Genes In Rat Hippocampus Research Articles

Bioinformatic analysis identifies key transcriptome signatures in temporal lobe epilepsy.

AimsTo identify transcriptome signatures underlying epileptogenesis in temporal lobe epilepsy (TLE).MethodsRobust rank aggregation analysis was used to integrate multiple microarrays in rodent models of TLE and determine differentially expressed genes (DEGs) in acute, latent, and chronic stages. Functional annotation and protein‐protein interaction analysis were performed to explore the potential functions of the DEGs and identify hub genes with the highest intramodular connectivity. The association between hub genes and hippocampal sclerosis/seizure frequency was analyzed using publicly available RNA‐sequencing datasets from TLE patients. We subsequently established a pilocarpine‐induced status epilepticus (SE) model in rats and validated mRNA expression of hub genes by quantitative reverse transcription PCR (qRT‐PCR).ResultsThe DEGs in the acute, latent, and chronic phases of TLE in animal models were prominently enriched in inflammatory response. Hub genes identified in the acute phase mainly participated in biological processes including inflammation, blood‐brain barrier damage, and cell adhesion. The hub genes in the latent phase were related to microglia/macrophage activation (Emr1 and Aif1) and phagocytosis (Cd68, Tyrobp, and Lyz). In the chronic phase, the hub genes were associated with activation of complements and microglia/macrophages. We further found that some hub genes identified in human TLE, such as Tlr2, Lgals3, and Stat3, were positively correlated with seizure frequency. Other hub genes, including Lgals3 and Serpine1, were associated with hippocampus sclerosis. qRT‐PCR analysis confirmed that the mRNA levels of hub genes in rat hippocampus were significantly up‐regulated after SE induction.ConclusionsOur integrated analysis identified hub genes in different stages of epilepsy. The functional annotations suggest that the activation and phagocytic activities of microglia/macrophages may play critical roles in epileptogenesis of TLE.

Genetic regulatory subnetworks and key regulating genes in rat hippocampus perturbed by prenatal malnutrition: implications for major brain disorders.

Objective: Many population studies have shown that maternal prenatal nutrition deficiency may increase the risk of neurodevelopmental disorders in their offspring, but its potential transcriptomic effects on brain development are not clear. We aimed to investigate the transcriptional regulatory interactions between genes in particular pathways responding to the prenatal nutritional deficiency and to explore their effects on neurodevelopment and related disorders.Results: We identified three modules in rat hippocampus responding to maternal prenatal nutritional deficiency and found 15 key genes (Hmgn1, Ssbp1, LOC684988, Rpl23, Gga1, Rhobtb2, Dhcr24, Atg9a, Dlgap3, Grm5, Scn2b, Furin, Sh3kbp1, Ubqln1, and Unc13a) related to the rat hippocampus developmental dysregulation, of which Hmgn1, Rhobtb2 and Unc13a related to autism, and Dlgap3, Grm5, Furin and Ubqln1 are related to Alzheimer’s disease, and schizophrenia. Transcriptional alterations of the hub genes were confirmed except for Atg9a. Additionally, through modeling miRNA–mRNA-transcription factor interactions for the hub genes, we confirmed a transcription factor, Cebpa, is essential to regulate the expression of Rhobtb2. We did not find singificent singals in the prefrontal cortex responding to maternal prenatal nutritional deficiency.Conclusion: These findings demonstrated that these genes with the three modules in rat hippocampus involved in synaptic development, neuronal projection, cognitive function, and learning function are significantly enriched hippocampal CA1 pyramidal neurons and suggest that three genetic regulatory subnetworks and thirteen key regulating genes in rat hippocampus perturbed by a prenatal nutrition deficiency. These genes and related subnetworks may be prenatally involved in the etiologies of major brain disorders, including Alzheimer’s disease, autism, and schizophrenia.Methods: We compared the transcriptomic differences in the hippocampus and prefrontal cortex between 10 rats with prenatal nutritional deficiency and 10 rats with prenatal normal chow feeding by differential analysis and co-expression network analysis. A network-driven integrative analysis with microRNAs and transcription factors was performed to define significant modules and hub genes responding to prenatal nutritional deficiency. Meanwhile, the module preservation test was conducted between the hippocampus and prefrontal cortex. Expression levels of the hub genes were further validated with a quantitative real-time polymerase chain reaction based on additional 40 pairs of rats.

