Gene Expression changes induced by exposure to field water samples collected at Walker Mine, CA

Our research goal is to illustrate the potential of gene expression profiling to discriminate between polluted and non-polluted field sites and predict the presence of a specific contaminant. Using a gene expression analysis, we challenged our custom Daphnia magna cDNA microarray to determine the presence of a specific metal toxicant in blinded field samples collected from two copper mines in California. We compared the gene expression profiles from our field samples to previously established expression profiles for Cu, Cd, and Zn. The expression profiles from the Cu containing field samples clustered with the Cu specific gene expression profiles. Many of the previously discovered copper biomarkers were also differentially expressed in the field samples, suggesting that gene expression analysis is capable of producing robust biomarkers of exposure, which can be validated in field studies. In addition, our study revealed that upstream field samples containing undetectable levels of Cu caused the differential expression of only a few genes, lending support for the concept of a No Observed Transcriptional Effect Level (NOTEL). If confirmed by further studies, the NOTEL may play an important role in discriminating polluted and non-polluted sites in future monitoring efforts. Keywords: ecotoxicogenomic exposure study We collected water samples from 4 sites at Walker Mine. Each site was contaminated with a different amount of Cu. For each site, we performed 3 exposures and 2 technical replicates (as dye swap) for each exposure (6 microarrays total). All field sample exposures were compared to a unexposed laboratory control (COMBO media).