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Pathway-based analysis of fish transcriptomics data along effluent gradients in Minnesota rivers
Citation:
Berninger, J., D. Martinovic-Weigelt, G. Ankley, AND Dan Villeneuve. Pathway-based analysis of fish transcriptomics data along effluent gradients in Minnesota rivers. Presented at Society for Environmental Toxicology and Chemistry.
Impact/Purpose:
Not applicable
Description:
As part of a larger effort to assess the health of streams and rivers influenced by municipal effluents in Minnesota, fathead minnows (Pimephales promelas; FHM) were exposed to ambient surface waters from three locations. The locations were generally representative of the state: urban Rochester, agricultural Hutchinson; rural/forested Ely. Fish were exposed in aerated mobile exposure units supplied with water from upstream, at, or downstream of a wastewater treatment plant (WWTP) outfall. While multiple endpoints were evaluated, this study focuses FHM female ovary transcriptomics following a 4 day exposure. Comparing between treatment groups (upstream, downstream, at effluent) within each location, the number of significantly differentially expressed genes (DEGs) were highest in Rochester (5847), than Hutchinson (1295) and Ely (867). Among the DEGs, hierarchical clustering and PCA showed distinct separation of the upstream, downstream, and effluent treatments at each location. Gene Set Enrichment Analysis (GSEA) showed the overall number of gene sets enriched followed the same pattern as the differential expression, with highest enrichment in Rochester and lowest in Ely. Comparing along the effluent gradient, different patterns were observed at each site. There were, however, a few gene sets that showed consistent responses to the effluent gradient across all three locations. Enrichment moving upstream was seen in two gene sets putatively linked with the promotion of oocyte maturation, (through gene sets associated with cyclin B and cathepsin D). Another gene set, a putative inhibitor of oocyte maturation (through a TGFB1 associated gene set), exhibited enrichment along the downstream gradient at all locations. Given the substantial differences in land use, human population, and pollutant chemistry the consistent impact on oocyte maturation-related gene sets suggests an emerging trend across effluent gradients. In general, results from female FHM ovary transcript