SRA

Chemical risk assessment for avian species typically depends on information from toxicity tests performed in adult birds. Early-life stage (ELS) toxicity tests have been proposed as an attractive alternative, but incorporation of these data into existing frameworks will require knowledge about the similarities/differences between ELS and adult responses. The present study uses transcriptomics to assess hepatic gene expression in ELS and adult Japanese quail following exposure to ethinylestradiol (EE2). ELS quail were dosed with 0, 3.33, and 33.3 µg EE2/g egg via air cell injection prior to incubation. Adult quail were fed a single dose of EE2 at 0, 0.5, and 5 mg/kg body weight by gavage. Liver tissue was collected from 5-6 individuals per dose group at mid-incubation for ELS quail, and 4 days after dosing for adult birds. A total of 283 and 111 differentially expressed genes (DEGs) were detected in ELS and adult quail, respectively, 16 of which were shared across life stages. Shared DEGs included estrogenic biomarkers such as vitellogenin genes and Apovitellenin-1. For the dose groups that resulted in the highest number of DEGs (ELS [3.3 µg/g]; adult [5 mg/kg]), 21 and 35 KEGG pathways were enriched, respectively. Ten of these pathways were shared between life stages, including pathways involved with signaling molecules and interaction, and endocrine system. Taken together, our results suggest conserved mechanisms of action following estrogenic exposure across two life stages, with evidence from differentially expressed genes and enriched pathways. This study contributes to the development and evaluation of toxicogenomic and ELS approaches as alternative toxicity testing methods and supports the use of the ELS test for screening estrogenic chemicals. Overall design: Liver mRNA profile of 12-week old Japanese quail following single exposure to either solvent or ethinylestradiol