Project description:Studying chemical disturbances during neural differentiation of mES cells has been established as an alternative in vitro testing approach for the identification of developmental toxicants. miRNAs represent a class of small regulatory RNA molecules, which bind to target mRNAs thereby repressing their translation. Many studies have shown an essential role of miRNAs in regulation of gene expression during development and ESC differentiation. Thus, neural differentiation of ESC in vitro allows investigating the role of miRNAs in chemical-mediated developmental toxicity. We analyzed the expression of miRNAs and transcriptomics changes during neural differentiation of mESC exposed to the developmental neurotoxicant sodium valproate (VPA). A total of 110 miRNAs and 377 mRNAs were identified differently expressed in neural differentiating mES cells under VPA treatment (300ÂµM) compared to solvent control on day 16 of differentiation. Analysis of miRNA expression revealed that valproate switches the lineage specification from neural to myogenic differentiation (upregulation of muscle-enriched miRNAs mir-206, mir-133a and mir-10a and downregulation of neuro-specific miRNAs mir-124a, mir-128 and mir-137). The findings on the miRNA level could be confirmed on mRNA level (induction of expression of myogenic regulatory factors (MRFs) as well as muscle specific genes (Actc1, calponin, myosin light chain, asporin, decorin) and repression of genes involved in neurogenesis (Otx1 and 2, Zic3, 4, 5)) as well as morphologically by immunocytochemistry. The observed results were VPA specific and most probably due to inhibition of histone deacetylase (HDAC) activity of VPA for two reasons: (i) we did not observe any induction of muscle specific miRNAs in neural differentiating ES cells exposed to the unrelated developmental neurotoxicant sodium arsenite; (ii) expression of muscle specific mir-206 and muscle enriched mir-10a was similarly increased in cells exposed to a structurally different HDAC inhibitor, trichostatin A (TSA). Furthermore, using our in vitro cell system we could confirm an aberrant expression of known VPA target genes and genes involved in neural tube closure. We conclude that miRNA expression profiling is a suitable molecular endpoint for developmental neurotoxicity. Observed lineage shift into myogenesis, where miRNAs play a significant role, could be a major developmental neurotoxical mechanism of VPA. We used microarray approach to identify altered miRNA expression in neural differentiated mES cells exposed to two known developmental neurotxicants and epigenetic active substances, sodium valproate (VPA) and sodium arsenite (As) mES cells line W4 were induced to differnetiate into neurons under exposure to VPA for 16 days. RNA for microarrays was collected on day 16 of differentiation from three biological replicates of solvent control (PBS) and VPA treated cells.

Project description:Studying chemical disturbances during neural differentiation of mES cells has been established as an alternative in vitro testing approach for the identification of developmental toxicants. miRNAs represent a class of small regulatory RNA molecules, which bind to target mRNAs thereby repressing their translation. Many studies have shown an essential role of miRNAs in regulation of gene expression during development and ESC differentiation. Thus, neural differentiation of ESC in vitro allows investigating the role of miRNAs in chemical-mediated developmental toxicity. We analyzed the expression of miRNAs and transcriptomics changes during neural differentiation of mESC exposed to the developmental neurotoxicant sodium valproate (VPA). A total of 110 miRNAs and 377 mRNAs were identified differently expressed in neural differentiating mES cells under VPA treatment (300ÂµM) compared to solvent control on day 16 of differentiation. Analysis of miRNA expression revealed that valproate switches the lineage specification from neural to myogenic differentiation (upregulation of muscle-enriched miRNAs mir-206, mir-133a and mir-10a and downregulation of neuro-specific miRNAs mir-124a, mir-128 and mir-137). The findings on the miRNA level could be confirmed on mRNA level (induction of expression of myogenic regulatory factors (MRFs) as well as muscle specific genes (Actc1, calponin, myosin light chain, asporin, decorin) and repression of genes involved in neurogenesis (Otx1 and 2, Zic3, 4, 5)) as well as morphologically by immunocytochemistry. The observed results were VPA specific and most probably due to inhibition of histone deacetylase (HDAC) activity of VPA for two reasons: (i) we did not observe any induction of muscle specific miRNAs in neural differentiating ES cells exposed to the unrelated developmental neurotoxicant sodium arsenite; (ii) expression of muscle specific mir-206 and muscle enriched mir-10a was similarly increased in cells exposed to a structurally different HDAC inhibitor, trichostatin A (TSA). Furthermore, using our in vitro cell system we could confirm an aberrant expression of known VPA target genes and genes involved in neural tube closure. We conclude that miRNA expression profiling is a suitable molecular endpoint for developmental neurotoxicity. Observed lineage shift into myogenesis, where miRNAs play a significant role, could be a major developmental neurotoxical mechanism of VPA. We used microarray approach to identify altered miRNA expression in neural differentiated mES cells exposed to two known developmental neurotxicants and epigenetic active substances, sodium valproate (VPA) and sodium arsenite (As) mES cells line W4 were induced to differnetiate to neurons under exposure to VPA and As for 16 days. RNA for microarrays was collected on day 16 of differentiation from three biological replicates of solvent controls (PBS was used as a solvent for VPA and H20 for As) or substance treated cells.

