Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling of rat embryos at 11 days in culture treated at 10, 30, 60, 180, 360, min with 1 mM NMDA vs. neuronal cultures

ABSTRACT: Nicotinic receptors (nAChR) are widely distributed in the adult brain where they mediate excitatory postsynaptic transmission and presynaptic release of other neurotransmitters. Functional nicotinic receptors are also present in the embryonic brain. Several studies have suggested a role for nAChRs in cognitive functions (learning and memory) and cellular events such as degeneration and survival. In vitro, activation of nAChR can differentially modulate neuritic outgrowth, and enhance early gene expression prior to neuronal differentiation. Furthermore, several reports have shown that nicotine can prevent cell death induced by activation of glutamatergic receptors, NMDA-subtype. Little is known of these events in the cerebral cortex. Knowledge of the genes activated by exposure of cortical neurons to nicotine or to an excitotoxic agent such as the glutamatergic agonist NMDA could potentially lead to new strategies for adult brain protection and repair. The effect of nicotine and the cembranoid 4R, a novel nicotinic receptor non competitive antagonist, will be analyzed in primary cultures of cortical neurons, in the presence or the absence of NMDA, to identify which genes affected by NMDA receptor activation are modulated nicotine or 4R. We hypothesize that the neuroprotective effect of nAChRs is mediated by modulation of the changes in gene expressions elicited by NMDA. In order to detect early changes in gene expression, primary culture of cortical neurons prepared from 16 day old Sprague Dawley rat embryos at 11 days in culture will be treated for different times (10, 30, 60, 180, 360, min) with 1 mM NMDA and then harvested. In a second set of experiments, neuronal cultures will be treated with NMDA for 10, 30 and 60 min then the drug will be washed out and the cells will be harvested 24 h later. It was reported that 8-24 h pretreatment of neurons with 10 micromolar nicotine is neuroprotective, therefore we will treat separate cultures with either 10 micromolar nicotine or 2 micromolar 4R for 18 h and then with NMDA for 30 min or 1 h. The cells will be either harvested soon after NMDA treatment or the drugs will be washed out and the cells harvested 24 h later. We will also examine sample treated only with either 4R or nicotine for 15 min or 18 h in order to determine which genes are differentially regulated by these drugs. These experiments will allow us to detect any change in gene expression elicited soon by each treatment or with some delay. The samples in Trizol will be kept at -70 until all the 3 or 5 replicates are harvested and then the RNA will be purified. RNA from 3-5 independent experiments for each different protocol or treatment together with controls will be sent to the facility.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Elizabeth Salomon

PROVIDER: E-GEOD-4242 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Nicotinic receptors (nAChR) are widely distributed in the adult brain where they mediate excitatory postsynaptic transmission and presynaptic release of other neurotransmitters. Functional nicotinic receptors are also present in the embryonic brain. Several studies have suggested a role for nAChRs in cognitive functions (learning and memory) and cellular events such as degeneration and survival. In vitro, activation of nAChR can differentially modulate neuritic outgrowth, and enhance early gene expression prior to neuronal differentiation. Furthermore, several reports have shown that nicotine can prevent cell death induced by activation of glutamatergic receptors, NMDA-subtype. Little is known of these events in the cerebral cortex. Knowledge of the genes activated by exposure of cortical neurons to nicotine or to an excitotoxic agent such as the glutamatergic agonist NMDA could potentially lead to new strategies for adult brain protection and repair. The effect of nicotine and the cembranoid 4R, a novel nicotinic receptor non competitive antagonist, will be analyzed in primary cultures of cortical neurons, in the presence or the absence of NMDA, to identify which genes affected by NMDA receptor activation are modulated nicotine or 4R. We hypothesize that the neuroprotective effect of nAChRs is mediated by modulation of the changes in gene expressions elicited by NMDA. In order to detect early changes in gene expression, primary culture of cortical neurons prepared from 16 day old Sprague Dawley rat embryos at 11 days in culture will be treated for different times (10, 30, 60, 180, 360, min) with 1 mM NMDA and then harvested. In a second set of experiments, neuronal cultures will be treated with NMDA for 10, 30 and 60 min then the drug will be washed out and the cells will be harvested 24 h later. It was reported that 8-24 h pretreatment of neurons with 10 micromolar nicotine is neuroprotective, therefore we will treat separate cultures with either 10 micromolar nicotine or 2 micromolar 4R for 18 h and then with NMDA for 30 min or 1 h. The cells will be either harvested soon after NMDA treatment or the drugs will be washed out and the cells harvested 24 h later. We will also examine sample treated only with either 4R or nicotine for 15 min or 18 h in order to determine which genes are differentially regulated by these drugs. These experiments will allow us to detect any change in gene expression elicited soon by each treatment or with some delay. The samples in Trizol will be kept at -70 until all the 3 or 5 replicates are harvested and then the RNA will be purified. RNA from 3-5 independent experiments for each different protocol or treatment together with controls will be sent to the facility. Keywords: time-course

Project description:Nicotine, acting through the neuronal nicotinic acetylcholine receptors (nAChR), can induce seizures in mice. We aimed to study brain transcriptional response to seizure and to identify genes whose expression is altered after nicotine-induced seizures. Whole brains of untreated mice were compared to brains one hour after seizure activity, using Affymetrix U74Av2 microaarays. Experimental groups included wild-type mice and both nicotine-induced seizures sensitive and resistant nAChR mutant mice. Each genotype group received different nicotine doses to generate seizures. This approach allowed the identification of significantly changed genes whose expression was dependent on seizure activity, nicotine administration or both, but not on the type of nAChR subunit mutation or the amount of nicotine injected. Significant expression changes were detected in 62 genes (p < 0.05, FDR correction). Among them, GO functional annotation analysis determined that the most significantly over-represented categories were of genes encoding MAP kinase phosphatases, regulators of transcription and nucleosome assembly proteins. In-silico bioinformatic analysis of the promoter regions of the 62 changed genes detected the significant enrichments of 16 transcription regulatory elements (TREs), creating a network of transcriptional regulatory responses to seizures. The TREs for ATF and SRF were most significantly enriched, supporting their association with seizure activity. Our data suggest that nicotine-induced seizure in mice is a useful model to study seizure activity and its global brain transcriptional response. The differentially expressed genes detected here can help understand the molecular mechanisms underlying seizures in animal models, and may also serve as candidate genes to study epilepsy in humans. Experiment Overall Design: Whole brain expression profiles were determined in two experimental groups of mice, sixteen mice that were not treated with nicotine and twelve mice one hour after experiencing nicotine-induced seizure. The untreated group included six wild-type mice, five alpha7+/T and five beta4-/- mice. The group of mice that underwent nicotine-induced seizures included three wild-types, five alpha7+/T and four beta4-/- mice. Different doses of nicotine were injected intraperitoneally (i.p.) to each genotype group of mice in order to achieve a similar seizure score in all three genotypes.

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Transcription profiling of rat embryos at 11 days in culture treated at 10, 30, 60, 180, 360, min with 1 mM NMDA vs. neuronal cultures

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