Project description:Juvenile rainbow trout were fed Biodiet starter (4% body weight per day) with MeHg added at 0, 0.5, 5 and 50 ppm for six weeks. Atomic absorption spectrometry was applied to measure the level of MeHg in the whole fish body. Trout at six weeks were sampled from each group for gene expression analysis by cGRASP 16K cDNA microarrays. MeHg-exposed rainbow trout did not show overt signs of toxicity, nor were significant differences seen in mortality, length, mass, or condition factor. The chronic accumulation of total Hg in trout exhibited dose- and time-dependent patterns. The dysregulated genes have multiple functional annotations, such as involving metabolism, cellular development, ion binding and homeostasis, stress response, immune response, transcriptional regulation, hemolytic development, and apoptotic pathways. These results show that numerous molecular pathways involved in the growth and development of multiple organ systems are disrupted by exposure to moderate levels of dietary MeHg. The dysregulated genes will be selected by further analysis and used as biomarkers for MeHg exposure in aquatic environments. Juvenile rainbow trout (Oncorhynchus mykiss, average body 0.118g) were fed Biodiet Starter (Bio-Oregon) 4% of body weight per day with MeHg added at 0ppm, 0.5ppm, 5ppm and 50ppm (with ethanol as vehicle). Trout at six weeks were sampled from each group for gene expression analysis. Total RNA from individual fish was isolated using Trizol reagent (Invitrogen) and further purified using the RNeasy MiniElute cleanup kit (Qiagen).RNA of ten fish from control group was pooled as a common reference, and total RNA of five individual fish from control and MeHg-treated groups were randomly selected for microarray experiment. cDNA was synthesized from 1 M-NM-<g pooled RNA using SuperScript II Reverse Transcriptase (Invitrogen) according to the manufacturerM-bM-^@M-^Ys protocol. The common reference cDNA targets were labeled with Cy3 and cDNA of individual fish from each group was labeled with Cy5 using the Array 900 Expression Array Detection kit (Genisphere) according to the manufacturerM-bM-^@M-^Ys protocol. The labeled cDNA targets were hybridized to cGRASP 16K cDNA microarrays at 50M-BM-0C for 16 hours. Following the first hybridization, arrays were washed in 2X SSC, 0.2% SDS solution at 50 C 1 x 15 min, 2X SSC 1 x 15 min at room temperature, then 0.2X SSC for 1 x 15 min at room temperature. The fluorescent labeling hybridization (50 C for 4hr) utilized the Genisphere 3DNA Cy3 and Cy5 capture reagents in formamide hybridization buffer. The slides were washed as described above, and the arrays were dried by centrifugation. were scanned using the ScanArray Express (PerkinElmer) at 10 um resolution. The TIFF images of arrays were generated with ScanArray Express software and the intensities of raw data of two-channel arrays were collected by the ImaGene 6.0 (BioDiscovery). Statistical analysis of microarray data was performed using scripts written in R language with LIMMA package.

