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Integration of genomic endpoints into toxicity identification evaluations
Citation:
BIALES, A. D., K. T. HO, R. M. BURGESS, M. M. Perron, M. KOSTICH, AND M. REISS. Integration of genomic endpoints into toxicity identification evaluations. Presented at SETAC, Tampa, FL, November 16 - 20, 2008.
Impact/Purpose:
The indeterminate condition of exposure indicator research stands to change markedly with the ability to connect molecular biological technologies with cellular or tissue effects and outcomes. Three focal areas of ecological research aim to develop a sequence of approaches where "the earliest recognizable signatures of exposure" (i.e., unique patterns of up- and down-regulated genes and proteins) are identified for numerous stressors, demonstrable in case studies and incorporated into Agency, State and Regional studies supported by EMAP and other programs.
Description:
Toxicity identification and evaluations (TIEs) use physical/chemical manipulation of a sample to isolate or change the potency of different groups of toxicants potentially present in a sample. Organisms are then exposed to these fractions to determine if their toxicity has changed. TIEs focus on mortality to detect toxicity; however, this endpoint gives no information as to the identity of the active toxicant(s). It has been suggested that gene expression profiles may be useful in identifying toxic substances fromunknown samples. This is accomplished through the development of expressionn profiles, consisting of a number of genes, which respond in a specific manner to a given contaminant. Transcriptional profiling of toxicants is usually accomplished using microarrays; however, this technological platform does not currently exist for a common model organism used in TIEs, the amphipod, Ampelisca abdita. Therefore, normalized libraries for A. abdita were constructed. Organisms used in library construction were selected to be diverse as possible to increase the number of transcripts included in the library and included multiple age groups, populations from different geographic areas and organisms that were subjected to chemical exposures. Over 6000 clones were sequenced in both directions and will be spotted in duplicate on microarrays. For transcriptional profiling, A. abdita were exposed in sediments to 7 chemicals, a binary mixture and a grand mixture of all test chemicals at a dilution corresponding to 10% of the LC50 value for each chemical. Each exposure consisted of 6 independent replicates. Each replicate consisted of a pool of 10 individuals. Transcriptional fingerprints will be established for each chemical and the stability of these profiels will be evaluated in the mixtures. Following establishment of chemical specific transcriptional profiels, A. abdita will be exposed to an environmentally contaminated sediment sample, on which a TIE will be performed. Exposed individuals will be usbject to microarray screening to determine if active toxic substances can be identified. These results will subsequently be compared to the TIE outcome. This will be among the first projects to integrate genomic technology into existing toxicity assessment experimental platforms.