Project description:Neurodegenerative brain disorders become more common in the aged. Most of these disorders are associated with or caused by selective death of certain neuronal subpopulations. The mechanisms underlying the differential vulnerability of certain neuronal populations are still largely unexplored and few neuroprotective treatments are available to date. Elucidation of these mechanisms may lead to a greater understanding of the pathogenesis and treatment of neurodegenerative diseases. Moreover, preconditioning by a short seizure confers neuroprotection following a subsequent prolonged seizure. Our goal is to identify pathways that confer vulnerability and resistance to neurotoxic conditions by comparing the basal and preconditioned gene expression profiles of three differentially vulnerable hippocampal neuron populations. Hippocampal CA1 and CA3 pyramidal neurons are highly susceptible to seizures and ischemia, whereas dentate gyrus granule cells are relatively resistant. A brief preconditioning seizure confers protection to the pyramidal cells. We will first determine gene expression profiles of untreated rat CA1 and CA3 pyramidal cells, and dentate granule cells, using laser capture microscopy to obtain region-specific neuronal mRNA. We will then determine the effect of a brief preconditioning seizure, which is neuroprotective in CA1 and CA3, on these expression profiles. We hypothesize that common molecular mechanisms exist in neurons that determine their susceptibility to seizure-induced injury. Intrinsic differences in gene expression exist between hippocampal glutamatergic CA1 and CA3 pyramidal neurons, on the one hand, and dentate granule cells on the other, which contribute to the greater susceptibility of pyramidal neurons to degeneration in experimental stroke and epilepsy. We specifically hypothesize that differences in basal energy metabolism genes may confer differential susceptibility to neurodegeneration produced by seizures and ischemia. Anesthetized animals will be sacrificed by decapitation, and frozen 10 micron sections will be lightly stained with cresyl violet to identify cell layers in the hippocampus. Approximately 1000 neurons from each of the three cell layers will be isolated by LCM. Poly-A RNA will be amplified using a modified Eberwine protocol. The quality of our aRNA will be evaluated by quantitative RT-PCR of GluR6 and KA2 mRNA levels before we send the samples to the Center for labeling and hybridization to Affymetrix rat 230A arrays. We will provide a one-round amplification cDNA product to the center for labeling and hybridization. This protocol is identical to a previously approved study by Jim Greene in our laboratory.
Project description:Neurodegenerative brain disorders become more common in the aged. Most of these disorders are associated with or caused by selective death of certain neuronal subpopulations. The mechanisms underlying the differential vulnerability of certain neuronal populations are still largely unexplored and few neuroprotective treatments are available to date. Elucidation of these mechanisms may lead to a greater understanding of the pathogenesis and treatment of neurodegenerative diseases. Moreover, preconditioning by a short seizure confers neuroprotection following a subsequent prolonged seizure. Our goal is to identify pathways that confer vulnerability and resistance to neurotoxic conditions by comparing the basal and preconditioned gene expression profiles of three differentially vulnerable hippocampal neuron populations. Hippocampal CA1 and CA3 pyramidal neurons are highly susceptible to seizures and ischemia, whereas dentate gyrus granule cells are relatively resistant. A brief preconditioning seizure confers protection to the pyramidal cells. We will first determine gene expression profiles of untreated rat CA1 and CA3 pyramidal cells, and dentate granule cells, using laser capture microscopy to obtain region-specific neuronal mRNA. We will then determine the effect of a brief preconditioning seizure, which is neuroprotective in CA1 and CA3, on these expression profiles. We hypothesize that common molecular mechanisms exist in neurons that determine their susceptibility to seizure-induced injury. Intrinsic differences in gene expression exist between hippocampal glutamatergic CA1 and CA3 pyramidal neurons, on the one hand, and dentate granule cells on the other, which contribute to the greater susceptibility of pyramidal neurons to degeneration in experimental stroke and epilepsy. We specifically hypothesize that differences in basal energy metabolism genes may confer differential susceptibility to neurodegeneration produced by seizures and ischemia. Anesthetized animals will be sacrificed by decapitation, and frozen 10 micron sections will be lightly stained with cresyl violet to identify cell layers in the hippocampus. Approximately 1000 neurons from each of the three cell layers will be isolated by LCM. Poly-A RNA will be amplified using a modified Eberwine protocol. The quality of our aRNA will be evaluated by quantitative RT-PCR of GluR6 and KA2 mRNA levels before we send the samples to the Center for labeling and hybridization to Affymetrix rat 230A arrays. We will provide a one-round amplification cDNA product to the center for labeling and hybridization. This protocol is identical to a previously approved study by Jim Greene in our laboratory. Keywords: other
