National Center for Computational Toxicology

Key Contact: Gerald Ankley, Ph.D. Mid-Continent Ecology Division, NHEERL, Duluth, MN; ankley.gerald@epa.gov (218) 529-5147

We propose to use a combination of whole organism endpoints, genomic, proteomic, and metabonomic approaches, and computational modeling to (a) identify new molecular biomarkers of exposure to endocrine disrupting compounds (EDCs) representing several modes/mechanisms of action (MOA) and (b) link those biomarkers to effects that are relevant for both diagnostic and predictive risk assessments using small fish models. These goals will be achieved through a three-phase approach that incorporates expertise across EPA/ORD and capitalizes on partnerships with other federal and academic laboratories. During Phase 1, effects of a candidate list of nine compounds having different MOA within the hypothalamic-pituitary-gonadal (HPG) axis will be characterized using the fathead minnow (Pimephales promelas) The fathead minnow represents the small fish model most commonly used as the Agency's aquatic toxicological standard for both lab testing and field monitoring. Phase 1 results will provide input for population modeling and provide crucial data for anchoring for the markers identified in other phases. Phase 2 will take advantage of the well characterized zebrafish (Danio rerio) genome, to identify transcriptome and proteome level changes in addition to metabolite changes, associated with zebrafish exposure to the same suite of EDCs. Phase 2 data will be used to identify relevant molecular changes that could (a) serve as diagnostic markers for various types of EDC exposure and (b) begin to inform a systems-level characterization of the responses to those exposures. In Phase 3, candidate genes/diagnostic markers identified in zebrafish (Phase 2) will be validated in fathead minnows through focused toxicological testing aimed at examination of changes in specific gene expression and protein levels. Metabolite profiles in fathead minnows will be compared to those detected in zebrafish exposed to the same EDCs. In this way, changes at the genomic, proteomic, and metabonomic level will be linked to one another, linked across multiple teleost species, and ultimately linked to adverse effects at the individual- and, through modeling, population-level (i.e. linkage back to Phase 1) This three phase approach stands to greatly benefit EPA by identifying new, potentially cost-effective, diagnostic exposure markers for EDCs, and developing source-to-outcome linkages critical for effective use of biomarkers for risk assessments. Furthermore comparison to complementary mammalian studies could facilitate improved cross-species extrapolation. The three phase approach which takes advantage of the respective strengths of two small fish models, facilitated through an extensive interdisciplinary network of EPA and non-EPA partners is well equipped to support the objectives of the Computational Toxicology Program.

View Peer Reviewed Publications