Activation of transcription factors in zebrafish cell cultures by environmental pollutants

Many classes of environmental pollutants are found at significant levels in the aquatic environment. We are designing a fish model as an inexpensive a nd efficient system for the assessment of aquatic pollution, Three classes of environmental pollutants-halogenated and nonhalogenated aromatic hydroca rbons, heavy metals, and potent electrophiles-are known to upregulate parti cular mammalian genes via the activation of specific DNA motifs called arom atic hydrocarbon (AHREs), heavy metal (MREs), and electrophile (EPREs) resp onse elements, respectively. We have made plasmid constructs, using these m ammalian or trout response elements to drive the luciferase reporter gene. Here we show that transient transfection of the zebrafish ZEM2S cell line w ith these reporter constructs imparts dose-dependent gene induction upon ex posure to a variety of chemicals within each of these three classes of indu cers: [a] (AHRE-mediated) 2,3,7,8-tetrachlorodibenzo-p-dioxin, 3-methylchol anthrene, 3,4,5,3',4',5'-hexabromobiphenyl, Aroclor 1254, and benzo[a]pyren e; [b] (MRE-mediated) Cd2+, Zn2+, Hg2+, and Al3+; and [c] (EPRE-mediated) t ert-butylhydroquinone, Hg2+, Pb2+, As3+, Cu2+, and Cd2+. As expected, some agents gave a response to only one of the three classes, whereas others gav e a mixed (AHRE- plus EPRE-mediated or MRE- plus EPRE-mediated) response. I n response to several environmental agents, we found that differences in th e electrophoretic mobility shift assay, using the AHRE or MRE as probe, wer e consistent with the degree of transcriptional activation seen with the re porter constructs. Our data suggest that these reporter constructs might be valuable for the generation of transgenic zebrafish in order to carry out mechanistic and developmental studies of transcriptional activation by envi ronmental contaminants; moreover, such transgenic zebrafish lines might be useful as a sentinel for assessing aquatic pollution. (C) 2000 Academic Pre ss.