Project description:Background and Methods: High mercury (Hg) levels are a significant concern in many aquatic environments, and adverse effects of Hg exposure in fish can include altered behavior, reproduction, growth, and increased stress responses. In addition, human health concerns over Hg continue to warrant new research on its mechanisms of action. The objectives of this study were to investigate the impacts of Hg on the female largemouth bass (LMB) central nervous system transcriptome by conducting a laboratory injection experiment with 2.5 µg/g body weight in addition to sampling LMB from an environment that contains high levels of Hg (St. Mary’s River, Florida, USA). These animals were compared to LMB that inhibit river systems with lower Hg (Big Wekiva, Santa Fe and St. John’s Rivers Florida, USA). A LMB 8 x 15 K microarray was used for hypothalamic (laboratory) and whole brain (field) transcriptomics analysis. Results: Mercury in the blood of LMB collected from St Mary’s River was significantly elevated 3-fold (~ 0.1 ng Hg/ml blood) compared to LMB collected from the other three sites (~ 0.03 ng Hg/ml blood). In the hypothalamus of Hg injected LMB, there were 937 genes that showed differential expression (raw p = 0.05) but there were no probes that passed an FDR for multiple hypothesis correction. In contrast, in field collected LMB there were 2909 genes that that showed differential expression (raw p = 0.05) of which 38 were significant after correction for multiple hypothesis testing (FDR = 0.05). These included Hsp90 co-chaperone Cdc37, multicopper oxidase, mismatch repair protein Msh6, and 16 kDa heat shock protein A. Functional enrichment in whole brains of LMB collected from the field sites revealed that genes involved in the biological processes of protein folding and targeting, regulation of protein metabolic process, and protein degradation (i.e. ubiquitin cycle) were over-represented. Interestingly, gene set enrichment analysis identifed expression targets that were in common between the laboratory experiment (MeHg injected) and field collected LMB and these consisted of mainly homeobox transcription factors (PROP paired-like homeobox 1, LIM homeobox 3 and paired-like homeodomain 1 and 2). Lastly, prevalent themes emerged in the SNEA expression targets that included neuropeptide receptor signaling, steroid signaling, and structural components, such as beta-actin, integrins, and stress fibres. Conclusions: This study characterizes novel cell signaling pathways that underlie Hg toxicity in the teleostean central nervous system.

Project description:Background and Methods: High mercury (Hg) levels are a significant concern in many aquatic environments, and adverse effects of Hg exposure in fish can include altered behavior, reproduction, growth, and increased stress responses. In addition, human health concerns over Hg continue to warrant new research on its mechanisms of action. The objectives of this study were to investigate the impacts of Hg on the female largemouth bass (LMB) central nervous system transcriptome by conducting a laboratory injection experiment with 2.5 M-BM-5g/g body weight in addition to sampling LMB from an environment that contains high levels of Hg (St. MaryM-bM-^@M-^Ys River, Florida, USA). These animals were compared to LMB that inhibit river systems with lower Hg (Big Wekiva, Santa Fe and St. JohnM-bM-^@M-^Ys Rivers Florida, USA). A LMB 8 x 15 K microarray was used for hypothalamic (laboratory) and whole brain (field) transcriptomics analysis. Results: Mercury in the blood of LMB collected from St MaryM-bM-^@M-^Ys River was significantly elevated 3-fold (~ 0.1 ng Hg/ml blood) compared to LMB collected from the other three sites (~ 0.03 ng Hg/ml blood). In the hypothalamus of Hg injected LMB, there were 937 genes that showed differential expression (raw p = 0.05) but there were no probes that passed an FDR for multiple hypothesis correction. In contrast, in field collected LMB there were 2909 genes that that showed differential expression (raw p = 0.05) of which 38 were significant after correction for multiple hypothesis testing (FDR = 0.05). These included Hsp90 co-chaperone Cdc37, multicopper oxidase, mismatch repair protein Msh6, and 16 kDa heat shock protein A. Functional enrichment in whole brains of LMB collected from the field sites revealed that genes involved in the biological processes of protein folding and targeting, regulation of protein metabolic process, and protein degradation (i.e. ubiquitin cycle) were over-represented. Interestingly, gene set enrichment analysis identifed expression targets that were in common between the laboratory experiment (MeHg injected) and field collected LMB and these consisted of mainly homeobox transcription factors (PROP paired-like homeobox 1, LIM homeobox 3 and paired-like homeodomain 1 and 2). Lastly, prevalent themes emerged in the SNEA expression targets that included neuropeptide receptor signaling, steroid signaling, and structural components, such as beta-actin, integrins, and stress fibres. Conclusions: This study characterizes novel cell signaling pathways that underlie Hg toxicity in the teleostean central nervous system. field study with methyl mercury