Project description:Three-month old zebrafish were fed Biodiet starter (4% body weight per day) with MeHg added at 0, 0.5, 5 and 50 ppm for six weeks. Atomic absorption spectrometry was applied to measure the level of MeHg in the whole fish body. Zebrafish at six weeks were sampled from each group for gene expression analysis by NimbleGen Gene Expression 12X135K zebrafish microarrays. MeHg-exposed trout and zebrafish did not show overt signs of toxicity, nor were significant differences seen in mortality, length, mass, or condition factor. The chronic accumulation of total Hg in zebrafish exhibited dose- and time-dependent patterns. The dysregulated genes in MeHg-treated fish have multiple functional annotations, such as involving metabolism, cellular development, ion binding, stress response, transcriptional regulation, and apoptotic pathways. These results show that numerous molecular pathways involved in the growth and development of multiple organ systems are disrupted by exposure to moderate levels of dietary MeHg. The dysregulated genes will be selected by further analysis and used as biomarkers for MeHg exposure in aquatic environments. This study will allow us to assess the potential impacts of low-level exposure to environmental MeHg in the food chain and on the health of humans and animals. Three-month old zebrafish (Danio rerio, average body 0.149 g) were fed Biodiet Starter (Bio-Oregon) 4% of body weight per day with MeHg added at 0ppm, 0.5ppm, 5ppm and 50ppm (with ethanol as vehicle). Fish at six weeks were sampled from each group for gene expression analysis. Three fish from each treatment group were used for microarray experiments. Total RNA from individual fish was isolated using Trizol reagent (Invitrogen) and further purified using the RNeasy MiniElute cleanup kit (Qiagen). Double-strand cDNA was synthesized from 10ug total RNA of individual fish by using Superscript Double-Stranded cDNA synthesis Kit (Invitrogen). ). One ug double strand DNA was labeled with Cy3 using One-Color DNA labeling Kit (NimbleGen), then hybridized to NimbleGen 12X135K array. The arrays were scanned at 2um on a NimbleGen MS200 scanner with auto-gain adjust. The TIFF images were gridded and extracted using NimbleScan v. 2.6. Expression data were normalized using the Robust Multichip Average (RMA) algorithm.

Project description:We investigated the effects of chronic TCDD exposure on global gene expression in developing rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout (0.18M-BM-10.01g) were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100ppb, and ten fish were sampled and pooled from each group for microarray experiments at 28 days after initiation of the exposure. Gene expression analysis was performed using the Genomics Research on All Salmonids Project (cGRASP) 16K cDNA microarrays. TCDD-responsive whole body transcripts identified in the microarray experiments have putative functions involved in various biological processes including cellular process, metabolic process, biological regulation, and response to stimulus. In addition, TCDD caused leisons in multiple organ systems in juvenile rainbow, including skin, oropharynx, liver, gas bladder, intestine, pancreas, nose and kidney. Juvenile rainbow trout (0.18M-BM-10.01g) were fed Biodiet starter (Bio-Oregon) (4% body weight per day) with TCDD added at 0, 0.1, 1, 10 and 100 ppb. Fish were sampled after 28 days. Total RNA from individual fish was isolated using TRIzol reagent (Invitrogen). Total RNA of ten control trout were pooled as a common reference which were labeled with Cy3. Total RNA of ten fish of each treatment were labeled wih Cy5. cDNA were synthesized using SuperScript II Reverse Transcriptase (Invitrogen) (1 M-NM-<g pooled RNA per synthesis). Targets were labeled using the Array 900 Expression Array Detection kit (Genisphere) following the manufacture protocol. 1M-BM-5g RNA of pooled ten control fish were labled with Cy3 and 1M-BM-5g RNA of pooled ten TCDD-treated fish were labled with Cy5, then day-swap was performed. Two arrays were run for each comparison. Microarrays were scanned at 10 M-BM-5m resolution using a ScanArray Express (PerkinElmer Life Sciences, Inc, Boston, MA). The photomultiplier tube settings (PMT) for Cy3 and Cy5 were 70 and 65-66, respectively. TIFF images of arrays were generated with ScanArray Express software (PerkinElmer). Fluorescence intensity data for Cy3 and Cy5 channels were extracted from TIFF images using ImaGene 7.5 software (BioDiscovery Inc., El Segundo, CA). Background correction, data transformation (setting background corrected values < 0.01 to 0.01), Lowess normalization, and analysis (e.g. fold-change calculations) were performed using GeneSpring GX 7.3 (Agilent Technologies, Palo Alto, CA)