Project description:Injury of the CA1 subregion induced by a single injection of kainic acid (1M-CM-^WKA) is attenuated when juvenile animals (P20) have a history of two sustained neonatal seizures on P6 and P9. To identify gene candidates involved in the spatially protective effects produced by early life conditioning seizures, we profiled and compared the transcriptomes of CA1 subregions from control, 1M-CM-^WKA, and 3M-CM-^WKA treated animals. More genes were regulated following 3M-CM-^WKA (9.6%) than after 1M-CM-^WKA (7.1%). Following 1M-CM-^WKA, genes supporting oxidative stress, growth, development, inflammation, and neurotransmission were upregulated (e.g., Cacng1, Nadsyn1, Kcng1, Aven, S100a4, GFAP, Vim, Hrsp12, Grik1). After 3M-CM-^WKA, protective genes were differentially over-expressed (e.g., Cat, Gpx7, GAD1, Hspa12A, Foxn1, adenosine A1 receptor, Ca2+ adaptor and homeostatic proteins, Cacnb4, Atp2b2, anti-apoptotic Bcl-2 gene members, intracellular trafficking protein, Grasp, suppressor of cytokine signaling (Socs3)). Distinct anti-inflammatory interleukins not observed in adult tissues (e.g., IL6 transducer, IL23 and IL33 or their receptors (ILF2)) were also over-expressed. Several transcripts were validated by real-time polymerase chain reaction (QPCR) and immunohistochemistry. QPCR showed that casp 6 was increased after 1M-CM-^WKA but reduced after 3M-CM-^WKA; pro-inflammatory gene cox1 was either upregulated or unchanged after 1M-CM-^WKA but reduced by ~70% after 3M-CM-^WKA. Enhanced GFAP immunostaining following 1M-CM-^WKA was selectively attenuated in the CA1 subregion after 3M-CM-^WKA. The observed differential transcriptional responses may contribute to early life seizure-induced pre-conditioning and neuroprotection by reducing glutamate receptor-mediated Ca2+ permeability of the hippocampus and redirecting inflammatory and apoptotic pathways which could lead to new genetic therapies for epilepsy. The transcriptomes of the hippocampal CA1 region of Sprague Dawley 23-day-old male rats after 1 or 3 seizures induced by kainic acid injection were compared to the corresponding controls (injected with PBS) using Duke 27k oligonucleotide arrays.
Project description:Mesial temporal lobe epilepsy (MTLE) is the most common medically refractory epilepsy syndrome; kainic acid (KA) induced seizures have been studied as a MTLE model as limbic seizures produced by systemic injections of KA result in a distinctive pattern of neurodegeneration in the hippocampus that resembles human hippocampal sclerosis. In our "2-hit" seizure model, animals subjected to seizures during week 2 of life become more susceptible to seizures later in life and sustain extensive hippocampal neuronal injury after second KA seizures in adulthood. Using high-density oligonucleotide gene arrays, we began to elucidate the molecular basis of this priming effect of early-life seizures and of the age-specific neuroprotection against seizure-induced neuronal injury. We seek to identify target genes for epileptogenesis and cell death by selecting transcripts that are differentially regulated at various times in the P15 and P30 hippocampus. To screen for and identify candidate genes responsible for epileptogenesis and seizure-induced cell death. We hypothesize that active process of cell death signaling and long-term synaptic changes leading to chronic epilepsy is mediated by distinct transcriptional responses in mature brain that are different from those in immature brain. We will select for transcripts that are highly regulated at 1, 6, 24, 72 and 240 hours (h) after KA-induced seizures at P30 compared to P15. These differentially regulated genes will serve as potential target genes for therapeutic intervention. Highly regulated genes identified in our array analysis will then be confirmed by real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Causative roles of select genes will be directly tested by gene silencing using RNA interference technology or by gene delivery using viral vectors.
Project description:Mesial temporal lobe epilepsy (MTLE) is the most common medically refractory epilepsy syndrome; kainic acid (KA) induced seizures have been studied as a MTLE model as limbic seizures produced by systemic injections of KA result in a distinctive pattern of neurodegeneration in the hippocampus that resembles human hippocampal sclerosis. In our "2-hit" seizure model, animals subjected to seizures during week 2 of life become more susceptible to seizures later in life and sustain extensive hippocampal neuronal injury after second KA seizures in adulthood. Using high-density oligonucleotide gene arrays, we began to elucidate the molecular basis of this priming effect of early-life seizures and of the age-specific neuroprotection against seizure-induced neuronal injury. We seek to identify target genes for epileptogenesis and cell death by selecting transcripts that are differentially regulated at various times in the P15 and P30 hippocampus. To screen for and identify candidate genes responsible for epileptogenesis and seizure-induced cell death. We hypothesize that active process of cell death signaling and long-term synaptic changes leading to chronic epilepsy is mediated by distinct transcriptional responses in mature brain that are different from those in immature brain. We will select for transcripts that are highly regulated at 1, 6, 24, 72 and 240 hours (h) after KA-induced seizures at P30 compared to P15. These differentially regulated genes will serve as potential target genes for therapeutic intervention. Highly regulated genes identified in our array analysis will then be confirmed by real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Causative roles of select genes will be directly tested by gene silencing using RNA interference technology or by gene delivery using viral vectors. Keywords: time-course
Project description:Transient brain insults including status epilepticus (SE) can initiate a process termed ‘epileptogenesis’ that results in chronic temporal lobe epilepsy (TLE). As a consequence, the entire tri-synaptic circuit of the hippocampus is fundamentally impaired. A key role in epileptogenesis has been attributed to the CA1 region as the last relay station in the hippocampal circuit and as site of aberrant plasticity, e.g. mediated by acquired channelopathies. The transcriptional profiles of the distinct hippocampal neurons are highly dynamic during epileptogenesis. Here, we aimed to elucidate the early SE-elicited mRNA signature changes and the respective upstream regulatory cascades in CA1. RNA sequencing of CA1 was performed in the mouse pilocarpine-induced SE model at multiple time points ranging from 6 to 72 hours after the initial insult. Bioinformatics was used to decipher altered gene expression, signalling cascades and their corresponding cell type profiles. Robust transcriptomic changes were detected at 6h after SE and at subsequent time points during early epileptogenesis. Major differentially expressed mRNAs encoded primarily immediate early and excitability-related gene products, as well as genes encoding immune signalling factors.