Project description:Background and Methods: High mercury (Hg) levels are a significant concern in many aquatic environments, and adverse effects of Hg exposure in fish can include altered behavior, reproduction, growth, and increased stress responses. In addition, human health concerns over Hg continue to warrant new research on its mechanisms of action. The objectives of this study were to investigate the impacts of Hg on the female largemouth bass (LMB) central nervous system transcriptome by conducting a laboratory injection experiment with 2.5 M-BM-5g/g body weight in addition to sampling LMB from an environment that contains high levels of Hg (St. MaryM-bM-^@M-^Ys River, Florida, USA). These animals were compared to LMB that inhibit river systems with lower Hg (Big Wekiva, Santa Fe and St. JohnM-bM-^@M-^Ys Rivers Florida, USA). A LMB 8 x 15 K microarray was used for hypothalamic (laboratory) and whole brain (field) transcriptomics analysis. Results: Mercury in the blood of LMB collected from St MaryM-bM-^@M-^Ys River was significantly elevated 3-fold (~ 0.1 ng Hg/ml blood) compared to LMB collected from the other three sites (~ 0.03 ng Hg/ml blood). In the hypothalamus of Hg injected LMB, there were 937 genes that showed differential expression (raw p = 0.05) but there were no probes that passed an FDR for multiple hypothesis correction. In contrast, in field collected LMB there were 2909 genes that that showed differential expression (raw p = 0.05) of which 38 were significant after correction for multiple hypothesis testing (FDR = 0.05). These included Hsp90 co-chaperone Cdc37, multicopper oxidase, mismatch repair protein Msh6, and 16 kDa heat shock protein A. Functional enrichment in whole brains of LMB collected from the field sites revealed that genes involved in the biological processes of protein folding and targeting, regulation of protein metabolic process, and protein degradation (i.e. ubiquitin cycle) were over-represented. Interestingly, gene set enrichment analysis identifed expression targets that were in common between the laboratory experiment (MeHg injected) and field collected LMB and these consisted of mainly homeobox transcription factors (PROP paired-like homeobox 1, LIM homeobox 3 and paired-like homeodomain 1 and 2). Lastly, prevalent themes emerged in the SNEA expression targets that included neuropeptide receptor signaling, steroid signaling, and structural components, such as beta-actin, integrins, and stress fibres. Conclusions: This study characterizes novel cell signaling pathways that underlie Hg toxicity in the teleostean central nervous system. 4 control and 3 treated hypothalami

Project description:BackgroundOocyte maturation in fish involves numerous cell signaling cascades that are activated or inhibited during specific stages of oocyte development. The objectives of this study were to characterize molecular pathways and temporal gene expression patterns throughout a complete breeding cycle in wild female largemouth bass to improve understanding of the molecular sequence of events underlying oocyte maturation.MethodsTranscriptomic analysis was performed on eight morphologically diverse stages of the ovary, including primary and secondary stages of oocyte growth, ovulation, and atresia. Ovary histology, plasma vitellogenin, 17β-estradiol, and testosterone were also measured to correlate with gene networks.ResultsGlobal expression patterns revealed dramatic differences across ovarian development, with 552 and 2070 genes being differentially expressed during both ovulation and atresia respectively. Gene set enrichment analysis (GSEA) revealed that early primary stages of oocyte growth involved increases in expression of genes involved in pathways of B-cell and T-cell receptor-mediated signaling cascades and fibronectin regulation. These pathways as well as pathways that included adrenergic receptor signaling, sphingolipid metabolism and natural killer cell activation were down-regulated at ovulation. At atresia, down-regulated pathways included gap junction and actin cytoskeleton regulation, gonadotrope and mast cell activation, and vasopressin receptor signaling and up-regulated pathways included oxidative phosphorylation and reactive oxygen species metabolism. Expression targets for luteinizing hormone signaling were low during vitellogenesis but increased 150% at ovulation. Other networks found to play a significant role in oocyte maturation included those with genes regulated by members of the TGF-beta superfamily (activins, inhibins, bone morphogenic protein 7 and growth differentiation factor 9), neuregulin 1, retinoid X receptor, and nerve growth factor family.ConclusionsThis study offers novel insight into the gene networks underlying vitellogenesis, ovulation and atresia and generates new hypotheses about the cellular pathways regulating oocyte maturation.

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Characterizing gene regulatory networks in the brain of largemouth bass inhabiting rivers containing high levels of methyl-mercury

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