School of BioSciences - Theses

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    Estrogenic endocrine disruptors directly impact erectile tissue development and function
    Cripps, Samuel Michael ( 2024-02)
    Erectile Dysfunction (ED) is one of the most common chronic conditions affecting males globally. ED is characterised by the repeated inability to gain or maintain erection sufficient for satisfactory sexual performance, which in turn can impact fertility, quality of life, and even serve as an early indicator for cardiovascular disease. The economic burden of ED treatment in the U.S. increased by a staggering $145 million between 1994-2000. An increased ageing population can partially explain the increasing prevalence of ED. However, exceptional rates of ED also among younger men (<40) suggests the existence of other, independent risk factors. A balance of androgens to estrogens controls the development and physiology of the erectile tissue within the penis. Exposure to endocrine disrupting chemicals (EDCs) is known to impact penis development and may independently increase the risk of ED. However, due to lack of sufficient research, a role for EDC exposure in ED aetiology remains unknown. Further limiting our ability to investigate such a link is an incomplete understanding of how endogenous hormones regulate erection physiology, particularly estrogen. Thus, in the present thesis, I investigated whether EDC exposure can disrupt development and function of the mouse erectile tissue. To provide a foundation for these findings, I also defined the role of endogenous estrogen in mouse erection physiology. Here, I exposed the isolated embryonic mouse penis to environmentally relevant levels of estrogenic-EDCs, demonstrating ectopic gene expression related to erectile tissue patterning, thus potentially increasing risk of ED in adulthood. To functionally validate these findings, I demonstrate that mice exposed to a potent estrogenic-EDC throughout development exhibit impaired ex vivo contractility of the primary erectile tissue, the corpus cavernosum (CC), via direct estrogenic interference with the target tissue. I also define a prominent role for endogenous estrogen in mouse CC physiology, conforming with its response to estrogenic-EDCs. Lastly, I attempted to establish a novel protocol for modelling and testing mouse erection in vivo, although further research is required. The findings here strongly demonstrate that estrogenic-EDC exposure is a risk factor for ED, as well as improve our understanding for the role of hormones in erection physiology. The present thesis provides valuable incentive for more stringent regulation of our exposure to estrogenic-EDCs which are already pervasive in the environment.
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    The effects of bisphenol A and atrazine on male development in the tammar wallaby (Macropus eugenii)
    Cunha Cyrino, João ( 2024-03)
    The mammalian gonad originates as a bipotential gonadal primordium before it differentiates into either a testis or ovary. During the process of differentiation, the gonad can differentiate either into a testis or ovary under the influence of genetic, hormonal and environmental influences. Both androgens and estrogens are critical to this process. Perturbations of these signals at critical stages of development by environmental endocrine disruptors (EEDs) can lead to gonadal sex reversal or gonadal dysgenesis. Xenoestrogens are EEDs that can bind to estrogen receptors, acting via multiple pathways, including the metabolism of reproductive steroids of the androgen synthesis pathway. EEDs are believed to contribute to the increasing incidence of disorders of sex development (DSDs) in vertebrates, including humans. Two of the commonest EEDs are bisphenol A (BPA), used in the production of plastics) and atrazine (the most commonly used herbicide in Australia). This study investigated the effects of bisphenol A and atrazine on testis and phallus differentiation in the tammar wallaby (Macropus eugenii). The tammar is an ideal mammalian model to study sexual development, because all sexual differentiation takes place after birth, when the developing young animals can be handled and treated while still in their mother’s pouches at stages that reflect the in utero stages of eutherian mammals. Developing tammar young were treated daily with BPA (50 microgram/kg/day), from day 0 postpartum (pp) to day 10 pp or from day 20 pp to day 40 pp, and atrazine (5 mg/kg/day), from day 20 pp to day 50 pp, during the male programming window (MPW). The BPA group was analysed immediately after the last treatment on day 10 pp and day 40 pp. Half of the atrazine group were analysed after treatment from day 20 to day 50 pp and the remainder at day 150 pp to assess long term effects. To analyse the role of estrogen on normal male differentiation, an additional group was treated daily with an estrogen receptor degrader, fulvestrant (1 mg/kg) between days 20 to 90 pp and analysed at day 150 pp. BPA treatment significantly downregulated the expression of SOX9 at day 10 pp, reduced the number of Sertoli cells at day 10 pp and downregulated androgen receptor (AR), SOX9, DHH, and androgen pathway genes STAR, CYP17A1, POR, CYP11A1 and PTCH1 at day 40 pp in testes. Atrazine treatment significantly downregulated the expression of SOX9 and NR2F2 and upregulated POR expression at day 50pp in testes. Atrazine treatment also significantly upregulated DHH expression at day 150 pp. Fulvestrant treatment significantly downregulated AR expression in testis. The phallus at day 150 pp was significantly shorter than control phalluses after atrazine and fulvestrant treatments. The results from this research using an alternative model species to examine the effects of EEDs on sexual development highlight the importance of androgen-oestrogen balance for normal sexual male development of the pouch young as it does in developing eutherian mammals (Hess et al, 2021). Disturbance this balance after exposure to EEDs affects the key male sexual differentiation genes and interferes with normal testis and phallus development in the developing tammar.
