Gene Expression Profiles In Hippocampus Research Articles

Effect of Therapeutic Mild Hypothermia on the Genomics of the Hippocampus After Moderate Traumatic Brain Injury in Rats

Traumatic brain injury (TBI), a major cause of morbidity and mortality, is a serious public health concern. To evaluate the effect of mild hypothermia on gene expression in the hippocampus and to try to elucidate molecular mechanisms of hypothermic neuroprotection after TBI. Rats were subjected to mild hypothermia (group 1: n = 3, 33 degrees C, 3H) or normothermia (group 2: n = 3; 37 degrees C, 3H) after TBI. Six genome arrays were applied to detect the gene expression profiles of ipsilateral hippocampus. Functional clustering and gene ontology analysis were then carried out. Another 20 rats were randomly assigned to 4 groups (n = 5 per group): group 3, sham-normothermia; group 4, sham-hypothermia; group 5, TBI-normothermia; and group 6, TBI-hypothermia. Real-time fluorescent quantitative reverse-transcription polymerase chain reaction was used to detect specific selected genes. We found that 133 transcripts in the hypothermia group were statistically different from those in the normothermia group, including 57 transcripts that were upregulated and 76 that were downregulated after TBI (P < .01). Most of these genes were involved in various pathophysiological processes, and some were critical to cell survival. Analysis showed that 9 gene ontology categories were significantly affected by hypothermia, including the most affected categories: synapse organization and biogenesis (upregulated) and regulation of inflammatory response (downregulated). The mRNA expression of Ank3, Cmbp, Nrxn3, Tgm2, and Fcgr3 was regulated by hypothermia, TBI, or a combination of TBI and hypothermia compared with the sham-normothermia group. Their mRNA expression was significantly regulated by hypothermia in TBI groups. Posttraumatic mild hypothermia has a significant effect on the gene expression profiles of the hippocampus, especially those genes belonging to the 9 gene ontology categories. Differential expression of those genes may be involved in the most fundamental molecular mechanisms of cerebral protection by mild hypothermia after TBI.

Hippocampal gene expression profiling reveals changes in the phosphatidylinositol signaling and long-term potentiation pathways of aged senescence accelerated mice

Hippocampal gene expression profiling reveals changes in the phosphatidylinositol signaling and long-term potentiation pathways of aged senescence accelerated mice

Tonic Premarin dose-dependently enhances memory, affects neurotrophin protein levels and alters gene expression in middle-aged rats

Premarin™ is the most commonly prescribed estrogenic component of hormone therapy, given since 1942. The current study is the first examining cognitive effects of tonic Premarin treatment in an animal model. Middle-aged ovariectomized (Ovx) rats received vehicle or one of three doses of Premarin (12, 24 or 36μg daily). Rats were tested on a spatial working and reference memory maze battery. Both medium- and high-dose Premarin enhanced memory retention, while low-dose Premarin impaired learning and memory retention. Correlations with serum hormone levels showed that as the ratio of estrone:17β-estradiol increased, animals tended to show better working memory performance. Taken together with the dissociation of dose-specific estrogenic profiles, results suggest that higher levels of estrone, in the presence of 17β-estradiol concentrations higher than that of Ovx levels, may be beneficial for memory. Moreover, Premarin exerted dose and brain-region specific effects on BDNF and NGF protein levels, with most marked changes in cingulate and perirhinal cortices. Hippocampal gene expression profiling demonstrated significant Premarin-induced transcriptional changes in genes linked to plasticity and cognition. These findings indicate that Premarin can impact memory and the brain, and that dosing should be recognized as a clinically relevant factor possibly affecting the direction and efficacy of cognitive outcome.

Effect of profound hypothermia on genomics of hippocampus following complete cerebral ischemia in rats

Objective: To determine differential gene expression of hippocampus in rats following complete cerebral ischemia with treatment of profound hypothermia compared to normothermia.Methods: Six rats got 5 minutes of complete cerebral ischemia with circulatory arrest and randomly divided into two groups: normothermia ischemia group (37 ± 0.3°C, n=3) and profound hypothermia ischemia group (18 ± 0.5°C, n=3). Affymetrix U34A rat arrays were applied to detect the difference of gene expression profile in hippocampus between the two groups.Results: Expression profiles of a total of 75 transcripts in the profound hypothermia ischemia group were statistically different from those of the normothermia ischemia group, and 33 of them were significantly up-regulated and other 42 were significantly down-regulated (p<0.01).Conclusions: Compared with normothermia, profound hypothermia had a significant effect on the gene expression profiles following complete cerebral ischemia, which may be involved in the mechanisms of cerebral protection by profound hypothermia.

