dawn suggests presence in amacrine cells and a role in retinal rewiring. ArrDC3 appears to increase in the retina in a light-dependent manner - its change in localization in the inner nuclear layer suggests a role in modulation of inner retina response to light exposure.
Keywords: immunohistochemistry • retina: distal (photoreceptors, horizontal cells, bipolar cells) • retina: proximal (bipolar, amacrine, and ganglion cells)