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    Mechanical control of Arabidopsis thaliana seed development
    Bauer, Amélie ( 2023-10)
    Plant morphogenesis is the result of biochemical and mechanical interactions between cells and tissues. The implications of mechanical signals in the control of cellular processes in plants is well characterized, but their contribution to organ shape acquisition remains to be elucidated. Arabidopsis seeds, whose growth depends on mechanical interactions between two genetically and physically distinct compartments, the endosperm and the seed coat, allowed me to study the contribution of mechanical forces to the control of plant organ shape. During my thesis, I have shown that seeds exhibit two distinct growth phases, an initial phase of anisotropic growth followed by a phase of isotropic growth, and that this growth pattern depends on the mechanical properties of the outer integument of the seed coat. Thanks to the development of new technics of in vitro culture of developing seeds, I have shown that a specific population of cells in the outer integument controls the growth of the seed. Furthermore, I have demonstrated that mechanical signals control the anisotropic growth of these cells by organizing cortical microtubules so that cellulose can be deposited in the walls of the adaxial epidermis of the seed coat according to shape-driven stresses. Finally, I demonstrated that the transition from anisotropic to isotropic growth is not initiated by the differentiation of the load-bearing walls of the adaxial epidermis, but rather by a loss of microtubule organization in the outer walls of the integument of the abaxial epidermis.
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    Discovering synaptotagmins as unexpected mediators of sugar signalling in Arabidopsis: insights from a chemical genetic screen
    Li, Xiang ( 2024-01)
    Sugars are crucial primary metabolites and signalling molecules that contribute to plant growth and development. Understanding plant sugar signalling helps improve plant adaptability to different energy situations, which would potentially contribute to agriculture. However, the central role of sugars in cell function has made traditional genetic approaches difficult to define the molecular pathways of sugar signalling, either due to mutant lethality or gene redundancy. In my PhD study, a chemical genetic approach was taken to overcome these limitations and uncover novel components of sugar signalling. From a high-throughput luciferase-reporter screen of a pharmacologically active small molecule library, 68 chemicals emerged as modifiers of sugar-activated circadian gene expression in Arabidopsis seedlings. The subsequent comprehensive analysis of four selected hits, including an assessment of their effects on sugar-dependent phenotypes, transcriptome, and primary metabolome, indicate known and unknown sugar signalling pathways. One of these chemicals, pentamidine isethionate (PI), known to target calcium (Ca2+)-related proteins in animal cells, was selected for in-depth investigation. PI was confirmed to robustly disrupt Ca2+ dynamics and effectively suppress cytosolic Ca2+ concentrations elevated by sucrose, mirroring the effects of a calmodulin antagonist and a Ca2+ pump inhibitor. Thermal protein profiling and subsequent in vitro binding assays support a direct interaction between PI and SYNAPTOTAGMIN 1 (SYT1). Notably, the double mutation of SYT1 and SYT5, or the triple mutation of SYT1, SYT5 and SYT7, significantly reduced sugar-activated circadian gene expression. Split-luciferase assays confirmed the physical interaction between SYTs and key players in calcium signalling, including Ca2+ channels and calmodulin/calmodulin-like proteins. These findings shed light on the intricate interplay between sugar signalling and calcium dynamics, with SYTs emerging as previously unexpected mediators in Arabidopsis.
