Transgenic fish systems and their application in ecotoxicology

Abstract

The use of transgenics in fish is a relatively recent development for advancing understanding of genetic mechanisms and developmental processes, improving aquaculture, and for pharmaceutical discovery. Transgenic fish have also been applied in ecotoxicology where they have the potential to provide more advanced and integrated systems for assessing health impacts of chemicals. The zebrafish (Daniorerio) is the most popular fish for transgenic models, for reasons including their high fecundity, transparency of their embryos, rapid organogenesis and availability of extensive genetic resources. The most commonly used technique for producing transgenic zebrafish is via microinjection of transgenes into fertilized eggs. Transposon and meganuclease have become the most reliable methods for insertion of the genetic construct in the production of stable transgenic fish lines. The GAL4-UAS system, where GAL4 is placed under the control of a desired promoter and UAS is fused with a fluorescent marker, has greatly enhanced model development for studies in ecotoxicology. Transgenic fish have been developed to study for the effects of heavy metal toxicity (via heat-shock protein genes), oxidative stress (via an electrophile-responsive element), for various organic chemicals acting through the aryl hydrocarbon receptor, thyroid and glucocorticoid response pathways, and estrogenicity. These models vary in their sensitivity with only very few able to detect responses for environmentally relevant exposures. Nevertheless, the potential of these systems for analyses of chemical effects in real time and across multiple targets in intact organisms is considerable. Here we illustrate the techniques used for generating transgenic zebrafish and assess progress in the development and application of transgenic fish (principally zebrafish) for studies in environmental toxicology. We further provide a viewpoint on future development opportunities.

Nrf2 and Nrf2-related proteins in development and developmental toxicity: Insights from studies in zebrafish (Danio rerio)

“…Use of transgenic technologies [158, 285] will facilitate new insight into the cell and tissue specificity of the oxidative stress response in embryos. Initial studies have begun to address such questions, using molecular probes to localize oxidative stress [7] and transient [228, 286] and germ-line transgenics [279, 287] to measure the response.…”

Zebrafish: A complete animal model to enumerate the nanoparticle toxicity

“…After exposed to toxic chemicals, morphological changes are well noticeable in zebrafish [52]. Lee et al [53] developed a transgenic line of zebrafish embryos entitled as “huORFZ embryos” which can accurately detect various kinds of pollutants compounds and can be further used as water alarm system to monitor the disposal of hazardous pollutants in the water bodies.…”

Zebrafish in Toxicology and Environmental Health

“…A major advantage of using zebrafish for this work is that the embryos and larvae are transparent and generating transgenic animals is relatively easy. This has allowed the development of transgenic lines where a fluorescent protein or other measureable readout becomes activated in the presence of contaminants or environmental stressors provide a system to assess the level of response and the tissue specificity of the response (Carvan, Dalton, Stuart, & Nebert, 2000; Gorelick, Iwanowicz, Hung, Blazer, & Halpern, 2014; Lee, Green, & Tyler, 2015). In the earliest efforts, investigators developed transgenic zebrafish lines in which expression of the luciferase or green fluorescent protein ( GFP ) gene is driven by pollutant response elements that report on the presence of aromatic hydrocarbons, electrophiles/oxidants, metals, estrogenic compounds, or retinoids (Carvan et al, 2000).…”

“…Transgenic lines have been used not only to detect the presence of toxins, but can facilitate investigations into the molecular mechanisms underlying pathology associated with environmental exposures. The use of transgenic reporter zebrafish lines to measure exposure to heavy metals, organic chemicals, endocrine disruptors, and electrophilic agents has been expertly reviewed elsewhere (Lee et al, 2015) and are outlined in Table 1. We describe how such tools are used to both detect the presence of contaminants and to understand their physiological impact.…”

“…There are several important features of the huORFZ model that make it ideal for first-line pollution monitoring: (1) exposure to different chemical stressors results in distinct patterns of GFP expression, indicating the cell types and organ systems that respond to a given toxicant; (2) the system is responsive to several pollutants at the range of concentrations enforced by current World Health Organization guidelines; and (3) GFP expression decreased following the exposure period, which suggests that expression is a direct result of the physiological response upon toxicant exposure. Lee et al (2015) have demonstrated that this transgenic line can be used to detect the presence of environmental contaminants, including heavy metals and EDCs (Lee et al, 2014). The response of this transgenic line is not limited to a particular stressor and can be applied to a range of chemicals or toxicants that induce ER stress.…”