Date of Award

8-2023

Degree Type

Thesis

Degree Name

Master of Science in Biomedical Sciences

First Advisor

Dr. Arturo Bravo Nuevo

Second Advisor

Dr. Qian Chen

Third Advisor

Dr. Jocelyn Lippman-Bell

Abstract

The retina is located in the posterior aspect of the eye and is home to neurons that send electrical signals to the brain to process vision. Like all other brain areas, it undergoes a period of culling excess neurons deemed the critical period. Previous studies on the critical period have shown that supplemental oxygen decreased photoreceptor death in the retina during the critical period while hypoxic conditions increased photoreceptor death. RhoB is a small GTPase, part of the Rho GTPase family, and has been studied in the context of cancer, diabetes, and retinopathy of prematurity in regard to apoptosis, intracellular transport, and angiogenesis. Therefore, we asked the question of how RhoB -/- mice’s retina neurons would react during the critical period and aging after exposure to different oxygen concentrations during the critical period. To assess this, two groups of animals, RhoB -/- and control C57 mice, were used. TUNEL counts, retinal thickness, electroretinography (ERG), and intraocular pressure (IOP) were measured to compare how mice lacking in RhoB differed from control. In TUNEL counts, RhoB -/- exhibited significantly increased cell death when compared to control in the early phase of the critical period. At 4 weeks, RhoB -/- mice displayed significantly more GCL death compared to C57 in all oxygen conditions. At 1 year, RhoB -/- showed 4 times more death in its photoreceptors and thinner retinal layers in the ONL, INL and GCL with significance close to the optic nerve. ERG showed RhoB -/- mice have worse visual function due to lower A and B waves in times of stress like aging and hypoxia. Lastly, RhoB -/- have significantly higher IOP measurements. Therefore, it appears that RhoB -/- mice lacking RhoB GTPase are less resistant to stress and results in increased photoreceptor death.

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