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    Natural history and the effects of artificial light at night in an urban-exploiting orb-weaving spider
    Willmott, Nikolas John ( 2024-01)
    Spiders are the most speciose and abundant lineage of terrestrial predators on the planet. They play vital ecological roles as major consumers of insects across habitat types, and many spider species are now urban exploiters, taking advantage of the resources afforded by anthropogenic change. However, the degree to which the stressors present in these environments, including artificial light at night (ALAN), affect their behaviour, development and physiology remains largely untested. In this thesis, I explore how the natural history of spiders can help us understand urban exploitation, and examine some of the effects of ALAN on one of these important urban predators, the nocturnal Australian garden orb-weaving spider (Hortophora biapicata). My thesis begins with a general introduction (Chapter 1), outlining the rationale for my project. The core of the thesis is then divided as follows. In Section I (Chapters 2 and 3), I explore the current knowledge of urban exploitation. I start with a review of the ways in which a broad range of animals are able to exploit anthropogenic change despite the multitude of stressors present in these environments, how this exploitation shifts species interactions, and the likely ecological consequences (Chapter 2). Animals exploit anthropogenic resources such as abundant food sources and novel habitats, and the resulting shifts in species interactions can further benefit some species. However, this has costs such as decreased biodiversity, poorer food security, and increased spread of disease. Following this, I present a review of the urban ecology of spiders broadly (Chapter 3), highlighting which spiders are successful in cities, which urban habitats they occupy, and the many traits that can facilitate their success. This review establishes an important question at the centre of this thesis: why are some spiders more successful than others at exploiting urban habitats? Section II (Chapters 4 – 7) presents a case study of a particular urban-exploiter, H. biapicata. This section starts with a description of the natural history of H. biapicata, including their morphology, development, foraging, and mating (Chapter 4). This chapter highlights important traits for their urban exploitation, including generalist habitat and dietary preferences, and an ability to change colour between moults to camouflage on new surfaces. Supporting this, I then explore the flexibility they exhibit in foraging and mating behaviours, and discuss how an orb-weaver performing these tasks without an orb-web provides insight into the evolution of web loss (Chapter 5). The next two chapters move on from natural history to explore the effects of ALAN on these spiders. First, I test the impacts of ALAN exposure on development and climbing performance, highlighting the importance of the timing and duration of ALAN exposure: ALAN accelerates juvenile development but prolongs subadult development, and the resulting morphological shifts may impact climbing speed and other behaviours (Chapter 6). Second, I test the effects of ALAN on neuroanatomy in garden orb-weavers, finding that even short-term ALAN exposure negatively impacts brain volumes (Chapter 7). In particular, I find a negative effect of ALAN on the volume of the primary eye visual pathway, which is associated with the synthesis of melatonin. Melatonin is an important hormone in the brain, the suppression of which by ALAN is thought to be a major driver of the impacts of ALAN in general, potentially providing insight into both the mechanisms and consequences of these effects. Finally, I conclude my thesis with a general discussion that links natural history and responses to ALAN to urban exploitation in H. biapicata, explores how these findings can inform our understanding of the success of other animals in cities, and highlights important areas for future research (Chapter 8). Australian garden orb-weavers are charismatic and ecologically important predators across Australia, yet they are symbolic of the general lack of research for spiders in urban areas. The findings in this thesis convey the importance of natural history research, the value of both behavioural experiments and recent technological advancements for understanding biological processes, and the need to bridge the gap in knowledge about these vital but underappreciated predators. This not only improves our knowledge about spiders in cities, but because urban ecology is often taxonomically limited, will also help to develop more robust theory and predictions for the future of animals in a changing world.
