A microarray analysis of the effects of moderate hypothermia and rewarming on gene expression by human hepatocytes (HepG2)

The gene expression changes produced by moderate hypothermia are not fully known, but appear to differ in important ways from those produced by heat shock. We examined the gene expression changes produced by moderate hypothermia and tested the hypothesis that rewarming after hypothermia approximates a heat-shock response. Six sets of human HepG2 hepatocytes were subjected to moderate hypothermia (31°C for 16 h), a conventional in vitro heat shock (43°C for 30 min) or control conditions (37°C), then harvested immediately or allowed to recover for 3 h at 37°C. Expression analysis was performed with Affymetrix U133A gene chips, using analysis of variance-based techniques. Moderate hypothermia led to distinct time-dependent expression changes, as did heat shock. Hypothermia initially caused statistically significant, greater than or equal to twofold changes in expression (relative to controls) of 409 sequences (143 increased and 266 decreased), whereas heat shock affected 71 (35 increased and 36 decreased). After 3 h of recovery, 192 sequences (83 increased, 109 decreased) were affected by hypothermia and 231 (146 increased, 85 decreased) by heat shock. Expression of many heat shock proteins was decreased by hypothermia but significantly increased after rewarming. A comparison of sequences affected by thermal stress without regard to the magnitude of change revealed that the overlap between heat and cold stress was greater after 3 h of recovery than immediately following thermal stress. Thus, while some overlap occurs (particularly after rewarming), moderate hypothermia produces extensive, time-dependent gene expression changes in HepG2 cells that differ in important ways from those induced by heat shock.     

Developmental regulation and tissue-specific differences of heat shock gene expression in transgenic tobacco and Arabidopsis plants

The heat shock (hs) response during plant growth and development was analyzed in tobacco and Arabidopsis using chimaeric -glucuronidase reporter genes (hs-Gus) driven by a soybean hs promoter. Fluorimetric measurements and histochemical staining revealed high Gus activities in leaves, roots, and flowers exclusively after heat stress. The highest levels of heat-inducible expression were found in the vascular tissues. Without heat stress, a developmental induction of hs-Gus was indicated by the accumulation of high levels of Gus in transgenic tobacco seeds. There was no developmental induction of hs-Gus in Arabidopsis seeds. In situ hybridization to the RNA of the small heat shock protein gene Athsp17.6 in tissue sections revealed an expression in heat-shocked leaves but no expression in control leaves of Arabidopsis. However, a high level of constitutive expression of hs gene was detected in meristematic and provascular tissues of the Arabidopsis embryo. The developmental and tissue-specific regulation of the hs response is discussed.Abbreviations hs heat shock - Hsp heat shock protein(s) - hs Gus: heat-inducible Gus gene(s) - HSE heat shock element(s) - HSF heat shock factor - X-gluc 5-bromo-4-chloro-3-indolyl--D-glucuronide - Gus -glucuronidase - DAF days after flowering - SAR scaffold attachment region     

Menin links the stress response to genome stability in Drosophila melanogaster

Background

The multiple endocrine neoplasia type I gene functions as a tumor suppressor gene in humans and mouse models. In Drosophila melanogaster, mutants of the menin gene (Mnn1) are hypersensitive to mutagens or gamma irradiation and have profound defects in the response to several stresses including heat shock, hypoxia, hyperosmolarity and oxidative stress. However, it is not known if the function of menin in the stress response contributes to genome stability. The objective of this study was to examine the role of menin in the control of the stress response and genome stability.

Methodology/Principal Findings

Using a test of loss-of-heterozygosity, we show that Drosophila strains lacking a functional Mnn1 gene or expressing a Mnn1 dsRNA display increased genome instability in response to non-lethal heat shock or hypoxia treatments. This is also true for strains lacking all Hsp70 genes, implying that a precise control of the stress response is required for genome stability. While menin is required for Hsp70 expression, the results of epistatic studies indicate that the increase in genome instability observed in Mnn1 lack-of-function mutants cannot be accounted for by mis-expression of Hsp70. Therefore, menin may promote genome stability by controlling the expression of other stress-responsive genes. In agreement with this notion, gene profiling reveals that Mnn1 is required for sustained expression of all heat shock protein genes but is dispensable for early induction of the heat shock response.

Conclusions/Significance

Mutants of the Mnn1 gene are hypersensitive to several stresses and display increased genome instability when subjected to conditions, such as heat shock, generally regarded as non-genotoxic. In this report, we describe a role for menin as a global regulator of heat shock gene expression and critical factor in the maintenance of genome integrity. Therefore, menin links the stress response to the control of genome stability in Drosophila melanogaster.     

Downregulation of both gene expression and activity of Hsp27 improved maturation of mouse oocyte in vitro

Background  

Heat shock protein 27 (Hsp27), a member of the small heat shock protein family, is an apoptosis regulator. Our previous proteomic study showed that Hsp27 mainly expressed in human oocyte, and that Hsp27 expression was downregulated in the ovaries derived from women with the polycystic ovary syndrome (PCOS), a well known endocrinal disorder with abnormal apoptotic activity and folliculogenesis. However, the exact effects of Hsp27 downregulation on oocyte development have not yet been clarified.     

Regulation of tight junction assembly and epithelial morphogenesis by the heat shock protein Apg-2

Background  

Tight junctions are required for epithelial barrier formation and participate in the regulation of signalling mechanisms that control proliferation and differentiation. ZO-1 is a tight junction-associated adaptor protein that regulates gene expression, junction assembly and epithelial morphogenesis. We have previously demonstrated that the heat shock protein Apg-2 binds ZO-1 and thereby regulates its role in cell proliferation. Here, we addressed the question whether Apg-2 is also important for junction formation and epithelial morphogenesis.     

