Abstract
Purpose :
Neuronal homeostasis is tightly governed by the balance between the synthesis and degradation of different cellular components, ranging from macromolecules to organelles. As retinal ganglion cells (RGCs) are long-lived and post-mitotic, they are highly susceptible to accumulating misfolded protein aggregates and dysfunctional organelles. RGCs rely predominantly on catabolic processes including autophagy for quality control and maintenance of homeostasis. The primary objective of the study is to determine whether autophagy is critical for RGC function and survival, and loss of autophagy leads to neurodegeneration.
Methods :
ATG7 and ATG5 conditional knockout mice were injected with AAV2 (Null, n=13; Cre, n=13,) targeting RGCs. Pattern electroretinogram (PERG) was carried out 3 weeks post injection. The animals were euthanized following PERG, and RGC soma and axons were analyzed using whole-mount RBPMS immunostaining and p-Phenylenediamine (PPD) staining of optic nerves (ONs). Unpaired t-test was used to determine the significance between the groups.
Results :
PERG measurements revealed a significant reduction (p<0.0001) in the amplitudes of Cre-injected mice compared to the Null group indicating functional deficit following ATG7 (Null,17.5 ± 3.5; Cre, 11.2 ± 3.7) and ATG5 (Null, 20.5 ± 2.6; Cre, 11.7 ± 4.5) conditional knockout. Additionally, a 28% and 51.5% reduction in RGCs was evident with RBPMS staining demonstrating structural loss in ATG7 and ATG5 conditional knockouts respectively. Further, analysis of ON sections from these knockouts exhibited axonal neurodegeneration and gliosis as a result of impaired autophagy.
Conclusions :
Conditional Knockout of ATG7 or ATG5, key regulators of autophagy, revealed functional and structural loss of RGCs suggesting that basal autophagy is required for RGC homeostasis. In addition to the physiological standpoint, these results will improve our understanding of autophagy’s contribution towards the pathological condition, primary open angle glaucoma where RGC loss and progressive neurodegeneration are the hallmark characteristic features.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.