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    Bioengineering coral-microalgae symbioses to improve the thermal bleaching resilience of adult corals
    Scharfenstein, Hugo ( 2023-12)
    Tropical coral reefs are hotspots of marine biodiversity valued for their ecological, socioeconomic and cultural significance. These ecosystems are supported by reef-forming corals (Scleractinia), which rely on photosymbionts (Symbiodiniaceae) for nutrition. Under stress, this intricate symbiosis can break down, resulting in coral starvation and possibly death. Vast swathes of coral reefs have been lost to anthropogenic activity. In the last decade, marine heatwaves – exacerbated by climate change – had the most widespread and devastating impact on coral cover. At current warming rates, coral reefs as we know them are projected to disappear before the turn of the century. To avert this decline, (human)-assisted evolution of coral thermal tolerance is actively researched as a strategy to mitigate worsening coral loss to marine heatwaves. Host-centric breeding and microbial manipulation methods are being explored to achieve this objective. This thesis focused on the enhancement of coral thermal tolerance through the manipulation of their algal symbiont communities. Algal symbiont manipulation is founded on the knowledge that coral thermal tolerance is largely underpinned by their Symbiodiniaceae community. Using experimental evolution, Symbiodiniaceae thermal tolerance can be enhanced in vitro. Preliminary studies demonstrated that introduction of heat-evolved photosymbionts into coral early life stages can boost host performance during thermal stress, with no apparent trade-off. However, key knowledge gaps need to be filled prior to the implementation of this strategy, some of which are addressed in this thesis. Chapter 1 provides an introduction to the coral-algal symbiosis, threats faced by corals, progress made in algal symbiont manipulation using experimentally evolved Symbiodiniaceae and the hurdles to implementation. In Chapters 2 and 3, novel strategies to increase the thermal tolerance of photosymbiont cultures are assessed. Mutagenesis prior to thermal selection yielded increased thermal tolerance, but it also led to trade-offs in growth and photochemical efficiency (Chapter 2). Selection under diurnal temperature fluctuations was identified as a promising strategy to experimentally evolve Symbiodiniaceae thermal tolerance (Chapter 3). In Chapter 4, I optimise a method (chemical bleaching) to remove the native photosymbionts from adult corals. I then demonstrate that a taxonomically diverse range of coral species can establish new symbioses with cultured Symbiodiniaceae, when these are heterologous to the host. In a team effort, novel pairings between adult corals and heat-evolved photosymbionts were generated and subjected to a simulated heatwave. In Chapter 5, I investigate the transcriptomic responses of these symbioses to heat. I identify a dampened response of heat-evolved photosymbionts to thermal stress, characterized by a reduced expression of oxidative stress and cellular damage response pathways. In Chapter 6, recommendations are provided to progress the experimental evolution of Symbiodiniaceae for coral reef restoration, and a preliminary assessment is made on the efficacy of heat-evolved photosymbiont lineages to improve adult coral thermal tolerance. Remaining challenges to the implementation of this strategy are also discussed. Overall, this thesis reduces the barriers to implementation of algal symbiont manipulation by delivering novel strategies for experimental evolution, and provides molecular evidence of reduced susceptibility of heat-evolved photosymbionts to thermal stress when in symbiosis.
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    Conservation of freshwater macroinvertebrates through molecular methods
    Tsyrlin, Edward ( 2023-09)
    Freshwater macroinvertebrates are a diverse group of aquatic animals that lack backbones, including insects, worms, crustaceans, and molluscs, with sizes larger than one-third of a millimetre. For over a century, this group has primarily served as an indicator of stream health, and for practical reasons, have been typically identified at the family level. While potentially suitable for generic ‘waterway health’ assessments, the recent evidence of the biodiversity loss within freshwater ecosystems globally, requires reliable methods that go beyond the family level to more accurately measure biodiversity, including species richness and composition within this group. To address this need, in Chapter 2, Marxan conservation planning software was used to analyse a dataset collected from 140 sites in Greater Melbourne, Australia, spanning from 1993 to 2009. Our analysis demonstrated the inadequacy of the family-level data analysis in assessing species-level diversity. Specifically, the minimum number of sites required to observe all families or all species in Greater Melbourne was compared to show that the use of family-level data leads to an insufficient sampling effort for the purpose of biodiversity assessments. Furthermore, the selection of 17% and 50% of optimal conservation sites using family-level data versus species-level data revealed that the use of family-level data would result in important omissions, jeopardizing the conservation of rare species in the Melbourne area. The adoption of DNA metabarcoding as a routine species identification method is advocated for biomonitoring, including biodiversity assessments. This approach offers greater insights into local and regional biodiversity values, facilitates the detection of subtle changes in site community composition, and reinvigorates the study of species-level taxonomy among freshwater macroinvertebrates. Subsequent studies in this thesis focus on employing molecular techniques to enhance our understanding of the biodiversity and taxonomy of critically endangered and poorly known freshwater macroinvertebrates. Chapter 3 aimed to improve our knowledge of the distribution of two endangered amphipod species, Austrogammarus australis and Austrogammarus haasei, also known as Dandenong and Sherbrooke amphipods, within the Dandenong Ranges, Victoria, Australia. While the previous delineation of A. haasei was well