Development and validation of an OECD test guideline incorporating a transgenic fish model

Concern about the effects of Endocrine Disrupting Chemicals (EDCs) to fish and humans reproductive health has stimulated the development of tests to identify endocrine active substances and quantify their effects. Despite important progress that has been made in that direction during the past decade, one major challenge to ecotoxicology is still to develop specific biological tools that allow rapid and cost-efficient assessment of EDCs for environmental hazard and risk assessment. In 2012, an in vivo mechanism-based zebrafish embryo assay was developed (Brion et al., 2012) and called EASZY for Detection of Endocrine Active Substances, acting through estrogen receptors, using transgenic cyp19a1b-GFP Zebrafish embrYos. The relevance of the EASZY assay for assessing the estrogenic potency of test substances was evaluated by testing more than 60 chemicals and it was found that, in the EASZY assay, GFP was induced in a ER-specific manner by (i) compounds that bind directly to estrogen receptors as agonists (ii) compounds that require metabolic activation into estrogenic metabolites (iii) aromatizable androgens as well as some non aromatizable androgens. Since the EASZY assay emerged as a fast, simple, specific and sensitive in vivo assay for quantifying the estrogenic potency of chemicals at very early critical developmental stages, a Standard Project Submission Form (SPSF) was submitted by the lead country France to OECD test guidelines program in 2012 and the EASZY was accepted to the Validation Management Group for Ecotoxicity (VMG-Eco) working program in December 2013. The first objectives of the validation were (i) to ensure training persons to conduct the test (ii) to assess the transferability of the transgenic model and the test method to the participating laboratories (iii) to assess the intra- and inter-laboratory reproducibility by testing a set of reference ligands including both positive and negative test substances. At the occasion of this oral presentation the current progress of the validation of the EASZY assay will be presented while considering the strengths (and the limits) of transgenic models for environmental hazard and risk assessment. Acknowledgement – Study support by the DRC-50 “Perturbateurs Endocriniens et impacts environnementaux” of the French Ministry of Environment