Project description:The proliferative darkening syndrome (PDS) is an annually recurring disease that causes species-specific die-off of brown trout (Salmo trutta fario) in PDS-impacted pre-alpine rivers of central Europe. The mortality rate for PDS is near 100% and consequently the survival of brown trout populations in the impacted regions is threatened. The progression of PDS occurs in two stages, a subclinical stage and a symptomatic stage, over a time period of more than 3 months starting in spring and culminating with the die-off of brown trout in late summer. Based on experimental evidence it is hypothesized that PDS is caused by an infectious agent. To substantiate this working hypothesis as well as to discern the type of pathogen likely to be responsible for PDS, microarray analysis were conducted using a salmonid-specific cDNA microarray to assess the hepatic immune response of brown trout during the progression of PDS in 7-day intervals over a time period of 98 days.The microarray analysis revealed that brown trout suffering from PDS exhibit increased hepatic expression of important anti-viral genes both during the subclinical stage of PDS, namely the Barrier-to-autointegration factor, and during the symptomatic stage of PDS, namely the interferon regulatory factor 1 as well as the Guanylate-binding protein 1. Additionally, during the symptomatic stage of PDS there is strong hepatic up-regulation of the chemokine CCL19, complement components C1QC and C6, Proteasome activator complex subunits 1 and 2 as well as a variety of both MHC class I and MHC class II transcripts. In conclusion, the increased expression of hepatic immune response genes involved in a variety of immune system processes that mediate defense against infection identified by the microarray analysis during the progression of PDS support the working hypothesis that PDS is caused by an infectious agent. Furthermore, the up-regulation of antiviral immune response genes during both the subclinical stage and the symptomatic stage of PDS suggests that this disease is caused by a pathogenic virus. On May 29, 2008, brown trout (Salmo trutta fario) of the same age class (1+) with an individual weight ranging between 25-85 grams were obtained from a single hatchery (Schwäbischer Fischereihof Salgen, Fachberatung für Fischerei Schwaben, Germany) and randomly allocated to one of two different experimental stations that are both located along the Iller river, named here simply the control station (location by Oberstdorf, Germany) and the treatment station (location by Kempten, Germany). At both experimental stations brown trout were held in tanks (n=750 at the treatment station and n=70 at the control station) that were supplied with water from the Iller river in a flow-through system. Sampling at both experimental stations started on May 29, 2008, which was also the day on which the fish were first transferred to their exposure tanks (referred to as 0 day post exposure; d.p.e), and ended on the 5th of September 2008. At the treatment station 3 fish were sampled each day (always at 2pm), whereas at the control station 3 fish were sampled in 7-day intervals (always at 12 noon). Fish were anaesthetized by a blow to the head and organ tissue of interest (liver, kidney, spleen, gill, muscle, stomach and foregut tissue) were immediately harvested from sacrificed fish, snap-frozen in liquid nitrogen and subsequently stored at -80°C. Livers from the three brown trout (n=3) that were sampled concurrently from both treatment and control group (n=2) in 7-day intervals starting 7 d.p.e (7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91 and 98 d.p.e; n=14) were recruited for the use in the microarray analysis. Microarray analyses were performed using a direct comparison two-channel design in which equimolar amounts of liver sample of one brown trout from both treatment and control group were co-hybridized on the same microarray. For each time point (n=14) microarray co-hybridizations were repeated in triplicate (n=3) and included one dye-swap in order to reduce dye-bias. Thus a total of 42 microarray slides were used in this study (3 biological replicate microarrays x 14 time points = 42 microarrays).

