Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

First Advisor

Yuk Fai Leung

Committee Member 1

Donna M Fekete

Committee Member 2

Henry Chang

Committee Member 3

Joseph P Ogas

Abstract

Classical studies have shown that Notch-Delta signaling is essential for the maintenance of retinal progenitor cells. However, the specific roles of different Delta ligands on retinal development are not well characterized. The focus of this study was to investigate the specific functions of the Delta ligands, deltaC (Dlc) and deltaD (Dld), in zebrafish retinal development by using dlcb663 and dldtg249 mutant embryos. The retinal expression pattern of dlc and dld, determined by whole-mount in situ hybridization, demonstrated that both ligands have similar and distinct expression patterns in WT retinas throughout retinal development. In mutant retinas where dlc and dld are absent, whole-mount in situ hybridization and immunohistochemistry analyses indicated a disruption in the spatial patterning of rods and cones, as well as a stunted photoreceptor differentiation. Blue cone differentiation was affected in the dlcb663 embryos, whereas red and green cone differentiation was affected in dldtg249 embryos. In order to demonstrate the effects of a disrupted retinal development on the zebrafish visual behavior, the visual motor response (VMR) and optokinetic reflex (OKR) of mutant embryos were analyzed. The OKR showed a reduced ability of mutant embryos to detect moving objects on their visual field, whereas each mutant presented a characteristic VMR. This study demonstrated that different Delta ligands contribute to specific aspects of retinal functionality.

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