Temporal gene expression profile in hippocampus of mice treated with D-galactose.

(1) Rodent chronically treated with D-galactose (D-gal) is increasingly used in pharmacological studies on aging; however, its mechanism remains unclear. The present study investigated the alterations of gene expression in the hippocampus of D-gal-treated mice. (2) C57 mice were subcutaneously injected with D-gal for 2, 4, and 8 weeks or vehicle, and then were subjected to behavioral tests. Gene expression profiles in hippocampus of each group were finally examined with cDNA microarray. (3) Both 4- and 8-week D-gal treatment led to a decrease of discrimination index in object recognition test, and 8-week D-gal-treated mice showed significant spatial learning & memory impairment in Morris water maze test. In comparison with the vehicle control group, the 2-, 4-, and 8-week D-gal treatment repressed the expression of 10, 13, and 30 genes by 2-fold or more, respectively. The early pattern was mainly characterized by down regulation of genes involved in ion transport. The delayed pattern included genes involved in protein biosynthesis, transport and signal transduction, which were highly related to synaptic functions. (4) These findings will contribute to the understanding of the mechanism of learning and memory impairment in mice treated with D-galactose.

Hippocampal gene expression profiling reveals the possible involvement of Homer1 and GABAB receptors in scopolamine‐induced amnesia

Scopolamine-treated rats are commonly used as a psychopharmacological model of memory dysfunction and have been extensively studied to establish the effectiveness of acetylcholinesterase inhibitors in the treatment of Alzheimer's disease. Scopolamine is a muscarinic acetylcholine receptor antagonist that induces memory deficits in young subjects similar to those occurring during aging. The amnesic effect of scopolamine is well established but the molecular and cellular mechanisms that sustain its neuropharmacological action are still unclear. The present genome wide study investigates hippocampal gene expression profiling in scopolamine-treated adult rats following stimulation in a spatial memory task. Using microarray and quantitative real-time RT-PCR approaches, we identified several genes previously known to be associated with memory processes (Homer1, GABA(B) receptor, early growth response 1, prodynorphin, VGF nerve growth factor inducible) and multiple novel candidate genes possibly involved in cognition (including calcium/calmodulin-dependent protein kinase kinase 2, dual specificity phosphatase 5 and 6, glycophorin C) that were altered following scopolamine treatment. Moreover, we found that stable over-expression of glutamatergic components Homer1a and 1c in the hippocampus of adult rats induced by recombinant adeno-associated virus vector abolished memory improvement produced by the GABA(B) receptor antagonist SGS742 in scopolamine-treated rats. Taken together, these results reveal novel genes and mechanisms involved in scopolamine-induced amnesia, and demonstrate the involvement of both GABA and glutamate neurotransmission in this animal model of cognitive dysfunctions.

Development of the first marmoset-specific DNA microarray (EUMAMA): a new genetic tool for large-scale expression profiling in a non-human primate.

BackgroundThe common marmoset monkey (Callithrix jacchus), a small non-endangered New World primate native to eastern Brazil, is becoming increasingly used as a non-human primate model in biomedical research, drug development and safety assessment. In contrast to the growing interest for the marmoset as an animal model, the molecular tools for genetic analysis are extremely limited.ResultsHere we report the development of the first marmoset-specific oligonucleotide microarray (EUMAMA) containing probe sets targeting 1541 different marmoset transcripts expressed in hippocampus. These 1541 transcripts represent a wide variety of different functional gene classes. Hybridisation of the marmoset microarray with labelled RNA from hippocampus, cortex and a panel of 7 different peripheral tissues resulted in high detection rates of 85% in the neuronal tissues and on average 70% in the non-neuronal tissues. The expression profiles of the 2 neuronal tissues, hippocampus and cortex, were highly similar, as indicated by a correlation coefficient of 0.96. Several transcripts with a tissue-specific pattern of expression were identified. Besides the marmoset microarray we have generated 3215 ESTs derived from marmoset hippocampus, which have been annotated and submitted to GenBank [GenBank: EF214838 – EF215447, EH380242 – EH382846].ConclusionWe have generated the first marmoset-specific DNA microarray and demonstrated its use to characterise large-scale gene expression profiles of hippocampus but also of other neuronal and non-neuronal tissues. In addition, we have generated a large collection of ESTs of marmoset origin, which are now available in the public domain. These new tools will facilitate molecular genetic research into this non-human primate animal model.

