Gene expression in Rainbow trout (Oncorhynchus mykiss) fry gonads after a chronic exposure to a range of 17α-ethynylestradiol concentrations

Sex steroids play a key role in triggering sec differentiation in fish and the use of exogenous hormone treatment leads to partial or complete sex reversal. This phenomenon has attracted attention since the discovery taht even low environmental doses of exogenous steroids can adversely affect gonad morphology (ovotestis development) and induce reproductive failure. Modern genomic-based technologies have enhanced opportunities to find mechanisms of action (MOA) and dentify biomarkers for the toxic action of a compound. The goal of this study are to improve the understanding of feminization in fish by analyzing gene expression patterns in the gonads of rainbow trout fry after a chronic exposure to several doses (0.01, 0.1, 1 and 10 μg/L) of ethynylestradiol (EE2) and to offer target genes as potential biomarkers of ovotestis development. An all-male population of Rainbow trout fry was exposed during 76 days (from 60 to 136 days post-fertilization (dpf)) to five nominal concentrations of 17α-ethynylestradiol (0-solvent control-, 0.01, 0.1, 1 and 10 μg EE2/L of water), using 3 tanks per condition. In total, 30 samples were analyzed independantly: 6 samples per concentration tested (two samples per tank, three tanks per concentration), each sample being a pool of 10 pairs of gonads.