Alteration in the Expression of Parkinson’s-Related Genes in Rat Hippocampus by Exercise and Morphine Treatments

Parkinson’s disease (PD) as a genetically heterogeneous disease is the second common neurological disorder which is associated with motor deficits and dementia owing to a spreading process of neuronal loss in the brain. Little is known about what affects Parkinson disease, but global efforts are underway to make medicines for treatment of this disease. We suppose, exercise as one of the golden key for overall health and brain-derived neurotrophic factor (BDNF) modulator must have some effects on the degree of PD severity. On the other hand, given the dopamine is one of the indispensable components for the endogenous morphine biosynthesis, a decrease in the level of morphine, may be associated with this disorder. We investigate the rate of true effect of exercise and morphine treatments on the expression of some major heritable genes in PD, including SNCA, LRRK2, Parkin, and DJ-1, by real-time PCR in rat hippocampus. The results indicated that under exercise and morphine treatments, the expression of alpha-synuclein and LRRK2 genes declined, while the expression of Parkin and DJ-1 genes raised. Since this genes expression pattern has been observed in the normal individuals, it can be concluded that exercise and morphine treatments have a positive effect on the improvement of Parkinson disease, and it might act in similar way in humans.

Transgenerational Inheritance of Betaine-Induced Epigenetic Alterations in Estrogen-Responsive IGF-2/IGFBP2 Genes in Rat Hippocampus.

Betaine serves as a methyl donor for DNA methylation. Here, the effects of betaine on hippocampal expression of neurogenesis genes and their DNA methylation status across three generations are investigated. Pregnant rats (F0) are fed control and betaine-supplemented diets throughout gestation and lactation. Female F1 and F2 offspring at weaning, together with the F0 dams, are used in the study. Hippocampal expression of aromatase, estrogen receptor α, and estrogen-related receptor β is downregulated in F1, together with the estrogen-responsive insulin-like growth factor 2/insulin-like growth factor binding protein 2 (IGF-2/IGFBP2) genes. However, all these genes are upregulated in F2, which follows the same pattern of F0. In agreement with changes in mRNA expression, the imprinting control region (ICR) of IGF-2 gene is hypomethylated in F1 but hypermethylated in F2 and F0. In contrast, the promoter DNA methylation status of all the affected genes is hypermethylated in F1 but hypomethylated in F2 and F0. Methyl transfer enzymes, such as betaine homocysteine methyltransferase and DNA methyltransferase 1, follow the same pattern of transgenerational inheritance. These results indicate that betaine exerts a transgenerational effect on hippocampal expression of estrogen-responsive genes in rat offspring, which is associated with corresponding alterations in DNA methylation on ICR of IGF-2 gene and the promoter of affected genes.

Alteration in the Expression of Alzheimer's-Related Genes in Rat Hippocampus by Exercise and Morphine Treatments

Alteration in the Expression of Alzheimer's-Related Genes in Rat Hippocampus by Exercise and Morphine Treatments

The impact of sensory and motor enrichment on the epigenetic control of steroidogenic-related genes in rat hippocampus

In the present study, we analyzed the effects of a short-term environmental enrichment on the mRNA expression and DNA methylation of steroidogenic enzymes in the hippocampus. Thus, young adult (80-day-old) and middle-aged (350-day-old) Wistar female rats were exposed to sensory (SE) or motor (ME) enrichment during 10 days and compared to animals housed under standard conditions. SE was provided by an assortment of objects that included plastic tubes and toys; for ME, rodent wheels were provided. In young adult animals, SE and ME increased the mRNA expression of cytochrome P450 17α-hydroxylase/c17,20-lyase, steroid 5α-reductase type 1 (5αR-1) and 3α-hydroxysteroid dehydrogenase and decreased the methylation levels of 5αR-1 gene. In middle-aged rats, ME and SE upregulated the gene expression of aldosterone synthase and decreased the methylation state of its promoter. These results propose that SE and ME differentially regulate the transcription of neurosteroidogenic enzymes through epigenetic mechanisms in young and aged rats.