Single prolonged stress increases contextual freezing and the expression of glycine transporter 1 and vesicle-associated membrane protein 2 mRNA in the hippocampus of rats

Rats subjected to single prolonged stress (SPS) show enhanced HPA negative feedback, exaggerated acoustic startle response, and enhanced contextual freezing 7 days after SPS, and accordingly, SPS is an animal model of PTSD. To elucidate the influence of contextual fear on gene expression in the hippocampus of SPS rats, we used cDNA microarray followed by real-time quantitative PCR analyses to compare the hippocampal gene expression profiles between rats that were or were not subjected to SPS during exposure to contextual fear. In the behavioral experiments, spontaneous locomotor activity was measured 7 days after SPS. Twenty-four hours after footshock conditioning (7 days after SPS), freezing behavior was measured during re-exposure to the chamber in which footshock was delivered. Based on the behavioral analysis, rats subjected to SPS exhibited a significant enhancement of contextual freezing compared to rats not subjected to SPS, without any changes in locomotor activity. Analyses using cDNA microarray and RT-PCR showed that the hippocampal levels of glycine transporter 1 (Gly-T1) and vesicle-associated membrane protein 2 (VAMP2) mRNA in rats subjected to SPS were significantly increased relative to sham-treated rats. Administration of SPS alone did not affect the expression of these 2 genes. These findings suggest that the upregulation of Gly-T1 and VAMP2 in the hippocampus may be, at least in part, involved in the enhanced susceptibility to contextual fear in rats subjected to SPS.

Brain pH has a significant impact on human postmortem hippocampal gene expression profiles

Studies of neurobiological disorders in the brain, including schizophrenia, rely on the use of postmortem brain tissues, in which an understanding of the effects of various pre- and postmortem variables on gene expression is critical. In several different brain regions, pH has been shown to have a large effect on postmortem brain gene expression patterns. One region that has not yet been evaluated in such studies is the hippocampus, a region often implicated in schizophrenia research. In the present study, we show that postmortem brain pH is similar across different brain regions. Brain pH accounted for greater variation in hippocampal gene expression profiles than any other parameter evaluated, including gender and schizophrenia. The predictive value of brain pH in an independent sample set was also greater than the disease, demonstrating that pH represents one of the most important control parameters in human postmortem gene expression studies in schizophrenia.

Strain‐dependent regulation of neurotransmission and actin‐remodelling proteins in the mouse hippocampus

Individual mouse strains differ significantly in terms of behaviour, cognitive function and long-term potentiation. Hippocampal gene expression profiling of eight different mouse strains points towards strain-specific regulation of genes involved in neuronal information storage. Protein expression with regard to strain- dependent expression of structures related to neuronal information storage has not been investigated yet. Herein, a proteomic approach based on two-dimensional gel electrophoresis coupled with mass spectrometry (MALDI-TOF/TOF) has been chosen to address this question by determining strain-dependent expression of proteins involved in neurotransmission and activity-induced actin remodelling in hippocampal tissue of five mouse strains. Of 31 spots representing 16 different gene products analysed and quantified, N-ethylmaleimide-sensitive fusion protein, N-ethylmaleimide-sensitive factor attachment protein-alpha, actin-like protein 3, profilin and cofilin were expressed in a strain-dependent manner. By treating protein expression as a phenotype, we have shown significant genetic variation in brain protein expression. Further experiments in this direction may provide an indication of the genetic elements that contribute to the phenotypic differences between the selected strains through the expressional level of the translated protein. In view of this, we propose that proteomic analysis enabling to concomitantly survey the expression of a large number of proteins could serve as a valuable tool for genetic and physiological studies of central nervous system function.