supported by the DNA analyses, A. australis was separated into six distinct genetic lineages. Three other genetically distinct groups were found outside of the Dandenong Ranges. Further research is required to taxonomically classify these lineages, potentially leading to changes in the conservation status and management priorities for these groups. This study highlights the value of DNA barcoding techniques for detecting cryptic species, particularly when these species already hold conservation significance. In Chapter 4, DNA barcoding was also employed to detect environmental DNA (eDNA) of another critically endangered freshwater invertebrate, the Mount Donna Buang wingless stonefly (Riekoperla darlingtoni), to potentially identify new populations outside its known range. The survey revealed two new localities located 2.5 km west of previously known populations, expanding the extent of occurrence to 0.37 square km, across a total of five localities. A significant decline in the abundance of the main population correlated with climate warming. This study demonstrated that eDNA survey methods are sensitive and reliable for detecting freshwater invertebrate species occurring at low densities and difficult to sample habitats, compared to conventional methods. These results provided the necessary data for a submission to list the species under the Australian federal Environment Protection and Biodiversity Conservation Act (EPBC) 1999. The study also contributed to a case to protect the species from a proposed development within its range and attracted international recognition to this unique and vulnerable species through the IUCN. Chapter 5 addresses the common challenge of associating aquatic juvenile and terrestrial adult life stages. DNA barcoding has the advantage of reducing the need for rearing juvenile stages by associating both stages through their DNA. Additionally, DNA data facilitated the examination of relationship among the species in this study. This approach was applied to associate larval stages with previously described adults and to redescribe the larval stage of the diving beetle Chostonectes nebulosus. An identification key to all known Chostonectes was constructed using morphological characters. The increasingly pivotal role of DNA methods in detecting and discovering freshwater macroinvertebrate species is highlighted throughout the manuscript. These methods are expected to greatly improve the assessment and management of invertebrate diversity, laying a solid foundation for making well-informed decisions in conservation management and shaping evidence-based environmental policies.
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    The influence of circadian clock variation on local adaptation in Arabidopsis and agronomic traits in wheat
    Buckley, Christopher Robert ( 2023-11)
    Plants have evolved diverse mechanisms to cope with changes in their environment. Among the most important of these, the plant circadian clock adjusts physiology and development in response to daily and seasonal environmental rhythms. The cues perceived by plant circadian clocks are non-uniform across the biogeographical environment, and variation of circadian function is required between and within species. The overarching aim of this thesis was to identify how this functional clock variation arises in plants. Extant phenotypic variation in circadian rhythms across a naturally occurring species, Arabidopsis thaliana, and a cultivated species, bread wheat (Triticum aestivum), was quantified and compared. The respective contributions of this variation to local adaptation in Arabidopsis and agronomic traits in wheat were rigorously assessed. In Chapter 2, a transient luciferase imaging assay was used to measure circadian rhythms of 287 natural Arabidopsis accessions. Through genome-wide association mapping, three SNPs were identified in the evening-expressed clock gene EARLY FLOWERING 3 (ELF3) that were highly associated with variation in circadian period. Accessions harbouring these SNPs primarily occupy continental climates of Eastern Europe and Central Asia, and through physiological and population genetic analyses, evidence is provided that ELF3 has aided local adaptation to highly seasonal climates. The circadian rhythms of elite Australian wheat cultivars were measured using delayed leaf fluorescence in Chapter 3, and a large range in circadian period was detected. By leveraging existing and novel clock gene markers, specific combinations of clock gene alleles (chronotypes) were defined that are associated with circadian period. To test the importance of circadian rhythm variation to agricultural traits, the timing of leaf senescence and grain nutrition traits were measured across the same cultivars, and strong associations with circadian period were observed. A specific effect on timing of senescence and grain protein content was found for a widespread deletion in TaELF3-D1 using pairs of near-isogenic lines (NILs). To define the global transcriptional response of circadian rhythms to senescence, in Chapter 4 48-hour ‘circadian transcriptomes’ were generated in both mature and senescent flag leaves. This analysis revealed that the output of the clock expands and diversifies at senescence, and this response is associated with increasing rhythmicity of WRKY transcription factor expression. The average circadian period of transcripts shortens by 0.5 h in senescent tissue, akin to previous studies of circadian rhythms during ageing. Interestingly, the pace of circadian oscillator genes is largely unchanged. Instead, clock genes are enriched amongst transcripts that exhibit significant advancement of phase, which is perhaps a driver of the changing period of global gene expression. These findings demonstrate abundant phenotypic variation in the circadian clocks of naturally occurring and domesticated plant species. This variation is not only consequential for traits related to seasonal development (e.g. flowering or senescence); it can also have pleiotropic effects on traits like response to high temperature and nutrient use efficiency. Clock gene variation has been co-opted by the forces of natural and artificial selection and thus holds promise for the finetuning of agricultural traits in future changing environmental conditions.
