Abstract
Purpose :
Genome-wide association studies (GWAS) have linked GLIS1 variants with primary open-closure glaucoma (POAG). Notably, we have demonstrated that Glis1-deficient mice manifest progressive degeneration and dysfunction in the TM, a tissue with heightened Glis1 expression, resulting in elevated IOP—a risk factor for glaucoma. The Glis1-deficient mice, while largely exhibiting normal traits, notably develop elevated IOP as early as 2 months. Hence, Glis1-/- mice could represent a valuable model of early onset glaucoma.
Methods :
To determine the suitability of Glis1-/- mice as an early-onset glaucoma model, we conducted a comprehensive assessment using a combination of imaging, histological, and molecular methodologies. Glis1-/- mice and their control littermates were observed and evaluated up to 9 months of age. Glaucoma phenotypes assessed between 3 to 9 months.
Retinal Imaging: Live imaging of mouse eyes was performed utilizing an in vivo ocular imaging system (Bioptigen).
Histology: Eyes were embedded in plastic, and serial sections were collected and stained with Hematoxylin and Eosin to assess the status of retina and the optic nerve.
Optic Nerve and Retinal Evaluation: Optic nerves were collected from the intracranial portion and their cross-sections assessed for glaucomatous damage employing a para-phenylenediamine (PPD) staining protocol, allowing detection of axonal injury and loss. Retinal flat mounts were immunolabeled for pan-retinal ganglion cells (RGCs) using an anti-RBPMS antibody for assessing RGC morphology and quantification.
Results :
Utilizing SD-OCT, we observed progressive optic nerve excavation in Glis1-/- mice starting at 4 months, progressing in severity with age. Histological examinations revealed that apart from the loss of RGCs, thinning of the nerve fiber layer and optic nerve excavation the retinal layers of Glis1-/- eyes remained morphologically similar to age-matched control eyes. PPD staining detected axonal degeneration following IOP elevation, with the majority of optic nerves being severely damaged by 7 months of age. Glis1-/- mice exhibited significant RGC loss compared to controls, with over 50% reduction at 6 months.
Conclusions :
Our characterization of Glis1-deficient mice reveals their potential as an early-onset model mirroring hallmark features of human glaucoma. This includes elevated IOP induced by TM dysfunction, IOP-dependent optic nerve excavation, axonal degeneration, and RGC loss.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.