Abstract
Purpose :
Glaucoma is the most commonly acquired optic neuropathy and the second leading cause of irreversible blindness globally. While the primary cause of glaucoma remains unknown, pan-genetic and pan-proteomic studies have revealed ephrin signaling as one of the most highly dysregulated signaling pathways in the pathophysiology. In this study, we hypothesize that the synaptic instability, neurite retraction, and inner plexiform layer thinning that ultimately lead to glaucoma are initiated in part by the reactivation of repulsive ephrin forward signaling
Methods :
We used a commonly studied animal model of glaucoma, the DBA/2J mouse along with its genetically matched control DBA/2J-Gpnmb+/SjJ which do not develop glaucomatous defects. Animal retinas were dissected from young (2mo) and old (20mo) mice to elucidate temporal changes in the phosphoproteome profile as the animals progress into patent glaucoma. Retinal proteins were isolated from retinal tissue using a combination of mechanical homogenization and enzymatic digestion. Protein quantification was performed using the DC Protein Quantification Assay and 250ug of total protein per sample was used to profile activated receptor tyrosine kinase including ephrin receptors using Proteome Profiler Mouse Phospho-RTK Array Kit. Phosphorylation intensity was measured using the fluorescent intensity quantification tool on ImageJ
Results :
Our results show that ephrin receptor phosphorylation is significantly increased in the 2-month-old DBA/2J for the EphA1, EphA2, EphA6, EphA7, EphB2, and EphB6 receptors (p=<0.05) when compared to the genetically-matched controls. At 20 months of age, the EphA1, EphA2, EphA3, and EphA6 receptors remained significantly phosphorylated (p=<0.05) as compared to controls. Interestingly, there were no age-dependent differences observed in Eph-receptor phosphorylation in this mouse model. Immunohistochemistry confirmed the expression of the phosphorylated form of the Eph receptors identified in the inner retina
Conclusions :
These results indicate that Ephrin receptor activation and repulsive forward signaling may play a role in the neuropathic progression of glaucoma. The results further demonstrate that Eph activation can be observed as early as 2 months of age prior to any manifested visual dysfunction in this model. Further research is ongoing to fully characterize the role of reactivated Ephrin receptors in the pathogenesis of glaucoma
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.