Fetal Exposure of low dose Methylmercury Enhances CREB Activity to Induce Premature Neuronal Differentiation During Embryonic Cortex Development
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE178929 | GEO | 2023/02/13
REPOSITORIES: GEO
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Project description:The greatest concern for exposure to methylmercury (MeHg) lies with the fetus and young children, as exemplified in historic cases of Congenital Minamata Disease (CMD) resulting from prenatal exposure. Children that experience CMD characteristically present with various degrees of cognitive and motor symptoms and signs, much like cerebral palsy. MeHg has thus been characterized as a neurotoxicant, where motor deficits are ascribed to central nervous system targets. Skeletal muscle as a post-synaptic MeHg target and contributor to the etiology of CMD has garnered far less attention. Prior studies using Drosophila to model CMD revealed that developmental exposure of MeHg in the larval/pupal stages can elicit graded and latent dose responses affecting adult flight behavior at lower doses (0.4-2.5 ppm in food) and eclosion (emergence from the pupa case) at higher doses (>2.5 ppm in food). The latter phenotype is accompanied by dysmorphogenesis of skeletal muscles. Here, we investigate respective roles for muscle and neural targets in MeHg toxicity. Using RNA-seq analysis, we find that developmental MeHg exposure produces 10-times as many differentially expressed transcripts in indirect flight muscle (IFM) compared to the VNC. Among known MeHg response genes, Nrf2 antioxidant response pathway genes showed muscle-specific MeHg-induced expression changes. Within the muscle transcriptome, the most enriched and significant Gene Ontology terms identified genes required for mitochondrial ribosomal translation at the pupa stage and mitochondrial function (respiratory chain complex I) and vesicle trafficking (ESCRT III) pathways in adults, all showing decreased expression with MeHg exposure. By using an intact, whole-animal developmental model, we identify preferential candidates to evaluate a novel role for muscle-specific mitochondria and intercellular vesicular communication mechanisms as targets in MeHg toxicity and the etiology of CMD.
2024-11-26 | GSE282865 | 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
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) 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) is an environmental pollutant of global public health concern. MeHg is associated with immune dysfunction but the underlying mechanisms are unclear. The most common route of MeHg exposure is through consumption of fatty fish that contain beneficial n-3 polyunsaturated fatty acids (PUFA) that may protect against MeHg toxicity. To better inform individual costs and benefits of fish consumption, we aimed to identify candidate epigenetic biomarkers of biological responses that reflect MeHg toxicity and PUFA protection.
2022-10-06 | GSE207443 | GEO
Project description:Methylmercury (MeHg) is a highly toxic environmental pollutant. To understand the mechanisms of toxicity of the compound and possibly to discover new biomarkers for environmental monitoring, we have conducted toxicogenomics studies. We designed 126k-cod-oligonucleotide arrays and performed genome-wide gene expression assays in liver samples from juvenile cod treated with MeHg (0.5 and 2 mg/kg body weight). Microarray analysis showed MeHg differentially regulated hundreds of genes. Gene Ontology and pathway analyses of differentially regulated genes revealed that MeHg modulated mainly genes involved in immune response, oxidative stress response, tissue remodelling, and energy pathways such as lipid, carbohydrate and amino acid metabolism. The results provide insights into the mechanisms of toxicity of MeHg and provide candidate biomarkers of exposure to MeHg for further evaluation. Analyzed 5 samples from each of 3 groups: control, 0.5 mg/BW MeHg treated, and 2 mg/BW MeHg treated. Liver total RNA was reverse transcribed, Cy3-labeled, and hybridized (one-color hybridzation).
2013-01-22 | E-GEOD-38746 | biostudies-arrayexpress
Project description:Methylmercury (MeHg) is a highly toxic environmental pollutant. To understand the mechanisms of toxicity of the compound and possibly to discover new biomarkers for environmental monitoring, we have conducted toxicogenomics studies. We designed 126k-cod-oligonucleotide arrays and performed genome-wide gene expression assays in liver samples from juvenile cod treated with MeHg (0.5 and 2 mg/kg body weight). Microarray analysis showed MeHg differentially regulated hundreds of genes. Gene Ontology and pathway analyses of differentially regulated genes revealed that MeHg modulated mainly genes involved in immune response, oxidative stress response, tissue remodelling, and energy pathways such as lipid, carbohydrate and amino acid metabolism. The results provide insights into the mechanisms of toxicity of MeHg and provide candidate biomarkers of exposure to MeHg for further evaluation.
2013-01-22 | GSE38746 | 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
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