Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression profiles of Daphnia magna exposed to Cd at the 1/10 LC50

ABSTRACT: Cadmium (Cd) is a toxic metal causing sublethal and chronic effects in crustaceans. Omic technologies offer unprecedented opportunities to better understand modes of toxicity by providing a holistic view of the molecular changes underlying physiological disruption. We sought to use gene expression and metabolomic analyses to reveal the processes leading to chronic Cd toxicity in the indicator species, Daphnia magna, after a 24-h sublethal exposure (18 ug/L, corresponding to 1/10 LC50). We first confirmed that metabolites can be detected and identified in small volumes (~3-6 ul) of D. magna hemolymph using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and NMR spectroscopy. We then compared the altered metabolite levels from a mass spectrometry metabolomics study to differentially expressed genes identified by a D. magna 44k oligonucleotide microarray. Metabolomics identified several essential amino acids, nucleotides and fatty acids as decreased in D. magna hemolymph following Cd exposure. Transcriptional changes included decreased levels of digestive enzymes and increased expression of genes related to embryonic development. The integration of metabolomic and transcriptomic profiles, as well as incorporation of results from previous studies, has enabled construction of a conceptual model detailing how sublethal Cd disrupts energy reserves and reproduction resulting in chronic toxicity. Daphnia magna were exposed to 18 micrograms/L Cadmium sulfate for 24 hours. RNA was extracted and hybridized to a custom Daphnia magna microarray to determine genes differentially expressed by the treatment. Two treament experiment:Unexposed and Cd treatment, 6 replicates for each condition

ORGANISM(S): Daphnia magna

SUBMITTER: Helen Poynton

PROVIDER: E-GEOD-20218 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Nanowires (NWs), high-aspect-ratio nanomaterials, are increasingly used in technological materials and consumer products and may have toxicological characteristics distinct from nanoparticles. We carried out a comprehensive evaluation of the physicochemical stability of four silver nanowires (AgNWs) of two sizes and coatings and their toxicity to Daphnia magna. Inorganic aluminum-doped silica coatings were less effective than organic poly(vinyl pyrrolidone) coatings at preventing silver oxidation or Ag+ release and underwent a significant morphological transformation within 1 h following addition to low ionic strength Daphnia growth media. All AgNWs were highly toxic to D. magna but less toxic than ionic silver. Toxicity varied as a function of AgNW dimension, coating, and solution chemistry. Ag+ release in the media could not account for observed AgNW toxicity. Single-particle inductively coupled plasma mass spectrometry distinguished and quantified dissolved and nanoparticulate silver in microliter-scale volumes of Daphnia magna hemolymph with a limit of detection of approximately 10 ppb. The silver levels within the hemolymph of Daphnia exposed to both Ag+ and AgNW met or exceeded the initial concentration in the growth medium, indicating effective accumulation during filter feeding. Silver-rich particles were the predominant form of silver in hemolymph following exposure to both AgNWs and Ag+. Scanning electron microscopy imaging of dried hemolymph found both AgNWs and silver precipitates that were not present in the AgNW stock or the growth medium. Both organic and inorganic coatings on the AgNW were transformed during ingestion or absorption. Pathway, gene ontology, and clustering analyses of gene expression response indicated effects of AgNWs distinct from ionic silver on Daphnia magna. Four replicates each of five toxicant exposure groups of ~20 animals and four replicates of control, unexposed animals. Each control was compared to each exposed data set for a total of 16 comparisons per chemical condition.

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Gene expression profiles of Daphnia magna exposed to Cd at the 1/10 LC50

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