Early life exposure to ethinylestradiol enhances subsequent responses to environmental estrogens measured in a novel transgenic zebrafish

This is the author accepted manuscript. The final version is available from Nature Publishing Group via the DOI in this record.Estrogen plays fundamental roles in a range of developmental processes and exposure to estrogen mimicking chemicals has been associated with various adverse health effects in both wildlife and human populations. Estrogenic chemicals are found commonly as mixtures in the environment and can have additive effects, however risk analysis is typically conducted for single-chemicals with little, or no, consideration given for an animal's exposure history. Here we developed a transgenic zebrafish with a photoconvertable fluorophore (Kaede, green to red on UV light exposure) in a skin pigment-free mutant element (ERE)-Kaede-Casper model and applied it to quantify tissue-specific fluorescence biosensor responses for combinations of estrogen exposures during early life using fluorescence microscopy and image analysis. We identify windows of tissue-specific sensitivity to ethinylestradiol (EE2) for exposure during early-life (0-5 dpf) and illustrate that exposure to estrogen (EE2) during 0-48 hpf enhances responsiveness (sensitivity) to different environmental estrogens (EE2, genistein and bisphenol A) for subsequent exposures during development. Our findings illustrate the importance of an organism's stage of development and estrogen exposure history for assessments on, and possible health risks associated with, estrogen exposure.This work was co-funded by a BBSRC CASE studentship with AstraZeneca (reference 620033640) supporting J.M.G, a BBSRC small grant (reference BB/L01548X/1) to C.R.T., and by the AstraZeneca Global Safety, Health and Environment research programme. S.F.O. is an employee of AstraZeneca, a biopharmaceutical company specialized in the discovery, development, manufacturing and marketing of prescription medicines. AstraZeneca provided support in the form of studentship and salary for author S.F.O. but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Special thanks to Dr. Nicola Rogers for editing this manuscript