P.1.a.015 Strain differences in susceptibility to unpredictable chronic mild stress as assessed by hippocampal gene expression profiling

Major depression is a common long-lasting or recurrent psychiatric disease with high lifetime prevalence and high incidence of suicide. The main purpose of the current study was to verify whether liquiritigenin conferred an antidepressant-like effect on the depressive mouse model established by unpredictable chronic mild stress (UCMS) and explore its possible mechanism. The results of depression-related behaviors including sucrose preference test (SPT), open field test (OFT), forced swimming test (FST) and tail suspension test (TST) indicated that both liquiritigenin (7.5 mg/kg, 15 mg/kg) and fluoxetine (20 mg/kg) dramatically improved the depression symptoms. Enzyme-linked immunosorbent assay (ELISA) revealed that treatment with liquiritigenin significantly reduced the concentrations of pro-inflammatory cytokines including interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α in serum and hippocampus. Compared with the UCMS group, the administrations of liquiritigenin, increased levels of superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), and decreased Malondialdehyde (MDA) content. Meanwhile, glucocorticoids (GC) content was reduced in the liquiritigenin group, which suggested that liquiritigenin exhibiting the ameliorative effect on activated hypothalamic-pituitary-adrenal (HPA) axis stimulated with UCMS. Mice treated with liquiritigenin showed restored levels of neurotransmitter norepinephrine (NE) and serotonin (5-HT). Western blot analysis displayed up-regulated expressions of p-phosphatidylinositol 3-kinase (PI3 K), p-Akt, p- mammalian target of rapamycin (mTOR), p-tropomyosin-related kinase B (TrkB), brain-derived neurotrophic factor (BDNF). Thus, it was supposed that liquiritigenin might be useful for the treatment of chronic depression possibly through PI3 K/Akt/mTOR mediated BDNF/TrkB pathway.

Strain-dependent expression of signaling proteins in the mouse hippocampus

Individual mouse strains may differ significantly in terms of behavior and cognitive function. Hippocampal gene expression profiling on several mouse strains has been carried out and points toward substantial strain-specific variation of more than 200 genes including components of major signaling pathways involved in neuronal information storage. Strain-specific hippocampal protein expression, however, has not been investigated yet. A proteomic approach based on two-dimensional gel electrophoresis coupled with mass spectrometry has been chosen to address this question by determining strain-dependent expression of signaling proteins in hippocampi of four inbred and one outbred mouse strain. Forty-six spots corresponding to 37 different signaling proteins have been analyzed and quantified. Statistical analysis revealed strain-dependent expression of serine/threonine protein phosphatase 1, serine/threonine protein phosphatase 2A, large GTP binding protein OPA1, guanine nucleotide-binding protein beta, putative GTP-binding protein Ran, receptor of activated protein kinase C1, WASP-family protein member 1, voltage-dependent anion channel 2 and 14-3-3 protein gamma. Differential expression of signaling proteins in the hippocampus may contribute to the molecular understanding of strain-dependent behavioral and cognitive performance. Moreover, these data highlight the importance of the genetic background for the analysis of signaling pathways in the hippocampus in wild-type mice as well as in gene-targeting experiments.

Distinct gene expression profiles in hippocampus and amygdala after fear conditioning

It is well known that the hippocampus and amygdala are involved in the formations of fear conditioning memories, and both contextual and cued fear memory requires activation of the NMDA receptors. However, the global molecular responses in the hippocampus and amygdala have not been investigated. By applying high-density microarrays containing 11,000 genes and expressed sequence tags, we examined fear conditioning-induced gene expression profiles in these two brain regions at 0.5, 6, and 24 h. We found that 222 genes in the amygdala and 145 genes in the hippocampus showed dynamic changes in their expression levels. Surprisingly, the overall patterns of gene expression as well as the individual genes for the amygdala and hippocampus were drastically different and only small number of genes exhibited the similar regulation in both brain regions. Based on expression kinetics, the genes from the amygdala can be further grouped into eight unique clusters, whereas the genes from the hippocampus were placed into six clusters. Therefore, our study suggests that different genomic responses are initiated in the hippocampus and amygdala which are known to play distinct roles in fear memory formation.

