SRA

Species difference in susceptibility to toxicants is a critical issue in ecotoxicology. Transcriptomics is being proposed as a strategy to improve toxicity testing for regulatory risk assessment; however, different responses among species have not been extensively explored using this approach. In the present study, we identified dysregulated genes and pathways in Japanese quail (JQ) and double-crested cormorant (DCCO) embryos following exposure to ethinylestradiol (EE2). The objectives were to evaluate unique and overlapping transcriptomic responses to estrogenic exposure in the two species, and to determine whether these responses correspond to previously reported sensitivity difference at the organismal level. Exposures were conducted according to an avian egg injection protocol that we have proposed for standardization. EE2 was dissolved in dimethyl sulfoxide and injected into the air cell of eggs prior to incubation at nominal concentrations of 0, 3.33, and 33.3 µg/g egg weight. After 9-days (JQ) or 16-days (DCCO) of incubation (representing mid-incubation stage), liver tissues were collected from 5 embryos per treatment group for RNA-sequencing. Data were processed and analyzed using EcoOmicsAnalyst (www.ecoomicsanalyst.ca) and ExpressAnalyst (www.expressanalyst.ca). Following exposure to EE2, JQ and DCCO had 238 and 1987 differentially expressed genes, respectively, having 78 of them in common. The results of this study will contribute to a better understanding of the estrogenic effects of contaminants in birds, the expansion of taxonomic coverage in chemical risk assessment from model to non-model species, and the evaluation of transcriptomics and early-life stage tests as alternative toxicity testing methods. This study was conducted as a part of a large-scale Genome Canada-funded project, EcoToxChip project (www.ecotoxchip.ca). Overall design: Liver mRNA profiles of embryonic day 9 Japanese quail and embryonic day 16 double-crested cormorant following single exposure to either solvent or ethinylestradiol solution