Characterization of the Zebrafish bug eye Mutation, Exploring a Genetic Model for Pressure-induced Retinal Cell Death

Abstract

Abstract: : Purpose: Glaucomas are complex, vision impairing diseases characterized by retinal ganglion cell death, and frequently associated with harmfully elevated intraocular pressure (IOP). Due to the complexity of glaucoma phenotypes, the molecular and genetic etiology has largely remained elusive. Zebrafish provide a powerful model organism for studying complex genetic diseases. To study the relationship between raised IOP and retinal cell death, we have isolated a zebrafish mutant, bug eye, that develops elevated IOP and retinal cell death. Methods: Pedigree analysis, visual behavioral assays, histology, electron microscopy, and intraocular pressures measurements were conducted in normal and mutant zebrafish. Results: We have described basic ocular anatomy and have established IOP measurement techniques for zebrafish. The bug eye mutation is complex requiring the interaction of at least two unlinked loci. Mutant fish are viable, but display enlarged eyes shortly after sexual maturation. Buphthalmic fish are blind, and initial analysis identified raised IOP. Wild type IOPs average 14.7±3.6 mmHg (n=4), while bug eye mutants average 32.9±16.2 mmHg (n=4). Histology and electron microscopy revealed progressive retinal cell loss, retinal disorganization, and vascular defects in the mutant eyes. Conclusions: The bug eye mutants develop enlarged eyes, elevated IOP and retinal cell loss. They provide a tractable model organism for studying cell death in eyes with elevated IOP. These studies and methods have broad implications for using this genetically powerful teleost to study glaucoma. *SWMJ is an Associate Investigator of HHMI

Keywords: animal model • genetics • anatomy