Hippocampal transcriptome profiling in the aged rat brain for the prediction of age-associated cognitive decline

Event Abstract Back to Event Hippocampal transcriptome profiling in the aged rat brain for the prediction of age-associated cognitive decline Hanafi A. Damanhuri1*, Nur Aliah Achin1, Suzana Makpol1, Musalmah Mazlan2 and Wan Zurinah Wan Ngah1 1 Universiti Kebangsaan Malaysia, Department of Biochemistry, Faculty of Medicine, Malaysia 2 Universiti Teknologi Mara, Faculty of Medicine, Sungai Buloh Campus, Malaysia Cognitive decline is present in continuum with advancing of age. To date, the indicator between physiological and pathological cognitive deterioration is still uncertain. This study is aimed to determine the differentially expressed genes in rat hippocampus at different ages and correlate the findings with the cognitive functions that may predispose to the brain ageing process. Cognitive functions were determined through open field, Morris water maze and object recognition test on 3, 14, 18, 23 and 27 months-old Sprague Dawley rats. Upon the completion of cognitive assessment at each age, hippocampus (HC) was carefully dissected and the total RNA was extracted and proceeded with microarray analysis (Affymetrix GeneChip® Rat Gene 2.0 ST Array). Raw signal intensity data was subjected to background subtraction and quantile normalization by Affymetrix® Expression ConsoleTM Software. Analysis of variance (ANOVA), Gene Set Enrichment Analysis (GSEA) and pathway enrichment analysis of normalized probe intensities values were performed using Partek® Genomic Suite® (v6.6). Our data indicated that ageing not only affects the spatial and non-spatial memory but also decreased the exploratory behaviours in our animal model. The levels of anxiety were also higher in the older rats. From the microarray data, a total of 4,619 genes were differentially expressed (p<0.05) in 14, 18, 23, and 27 months-old HC when compared with 3 months old group. Among these genes, 2,384 genes were downregulated and 2,235 genes were upregulated. These genes were enriched, showing that the genes were involved in 22 KEGG pathways with enrichment score more than 3.0 (p<0.05), which include ErbB signaling pathway, synthesis and degradation of ketone bodies, antigen processing and presentation, metabolic pathways and oxidative phosphorylation as well as SNARE interactions. As conclusion, transcriptome profiling in hippocampus could be utilized to gain more comprehensive understanding of brain ageing process and identify potential biomarkers for age-associated cognitive decline. Acknowledgements This study was funded by Long term Research Grant Scheme (LRGS/BU/2012/UKM-UKM/K/04) and Fundamental Research Grant Scheme (FRGS/2/2013/SKK01/UKM/03/4) from Ministry of Higher Education Malaysia Keywords: Gene Expression, Hippocampus, Oxidative Stress, neurodegeneration, antioxidant Conference: 14th Meeting of the Asian-Pacific Society for Neurochemistry, Kuala Lumpur, Malaysia, 27 Aug - 30 Aug, 2016. Presentation Type: Symposium 7: New Insights on Oxidative Stress in Neurodegenerative Diseases and Therapeutic Potential of Anti- Oxidants as a Drug for the Pre-Emptive Medicine Topic: 14th Meeting of the Asian-Pacific Society for Neurochemistry Citation: Damanhuri HA, Achin N, Makpol S, Mazlan M and Wan Ngah W (2016). Hippocampal transcriptome profiling in the aged rat brain for the prediction of age-associated cognitive decline. Conference Abstract: 14th Meeting of the Asian-Pacific Society for Neurochemistry. doi: 10.3389/conf.fncel.2016.36.00030 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Jul 2016; Published Online: 11 Aug 2016. * Correspondence: Dr. Hanafi A Damanhuri, Universiti Kebangsaan Malaysia, Department of Biochemistry, Faculty of Medicine, Cheras, Kuala Lumpur, Malaysia, hanafi.damanhuri@ppukm.ukm.edu.my Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Hanafi A Damanhuri Nur Aliah Achin Suzana Makpol Musalmah Mazlan Wan Zurinah Wan Ngah Google Hanafi A Damanhuri Nur Aliah Achin Suzana Makpol Musalmah Mazlan Wan Zurinah Wan Ngah Google Scholar Hanafi A Damanhuri Nur Aliah Achin Suzana Makpol Musalmah Mazlan Wan Zurinah Wan Ngah PubMed Hanafi A Damanhuri Nur Aliah Achin Suzana Makpol Musalmah Mazlan Wan Zurinah Wan Ngah Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Prophylactic treatment with melatonin before recurrent neonatal seizures: Effects on long-term neurobehavioral changes and the underlying expression of metabolism-related genes in rat hippocampus and cerebral cortex