Transcriptional mechanisms of hippocampal aging

Aging related cognitive decline is an increasing health problem but affects only a subset of elderly humans. This research uses outbred young (Y) and aged rats. Behavioral characterization distinguishes aged rats with impaired spatial learning (AI) and aged rats with unimpaired learning ability (AU), mimicking the varied susceptibility of the human population to age-associated learning impairment. Studies are testing a hypothesis that hippocampal transcriptional mechanisms and gene expression profiles linked to activator protein-1 (AP-1) and glucocorticoid receptor (GR), mineralocorticoid receptor (MR) or cyclic AMP response element binding protein (CREB) families of transcription factors distinguish successful or unsuccessful aging and cognition. Results from mRNA assays, in situ hybridization, electromobility shift assays and western immunoblot indicate changes in GR and CREB in AI rats. State of the art future approaches to define downstream transcription targets are described.

Aging and acupuncture effects on hippocampal gene expression profile of SAMP10

In order to explore the pathogenic mechanisms of cerebral senescence and its possible effective acupuncture therapy, we applied cDNA array technique to study expression of the aging-related genes in hippocampus and acupuncture effect on them. SAMP10 and SAMR1 were selected and randomly divided into four groups: R1 control group, P10 control group, P10 acupuncture group and P10 pseudo-acupuncture group. The results showed that acupuncture not only could partly or completely reverse the effect of aging on hippocampal gene expression, but also influence some gene expression which were unrelated to aging. However, pseudo-acupuncture had some effect on aging-unrelated gene expression and little or no effect on aging-related genes. Therefore, we suspect that acupuncture points may have both therapeutic effect and “stress-inducing reaction”. Pseudo-acupuncture has only “responsiveness” without therapeutic effect.

GeneChip analysis of hippocampal gene expression profiles of short‐ and long‐attack‐latency mice: Technical and biological implications

To gain insight into the molecular mechanisms underlying the behavioral differences between two mouse lines genetically selected for long and short attack latency (LAL and SAL mice, respectively), we have recently applied the large-scale gene expression profiling method known as serial analysis of gene expression (SAGE) to generate hippocampal gene expression profiles of these mice. The aim of the present study is to extend and validate the SAGE expression profile of hippocampi of LAL and SAL mice using GeneChips (Affymetrix, Santa Clara, CA; one array per mouse, n = 5 per mouse line). As was the case with SAGE, GeneChips detect only medium- to high-abundance genes in the hippocampus. Extensive analysis of GeneChip data using very stringent parameters shows differential expression of 122 genes, all except one of which were expressed at higher levels in LAL mice (P < 0.01). As predicted by SAGE, our data indicate higher expression of several cytoskeleton genes in LAL mice, suggesting longer axonal and dendritic projections in the hippocampus of these mice. This is consistent with our tentative model, in which the behavioral differences between LAL and SAL mice may be related to structural differences in the hippocampus. In addition, a group of 76 genes with diverse biological function and 46 expressed sequence tags (ESTs) were all expressed at higher levels in LAL mice. A novel finding in this study was the significantly lower expression of only a single gene, growth arrest-specific gene (gas5), in LAL mice. As gas5 does not encode a protein but several small nuclear RNAs, our data suggest that small RNAs may contribute to the molecular mechanisms underlying the extreme behavioral differences between LAL and SAL mice.

Hippocampal gene expression profiling in spatial discrimination learning

Learning and long-term memory are thought to involve temporally defined changes in gene expression that lead to the strengthening of synaptic connections in selected brain regions. We used cDNA microarrays to study hippocampal gene expression in animals trained in a spatial discrimination-learning paradigm. Our analysis identified 19 genes that showed statistically significant changes in expression when comparing Naı̈ve versus Trained animals. We confirmed the changes in expression for the genes encoding the nuclear protein prothymosin α and the δ-1 opioid receptor (DOR1) by Northern blotting or in situ hybridization. In additional studies, laser-capture microdissection (LCM) allowed us to obtain enriched neuronal populations from the dentate gyrus, CA1, and CA3 subregions of the hippocampus from Naı̈ve, Pseudotrained, and spatially Trained animals. Real-time PCR examined the spatial learning specificity of hippocampal modulation of the genes encoding protein kinase B (PKB, also known as Akt), protein kinase C δ (PKC δ), cell adhesion kinase β (CAK β, also known as Pyk2), and receptor protein tyrosine phosphatase ζ/β (RPTP ζ/β). These studies showed subregion specificity of spatial learning-induced changes in gene expression within the hippocampus, a feature that was particular to each gene studied. We suggest that statistically valid gene expression profiles generated with cDNA microarrays may provide important insights as to the cellular and molecular events subserving learning and memory processes in the brain.