title: Identification of conserved hepatic transcriptomic responses to 17β-estradiol using high-throughput sequencing in brown trout.
abstract: Estrogenic chemicals are major contaminants of surface waters and can threaten the sustainability of natural fish populations. Characterization of the global molecular mechanisms of toxicity of environmental contaminants has been conducted primarily in model species rather than species with limited existing transcriptomic or genomic sequence information. We aimed to investigate the global mechanisms of toxicity of an endocrine disrupting chemical of environmental concern [17β-estradiol (E2)] using high-throughput RNA sequencing (RNA-Seq) in an environmentally relevant species, brown trout (Salmo trutta). We exposed mature males to measured concentrations of 1.94, 18.06, and 34.38 ng E2/l for 4 days and sequenced three individual liver samples per treatment using an Illumina HiSeq 2500 platform. Exposure to 34.4 ng E2/L resulted in 2,113 differentially regulated transcripts (FDR < 0.05). Functional analysis revealed upregulation of processes associated with vitellogenesis, including lipid metabolism, cellular proliferation, and ribosome biogenesis, together with a downregulation of carbohydrate metabolism. Using real-time quantitative PCR, we validated the expression of eight target genes and identified significant differences in the regulation of several known estrogen-responsive transcripts in fish exposed to the lower treatment concentrations (including esr1 and zp2.5). We successfully used RNA-Seq to identify highly conserved responses to estrogen and also identified some estrogen-responsive transcripts that have been less well characterized, including nots and tgm2l. These results demonstrate the potential application of RNA-Seq as a valuable tool for assessing mechanistic effects of pollutants in ecologically relevant species for which little genomic information is available.
authors.affiliation: Biosciences, College of Life & Environmental Sciences, University of Exeter, Exeter, United Kingdom.
authors.forename: Tamsyn M
authors.initials: TM
authors.lastname: Uren Webster
authors.affiliation: Biosciences, College of Life & Environmental Sciences, University of Exeter, Exeter, United Kingdom.
authors.forename: Janice A
authors.initials: JA
authors.lastname: Shears
authors.affiliation: Biosciences, College of Life & Environmental Sciences, University of Exeter, Exeter, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Moore
authors.affiliation: Biosciences, College of Life & Environmental Sciences, University of Exeter, Exeter, United Kingdom E.Santos@exeter.ac.uk.
authors.forename: Eduarda M
authors.initials: EM
authors.lastname: Santos
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D054750:Ecotoxicology / Q000379:methods; D052244:Endocrine Disruptors / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D059014:High-Throughput Nucleotide Sequencing; D008099:Liver / Q000187:drug effects* / Q000502:physiology; D008297:Male; D017683:Oncorhynchus / Q000235:genetics*; D014874:Water Pollutants, Chemical / Q000494:pharmacology
chemical_list: D052244:Endocrine Disruptors; D029941:Fish Proteins; D014874:Water Pollutants, Chemical; D004958:Estradiol
keywords: Illumina; RNA-Seq; salmonid; sequencing; transcriptomics