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Estrogen modulates hepatic gene expression and survival of rainbow trout infected with pathogenic bacteria Yersinia ruckeri.

ABSTRACT: Juvenile rainbow trout were exposed to two different concentrations of 17β-estradiol (E2) (2 or 20 mg/kg feed), and then infected with three concentrations of Yersinia ruckeri, a bacterial pathogen causing massive losses in wild and farmed salmonid populations. Infection with Y. ruckeri caused mortality of trout, and this effect was significantly enhanced by simultaneous exposure to high E2 dose. Analysis of hepatic gene expression profiles revealed complex regulations of pathways involved in immune responses, stress responses and detoxicification pathways. E2 markedly reduced expression of several genes implicated in xenobiotic metabolism. The results suggest that the interaction between pathogen and E2 interfered with the fish’s capability of clearing toxic compounds. The findings of the current study add to our understanding of multiple exposure responses in fish.

ORGANISM(S): Oncorhynchus mykiss

PROVIDER: GSE38763 | GEO | 2012/06/17

SECONDARY ACCESSION(S): PRJNA168566

REPOSITORIES: GEO

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Project description:Whirling disease, caused by the pathogen Myxobolus cerebralis, afflicts several salmonid species. Rainbow trout are particularly susceptible and suffer high mortality rates. The disease is persistent and spreading in hatcheries and natural waters of several countries, including the U.S., and the economic losses associated with whirling disease have been extremely large. In this study, gene expression profiling was conducted for resistant and susceptible rainbow trout strains following pathogen exposure with the primary objective of identifying specific genes associated with whirling disease resistance. Several genes were significantly up-regulated in skin following pathogen exposure for both the resistant Hofer and susceptible Trout Lodge rainbow trout strains. For both strains, response to infection appears to be associated with the interferon system. Metallothionein is differentially expressed between the resistant and susceptible strains and is a good candidate for future studies due to its diverse functional roles in inflammation and immune response. The present study has provided the first examination into the genetic basis underlying rainbow trout’s immune response and resistance to the whirling disease pathogen. The identified genes have allowed us to gain initial insight into the molecular mechanisms associated with a salmonid host’s immune response and resistance to whirling disease infection. Keywords: Disease state comparison. 1st comparison: exposed vs control. 2nd comparison: resistant vs susceptible strains Resistant (Hofer) and susceptible (Trout Lodge) rainbow trout strains were exposed to 2,000 triactinomyxons (whirling disease pathogen) per fish. Unexposed controls for each strain were treated identically to exposed other than their lack of pathogen exposure. After twenty-four hours, caudal fin tissue was collected for RNA extraction. Amplified RNA was competitively hybridized (exposed versus control) for each strain. Four biological replicates were used for each experimental condition and a balanced block design was incorporated.

Project description:These studies aimed to investigate the hepatic transcriptional response of brown trout to the natural estrogen, E2, and the herbicide linuron. We exposed mature male brown trout to three concentrations of each chemical for 4 days and sequenced the hepatic transcriptome of 3 individuals per treatment group in order to determine the global mechanisms of toxicity of these environmental contaminants. We assembled the brown trout transcriptome using a de novo approach. Subsequent differential expression analysis identified a total of 2113 differentially-regulated transcripts in the group exposed to the highest E2 treatment concentration, and 822 differentially-regulated transcripts across all linuron treatments. For E2, differentially-expressed transcripts included those encoding known oestrogen-responsive genes, while regulated processes included those associated with vitellogenesis including lipid metabolism, cellular proliferation and ribosome biogenesis. For linuron, there was a striking down-regulation of transcripts encoding the majority of the enzymes involved in the cholesterol biosynthesis pathway, and also a considerable induction of transcripts involved in cellular stress response including Cyp1a. Fish were exposed to 3 concentrations of E2 (measured concentrations were 1.9, 18.1 and 34.4 ng/L), 3 concentrations of linuron (measured concentrations were 1.7, 15.3 and 225.9 µg/L) and water controls for 4 days. Liver mRNA from 3 replicate individuals per treatment was sequenced in an Illumina HiSeq 2500 platform. Two control groups (n=6 fish in total) were included. Using a de novo approach, we assembled the hepatic transcriptome for brown trout. Sequence reads were re-mapped to the assembled transcriptome using Bowtie2 and transcript expression profiling was conducted using EdgeR. ERCC spike controls were added to all individual samples, allowing for the assessment of the reproducibility and dynamic range for transcript expression quantification in our experiments.

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Estrogen modulates hepatic gene expression and survival of rainbow trout infected with pathogenic bacteria Yersinia ruckeri.

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