Although it has been suggested that the protective effect of melatonin against seizure-induced neurotoxicity involves inhibition of neuronal lipid peroxidation, current data concerning the exact molecular mechanism are still limited. This study was undertaken to investigate the changes in neurobehavioral, cognitive and lipid metabolism-related gene expressions in both hippocampus and cerebral cortex of rats subjected to recurrent neonatal seizures, and the effects of melatonin treatment before seizure (55mg/kg, 1mg/ml). 6-day-old (P6) SD rats were randomly divided into four groups of control (CONT, the same below), melatonin treated control (Mel), recurrent neonatal seizure (RS) and melatonin and RS combination treatment (Mel+RS). Neurological behavioral parameters of brain damage (plane righting reflex, negative geotaxis reaction reflex, Cliff avoidance reflex, forelimb suspension reflex) were observed on P31. Morris water maze test was performed during P29–P35. Then the protein levels of ACAT1, Cathepsin-E and Ca2+/calmodulin-dependent protein kinase II (CAMK II) in hippocampus and cerebral cortex were detected by western blot method. As expected, RS group showed a significant delay or reduce of the four reflexes, as well as bad performance in the Morris water maze test. Flurothyl-induced neurobehavioral toxicology was blocked by pre-treatment with melatonin. In parallel with these behavioral changes, gene expression by western blot method demonstrated that rats pretreated with melatonin (Mel+RS) showed a significant down-regulated expression of ACAT-1, Cathepsin-E and up-regulated CAMK II in hippocampus and cerebral cortex when compared with RS group. Our findings provide support for ACAT-1/Cathepsin-E as well as CaMK II being potential targets for the treatment of neonatal seizure-induced brain damage by melatonin.

Effect of pregabalin on apoptotic regulatory genes in hippocampus of rats with chronic temporal lobe epilepsy

Objective To observe the effect of pregabalin on the expression of Bcl⁃2 and Bax in hippocampus of chronic epileptic rats induced by pilocarpine, to explore the anti⁃epileptic pharmacology mechanism of pregabalin, and its anti ⁃ apoptotic effect on hippocampal neurons of rats. Methods The model of chronic temporal lobe epileptic rats induced by lithium⁃pilocarpine was established, then the rats in pregabalin treatment group received intraperitoneal injection of pregabalin (40 mg/kg) once daily for three weeks. The expression of Bcl⁃2 and Bax in hippocampus of all rats was detected by immunohistochemical technique and Western blotting. Results Compared with normal saline group rats, the expression of Bcl⁃2 and Bax in hippocampus of rats with chronic temporal lobe epilepsy was significantly increased (P = 0.000, for all). Pregabalin can down⁃regulate the expression of Bax and up⁃regulate the expression of Bcl⁃2 in hippocampus of rats compared to model group rats (P = 0.000, for all). Conclusion Pregabalin may have the effects of inhibiting cell apoptosis and protecting neurons through lowing Bax level and increasing Bcl⁃2 level in hippocampus of chronic temporal lobe epileptic rats. DOI：10.3969/j.issn.1672⁃6731.2012.02.018

Mitochondrial targeted neuron focused genes in hippocampus of rats with traumatic brain injury

