MRNA-Seq of zebrafish embryos (96hpf) exposed to different concentrations of the organochloride Methoxychlor below acute toxicity levels against untreated control groups
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ABSTRACT: The aim of this mRNA expression profiling experiment was to screen for ecotoxicogenomic fingerprints in zebrafish (Danio rerio) embryos as aquatic vertebrate non-target model exposed to sub lethal concentrations of synthetic organochloride insecticide Methoxychlor (CAS 72-43-5). It is structurally highly similar to its precursor molecule DDT (Dichlorodiphenyltrichloroethane). Like its precursor, today Methoxychlor is banned from the use as pesticide in the United States and the European Union due to its acute toxicity, high bioaccumulation potential and endocrine disruption activity. The Insecticide Resistance Action Committee (IRAC) classified Methoxychlor after its mode of action (MoA) in the target organism as a sodium channel modulator (Group 3B). Our goal is to identify toxicogenomic profiles with predictive character and potential molecular key events (KE) explaining upstream adverse effects in aquatic non-target organisms for this substance of particularly high environmental concern. This will provide useful information to refine and improve existing adverse outcome pathways (AOP). Furthermore, integrating the obtained profiles for this and other tested chemicals in a collective database will enable us in the future to derive predictions about the ecotoxicological hazard for chemcials with unknown apical effects, based on similarly altered transcriptomic and proteomic profiles. In a modified version of the zebrafish embryo toxicity test (OECD 236), 15 fertilized eggs were exposed to two different sub lethal concentrations of Methoxychlor for 96 hours under semi-static conditions. Each test comprised of a low exposure (LE, 20 µg/L), mid exposure (ME, 60 µg/L), high exposure (HE, 180 µg/L) and negative control (NC) group and was performed in triplicates. At 96 hours post fertilization (hpf), 10 larvae were randomly picked for each sample and pooled for RNA and protein extraction with NucleoSpin RNA/Protein kit (Macherey-Nagel). RNA quality was assessed with a 2100 Bioanalyzer system (Agilent) before coding RNA was purified (PolyA selection with TruSeq RNA Library Prep Kit v2) and sequenced on an Illumina HiSeq 4000 System (Illumina) in 50 bp single read mode, producing roughly 30 million reads per sample. Adapter sequences were removed with trimmomatic and sequences were aligned to the D.rerio reference genome GRCz11 with STAR. Counting of feature mapped reads was performed through featureCounts. Library gene count tables were then merged to a single count matrix as input for differential gene expression analysis with DESeq2.
INSTRUMENT(S): Illumina HiSeq 4000
ORGANISM(S): Danio rerio
SUBMITTER: Sebastian Eilebrecht
PROVIDER: E-MTAB-9860 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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