Establishing Zebrafish as an Animal Model to Study Drusen

• Author / Creator

  Humaira, Tasnuva

• Drusen are extracellular deposits that accumulate in the retina and are a hallmark of age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Sometimes drusen have also been detected in otherwise healthy eyes of younger and elderly patients. Despite their clinical significance, the underlying mechanisms that lead to drusen formation and their impact on retinal function remain poorly understood. Therefore, specific diagnostic tests and treatment are also unavailable.

  Animal models can be an essential tool for studying drusen. Zebrafish (Danio rerio), from its first published used in 1981, have emerged as a valuable model organism due to their genetic similarity to humans, ease of genetic manipulation, and fast development. They also share similarity with human eyes and visual system. Rodents are the most common, animal model for vision research. However, they are not well-suited for drusen research because rodents are nocturnal, and their retina is structurally different than the part of human retina where drusen appear. This presents some challenge with using rodents for drusen studies because drusen appears in and degenerates within cone-rich macula of human eye. Zebrafish retina, is cone-rich and more adapted to diurnal light variations, thus overcoming the challenge we face with rodents.

  This project determines the earliest age when drusen-like deposits become detectable in rp1l1-/- zebrafish using histological staining techniques. It is the zebrafish line where a mutation has been introduced into the Retinitis pigmentosa 1-like 1 (rp1l1) gene to demonstrate the ocular disease, retinitis pigmentosa. Oil Red O-stained deposits were first detected sporadically in rp1l1-/- fish at 55 days post-fertilization (dpf) and progressed to appear bilaterally in the following months. These progressively increased in size with age, increasing about 3-fold in area in fish up to 1-year post fertilization age. Coincident with the accumulating drusen, the data revealed progressive decreases in the size of the zebrafish Outer Nuclear Layer (ONL).

  Unexpectedly, drusen were also detected infrequently in older (1 year old) otherwise normal wildtype zebrafish retinas. This suggests that zebrafish might also be used to model the drusen that appear in healthy human non-AMD retinas, as well as providing the chance to explore structural components of drusen in AMD. Finally, the presence of drusen in 4-year post fertilization WT and rp1l1-/- fish supports the age-related drusen events successfully replicating into zebrafish.

  New and advanced animal models are always essential to understand human conditions – both developmental and pathological. Zebrafish is a well-accepted animal model, and this project has laid the groundwork that using the novel rp1l1-/- zebrafish can provide us with the opportunity to understand a complex polygenic condition like drusen and to explore AMD in a comprehensive manner.

• Subjects / Keywords

  • Molecular biology

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-70s3-sc23

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.