Context:Mild traumatic brain injury (mTBI) represents a major health problem in civilian populations as well as among the military service members due to (1) lack of effective treatments, and (2) our incomplete understanding about the progression of secondary cell injury cascades resulting in neuronal cell death due to deficient cellular energy metabolism and damaged mitochondria.Aims:The aim of this study was to identify and delineate the mitochondrial targeted genes responsible for altered brain energy metabolism in the injured brain.Settings and Design:Rats were either grouped into naïve controls or received lateral fluid percussion brain injury (2–2.5 atm) and followed up for 7 days.Materials and Methods:Rats were either grouped into naïve controls or received lateral fluid percussion brain injury (2–2.5 atm) and followed for 7 days. The severity of brain injury was evaluated by the neurological severity scale—revised (NSS-R) at 3 and 5 days post TBI and immunohistochemical analyses at 7 days post TBI. The expression profiles of mitochondrial-targeted genes across the hippocampus from TBI and naïe rats were also examined by oligo-DNA microarrays.Results:NSS-R scores of TBI rats (5.4 ± 0.5) in comparison to naïe rats (3.9 ± 0.5) and H and E staining of brain sections suggested a mild brain injury. Bioinformatics and systems biology analyses showed 31 dysregulated genes, 10 affected canonical molecular pathways including a number of genes involved in mitochondrial enzymes for oxidative phosphorylation, mitogen-activated protein Kinase (MAP), peroxisome proliferator-activated protein (PPAP), apoptosis signaling, and genes responsible for long-term potentiation of Alzheimer's and Parkinson's diseases.Conclusions:Our results suggest that dysregulated mitochondrial-focused genes in injured brains may have a clinical utility for the development of future therapeutic strategies aimed at the treatment of TBI.

Gene expression profile analysis of genes in rat hippocampus from antidepressant treated rats using DNA microarray.

BackgroundThe molecular and biological mechanisms by which many antidepressants function are based on the monoamine depletion hypothesis. However, the entire cascade of mechanisms responsible for the therapeutic effect of antidepressants has not yet been elucidated.ResultsWe used a genome-wide microarray system containing 30,000 clones to evaluate total RNA that had been isolated from the brains of treated rats to identify the genes involved in the therapeutic mechanisms of various antidepressants, a tricyclic antidepressant (imipramine). a selective serotonin reuptake inhibitor (fluoxetine), a monoamine oxidase inhibitor (phenelzine) and psychoactive herbal extracts of Nelumbinis Semen (NS). To confirm the differential expression of the identified genes, we analyzed the amount of mRNA that was isolated from the hippocampus of rats that had been treated with antidepressants by real-time RT-PCR using primers specific for selected genes of interest. These data demonstrate that antidepressants interfere with the expression of a large array of genes involved in signaling, survival and protein metabolism, suggesting that the therapeutic effect of these antidepressants is very complex. Surprisingly, unlike other antidepressants, we found that the standardized herbal medicine, Nelumbinis Semen, is free of factors that can induce neurodegenerative diseases such as caspase 8, α-synuclein, and amyloid precursor protein. In addition, the production of the inflammatory cytokine, IFNγ, was significantly decreased in rat hippocampus in response to treatment with antidepressants, while the inhibitory cytokine, TGFβ, was significantly enhanced.ConclusionsThese results suggest that antidepressants function by regulating neurotransmission as well as suppressing immunoreactivity in the central nervous system.

SO2 inhalation modulates the expression of apoptosis-related genes in rat hippocampus via its derivatives in vivo

The possible neurotoxicity of SO2 has been implicated by determining morphological change, oxidative stress, DNA damage and membrane channel alteration in previous studies, however, its detailed mechanisms remain unclear. In the present study, we investigated SO2 inhalation-induced effects on the transcription and translation of several apoptosis-related genes (p53, bax, bcl-2, c-fos, and c-jun) in rat hippocampus, using real-time RT-PCR analysis and western blotting technique, respectively. The results demonstrate that SO2 statistically increased p53 expression and the ratio of bax to bcl-2 in a concentration-dependent manner. Also, mRNA and protein levels of c-fos and c-jun significantly elevated in proportion to exposure concentration. Then, we treated primary cultured hippocampal neurons with SO2 derivatives (bisulfite and sulfite, 3:1 M/M), and examined mRNA levels of above genes. The results show that P53, c-fos, c-jun mRNA expression and the ratio of bax to bcl-2 augmented as functions of SO2 derivative concentration and exposure time, and confirm that SO2 affected the transcription and translation process of apoptosis-related genes in central nervous system via its derivatives in vivo. The present data provide further evidence for SO2-caused neurological insults, and imply that two major pathways associated with p53 and AP-1 might play important roles in the pathogenesis.