Effect of temperature up-shift on fermentation and metabolic characteristics in view of gene expressions in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Background  

Escherichia coli induces heat shock genes to the temperature up-shift, and changes the metabolism by complicated mechanism. The heat shock response is of practical importance for the variety of applications such as temperature-induced heterologous protein production, simultaneous saccharification and fermentation (SSF) etc. However, the effect of heat shock on the metabolic regulation is not well investigated. It is strongly desired to understand the metabolic changes and its mechanism upon heat shock in practice for the efficient metabolite production by temperature up-shift. In the present research, therefore, we investigated the effect of temperature up-shift from 37°C to 42°C on the metabolism in view of gene expressions.     

Multiple enhancers contribute to spatial but not temporal complexity in the expression of the proneural gene, amos

Background  

The regulation of proneural gene expression is an important aspect of neurogenesis. In the study of the Drosophila proneural genes, scute and atonal, several themes have emerged that contribute to our understanding of the mechanism of neurogenesis. First, spatial complexity in proneural expression results from regulation by arrays of enhancer elements. Secondly, regulation of proneural gene expression occurs in distinct temporal phases, which tend to be under the control of separate enhancers. Thirdly, the later phase of proneural expression often relies on positive autoregulation. The control of these phases and the transition between them appear to be central to the mechanism of neurogenesis. We present the first investigation of the regulation of the proneural gene, amos.     

Threshold-dominated regulation hides genetic variation in gene expression networks

Background  

In dynamical models with feedback and sigmoidal response functions, some or all variables have thresholds around which they regulate themselves or other variables. A mathematical analysis has shown that when the dose-response functions approach binary or on/off responses, any variable with an equilibrium value close to one of its thresholds is very robust to parameter perturbations of a homeostatic state. We denote this threshold robustness. To check the empirical relevance of this phenomenon with response function steepnesses ranging from a near on/off response down to Michaelis-Menten conditions, we have performed a simulation study to investigate the degree of threshold robustness in models for a three-gene system with one downstream gene, using several logical input gates, but excluding models with positive feedback to avoid multistationarity. Varying parameter values representing functional genetic variation, we have analysed the coefficient of variation (CV) of the gene product concentrations in the stable state for the regulating genes in absolute terms and compared to the CV for the unregulating downstream gene. The sigmoidal or binary dose-response functions in these models can be considered as phenomenological models of the aggregated effects on protein or mRNA expression rates of all cellular reactions involved in gene expression.     

Inducible and constitutive heat shock gene expression responds to modification of Hsp70 copy number in Drosophila melanogaster but does not compensate for loss of thermotolerance in Hsp70 null flies

Background  

The heat shock protein Hsp70 promotes inducible thermotolerance in nearly every organism examined to date. Hsp70 interacts with a network of other stress-response proteins, and dissecting the relative roles of these interactions in causing thermotolerance remains difficult. Here we examine the effect of Hsp70 gene copy number modification on thermotolerance and the expression of multiple stress-response genes in Drosophila melanogaster, to determine which genes may represent mechanisms of stress tolerance independent of Hsp70.     

AI-2-dependent gene regulation in <Emphasis Type="Italic">Staphylococcus epidermidis</Emphasis>

Background  

Autoinducer 2 (AI-2), a widespread by-product of the LuxS-catalyzed S-ribosylhomocysteine cleavage reaction in the activated methyl cycle, has been suggested to serve as an intra- and interspecies signaling molecule, but in many bacteria AI-2 control of gene expression is not completely understood. Particularly, we have a lack of knowledge about AI-2 signaling in the important human pathogens Staphylococcus aureus and S. epidermidis.     

Multiple independent evolutionary solutions to core histone gene regulation

Background  

Core histone genes are periodically expressed along the cell cycle and peak during S phase. Core histone gene expression is deeply evolutionarily conserved from the yeast Saccharomyces cerevisiae to human.     

Isolation of the Chinese rose sHSP gene promoter and its differential regulation analysis in transgenic Arabidopsis plants

In our previous study, we identified a Rosa chinensis heat shock protein (HSP) gene, RcHSP17.8, which was induced by abiotic stresses, such as high temperature and osmotic stress. To analyze the expression of RcHSP17.8 and the function of cis-acting elements in the promoter region, a 1,910 bp fragment of the upstream sequence of the RcHSP17.8 translation initiation codon and five promoter deletion fragments were fused to a β-glucuronidase (GUS) report gene. These plasmids were transferred to Arabidopsis thaliana via Agrobacterium. GUS staining was seen in all the organs, especially in the vascular tissues after heat treatment. In transgenic Arabidopsis, GUS expression driven by the full length promoter was significantly higher under heat shock, but no GUS activity was detected under other abiotic stresses. Deletion analysis indicated that the region from −178 to −771 was essential for the promoter’s response to high temperature.     

Differential regulation drives plasticity in sex determination gene networks

Background  

Sex determination networks evolve rapidly and have been studied intensely across many species, particularly in insects, thus presenting good models to study the evolutionary plasticity of gene networks.     

Detecting microRNA activity from gene expression data

Background  

MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression by binding to the messenger RNA (mRNA) of protein coding genes. They control gene expression by either inhibiting translation or inducing mRNA degradation. A number of computational techniques have been developed to identify the targets of miRNAs. In this study we used predicted miRNA-gene interactions to analyse mRNA gene expression microarray data to predict miRNAs associated with particular diseases or conditions.