Expression profiling of five different xenobiotics using a C. elegans microarray
Using a C. elegans whole genome DNA microarray in this study, the effects of five different xenobiotics on the gene expression of the nematode were investigated. The exposure time for the following five applied compounds beta-NF (5 mg/l), Fla (0.5 mg/l), atrazine (25 mg/l), clofibrate (10 mg/l) and DES (0.5 mg/l) was 48+/-5 h. The analysis of the data showed a clear induction of 203 genes belonging to different families like the cytochromes P450, UDP-glucoronosyltransferases (UDPGT), glutathione S-transferases (GST), carboxylesterases, collagenes, C-type lectins and others. Under the applied conditions, fluoranthene was able to induce most of the induceable genes, followed by clofibrate, atrazine, beta-naphthoflavone and diethylstilbestrol. A decreased expression could be shown for 153 genes with atrazine having the strongest effect followed by fluoranthene, diethylstilbestrol, beta-naphthoflavone and clofibrate. For upregulated genes a change ranging from approximately 2.1- till 42.3-fold and for downregulated genes from approximately 2.1 till 6.6-fold of gene expression could be affected through the applied xenobiotics. Sample Treatments (by exptids) Clofibrate: 14317, 16443, 16505 Fluoranthene: 33664, 33667, 33669, 23484 beta-Naphthoflavone: 6844, 14320, 14316 Atrazin: 33672, 33674, 23487, 23486 DES: 33671, 23485 A compound treatment design type is where the response to administration of a compound or chemical (including biological compounds such as hormones) is assayed. Keywords: compound_treatment_design
cRNA amplification methods enhance microarray identification of transcripts expressed in the nervous system
Background: DNA microarrays provide a powerful method for global analysis of gene expression. The application of this technology to specific cell types and tissues, however, is typically limited by small amounts of available mRNA, thereby necessitating amplification. Here we compare microarray results obtained with two different methods of RNA amplification to profile gene expression in the C. elegans larval nervous system. Results: We used the mRNA-tagging strategy to isolate transcripts specifically from C. elegans larval neurons. The WT-Ovation Pico System (WT-Pico) was used to amplify 2 ng of Pan-neural RNA to produce labeled cDNA for microarray analysis. These WT-Pico-derived data were compared to microarray results obtained with a labeled aRNA target generated by two rounds of In Vitro Transcription (IVT) of 25 ng of Pan-neural RNA. WT-Pico results in a higher fraction of Present calls than IVT, a finding consistent with the proposal that DNA-DNA hybridization results in lower mismatch signals than the RNA-DNA heteroduplexes produced by IVT amplification. Microarray data sets from these samples were compared to a Reference profile of all larval cells to identify transcripts with elevated expression in neurons. These results were validated by the high proportion of known neuron-expressed genes detected in these profiles and by promoter-GFP constructs for previously uncharacterized genes in these data sets. Together, the IVT and WT-Pico methods identified 2,173 unique neuron-enriched transcripts. Only about half of these transcripts (1,044), however, are detected as enriched by both IVT and WT-Pico amplification. Conclusion: We show that two different methods of RNA amplification, IVT and WT-Pico, produce valid microarray profiles of gene expression in the C. elegans larval nervous system with a low rate of false positives. However, our results also show that each method of RNA amplification detects a unique subset of bona fide neural-enriched transcripts and thus a wider array of authentic neural genes are identified by the combination of these data sets than by the microarray profiles obtained with either method of RNA amplification alone. With its relative ease of implementation and greater sensitivity, WT-Pico is the preferred method of amplification for cases in which sample RNA is limiting. Keywords: expression profile