Project description:Methylmercury (MeHg) is a ubiquitous environmental toxicant that is often detected in the tissues of fish-eating species. It has been well established that prenatal exposure to MeHg can lead to widespread brain damage and impaired neurological development resulting in defects ranging from severe cerebral palsy and cognitive deficits to impaired motor and sensory function. A wide range of environmental toxicants have been shown to induce transgenerational inheritance of diseases via changes in DNA methylation—a well-known epigenetic modification. Our previous research has demonstrated that developmental MeHg exposure may yield transgenerational inheritance of neurological dysfunction in adult F3-lineage zebrafish via quantitative neurobehavioral assays that evaluated the visual startle response, retinal electrophysiology, and locomotor function. The objective of the current study was to examine the correlation between neurobehavioral phenotypes and the transcriptome activity in the brain and retina of F3 zebrafish by RNA sequencing (RNAseq). Transcriptomic analyses of F3 generation MeHg-treated zebrafish (compared to control) revealed significant gene dysregulation in both the brain and retina. There were 1648 and 138 differentially expressed genes in the retina and brain, respectively (FDR <0.05). Thirty-five genes were commonly dysregulated in both organs. Gene set enrichment analysis revealed significantly enriched pathways including: neurodevelopment, visual functions, phototransduction, and motor movement. Moreover, commonly dysregulated genes were associated with circadian rhythm and metabolic pathways, as well as arginine and proline metabolism. To our knowledge, this is the first evidence of a transgenerational transcriptome induced by ancestral developmental exposure to MeHg in any species. If the transgenerational phenotypes, transcriptome, homologous biomarkers, or similar molecular pathways hold true for human populations, our findings have significant impact on global public health in terms of identifying the susceptible populations using biomarkers and preventing transgenerational inheritance of MeHg-induced neurobehavioral deficits.

Project description:We investigated the effects of chronic TCDD exposure on global gene expression in developing rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout(0.18M-BM-10.01g) were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100ppb, and ten fish were sampled and pooled from 10 ppb group at 7, 14, 28 and 42 days for microarray experiments after initiation of the exposure. Gene expression analysis was performed using the Genomics Research on All Salmonids Project (cGRASP) 16K cDNA microarrays. TCDD-responsive whole body transcripts identified in the microarray experiments have putative functions involved in various biological processes including response to stimulus, cell wall organization or biogenesis, growth and cell proliferation. In addition, TCDD caused leisons in multiple organ systems in juvenile rainbow, including skin, oropharynx, liver, gas bladder, intestine, pancreas, nose and kidney. Juvenile rainbow trout (0.18M-BM-10.01g) were fed Biodiet starter (Bio-Oregon) (4% body weight per day) with TCDD added at 0, 0.1, 1, 10 and 100 ppb. Fish were sampled and from 10 ppb group at 7, 14, 28 and 42 days for microarray experiments after initiation of the exposure. Total RNA from individual fish was isolated using TRIzol reagent (Invitrogen).Total RNA of ten control trout were pooled as a common reference which were labeled with Cy3. Total RNA of ten fish of each treatment were labeled wih Cy5. cDNA were synthesized using SuperScript II Reverse Transcriptase (Invitrogen) (1 M-NM-<g pooled RNA per synthesis). Targets were labeled using the Array 900 Expression Array Detection kit (Genisphere) following the manufacture protocol. 1M-BM-5g RNA of pooled ten control fish were labled with Cy3 and 1M-BM-5g RNA of pooled ten TCDD-treated fish were labled with Cy5, then day-swap was performed. Two arrays were run for each comparison. Microarrays were scanned at 10 M-BM-5m resolution using a ScanArray Express (PerkinElmer Life Sciences, Inc, Boston, MA). The photomultiplier tube settings (PMT) for Cy3 and Cy5 were 70 and 65-66, respectively. TIFF images of arrays were generated with ScanArray Express software (PerkinElmer). Fluorescence intensity data for Cy3 and Cy5 channels were extracted from TIFF images using ImaGene 7.5 software (BioDiscovery Inc., El Segundo, CA). Background correction, data transformation (setting background corrected values < 0.01 to 0.01), Lowess normalization, and analysis (e.g. fold-change calculations) were performed using GeneSpring GX 7.3 (Agilent Technologies, Palo Alto, CA)

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Toxic effects of dietary methylmercury (MeHg) on juvenile rainbow trout

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