Toxicogenomic signatures associated with methylmercury induced developmental toxicity in the zebrafish embryos.
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ABSTRACT:
ORGANISM(S): Danio rerio
PROVIDER: GSE206531 | GEO | 2022/12/21
REPOSITORIES: GEO
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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
Project description:In order to investigate the underlying mechanisms of methylmecury (MeHg)-mediated toxicity to Atlantic cod (Gadus morhua), we analyzed the liver proteome of fish exposed in vivo to MeHg (0, 0.5, 2 mg/kg body weight) for 2 weeks. Label-free quantitative mass spectrometry enabled quantification of 1143 proteins, and 125 were differentially regulated between MeHg-treated samples and controls. Six proteins among the top differentially regulated (T23O, GLNA EPS8L2, APOA4, RAP1B, CZTZ) were analyzed using selected reaction monitoring (SRM). Supported by bioinformatics analyses, we conclude that MeHg disrupts mainly redox homeostasis and energy generating metabolic pathways in cod liver, the latter potentially modulated through MeHg-induced oxidative stress.
2016-08-09 | PXD004311 | Pride
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 µg 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.
2010-10-01 | GSE22662 | GEO
Project description:This series compares the effects that two pharmacologically distinct ligands at the mitochondrial peripheral-type benzodiazepine receptor (Bzrp). PK11195 (4.0 mg/kg, a presumed antagonist) has no observable adverse effects in pregnant mice on either 8 days post-coitus (d.p.c.) or 9 d.p.c. Furthermore, PK11195 is shown to rescue mouse fetuses from microphthalmia or microphthalmia-microcephaly induced with 2CdA or MeHg, respectively; effects of PK11195 on EtOH-induced craniofacial malformations are not yet unkown. Ro5-4864 (4.0 mg/kg, a presumed agonist) is weakly teratogenic on 8 d.p.c. (effects on 9 d.p.c. unknown) and this Bzrp ligand does not rescue fetuses from malformations induced with either 2CdA or MeHg; effects of Ro5-4864 on EtOH-induced craniofacial malformations is unknown for either sensitive (C57BL/6J) or insensitive (C57BL/6N) strains. The 4.0 mg/kg dose of Bzrp ligands is consistent with pharmacological activity in several studies. Pregnant mice were exposed to these agents on 8 d.p.c. (2CdA, EtOH) or 9 d.p.c. (MeHg). The test dose of 2.5 mg/kg 2CdA was modeled for a 5% increased risk of microphthalmia in term fetuses. Full remediation with PK11195 anticipated. The test dose of 5.0 mg/kg MeHg gives an estimated 20% increased risk of microphthalmia-microcephaly (encephalopathy) in term fetuses. Partial remediation with PK11195 is anticipated to <10% malformations. Again the effects of PK11195 on EtOH teratogenicity is not yet known. The sampling time was chosen as the time of p53 protein induction (3.0h to 4.5h post-treatment). Whereas co-treatment with PK11195 suppresses embryonic p53 protein induction Ro5-4864 does not block this reaction. All measurements were on RNA from the embryonic headfold (8 d.p.c.) or prosencephalon (9 d.p.c.). Keywords = peripheral benzodiazepine receptor Keywords = Bzrp ligands Keywords = PK11195 Keywords = Ro5-4864 Keywords = embryo Keywords = p53 protein induction
2010-06-09 | E-GEOD-1072 | biostudies-arrayexpress
Project description:The developing human brain is uniquely vulnerable to methylmercury (MeHg) intoxication. Given the limited experimental access to MeHg-intoxicated human fetal brain, neither the threshold levels for neurotoxic effects nor the mechanisms underlying neurodevelopmental MeHg toxicity are clear. The observed persistent and latent effects in human and animal exposures and the relatively nonspecific neurodevelopmental changes suggest that MeHg impacts fundamental neurodevelopmental processes. Human cortical development is characterized by the sequential emergence of different neural stem cells, precursors, intermediate progenitors and postmitotic neurons, a sequence that can be replicated in human-induced pluripotent stem cell (hiPSC)-derived differentiating neuronal cultures. As the developing human cortex has been shown to be particularly vulnerable to fetal MeHg exposure, we assessed here by means of single cell RNA sequencing (scRNAseq) MeHg’s effects on different stages of differentiation and cell types present in early cortical cultures differentiated from hiPSC cells. Cortical cultures differentiating from hiPSC were exposed to toxicologically relevant MeHg (0.1 and 1.0 µM) continuously for 6 days at two different time points (days 4-10; and/or days 14-20) of early cortical differentiation under conditions below the cytotoxic threshold. Previous analysis at days 21-23 revealed subtle changes in cortical differentiation markers and cellular energetics, but no effect on glutathione levels, a biomarker of acute MeHg toxicity. Therefore, here we assessed the possibility of persistent effects on neurodevelopment at day 38 of differentiation (18 or 28 days after cessation of MeHg exposure). At this time, we observed subtle but significant changes in the population size of different cell types and the fractions of cells present in the different phases of the cell cycle. The observed MeHg-induced changes were developmental-stage and MeHg paradigm-specific. We further assessed overall differential gene expression, quantifying the number of genes showing significantly up- or down-regulated expression and identifying the genes affected at least partially identified biological processes affected. Importantly, the MeHg-induced changes in gene expression were also developmental-stage and MeHg-exposure paradigm specific. Thus, our studies demonstrate for the first time in a human model that MeHg exposure induces persistent changes in gene expression well after cessation of exposure, these changes are cell type- and developmental stage-specific, and this outcome is highly dependent on the concentration and timing of MeHg exposure. We conclude hiPSC-derived developing neuronal cultures provide an excellent human model to study persistent neurodevelopmental toxicity of MeHg in the developing human cortex.
2021-06-11 | GSE169751 | GEO
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: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 well-known neurotoxicant, particularly harmful for the developing brain. Selenium is a nutrient previously shown to interact with MeHg, however the molecular mechanisms behind these interaction is not fully described. To explore the effect of selenium on MeHg, mice were exposed to selenomethionine (SeMet) and MeHg in a 2 x 3 full factorial design for 12 weeks. After termination, organs, including the brain, were collected for Hg and Se analysis. The hippocampus was collected and analysed using gel free proteomics and RNA sequencing (RNA-seq). The presence of SeMet reduced the amount of Hg in several organs, including the brain, while the level of Hg were increased in the feces. The presence of Hg also increased the concentration of selenium in liver and cortex. Proteomic and RNA-seq analyses showed that several known pathways of MeHg toxicity, such as oxidative stress, altered metabolism and calcium disruption were alleviated when SeMet were present. Our results suggest that SeMet can to a certain extent ameliorate the neurotoxic effects of MeHg in a mouse model. Although, whether this is due to decrease of body burden of Hg or through direct interactions with selenium in vivo remains unclear.
2020-08-29 | GSE135381 | 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.
2008-03-13 | E-GEOD-9271 | 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