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:Several studies have demonstrated that exposure to arsenic in drinking water adversely affects brain development and cognitive function in adulthood. While the mechanism by which arsenic induces adverse neurological outcomes remains elusive, studies suggest a link between reduced levels of histone acetylation and impaired performance on a variety of behavioral tasks following arsenic exposure. Using our developmental arsenic exposure (DAE) paradigm, we have previously reported reduced histone acetylation and associated histone acetyltransferase enzyme expression in the frontal cortex of C57BL/6J adult male mice, with no changes observed in the female frontal cortex. In the present study, we sought to determine if DAE produced sex-dependent deficits in frontal cortical executive function using the Y-maze acquisition and reversal learning tasks, which are specific for assessing cognitive flexibility. Further, we tested whether the administration of valproic acid, a class I-IIa histone deacetylase inhibitor, was able to mitigate behavioral and biochemical changes resulting from DAE. As anticipated, DAE inhibited acquisition and reversal learning performance in adult male, but not female, mice. Valproate treatment for 2 weeks restored reversal performance in the male arsenic-exposed offspring, while not affecting female performance. Protein levels of HDACs 1, 2, and 5 were elevated following behavioral assessment but only in DAE male mice; restoration of appropriate HDAC levels occurred after valproate treatment and was concurrent with improved behavioral performance, particularly during reversal learning. Female frontal cortical levels of HDAC enzymes were not impacted by DAE or valproate treatment. Finally, mRNA expression levels of brain-derived neurotrophic factor, Bdnf, which has been implicated in the control of frontal cortical flexibility and is regulated by HDAC5, were elevated in DAE male mice and restored to normal levels following HDACi treatment. Levels of mRNA encoding glutamate receptor ionotropic NMDA type subunits, which have been linked to cognitive flexibility, were not related to the reversal learning deficit in the DAE mice and were not altered by HDACi treatments. These findings demonstrate that DAE alters frontal cortical HDAC levels and Bdnf expression in males, but not females, and that these molecular changes are associated with sex-dependent differences in cognitive flexibility in a reversal-learning task.

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:Drosophila melanogaster adult flies fed on normal food (NF) containing 16 mg/ml of pentylenetetrazole (PTZ) in the food show a hyperkinetic behavior within 24 hours. Half of that concentration, i.e., 8 mg/ml, of the PTZ, if fed for seven days, though doesn’t cause seizure-like behavior, results in a decreased climbing speed in flies. This change in locomotor behavior is progressive and becomes significant only on seventh day of the treatment. This climbing deficit is ameliorated when flies are treated concomitantly with PTZ and either of the two antiepileptic drugs (AEDs), sodium valproate (NaVP) or levetiracetam (LEV). Further experiments based on different regimes of combination and singular PTZ treatment demonstrated that whereas NaVP show a weaker prophylactic and stronger symptomatic effect, LEV exhibit an opposite effect, i.e., stronger prophylactic and weaker symptomatic action. These observations are consistent with the therapeutic effect of antiepileptic drugs. Time series of microarray gene expression profiling (earlier GEO submission) during chronic PTZ provided evidence of underlying downregulation of three main categories of biological processes, synaptic remodeling, energy metabolism and transport, in that order, in fly head. Transcriptomic analysis secondary to NaVP and LEV (earlier GEO submission) was found to cause statistically significant upregulation of two biological process categories each, energy metabolism and transport in case of NaVP and synaptic remodeling and energy metabolism in case of LEV. Time series of genome wide expression profiling secondary to PTZ and LEV combination treatment (earlier GEO submission) showed neutralizing effect of LEV on PTZ induced expression changes. Mining of published transcriptomic and proteomic data pertaining to epilepsy or established rodent animal models of epileptogenesis supported the relevance of the fly model in understanding the underlying brain pathophysiology. Systems modeling using RNA interference and small molecules demonstrated the robustness of the fly model. In brief, the above results clearly showed that the fly model is valuable not only in screening of antiepileptic, antiepileptogenic, disease-modifying and neuroprotective agents, but also in advancing our knowledge of mechanisms of action of drugs used in treating human patients suffering from various neurological and neuropsychiatric conditions, pharmacogenomics of these drugs, identification of potential drug targets, and selection of potential candidate genes for association analysis in epilepsy. Considering the above fly locomotor behavior model as relevant in kindling attainment, it was of obvious interest to study the behavioral and transcriptomic changes post-kindling, i.e., after withdrawing PTZ following seven day long chronic PTZ administration. It was observed that when PTZ is discontinued and flies climbing speed is monitored for next seven days of PTZ discontinuation, climbing speed deficit initially disappears and then a progressive increase in climbing speed is detected. Behavioral pharmacology of AEDs in post-kindling regime, like fly kindling described above, showed its usefulness in screening of potential antiepileptic, antiepileptogenic, disease-modifying and neuroprotective agents. The present submission relates to transcriptomic changes in fly head secondary to NaVP treatment following discontinuation of PTZ for seven days (after seven days of chronic PTZ treatment). To delineate possible prophylactic or symptomatic effect of NaVP at behavioral level, flies were treated with NaVP for first three days and then shifted to NF for next four days (3 + 4 day regime) or flies treated with NF for first four days and then drug treated for next three days (4 + 3 day regime), in that order. At transcriptomic level, we have now examined the effect of NaVP in 3 + 4 day regime. Gene expression profiles have been generated at both time points, 3rd and 7th day, i.e., on 10th and 14th day from the beginning of PTZ treatment. Effect of three day long chronic NaVP treatment on fly head microarray gene expression profile, in otherwise normally grown flies, has already been determined (earlier GEO submission). Similarly, transcriptomic changes after one day, three days and seven days of PTZ discontinuation (i.e., 8th, 10th and 14th day of the beginning of chronic PTZ treatment) have already been deciphered (earlier GEO submission). Unlike the previous experiment in which flies were maintained in the same container during the post-kindling period of seven days, flies needed to be shifted in fresh vials once in the present experiment because of the demand of 3 + 4 day regime. Since change in housing conditions has the potential to influence head transcriptome, we have also generated microarray expression profile of fly head after treating flies with PTZ for seven days, maintaining the flies to NF containing vials for three days and then shifting and maintaining them in fresh NF containing vials for next four days (submitted in GEO previously). Keywords: Drug Response

Dataset Information

Exposure to Sodium Valproate during Pregnancy: Facial Features and Signs of Autism.

Publications

Exposure to Sodium Valproate during Pregnancy: Facial Features and Signs of Autism.

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