Gene expression profiling in Daphnia magna, Part III: Uncovering Biomarkers for Metal and ORC exposures
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ABSTRACT:
ORGANISM(S): Daphnia magna
PROVIDER: GSE13169 | GEO | 2008/10/16
SECONDARY ACCESSION(S): PRJNA109639
REPOSITORIES: GEO
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Project description:To determine toxicant specific effects of Ordnance Related Compound (ORC) exposure we performed microarray hybridizations with RNA isolated from Daphnia magna following different ORC exposures at the 1/10 LC50. The gene expression profiles revealed toxicant specific gene expression profiles allowed for the identification of specific biomarkers of exposure. Keywords: ecotoxicogenomic exposure study We exposed Daphnia magna the 1/10 LC50 of different Ordnance Related Compounds (Cu, Zn, Pb, WO4, RDX, TNT, 2-ADNT, 2-ADNT, TNB, DNB, 2,4-DNT, and 2,6-DNT) for 24 hours. For each exposure condition, we performed 3 exposures and 2 technical replicates (as dye swap) for each exposure (6 microarrays total, except TNT and Cu). All exposures were compared to a unexposed laboratory control (MHRW media).
2010-05-18 | E-GEOD-13169 | biostudies-arrayexpress
Project description:Background: Toxicogenomics provides new opportunities for innovative and proactive approaches to chemical screening, risk assessment, and predictive toxicology. If applied to ecotoxicology, genomics tools could greatly enhance the ability to detect toxicants and understand the modes of toxicity in an environmental setting. However, few studies have yet to illustrate the potential of genomic techniques in ecotoxicology. Objective: Therefore, our objective was to demonstrate the potential utility of gene expression profiling in ecotoxicology using Daphnia magna, a standard aquatic ecotoxicity test organism. Methods: D. magna were exposed to copper, cadmium, and zinc at the 1/10 LC50 for 24 hours. Following each exposure, RNA was isolated, reverse transcribed, and the cDNA was hybridized to a 5000 clone cDNA microarray for D. magna. Differentially expressed cDNAs were sequenced and homology searches revealed each gene product's potential function. Real time PCR was used to verify the differential expression of several genes, and enzyme assays were used to assess the significance of these changes. Results: We identified distinct expression profiles in response to acute copper, cadmium, and zinc exposures and discovered specific biomarkers of exposure including two probable metallothioneins, and a ferritin mRNA with a functional IRE. The gene expression patterns support known mechanisms of metal toxicity and reveal novel modes of action including zinc inhibition of chitinase activity. Conclusions: Using a cDNA microarray for traditional ecotoxicology organism, D. magna, we have identified novel biomarkers of exposure and revealed possible modes of toxicity, providing experimental support for the utility of ecotoxicogenomics. Keywords: comparative toxicant exposure
2006-12-22 | GSE4759 | GEO
Project description:Map ORC binding sites to identify replication origins in C. albicans by using polyclonal ORC antibodies (gift from Stephen Bell Lab). Due to the unsynchronized nature of Candida cells, log-phase cultures were taken to perfoem ChIP-chip experiments to find the genome-wide ORC binding sites.
2014-02-13 | GSE54923 | GEO
Project description:A convergence of technological breakthroughs in the past decade has facilitated the development of rapid screening tools for biomarkers of toxicant exposure and effect. Platforms using the whole adult organism to evaluate the genome-wide response to toxicants are especially attractive. Recent work demonstrates the feasibility of this approach in vertebrates using the experimentally robust zebrafish model. In the present study, we evaluated gene expression changes in whole adult zebrafish following an acute 24 hour exposure to three metals with known human health risks. Male adult zebrafish were exposed to nickel chloride, cobalt chloride, and sodium dichromate concentrations corresponding to their respective 96 hr LC20, LC40 and LC60. Histopathology was performed on a subset of metal-exposed zebrafish to phenotypically anchor transcriptional changes associated with each metal. Comparative analysis identified subsets of differentially expressed transcripts both overlapping and unique to each metal. Application of gene ontology (GO) and transcription factor enrichment algorithms revealed a number of key biological processes perturbed by metal exposures and the master transcriptional regulators mediating gene expression changes. Metal exposures differentially activated biological processes associated with ribosome biogenesis, proteosomal degradation and p53 signaling cascades, while repressing oxygen-generating pathways associated with amino acid and lipid metabolism. Despite appreciable effects on gene regulation, nickel exposures did not induce any morphological alterations in zebrafish organs and tissues. Histopathological effects of cobalt remained confined to the olfactory system, while chromium targeted the gills, pharynx and intestinal mucosa. A number of enriched transcription factors mediate the observed gene response to metal exposure, including known targets such as p53, HIF1M-oM-^AM-! and the myc oncogene and novel regulatory factors such as XBP1, GATA6 and HNF3M-oM-^AM-". This work uses an experimentally innovative approach to capture global responses to metal exposures and provides mechanistic insights into metal toxicity mechanisms. Metal induced changes in gene expression in zebrafish were measured after 24 h exposures to each of three metals (nickel, chromium or cobalt). A total of 48 arrays were processed - 16 arrays per metal with 4 replicates for each exposure condition (control, low, mid, and high).