Project description:Two decades after the introduction of oil-based vaccines in the control of bacterial and viral diseases in farmed salmonids, the mechanisms of induced side effects manifested as intra-abdominal granulomas remain unresolved. Side effects have been associated with generation of auto-antibodies and autoimmunity but underlying profile of the inflammatory and immune response has not been characterized. This study was undertaken with the aim to elucidate the inflammatory and immune mechanisms of granuloma formation at gene expression level associated with high and low side effect (granuloma) indices. Groups of Atlantic salmon parr were injected intraperitoneally with oil-adjuvanted vaccines containing either high or low concentrations of Aeromonas salmonicida or Moritella viscose antigens in order to induce polarized (severe and mild) granulomatous reactions. The established granulomatous reactions were confirmed by gross and histological methods at 3 months post vaccination when responses were known to have matured. The corresponding gene expression patterns in the head kidneys were profiled using salmonid cDNA microarrays followed by validation by real-time quantitative PCR (qPCR). qPCR was also used to examine the expression of additional genes known to be important in the adaptive immune response. Granulomatous lesions were observed in all vaccinated fish. Presence of severe granulomas were associated with a profile of up-regulation of innate immunity-related genes such as complement factors C1q and C6, mannose binding protein, lysozyme C, C-type lectin receptor, CD209, Cathepsin D, CD63, LECT-2, CC chemokine and metallothionein. In addition, IL-17A (Th17) was significantly up-regulated (p=0.009) in the group with severe granulomas as were arginase and IgM. None of the genes directly reflective of Th1 T cell lineage (IFN-γ, CD4) or Th2 (GATA-3) differentiation were differentially expressed. Granulomatous reactions following vaccination with oil-based vaccines in Atlantic salmon has the profile of strong expression of genes related to innate immune responses. The expression of IL-17A suggests an involvement of Th17 T cell lineage and is in conformity with strong infiltration of neutrophils and macrophages into inflamed areas. Arginase upregulation shows that macrophages in these reactions are alternatively activated, indicating a Th2-bias. To what extent the IL-17A profile reflects an autoimmune vaccine-based reaction remains elusive but would be in conformity with previous observations of autoimmune reactions in salmon vaccinated with oil-based vaccines. RNA from 12 head kidney samples (12 fish) per group were pooled into groups of 4. The RNA was amplified prior to hybridization to arrays. Three biological and 2 technical replicates (dye-swapped) were utilized in different combinations to hybridize to 18 arrays using RNA from fish with the least injection-site inflammatory reactions (FO-1) as the reference group. The assignment of microarrays to treatment groups for hybridization was randomised by using a random number generator. To minimize technical variability, target synthesis was done in batches of 6 where all treatment groups were equally represented.

Project description:Considerable interest and controversy has arisen over the potential effects of seismic surveys carried out during exploration for oil and gas deposits. Regarding fish, there is a concern that intense sound sources, such as seismic airguns, may injure their auditory system. In this study, salmonid cDNA microarrays, reciprocal suppression subtractive hybridization (SSH) cDNA libraries and quantitative reverse transcription – polymerase chain reaction (QPCR) were used to identify and study a responsive gene set in the inner ear of Atlantic salmon (Salmo salar) following seismic airgun exposure. Microarray analyses on pooled seismic exposed inner ear RNA versus pooled control inner ear RNA revealed 79 unique transcripts (passing background threshold) that were greater than 1.75-fold differentially-regulated by acoustic stress on at least 3 of the 4 slides in the study (including at least one dye-swap). QPCR analyses of 8 microarray-identified transcripts of interest revealed a significant up-regulation (P<0.05) of transcripts encoding nicotinamide riboside kinase 2 (1.89-fold) and hemoglobin subunit alpha-4 (3.78-fold), and a significant down-regulation (P<0.05) of a transcript encoding C14orf159 protein (1.35-fold). QPCR analyses also confirmed an overall up-regulation of transcripts encoding growth hormone I (7.78-fold), c-type lectin receptor A (2.20-fold) and retinol binding protein I (1.24-fold), however these differences were not considered to be statistically significant (P<0.05) due to the high biological variability in the seismic exposed group for these transcripts of interest. A total of 683 expressed sequence tags (ESTs) generated from SSH cDNA salmon ear libraries enriched for genes responsive to seismic airgun noise have been deposited in the GenBank dbEST. Targeted gene discovery in salmon ear allowed for the identification of novel transcripts, including some with sensory-relevant functional annotations, and represents a significant contribution to salmonid hearing research. Initial results demonstrate that genomics has the potential to greatly enhance our understanding of the impact of seismic airguns on gene and molecular pathways involved in hearing, and provide valuable molecular biomarkers that can act as an early warning sensor to acoustic stress. Juvenile Atlantic salmon (Salmo salar) smolt were obtained from North Water Products Ltd., Daniel’s Harbour, NL and held at ambient seawater temperature, in a flow-through system supplied with air at the Northwest Atlantic Fisheries Centre, St. John’s, NL. Two weeks prior to seismic airgun exposures, fish were divided into two 1m3 cages, one each for control (non-exposed) and exposed groups, in a 15,000L aquarium at ambient seawater temperature (0.2°C). Each cage was placed the same distance from the water intake and airstones were placed next to each cage. Fish were fasted for two days prior to exposure. Sixteen control (non-exposed) fish from one cage were sampled prior to seismic activity. Immediately following sampling of control fish, seventeen fish in the remaining cage were placed 2m from a 10in3 Texas Instruments airgun. Fish were subjected to 50 exposures, 1 exposure every 10 seconds, at an average sound pressure level of 204 dB peak-to-peak relative to 1µPa; considered to be a worse case scenario within a few hundred meters of a survey vessel. Seventeen seismic exposed fish were sampled 16 h following exposure. The only aquarium available that was suitable for seismic airgun exposures was not designed to have a regulated photoperiod. For this reason the fish were held under a constant daylight regime. Fish were collected by dip-net and euthanized by severing the spinal cord. The inner ears from each salmon were removed, placed immediately in RNase-free 2 ml tubes, and then flash frozen in liquid nitrogen. RNA isolated from the right inner ear of the 12 seismic exposed and 12 control individuals that gave the highest total RNA yields were used to generate 2 mRNA pools (a “seismic” pool and a “control” pool). Each sample contributed 4.0 µg column purified total RNA to each pool. Comparisons were made for the seismic exposed mRNA pool compared to the control (non-exposed) mRNA pool using the consortium for Genomic Research on All Salmonids Project (cGRASP) 16K (salmonid) cDNA array and the 3DNA Array 900 Detection Kit and instructions (Genisphere). Technical quadruplicate slides including 2 dye-swaps were run for the comparison. Slide GG003_011: Cy5-labeled control ear, Cy3-labeled seismic Slide GG003_012: Cy5-labeled control ear, Cy3-labeled seismic Slide GG003_013: Cy3-labeled control ear, Cy5-labeled seismic Slide GG003_014: Cy3-labeled control ear, Cy5-labeled seismic

