Abstract
Purpose :
Eye growth signals arising from the retina are highly responsive to light exposure and optical defocus. In myopia (short-sightedness) atypical growth signals arising from ill-defined environmental cues result in excessive eye elongation. It is believed that the retinal signals driving eye growth emerge from amacrine cells, but the mechanisms remain elusive. We have previously observed a class of nitric oxide producing amacrine cell (NOACs) in which the expression of neuronal nitric oxide synthase (nNOS) is modified in myopic eyes. Therefore we aimed to investigate the interactions between these cells and other factors known to be important in the regulation of eye growth: dopamine, retinoic acid, and early growth factor-1 (EGR1).
Methods :
Immunohistochemistry was performed on retinal slices and whole-mounted retina tissue extracted from four week-old domestic Guinea pigs (n=12) reared in white light (10am – 10pm). Antibodies used: nNOS (Sigma, 1:10000), ALDH1A2 (Abcam, 1:400), GABA (Sigma,1:100), tyrosine hydroxylase (Millipore, 1:800), CRABP (Invitrogen, 1:150), CRALBP (Abcam, 1:1000), and EGR1 (cell-signaling technologies, 1:250). Cell density was mapped from images taken from whole mounts sampled at 1 mm intervals along the 8 major radii.
Results :
All three types of NOACs (Type-1, 2 and displaced) were identified as GABAergic. Dendrites of type-1 displayed some overlap with dendrites of dopaminergic amacrine cells in layer 3 of the inner plexiform layer. A subset of type-2 NOACs expressed the cellular retinoic acid binding protein (CRABP). However, NOACs did not colocalise with labelling for cellular retinaldehyde binding protein (CRALBP) or retinaldehyde dehydrogenase 2 protein (ALDH1A2). Type-1, type-2 and a subset of displaced nNOS DACs labelled for the growth factor EGR1. Interestingly, the density of displaced NOACs was inversely correlated with that of cells within the retinal ganglion cell layer labelling for EGR1.
Conclusions :
The bio-molecular profiles of NOACs overlap with factors implicated in the regulation of eye growth. The opposing relationship between nNOS and EGR1, suggests that nitric oxide may regulate EGR1, a gene transcription factor important in the regulation of ocular growth.
This is a 2020 ARVO Annual Meeting abstract.