Project description:Studying chemical disturbances during neural differentiation of mES cells has been established as an alternative in vitro testing approach for the identification of developmental toxicants. miRNAs represent a class of small regulatory RNA molecules, which bind to target mRNAs thereby repressing their translation. Many studies have shown an essential role of miRNAs in regulation of gene expression during development and ESC differentiation. Thus, neural differentiation of ESC in vitro allows investigating the role of miRNAs in chemical-mediated developmental toxicity. We analyzed the expression of miRNAs and transcriptomics changes during neural differentiation of mESC exposed to the developmental neurotoxicant sodium valproate (VPA). A total of 110 miRNAs and 377 mRNAs were identified differently expressed in neural differentiating mES cells under VPA treatment (300µM) compared to solvent control on day 16 of differentiation. Analysis of miRNA expression revealed that valproate switches the lineage specification from neural to myogenic differentiation (upregulation of muscle-enriched miRNAs mir-206, mir-133a and mir-10a and downregulation of neuro-specific miRNAs mir-124a, mir-128 and mir-137). The findings on the miRNA level could be confirmed on mRNA level (induction of expression of myogenic regulatory factors (MRFs) as well as muscle specific genes (Actc1, calponin, myosin light chain, asporin, decorin) and repression of genes involved in neurogenesis (Otx1 and 2, Zic3, 4, 5)) as well as morphologically by immunocytochemistry. The observed results were VPA specific and most probably due to inhibition of histone deacetylase (HDAC) activity of VPA for two reasons: (i) we did not observe any induction of muscle specific miRNAs in neural differentiating ES cells exposed to the unrelated developmental neurotoxicant sodium arsenite; (ii) expression of muscle specific mir-206 and muscle enriched mir-10a was similarly increased in cells exposed to a structurally different HDAC inhibitor, trichostatin A (TSA). Furthermore, using our in vitro cell system we could confirm an aberrant expression of known VPA target genes and genes involved in neural tube closure. We conclude that miRNA expression profiling is a suitable molecular endpoint for developmental neurotoxicity. Observed lineage shift into myogenesis, where miRNAs play a significant role, could be a major developmental neurotoxical mechanism of VPA. We used microarray approach to identify altered miRNA expression in neural differentiated mES cells exposed to two known developmental neurotxicants and epigenetic active substances, sodium valproate (VPA) and sodium arsenite (As)

Project description:Arsenic (As) exposure is a significant worldwide environmental health concern. Low dose, chronic arsenic exposure has been associated with higher risk of skin, lung, and bladder cancer, as well as cardiovascular disease and diabetes. While arsenic-induced biological changes play a role in disease pathology, little is known about the dynamic cellular changes due to arsenic exposure and withdrawal. In these studies, we seek to understand the molecular mechanisms behind the biological changes induced by chronic low doses of arsenic exposure. We used a comprehensive approach involving chromatin structural studies and mRNA microarray analyses to determine how chromatin structure and gene expression patterns change in response to chronic low dose arsenic exposure and its subsequent withdrawal. Our results show that cells exposed to low doses of sodium arsenite have distinct temporal and coordinated chromatin, gene expression and miRNA changes that are consistent with differentiation and activation of multiple biochemical pathways. Most of these temporal patterns in gene expression are reversed when arsenic was withdrawn. However, some of the gene expression patterns remained altered, plausibly as a result of an adaptive response by these cells. Additionally, these gene expression patterns correlated with changes in chromatin structure, further solidifying the role of chromatin structure in gene regulatory changes due to arsenite exposure. Lastly, we show that arsenite exposure influences gene regulation both at the transcription initiation as well as at the splicing level. Thus our results suggest that general patterns of alternative splicing, as well as expression of particular gene regulators, can be indicative of arsenite-induced cell transformation. A total of eight (8) samples with two biological replicates under four separate conditions: wild-type treated with deionized H2O for 36 days (NT); chronic low-dose arsenic exposure of 1 uM of sodium arsenite (iAs-T) for 36 days; chronic arsenic exposure of 1 uM of sodium arsenite for 26 days followed by removal of sodium arsenite for 10 days, measured at day 36 (iAs-Rev); and chronic arsenic exposure of 1 uM of sodium arsenite for 26 days, followed by removal of sodium arsenite exposure for 10 days, followed by 1 uM of chronic sodium arsenite exposure for 10 days (measured at day 46) (iAs-Rev-T).

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