R3 AM Ecotoxicogenomics of Emerging Chemical Issues
Thursday, 17 November 2005: 8:00 AM - 11:40 AM in Ballroom 3

(DEN-1117-861597) Gene expression profiles for fathead minnows exposed to ethinylestradiol.

Denslow, N¹, Orlando, E², Sepulveda, M³, Watanabe, K⁴, Knoble, I⁵, Lazorchak, J⁵, Miracle, A⁶, Collette, T⁷, Villeneuve, D⁸, Ankley, G⁸, ¹ University of Florida, Gainesville, FL, USA² Florida Atlantic University, Boca Raton, FL, USA³ Purdue University, Lafayette, IN, USA⁴ Oregon Health & Science University, Beaverton, OR, USA⁵ U.S. EPA, ORD, NERL, EERD, Cincinnati, OH, USA⁶ Pacific Northwest National Laboratory, Richland, WA, USA⁷ U.S. EPA, ORD, NERL, ERD, Athens, GA, USA⁸ U.S. EPA, ORD, NHEERL, MED, Duluth, MN, USA

ABSTRACT- As part of a joint collaborative effort, we are exposing fathead minnows (FHM, Pimephales promelas) to endocrine disrupting chemicals to develop a systems toxicology approach to understand their mechanisms of action. Specifically we are developing tools to study the interaction between genes and environmental stressors, combining studies of transcriptomics, proteomics, and metabolomics with traditional endpoints for reproduction. To determine predictive gene expression profiles for compounds with known modes of action, we have exposed FHM to 2, 10 and 50 ng/L 17--ethinylestradiol (EE2) for 48 hrs. Gene expression patterns for brain, liver and gonad were analyzed using a 2000-gene fathead minnow microarray. We have also developed quantitative real time PCR assays for vitellogenin, estrogen receptor alpha, estrogen receptor beta-1, aromatase-b, among others to verify the changes in gene expression predicted from the microarrays. Some mRNAs increase in a dose responsive manner with dose of EE2, while others decrease. There appears to be a threshold effect for activation of some genes, suggesting that as the normal concentration of E2 fluctuates, different banks of genes become activated. Genes that are altered include genes involved in reproduction, stress, energy production, blood coagulation, fatty acid transport, sex hormone synthesis and metabolism, among others. Molecular biomarkers offer the promise of providing (1) early detection of environmental stress, (2) inferred mechanisms of action and (3) relatively efficient monitoring of the environment. To be useful, these novel molecular biomarkers must be integrated with traditional end points, which point to adverse effects in growth, reproduction and stability of populations.

Key words: toxicogenomics, gene profiling, vitellogenin, aromatase