Gene expression changes in the female zebrafish (Danio rerio) brain in response to acute exposure to methylmercury
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ABSTRACT:
ORGANISM(S): Danio rerio
PROVIDER: GSE22662 | GEO | 2010/10/01
SECONDARY ACCESSION(S): PRJNA127997
REPOSITORIES: GEO
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Project description:Methylmercury (MeHg) is a potent neurotoxin and endocrine disruptor that accumulates in aquatic systems. Previous studies have shown suppression of hormone levels in both male and female fish, suggesting effects on gonadotropin regulation in the brain. We investigated the gene expression profile in adult female zebrafish whole brain induced by acute (96 hr) MeHg exposure. Fish were exposed by injection to 0 or 0.5 M-BM-5g MeHg/g. Gene expression changes in the brain were examined using a two-color 22,000 feature zebrafish microarray. At a significance level of p<0.01, 79 genes were up-regulated and 76 genes were down-regulated in response to MeHg exposure. Individual genes exhibiting altered expression in response to MeHg exposure implicate effects on glutathione metabolism and GABA-A receptors in the mechanism of MeHg neurotoxicity. Gene ontology (GO) terms significantly enriched among altered genes included protein folding, cell redox homeostasis, and steroid biosynthetic process. The most affected biological functions were related to the nervous system development and function, as well as lipid metabolism and molecular transport. These results support the involvement of oxidative stress and effects on protein structure in the mechanism of action of MeHg in the female brain. Future studies will compare the gene expression profile induced in response to MeHg with that induced by other toxins and investigate responsive genes as potential biomarkers of MeHg exposure. Wild-type strain AB-1 zebrafish (Zebrafish International Resource Center, University of Oregon, Eugene, OR) were cultured at the Columbia Environmental Research Center (CERC), USGS, for MeHg exposures. Adult female zebrafish were injected with 0 M-NM-<g/g or 0.5 M-NM-<g/g MeHg in 2 M-BM-5L Na2CO3 (pH 6.98)/g body weight. After 96 hr, fish were anesthetized using ethyl 3-aminobenzoate methanesulfonate (MS-222, Sigma, St. Louis, MO). Whole brains were removed, flash frozen with liquid nitrogen and stored at 80M-BM-0C. For the microarray experiment, two zebrafish brains were pooled per sample. Four pooled samples were taken from fish treated with 0.5 M-NM-<g/g of MeHg, and the other five were taken from control fish treated with sodium carbonate. Array hybridizations were performed using a reference design, where each sample was compared to a reference sample. The reference sample consisted of equal amounts of RNA from control and treated female brains. Five replicates for the control and four replicates for the treated were analyzed. cDNA synthesis, cRNA labeling, amplification and hybridization were performed following the manufacturerM-bM-^@M-^Ys kits and protocols (Agilent Low RNA Input Fluorescent Linear Amplification Kit and Agilent 60-mer oligo microarray processing protocol; Agilent, Palo Alto, CA).
2010-09-30 | E-GEOD-22662 | biostudies-arrayexpress
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.
2013-06-01 | GSE32430 | GEO
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.
2013-06-01 | E-GEOD-32430 | biostudies-arrayexpress
Project description:This study sought to evaluate the effects of dietary MeHg exposure on adult female yellow perch (Perca flavescens) and zebrafish (Danio rerio) reproduction by relating controlled exposures with subsequent reproductive effects. Yellow perch were used in the study for their socioeconomic and ecological importance within the Great Lakes basin, and the use of zebrafish allowed for a detailed analysis of the molecular effects of MeHg. MeHg exposures at environmentally relevant levels were done in zebrafish for a full life cycle, mimicking a realistic exposure scenario, and in adult yellow perch for twenty weeks, capturing early seasonal ovarian development. In zebrafish, several genes involved in reproductive processes were shown to be dysregulated by RNA-seq and QPCR, but no significant phenotypic or physiological changes were observed with ovarian staging, fecundity, or embryo mortality. Yellow perch did not appear to be affected by MeHg, either at a molecular level, as assessed by QPCR of eight genes in the pituitary, liver, and ovary tissue, or a physiological level, as seen with ovarian somatic index, circulating estradiol, and ovarian staging. Lack of impact in yellow perch limits the usefulness of zebrafish as a model and suggests that the reproductive sensitivity to environmentally relevant levels of MeHg differs between yellow perch and zebrafish.
2018-01-01 | GSE73615 | GEO
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.
2018-01-01 | GSE73795 | GEO
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.
