Abstract
High acuity color vision, essential to many vertebrates, relies on cone photoreceptors in the retina. These specialized cells express light-sensitive proteins known as opsins that enable the detection of specific wavelengths of light. The spatiotemporal patterning of each opsin type has been well studied in model organisms, but the regulatory mechanisms underlying the spatiotemporal expression and maintenance of each cone type remain poorly understood. Investigating these regulatory pathways is essential for advancing our knowledge of retinal development and function. Mammals are unable to regenerate their tissues, which leads to permanent neuron loss in response to retinal damage or degenerative disease. Certain organisms, including the zebrafish, possess a remarkable capacity for regeneration of their retinal neurons. Understanding the mechanisms that enable this regenerative ability is a major area of interest, with the long-term goal of applying such insights to promote tissue regeneration in the mammalian retina and potentially reverse vision loss due to injury or degenerative conditions. In this dissertation, I begin with an overview of the visual system, discussing structure and function with a focus on the hormone mediated regulation of tandemly duplicated opsins and regenerative potential of the zebrafish neural retina. Next, I present my published work describing the time course of zebrafish retinal regeneration in response to a chemical-induced retinal lesion using electrophysiology and histology. The methods used in this study are further elucidated in Chapter 3, which details a published work describing the techniques used to chemically lesion the retina, assess for retinal damage, perform electroretinogram recordings, and perform histological analysis via retinal cryosections. Human long-wavelength sensitive (LWS) and medium-wavelength sensitive (MWS) opsin genes resulted from a tandem duplication event, which resulted in two spectrally divergent opsins. The regulation of this locus is of great interest, as LWS and MWS opsins are implicated in many retinal diseases. Zebrafish underwent a similar tandem duplication of their lws opsin genes, leading to two functionally divergent opsins, lws1 and lws2. Chapter 4 describes work in preparation for publication which aims to identify specific regions of the lws locus involved in its differential regulation. Chapter 5 continues with a discussion of future directions for the study of the lws locus and a preliminary investigation of a zebrafish transgenic line which reports TH signaling. This body of work significantly expands knowledge of retinal regeneration and the regulatory mechanisms involved in the expression of tandemly replicated opsins.