Project description:We investigated ecotoxicological effects and toxicogenomic responses in fathead minnows (Pimephales promelas) exposed to an environmentally-relevant concentration (0.83 mg/L) of the munitions compound cyclotrimethylenetrinitramine (RDX) in one year and multi-generational assays. In the one year assay, RDX effects were discerned by comparing breeding groups reared in control or RDX-exposure conditions for one year. RDX had no detectable effect on gonad-somatic index, or condition factor in females assayed at 1 day and at 1, 3, 6, 9, and 12 months, however the liver-somatic index was significantly increased versus controls only at the 12 month time point. RDX had no effect on live-prey capture rates at all time points assayed and no significant impacts on egg production, fertilization or hatch success in the 1-year exposure trial. Genomic analyses indicated that RDX exposure caused limited differential expression of transcripts within time points and no functional conservation of effects indicative of RDX exposure among time points for either brain or liver tissues in the one year exposure. In the multi-generational assay, the effects of acute (96h) exposure to RDX were compared in fish reared to the F2 generation in either control or RDX-exposure conditions. The RDX-reared fish were not observed to have appreciably enhanced RDX tolerance versus the control-reared fish. However, significant differences in gene expression were observed among the control and RDX-reared fish related to neuro-excitatory glutamate metabolism, sensory signaling and processes in neurological development. In total, our results indicate that exposure to an RDX concentration approximating maximum levels observed in the field (0.83 mg/L) caused limited impacts in fathead minnows in a one year exposure, however caused altered expression in genes involved in neural function in a multi-generational exposure. Adult fathead minnows were exposed to 0.83 mg/L (0.15 mg/L standard deviation) in experimental units including 2 male and 4 fish. Five replicate males were randomly sampled with replacement from each of 8 control and 8 RDX-exposed experimental units at 1d, 1mo, 3mo, 6mo, 9mo and 12mo sampling periods. Brain tissue was investigated for differential expression in response to RDX exposure. Data were analyzed in 3 separate investigations. First, the Reference vs Reference data were analysed to determine an empirical false positive detection rate. Next, in order to meet milestones set up by our upper management, we were forced to generate results prior to the end of the bioassay. Therefore, we investigated gene expression among Control and RDX-exposed fish in the 1 day - 6 month sampling periods. Investigation of gene expression among the control and RDX-exposed fish for the 9 month and 12 month time periods were investigated separately.

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Transcription profiling of gill, liver and kidney from amoebic gill disease infected and disease-free Atlantic salmon

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