2018-01-01 | GSE73794 | GEO
Project description:Methylmercury (MeHg) is a teratogen with adverse effects on embryogenesis from fish to man. The adverse developmental outcomes of MeHg are well understood, but molecular understanding of teratogenic effects is rather limited. We performed here a genome - wide transcriptional analyses of 6, 30 and 50 μg/L MeHg treated zebrafish embryos from 4 to 72 h post-fertilization (hpf) using RNA-sequencing and self-printed microarray, and conducted a systematical comparison of MeHg - induced transcriptomic responses observed in this and our previous studies. We found that genes linked to gene ontology in terms of oxidative stress, visual, photoreception and cilium, and GABAergic synapse were enriched in embryo exposed from 4 to 72 hpf. The significantly altered genes involved in MAP kinase, TGF beta signaling pathway, oxidative phosphorylation, and glutathione metabolism were enriched across different exposure scenarios. We obtain 22 genes significantly regulated by MeHg, particularly the significant changes were determined in embryos exposed to 6 μg/L MeHg, which did not cause obviously teratogenic effects. Our findings show that the genes whose expression is altered by MeHg in embryonic stages may play important roles in adverse developmental endpoints and might be served as signatures for teratogenic effects.
2022-12-21 | GSE206531 | GEO
Project description:The goal of this project is to identify neural and molecular biomarkers as predictors of MeHg exposure and deficits in specific neurobehavioral endpoints. Specifically, we are investigating the effects of sublethal MeHg exposure (1, 2 and 3.5 ppm of wild-caught walleye diet) on developing zebrafish by analyzing early lifestage (ELS) toxicity, changes in global gene expression by microarray analysis and quantitative real-time PCR (QPCR), and neurobehavioral dysfunction. Gene expression analysis in exposed embryos was performed using an 8,000 element custom zebrafish cDNA microarray. Microarray results were validated using QPCR. A number of the early life stage zebrafish genes found to be dysregulated by maternal MeHg have functional annotations involving cell division, cell cycle progression, neurodevelopment, liver development, ion-binding, transcriptional regulation and endopeptidase activity.
2016-09-27 | GSE21964 | GEO
Project description:Methylmercury (MeHg) is an environmental neurotoxicant known to cause adverse effects in fish, such as locomotor abnormalities, visual deficits or teratogenesis. However, very few studies have investigated the effects of environmentally realistic MeHg exposures on the gene expression of fish embryos. Since the primary source of MeHg exposure in wild fish is through the diet, this study analyzed differential gene expression in zebrafish embryos from parents that had been subjected to environmentally relevant dietary MeHg exposures (0, 1, 3, and 10ppm) throughout their whole life cycle.
2018-01-01 | GSE74416 | GEO
Project description:Methylmercury (MeHg) toxicity in humans manifests deficits in neurological function. Cases of prenatal exposure to mercury have established that the developing nervous system is most highly susceptible to perturbation by MeHg. At a cellular level, MeHg-induced defects result from altered neuronal proliferation, migration and pathfinding. However, the molecular targets of MeHg that give rise to these outcomes are not fully understood. In an overall effort to identify the fundamental molecular targets of MeHg in neural development, we are investigating the effects of MeHg on gene expression and protein function in the Drosophila model. Since the fundamental signaling pathways in development of multicellular animals have been extensively characterized in Drosophila, and demonstrate high degree of conservation in vertebrates, we believe these data will lead us to the most pertinent pathways affected by MeHg and begin to elucidate the mechanism of MeHg neural toxicity relevant to cases of human exposure to this prevalent environmental toxin. Our aim is to identify fundamental signaling pathways in neural development that are targets for MeHg poisoning. Our hypothesis is that MeHg, by direct interaction with cysteine thiol groups, alters the function signaling pathway proteins and subsequently alters transcription of target genes in the respective pathways. Our hypothesis is supported by our recent data demonstrating a direct action of MeHg in activating the Notch receptor pathway and upregulating target gene expression. We anticipate a microarray analysis will elucidate additional fundamental signaling pathways where transcription is affected by this toxin. Fertilized female flies are fed on food containing methylmercury (1-20 micromolar) or solvent control (DMSO) for a period of five days to allow for MeHg penetration in to eggs. Flies are then transfered to a cage for embryo collection for a discrete window of time (e.g. 1hr). Embryos are aged 16-24 hours and collected for total RNA extraction using the Trizol reagent. Total RNA is quantitated by spectrophotometry with a Nanodrop reader. While concentration dependent effects of MeHg are of interest, initial experiments will be conducted on samples exposed to a single concetration known to illicit effect in other bioassays (e.g. 10 micromolar). The goal is to see which genes are up- or down-regulated with MeHg exposure, as compared to control embryos that are not exposed. Emphasis in the analysis stage will be in identifying target genes of known signaling pathways. Keywords: dose response
2007-10-11 | GSE9271 | GEO