Identification of Igf2, Igfbp2 and Enpp2 as Estrogen-Responsive Genes in Rat Hippocampus

Estrogen has an important effect on higher brain function such as memory, learning, and emotion in which the hippocampus plays a critical role. The hippocampus expresses estrogen receptors, ER alpha and ERbeta, which are ligand-dependent transcription factors; however, the precise mechanism of estrogen action is not fully understood. We explored genes which are up-regulated by estrogen in the hippocampus using ovariectomized rat models. Microarray analysis revealed that mRNA levels of ectonucleotide pyrophosphatase/phosphodiesterase 2 (Enpp2), insulin like growth factor 2 (Igf2) and insulin-like growth factor binding protein 2 (Igfbp2) were increased by estrogen in the hippocampus. Quantitative-PCR analysis demonstrated that the levels of Enpp2, Igf2 and Igfbp2 mRNA were elevated by estrogen administration in the hippocampus but not in the hypothalamus. On the other hand, ERalpha, ERbeta and progesterone receptor (PR) mRNA expression was up-regulated by estrogen only in the hypothalamus. We further analyzed the time-dependent regulation of these genes using rat pituitary adenoma, MtT/S and GH3 cells, which are known to express ERalpha. In both MtT/S and GH3 cells, Igfbp2 and Enpp2 mRNAs were up- and down-regulated by estrogen, respectively, whereas Igf2 mRNA was increased only in GH3 cells. These results demonstrate a brain region- and cell type-specific responses to estrogen in rat brain, suggesting that Igf signaling may mediate the estrogen function in the hippocampus.

Neurotrophin gene expression in rat brain under the action of Semax, an analogue of ACTH 4–10

The heptapeptide Semax, an analogue of the N-terminal adrenocorticotropic hormone fragment (4–10) (ACTH 4–10), has been shown to exert a number of neuroprotective effects. There are some investigations that connected these effects with the increase of neurotrophin gene expression under the peptide drug application in neuron cell cultures [M.I. Shadrina, O.V. Dolotov, I.A. Grivennikov, P.A. Slominsky, L.A. Andreeva, L.S. Inozemtseva, S.A. Limborska, N.F. Myasoedov, Rapid induction of neurotrophin mRNAs in rat glial cell cultures by Semax, an adrenocorticotropic hormone analogue, Neurosci. Lett. 308 (2001) (2) 115–118]. In this work, we examined the action of Semax on rapid changes of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) gene expression in vivo. Male Wistar rats were treated for 1 h with Semax (50 μg/kg, single intranasal application) and neurotrophin gene expression in rat brain was analyzed by real-time polymerase chain reaction (PCR). It was revealed that an intranasal application of Semax increased the expression of both neurotrophin genes in rat hippocampus. Bdnf gene expression also increased in the brainstem and cerebellum. Ngf gene expression decreased in rat frontal cortex. Thus, Semax induces rapid, gene- and region-specific changes in neurotrophin gene expression in normal rat brain.

Identification of corticosteroid-responsive genes in rat hippocampus using serial analysis of gene expression.

Adrenal corticosteroids (CORT) have a profound effect on the function of the hippocampus. This is mediated in a coordinated manner by mineralocorticoid (MR) and glucocorticoid receptors (GR) via activation or repression of target genes. The aim of this study was to identify, using serial analysis of gene expression (SAGE), CORT-responsive hippocampal genes regulated via MR and/or GR. SAGE profiles were compared under different conditions of CORT exposure, resulting in the identification of 203 CORT-responsive genes that are involved in many different cellular processes like, energy expenditure and cellular metabolism; protein synthesis and turnover; signal transduction and neuronal connectivity and neurotransmission. Besides some previously identified CORT-responsive genes, the majority of the genes identified in this study were novel. In situ hybridization revealed that six randomly chosen CORT-responsive genes had distinct expression patterns in neurons of the hippocampus. In addition, using in situ hybridization, we confirmed that these six genes were indeed regulated by CORT, underscoring the validity of the SAGE data. Comparison of MR- and GR-dependent expression profiles revealed that the majority of the CORT-responsive genes were regulated either by activated MR or by activated GR, while only a few genes were responsive to both activated MR and GR. This indicates that the molecular basis for the differential effects of activated MR and GR is activation or repression of distinct, yet partially overlapping sets of genes. The putative CORT-responsive genes identified here will provide insight into the molecular mechanisms underlying the differential and sometimes opposing effects of MR and GR on neuronal excitability, memory formation and behaviour as well as their role in neuronal protection and damage.

