Unknown,Transcriptomics,Genomics,Proteomics

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Classifier analysis of gene expression profiles reveals a discriminatory gene set for soil containing different metals

ABSTRACT: Environmental pollution is a worldwide problem, and metals are the largest group of contaminants in soil. Microarray toxicogenomic studies with ecologically relevant organisms such as springtails, supplement traditional ecotoxicological research, but are presently rather descriptive. Classifier analysis, a more analytical application of the microarray technique, is able to predict biological classes of unknown samples. We used the uncorrelated shrunken centroid (USC) method to classify gene expression profiles of the springtail Folsomia candida exposed to soil spiked with six different metals (barium, cadmium, cobalt, chromium, lead, and zinc). We identified a gene set (classifier) of 188 genes that can discriminate between six different metals present in soil, which allowed us to predict the correct classes for samples of an independent test set with an accuracy of 83% (error rate = 0.17). This study shows further that in order to apply classifier analysis to actual contaminated field soil samples, more insight and information is needed on the transcriptional responses of soil organisms to different soil types (properties) and mixtures of contaminants. Gene expression was measured in springtails after exposure of 2 days to soil containing either EC10 or EC50 of 6 different metals. The exposure experiment was performed in two separate series (1 and 2), both containing a separate non-spiked (LUFA 2.2) soil control. Also, two field soil samples were tested. The samples were divided into a separate training set and a validation set for USC classifier analysis.

ORGANISM(S): Folsomia candida

SUBMITTER: Benjamin Nota

PROVIDER: E-GEOD-19353 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Gene expression analysis reveals a gene set discriminatory to different metals in soil.

Nota Benjamin B Verweij Rudo A RA Molenaar Douwe D Ylstra Bauke B van Straalen Nico M NM Roelofs Dick D

Toxicological sciences : an official journal of the Society of Toxicology 20100204 1

Environmental pollution is a worldwide problem, and metals are the largest group of contaminants in soil. Microarray toxicogenomic studies with ecologically relevant organisms, such as springtails, supplement traditional ecotoxicological research but are presently rather descriptive. Classifier analysis, a more analytical application of the microarray technique, is able to predict biological classes of unknown samples. We used the uncorrelated shrunken centroid method to classify gene expression ...[more]

PMID: 20133373

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Project description:Environmental risk assessment relies heavily on the use of bioassays to assess the environmental impact of chemicals. Gene expression is gaining acceptance as a valuable mechanistic endpoint in bioassays and effect-based screening. Data analysis and its results however, are often complex and not directly applicable in risk assessment. Classifier analysis is a promising method to turn complex gene expression analysis results into answers suitable for risk assessment. We have assembled a large gene expression dataset assembled from multiple studies and experiments in the springtail Folsomia candida, with the aim of selecting a set of genes that can be trained to classify general toxic stress. By performing differential expression analysis prior to classification we were able to select a set of 135 genes which was enriched in stress related processes. This set was then used to classify two test sets comprised of chemical spiked soils, polluted soils and clean soils and compared to another, more traditional feature selection for classification. The gene set presented here outperformed the more traditionally selected gene set. This gene set has the potential to be used as a biomarker to test for adverse effects caused by chemicals in springtails to provide endpoints in environmental risk assessment. The data presented in our manuscript is part of a larger experiment which was performed in single, large loop design. Only the samples used in the study presented here are named while the other samples will remain unnamed. All the data can still be used for normalization after which the analysis presented in the manuscript can be replicated. A single channel, interwoven loop design was used to test animals exposed to a control and to 5 concentrations of cadmium and phenanthrene (cadmium concentrations are: cad_1 till cad_5: 5.8, 14.5, 28.9, 57.9 and 115.8 mg/Kg respectively and phenanthrene concentrations are: phe_1 till Phe_5: 0, 4.6, 11.4, 22.9, 45.8 and 91.6 mg/Kg soil respectively). Exposures lasted for 2 days and used 4 biological replicates per condition each containing 30 grams soil and 30 individuals.

Dataset Information

Classifier analysis of gene expression profiles reveals a discriminatory gene set for soil containing different metals

Publications

Gene expression analysis reveals a gene set discriminatory to different metals in soil.

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