Developing and Validating Methods of Assessing Retinal Function of Genetically Modified Zebrafish using Electroretinography (ERG) and Optokinetic Responses (OKR)

Abstract

Loss of photoreceptor function in the retina leads to diminished vision and eventual blindness. Retinitis pigmentosa (RP) is the most common inherited disease of the retina, affecting about 1 in 5,000 people worldwide. Although mutations of the eyes shut homolog (EYS) and KIAA1549 are a common cause of RP, they were only recently discovered and characterized in humans. As a result, much novel research is needed to describe the precise biological role of EYS and KIAA1549, their interactions, and implication in disease. These specific proteins are of interest because our lab hypothesizes that they interact in photoreceptors. Unfortunately, common mammalian models such as rodents lack EYS, so our lab has developed novel EYS knockout (KO) and KIAA1549 KO zebrafish to mimic the disease progression of RP in humans. Successful characterization of EYS KO and KIAA1549 KO zebrafish will help us better understand the function of these genes and act as a baseline for future researchers to assess the performance of potential genetic treatments developed in zebrafish. To investigate the retinal function of these zebrafish, we will use electroretinograms (ERGs), a clinical test that measures the retina's electrical activation rates in response to light stimulation. ERGs for use on zebrafish are not widely-available, thus we have developed our own system. Next, we investigated the functional vision of the EYS KO zebrafish using a visual-behavioral task. The optokinetic response (OKR) in zebrafish is a stereotyped instinct of the eye to track whole-field motion, and its presence under variable conditions can be used to discern functional vision differences between zebrafish populations. We have developed and validated an OKR system and pioneered a standardized method of assessing the presence of eye saccades in video data. By characterizing these new EYS KO zebrafish and KIAA1549 KO zebrafish, greater knowledge on the mechanism of disorder for RP will be developed. This can provide key insights for novel, clinical gene therapy interventions. Since KIAA1549 is present in mouse, visual behavioral assays have also been developed and validated to evaluate the functional vision of WT mice and KIAA1549 KO mice.