Project description:Injury of the CA1 subregion induced by a single injection of kainic acid (1×KA) is attenuated when juvenile animals (P20) have a history of two sustained neonatal seizures on P6 and P9. To identify gene candidates involved in the spatially protective effects produced by early life conditioning seizures, we profiled and compared the transcriptomes of CA1 subregions from control, 1×KA, and 3×KA treated animals. More genes were regulated following 3×KA (9.6%) than after 1×KA (7.1%). Following 1×KA, genes supporting oxidative stress, growth, development, inflammation, and neurotransmission were upregulated (e.g., Cacng1, Nadsyn1, Kcng1, Aven, S100a4, GFAP, Vim, Hrsp12, Grik1). After 3×KA, protective genes were differentially over-expressed (e.g., Cat, Gpx7, GAD1, Hspa12A, Foxn1, adenosine A1 receptor, Ca2+ adaptor and homeostatic proteins, Cacnb4, Atp2b2, anti-apoptotic Bcl-2 gene members, intracellular trafficking protein, Grasp, suppressor of cytokine signaling (Socs3)). Distinct anti-inflammatory interleukins not observed in adult tissues (e.g., IL6 transducer, IL23 and IL33 or their receptors (ILF2)) were also over-expressed. Several transcripts were validated by real-time polymerase chain reaction (QPCR) and immunohistochemistry. QPCR showed that casp 6 was increased after 1×KA but reduced after 3×KA; pro-inflammatory gene cox1 was either upregulated or unchanged after 1×KA but reduced by ~70% after 3×KA. Enhanced GFAP immunostaining following 1×KA was selectively attenuated in the CA1 subregion after 3×KA. The observed differential transcriptional responses may contribute to early life seizure-induced pre-conditioning and neuroprotection by reducing glutamate receptor-mediated Ca2+ permeability of the hippocampus and redirecting inflammatory and apoptotic pathways which could lead to new genetic therapies for epilepsy.
Project description:Seizures that occur during early development are associated with adverse neurodevelopmental outcomes. Causation and mechanisms are currently under investigation. Induction of an early life seizure by kainic acid (KA) in immature rats on post-natal day (P) 7 results in behavioral changes in the adult rat that reflect social and intellectual deficits without overt cellular damage. Our previous work also demonstrated increased expression of CA1 hippocampal long-term potentiation (LTP) and reduced desensitization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type ionotropic glutamate receptors (AMPA-R) one week following a kainic acid induced seizure (KA-ELS). Here we used RNA sequencing (RNAseq) of mRNA from dorsal hippocampal CA1 to probe changes in mRNA levels one week following KA-ELS as a means to investigate the mechanisms for these functional changes. Ingenuity pathway analysis (IPA) confirmed our previous results by predicting an up-regulation of the synaptic LTP pathway. Differential gene expression results revealed significant differences in 7 gene isoforms. Additional assessments included AMPA-R splice variants and adenosine deaminase acting on RNA 2 (ADAR2) editing sites as a means to determine the mechanism for reduced AMPA-R desensitization. Splice variant analysis demonstrated that KA-ELS result in a small, but significant decrease in the "flop" isoform of Gria3, and editing site analysis revealed significant changes in the editing of a kainate receptor subunit, Grik2, and a serotonin receptor, Htr2c. While these specific changes may not account for altered AMPA-R desensitization, the differences indicate that KA-ELS alters gene expression in the hippocampal CA1 one week after the insult.
Project description:Analysis of biopsy hippocampal tissue of patients with pharmacoresistant temporal lobe epilepsy (TLE) undergoing neurosurgical removal of the epileptogenic focus for seizure control. Chronic TLE goes along with focal hyperexcitability. Results provide insight into molecular mechanisms that may play a role in seizure propensity 150 human hippocampus samples
Project description:Analysis of biopsy hippocampal tissue of patients with pharmacoresistant temporal lobe epilepsy (TLE) undergoing neurosurgical removal of the epileptogenic focus for seizure control. Chronic TLE goes along with focal hyperexcitability. Results provide insight into molecular mechanisms that may play a role in seizure propensity