Identification of maze learning-associated genes in rat hippocampus by cDNA microarray.

Long-term memory formation requires de novo RNA and protein synthesis. To assess gene-expression changes associated with learning and memory processes, we used cDNA microarray to analyze hippocampal gene expression in male Fischer-344 rats following training in a multiunit T-maze. Here, we report the identification of 28 clones (18 known genes and 10 ESTs) for which expression increased after the maze learning. Some of the known genes appear to be involved in Ca2+ signaling, Ras activation, kinase cascades, and extracellular matrix (ECM) function, which may regulate neural transmission, synaptic plasticity, and neurogenesis. The gene-expression profile presented here provides the groundwork for future, more focused research to elucidate the contribution of these genes in learning and memory processes.

Identification of differentially expressed genes in rat hippocampus after transient global cerebral ischemia using subtractive cDNA cloning based on polymerase chain reaction.

The purpose of this study is to identify new molecules that play important roles in the phenomena that occur in the hippocampus after transient global cerebral ischemia, as clues to better understanding of the mechanisms. A subtractive cDNA library was established by suppression subtractive hybridization of rat hippocampal tissues after transient global cerebral ischemia. With differential screening of the library, upregulated fragments were identified. The mRNA expression levels of selected genes were measured with semiquantitative reverse transcriptase polymerase chain reaction (PCR). Among more than 100 isolated fragments, approximately half were determined to be identical to known sequences. The rest showed high homology to known sequences, and only 2 did not exhibit homology to any known sequences. The expression of 5 genes identified in this study increased in 24 hours after ischemia to a level twice as high as that in sham-operated controls. These included furin, prosaposin, synaptotagmin IV, heat shock protein 105, and the neutral and basic amino acid transporter (NBAT). The increases in the mRNA expression levels of the genes except NBAT, as revealed by semiquantitative reverse transcription PCR, were statistically significant at both 6 and 24 hours after ischemia. Genes isolated are thought to be associated with production of proteins necessary for degeneration, neuroprotection, and reconstruction of neurons. How the expression of these genes relates to functional changes after ischemia remains to be determined. PCR-based subtractive cDNA cloning is demonstrated to be a useful tool for analyzing in vivo gene expression in animal ischemia models.

Adrenalectomy regulates apoptotic-associated genes in rat hippocampus.

Morphological studies of granular neurons of the hippocampus have shown that adrenalectomy (ADX) induces the cell death of granular neurons, an effect prevented by corticosterone replacement. We addressed the hypothesis that corticosterone regulates the expression of the apoptotic bcl-2 gene family. Five days after adrenalectomy, we observed morphological changes related to hippocampal granule cell apoptosis that was accompanied by terminal dUTP nick and labeling (TUNEL) labeling in nuclei located in the hilus region. Corticosterone replacement prevented the cell death induced by ADX. Using RT-PCR we found a reduction in mRNA levels of the antiapoptotic gene bcl-2 in whole hippocampus, an effect which was prevented by corticosterone administration to ADX rats. However, Bcl-2 protein levels were not altered by this treatment. We did not observe modifications in the level of bcl-X(L) mRNA however, we did find a 40% reduction in Bcl-X(L) protein levels, an effect not reversed by corticosterone. In contrast, we found a reduction in the mRNA of the antiapoptotic gene bax and Bax levels after ADX; both effects were prevented by corticosterone. The reduction in proapoptotic bax and in antiapoptotic bcl-2 mRNA levels in the whole hippocampus, suggests that local variations in these molecules could account for both neuronal viability of the CA1-CA3 and granular cell death detected by morphological means and observed after ADX.