- 452 views
- 395 downloads
Cryptochrome Expression in the Zebrafish Retina: Potential Implications for Magnetoreception
-
- Author / Creator
- Balay, Spencer D
-
A variety of organisms have been shown to use the Earth’s magnetic field to orient in local-spaces and to navigate long-distances. Although behavioural evidence of magnetoreception has been reported in a diverse range of taxa, the proximate mechanisms of this phenomenon have yet to be revealed. Some animals such as birds, appear to use a light-dependent radical-pair-based magnetic compass. Ancient, light-sensitive proteins called Cryptochrome (Cry) are currently the only known molecule found in vertebrates to create radical-pairs, and thus are putative receptors. Cry is associated with the visual system where it is co-localized with both short- and long-wavelength retinal cone photoreceptors in adult birds, and therefore well-suited for light-dependent magnetoreception. Unfortunately, due to the molecular inaccessibility of the avian model, Cry-cone interactions have seldom been manipulated, and the requirement of Cry for magnetoreception has yet to be tested in vertebrates. Additionally, Cry’s location in photoreceptors of other animal’s that display magnetic behaviors is largely unknown.
This thesis utilized zebrafish (Danio rerio) to test if cry was associated with cones in developing and adult fish retina. Zebrafish have six paralogs of cry and while most participate in the circadian clock, the function of cry2 and cry4 are unknown. Here, I show that cry4 is expressed in larval and adult zebrafish short-wavelength-sensitive (Ultraviolet-sensitive (UV)) cones. Using nitroreductase (NTR)-mediated cell ablation and reverse transcription quantitative-PCR (RT-qPCR), I found that cry4 expression decreased when UV cones were ablated but was unaffected when neighboring blue cones were ablated in larval and adult retina. cry2 did not appear to be expressed in UV cones and was unchanged after UV or blue cone ablation in both developmental stages. Although zebrafish magnetic behavior has only been reported in adults, this work suggests larval fish may also have the molecular framework for magnetoreception. While zebrafish are non-migratory, they can be used to model other fish that migrate long-distances. Salmonids regenerate UV cones as they prepare to migrate back to their natal streams for spawning. Currently, the functional significance of this process has yet to determined. These findings could provide one explanation for this as UV cones may enable magnetoreception via cry. In summary, I describe the localization of cry4 in the zebrafish retina towards understanding whether fish have the molecular mechanisms for light-dependent magnetoreception. -
- Graduation date
- Fall 2018
-
- Type of Item
- Thesis
-
- Degree
- Master of Science
-
- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.