2014-06-10 | E-GEOD-50648 | biostudies-arrayexpress
Project description:A convergence of technological breakthroughs in the past decade has facilitated the development of rapid screening tools for biomarkers of toxicant exposure and effect. Platforms using the whole adult organism to evaluate the genome-wide response to toxicants are especially attractive. Recent work demonstrates the feasibility of this approach in vertebrates using the experimentally robust zebrafish model. In the present study, we evaluated gene expression changes in whole adult zebrafish following an acute 24 hour exposure to three metals with known human health risks. Male adult zebrafish were exposed to nickel chloride, cobalt chloride, and sodium dichromate concentrations corresponding to their respective 96 hr LC20, LC40 and LC60. Histopathology was performed on a subset of metal-exposed zebrafish to phenotypically anchor transcriptional changes associated with each metal. Comparative analysis identified subsets of differentially expressed transcripts both overlapping and unique to each metal. Application of gene ontology (GO) and transcription factor enrichment algorithms revealed a number of key biological processes perturbed by metal exposures and the master transcriptional regulators mediating gene expression changes. Metal exposures differentially activated biological processes associated with ribosome biogenesis, proteosomal degradation and p53 signaling cascades, while repressing oxygen-generating pathways associated with amino acid and lipid metabolism. Despite appreciable effects on gene regulation, nickel exposures did not induce any morphological alterations in zebrafish organs and tissues. Histopathological effects of cobalt remained confined to the olfactory system, while chromium targeted the gills, pharynx and intestinal mucosa. A number of enriched transcription factors mediate the observed gene response to metal exposure, including known targets such as p53, HIF1 and the myc oncogene and novel regulatory factors such as XBP1, GATA6 and HNF3. This work uses an experimentally innovative approach to capture global responses to metal exposures and provides mechanistic insights into metal toxicity mechanisms.
2014-06-10 | GSE50648 | GEO
Project description:Map ORC binding sites to identify replication origins in C. albicans by using polyclonal ORC antibodies (gift from Stephen Bell Lab). Due to the unsynchronized nature of Candida cells, log-phase cultures were taken to perfoem ChIP-chip experiments to find the genome-wide ORC binding sites. ChIP-chip experiments from log-phase C. albicans culture. 7 different unsynchronized log-phase cultures as replicates.
2014-02-13 | E-GEOD-54923 | biostudies-arrayexpress
Project description:Determination of the genome-wide distribution of ORC by chromatin immunoprecipitation in the Drosophila Kc167 cell line at the beginning of S phase. Kc167 cells were arrested at the G1/S transition with hydroxyurea (HU). Goal was to test whether the ORC binding distribution remained the same between G1 and S. ChIP-Chip of ORC in HU compared to input genomic DNA. Biological Replicates: 1
2014-12-05 | E-GEOD-63914 | biostudies-arrayexpress
Project description:Determination of the genome-wide distribution of ORC by chromatin immunoprecipitation in the Drosophila Kc167 cell line at the beginning of S phase. Kc167 cells were arrested at the G1/S transition with hydroxyurea (HU). Goal was to test whether the ORC binding distribution remained the same between G1 and S.
2014-12-05 | GSE63914 | GEO
Project description:The budding yeast genome is marked by 250-350 origins of DNA replication. These origins are bound by the origin recognition complex (ORC) throughout the cell cycle. ORC has known DNA binding sequence preferences which, though necessary for binding, are not sufficient to fully specify a genomic locus as being bound by ORC, indicating that the cell must use additional chromosomal cues to specify ORC binding sites and origins of replication. Using high-throughput sequencing to precisely locate both ORC binding sites and nucleosome locations genome-wide, we find that a nucleosome depleted region (NDR) and precisely positioned nucleosomes are a ubiquitous feature of yeast replication origins. The ARS consensus sequence (ACS) and adjacent sequences are sufficient to maintain the nucleosome-free properties of the NDR. We use a temperature sensitive ORC1 mutant to demonstrate that ORC is required to maintain precisely positioned nucleosomes at origins of replication. These findings demonstrate the importance of local nucleosome positioning at replication origins, and that chromatin organization is an important determinant of origin selection.
2010-03-19 | GSE16926 | GEO
Project description:Eukaryotic DNA replication origins are selected in G1-phase when the origin recognition complex (ORC) binds chromosomal DNA, triggering a series of molecular events that culminate in the initiation of DNA replication (a.k.a. origin firing) during S-phase. Each chromosome requires multiple origins for its duplication, and each origin fires at a characteristic time during S-phase, creating a cell-type specific genome replication pattern with relevance to differentiation, genome stability and evolution. It is unclear whether ORC-origin interactions are relevant to the regulation of origin activation time. Here we applied a novel genome-wide strategy to classify origins in the model eukaryote Saccharomyces cerevisiae based on the types of molecular interactions used for ORC-origin binding. Specifically, origins were classified as DNA-dependent when the strength of ORC-origin binding in vivo could be explained by the affinity of ORC for origin DNA in vitro, and, conversely, as ‘chromatin-dependent’ when the ORC-DNA interaction in vitro was insufficient to explain the strength of ORC-origin binding in vivo. The two classes of origins were distinct in terms of local nucleosome architecture and dependence on origin-flanking sequences in plasmid replication assays, consistent with local features of chromatin promoting ORC binding at ‘chromatin-dependent’ origins. Importantly, origins that fired in late S-phase, but not those that fired in early S-phase, showed a significant dependence on the ORC-origin DNA interaction for ORC binding in vivo. Therefore we demonstrate for the first time a connection between ORC-origin binding mechanisms and the regulation of origin activation time at a genome-wide level.
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