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    Development of bacterial probiotics to increase thermal bleaching tolerance of corals
    Doering, Talisa ( 2023-12)
    Coral reefs host >30% of all marine eukaryotic species and hold significant ecological, economic, cultural and spiritual value. However, coral reefs are vanishing due to climate change-induced coral bleaching (i.e. the loss of photosymbiotic algae from the coral tissues) and mortality. Current models predict that coral reefs will be lost within this century if no action is taken. Besides reducing greenhouse gas emissions, the development of strategies that improve coral thermal tolerance is imperative as long-lived corals are not likely to naturally adapt in time to current rates of ocean warming. The health and survival of reef building corals depend on the symbioses with a diversity of microorganisms, such as photosynthetic algae and bacteria. Within the scope of assisted evolution approaches for corals, the manipulation of the coral bacterial microbiome via the use of probiotics, i.e. the addition of beneficial living microorganisms to improve host fitness, is still at the beginning. With the overall objective of developing bacterial probiotics to mitigate bleaching, this thesis (1) examined the cellular mechanisms of coral bleaching in two cnidarian models, the sea anemone Exaiptasia diaphana and the scleractinian coral Galaxea fascicularis, (2) identified G. fascicularis as a new coral model for developing bacterial probiotics, (3) cultured and genomically identified G. fascicularis-associated bacterial probiotic candidates and their traits, and (4) examined uptake and temporal association of four probiotic candidates with the coral host over 5.8 months. The findings of this thesis verified a key role of reactive oxygen species (ROS) in thermal bleaching of G. fascicularis and demonstrated a diverse potential of associated bacteria to mitigate bleaching, for instance through ROS-scavenging. Further, my findings demonstrated a potential of the probiotic strains Endozoicomonas sp., Ruegeria sp. and Roseibium sp. to remain associated with the coral for one to at least six months post-inoculation under ambient conditions. Further study is required to test whether these can confer thermal bleaching tolerance to the coral host. This thesis has provided important new knowledge that will help assess whether bacterial probiotics is a viable intervention for coral reefs.
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    Modelling gene-environment interactions for myopia development in zebrafish
    Xie, Jiaheng ( 2023-10)
    Myopia prevalence is increasing dramatically and is expected to affect up to 5 billion people by 2050. Myopia occurs when excessive eye growth leads to the light sensing retinal photoreceptors being located behind the visual input focal plane, resulting in blurred distance vision. It is thought that prolonged exposure to aberrant visual environments impairs emmetropisation processes leading to a mismatch between eye size to its optical power. Therefore, myopia can be induced environmentally in animal models by manipulating visual cues. There is ample evidence that emmetropisation relies on gene-environment interactions, but the underlying mechanisms remain largely unknown. Recent human genome-wide association studies (GWAS) have identified a large number of novel genetic variants associated with myopia. To understand the role of these genes in myopia development, high-throughput vertebrate models are needed for large-scale in vivo investigation of genes-environment interactions. In this project, a high-throughput gene manipulation and multi-level analysis platform was developed to show that modifying a GWAS-associated gene pdzk1, which has been linked to visual endophenotypes (e.g., contrast sensitivity) of neurodevelopmental disorders (e.g., schizophrenia and autism), resulted in zebrafish visual dysfunction (optomotor response and electroretinography; Chapter 2). Using a novel dark-rearing paradigm, robust myopia phenotypes were generated, with clear refractive anomalies as well as functional and anatomical sequalae (Chapter 3). Next, a CRISPR approach was employed to modify a GWAS-identified myopia-risk gene, EGF containing fibulin extracellular matrix protein 1 (efemp1) only in the retina. Retina-specific efemp1 mutant showed impaired eye growth regulation that was dependent on visual input (Chapter 4). Finally, using restricted-wavelength rearing along with disruption of retinal short-wavelength cone photoreceptors (S-cones), it was possible to show that S-cones play a crucial role in visually driven ocular development in zebrafish (Chapter 5). The availability of gene editing tools in zebrafish coupled with multi-level phenotypic assessment tools, and robust environmental myopia models provide an excellent platform for large-scale in vivo investigation of gene-environment interactions in myopia development. This platform has been used here to highlight the importance of the efemp1 gene and S-cones to myopia development and also provided insights as to the molecular mechanisms and the anatomical substrates through which they might modify eye growth in myopia.