MSc Exit Seminar – Abiramy Karunendiran (Stewart/Barzda labs)

MSc Exit Seminar

Tuesday September 22nd, 1:10 pm – HSC 332, University of Toronto at Mississauga

Abiramy Karunendiran (Stewart/Barzda labs)

“Measuring Changes in Membrane Structure and Rhodopsin levels in Drosophila Melanogaster Retinas using THG Microscopy”

Abstract

Third harmonic generation (THG) microscopy is a valuable imaging modality that can be used to reveal structural information in a biological system without staining. THG signal can be observed at an interface between two different refractive indices or third-harmonic susceptibilities and is augmented in the presence of molecules with long carbon chains. Previous studies have established that carotenoid compounds are ideal for THG microscopy. I therefore sought to determine whether THG from endogenous carotenoid-derived compounds, such as retinal in photoreceptors, could serve as a platform to develop THG microscopy for developmental studies.  I used the developing compound eye of Drosophila melanogaster as a model system because of its well-known anatomy, developmental profile, and the availability of genetic tools. The Drosophila eye contains 750-800 ommatidia, each housing photoreceptor neurons that utilize the visual pigment rhodopsin, G-protein coupled receptor containing retinal, for photo-transduction. In the first series of observations THG microscopy was shown to be an effective tool for monitoring normal photoreceptor development. In a second series of experiments, using dietary restrictions or genetic alleles that perturb rhodopsin expression, the absence of rhodopsin during pupal development causes membrane atrophy, resulting in photoreceptor degeneration. The results of this thesis demonstrated that THG microscopy can detect rhabdomere degeneration earlier than fluorescence microscopy. THG intensities measured throughout pupal development showed a distinct age-dependent curve, which changes in the absence of rhodopsin. In conclusion, THG microscopy can be used to monitor retinal development and presents itself as a new technique to detect retinal degeneration. Further development of this technology could aid in the early detection of human retinal degeneration syndromes, particularly those linked to mutations of human rhodopsin.