Reducing ER stress with chaperone therapy reverses sleep fragmentation and cognitive decline in aged mice

As the aging population grows, the need to understand age-related changes in health is vital. Two prominent behavioral changes that occur with age are disrupted sleep and impaired cognition. Sleep disruptions lead to perturbations in proteostasis and endoplasmic reticulum (ER) stress in mice. Further, consolidated sleep and protein synthesis are necessary for memory formation. With age, the molecular mechanisms that relieve cellular stress and ensure proper protein folding become less efficient. It is unclear if a causal relationship links proteostasis, sleep quality, and cognition in aging. Here, we used a mouse model of aging to determine if supplementing chaperone levels reduces ER stress and improves sleep quality and memory. We administered the chemical chaperone 4-phenyl butyrate (PBA) to aged and young mice, and monitored sleep and cognitive behavior. We found that chaperone treatment consolidates sleep and wake, and improves learning in aged mice. These data correlate with reduced ER stress in the cortex and hippocampus of aged mice. Chaperone treatment increased p-CREB, which is involved in memory formation and synaptic plasticity, in hippocampi of chaperone-treated aged mice. Hippocampal overexpression of the endogenous chaperone, binding immunoglobulin protein (BiP), improved cognition, reduced ER stress, and increased p-CREB in aged mice, suggesting that supplementing BiP levels are sufficient to restore some cognitive function. Together, these results indicate that restoring proteostasis improves sleep and cognition in a wild-type mouse model of aging. The implications of these results could have an impact on the development of therapies to improve health span across the aging population.

The Hallucinogenic Serotonin2A Receptor Agonist, 2,5-Dimethoxy-4-Iodoamphetamine, Promotes cAMP Response Element Binding Protein-Dependent Gene Expression of Specific Plasticity-Associated Genes in the Rodent Neocortex

Psychedelic compounds that target the 5-HT_2A receptor are reported to evoke psychoplastogenic effects, including enhanced dendritic arborization and synaptogenesis. Transcriptional regulation of neuronal plasticity-associated genes is implicated in the cytoarchitectural effects of serotonergic psychedelics, however, the transcription factors that drive this regulation are poorly elucidated. Here, we addressed the contribution of the transcription factor cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB) in the regulation of neuronal plasticity-associated genes by the hallucinogenic 5-HT_2A receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI). In vitro studies with rat cortical neurons indicated that DOI enhances the phosphorylation of CREB (pCREB) through mitogen-activated protein (MAP) kinase and calcium/calmodulin dependent kinase II (CaMKII) pathways, with both cascades contributing to the DOI-evoked upregulation of Arc, Bdnf1, Cebpb, and Egr2 expression, whilst the upregulation of Egr1 and cFos mRNA involved the MAP kinase and CaMKII pathway respectively. We observed a robust DOI-evoked increase in the expression of several neuronal plasticity-associated genes in the rat neocortex in vivo. This DOI-evoked upregulation of neuronal plasticity-associated genes was completely blocked by the 5-HT_2A receptor antagonist MDL100,907 in vitro and was also abrogated in the neocortex of 5-HT_2A receptor deficient mice. Further, 5-HT_2A receptor stimulation enhanced pCREB enrichment at putative cAMP response element (CRE) binding sites in the Arc, Bdnf1, Cebpb, cFos, but not Egr1 and Egr2, promoters in the rodent neocortex. The DOI-mediated transcriptional induction of Arc, cFos and Cebpb was significantly attenuated in the neocortex of CREB deficient/knockout (CREBαδ KO) mice. Collectively, these results indicate that the hallucinogenic 5-HT_2A receptor agonist DOI leads to a rapid transcriptional upregulation of several neuronal plasticity-associated genes, with a subset of them exhibiting a CREB-dependent regulation. Our findings raise the intriguing possibility that similar to slow-acting classical antidepressants, rapid-action serotonergic psychedelics that target the 5-HT_2A receptor may also recruit the transcription factor CREB to enhance the expression of neuronal plasticity-associated genes in the neocortex, which could in turn contribute to the rapid psychoplastogenic changes evoked by these compounds.

Zinc-mediated activation of CREB pathway in proliferation of pulmonary artery smooth muscle cells in pulmonary hypertension

BACKGROUND

Transcription factor CREB is involved in the development of pulmonary hypertension (PH). However, little is known about the role and regulatory signaling of CREB in PH.

METHODS

A series of techniques, including bioinformatics methods, western blot, cell proliferation and luciferase reporter assay were used to perform a comprehensive analysis of the role and regulation of CREB in proliferation of pulmonary artery smooth muscle cells (PASMCs) in PH.

RESULTS

Using bioinformatic analysis of the differentially expressed genes (DEGs) identified in the development of monocrotaline (MCT)- and hypoxia-induced PH, we found the overrepresentation of CRE-containing DEGs. Western blot analysis revealed a sustained increase in total- and phosphorylated-CREB in PASMCs isolated from rats treated with MCT. Similarly, an enhanced and prolonged serum-induced CREB phosphorylation was observed in hypoxia-pretreated PASMCs. The sustained CREB phosphorylation in PASMCs may be associated with multiple protein kinases phosphorylated CREB. Additionally, hierarchical clustering analysis showed reduced expression of the majority of CREB phosphatases in PH, including regulatory subunits of PP2A, Ppp2r2c and Ppp2r3a. Cell proliferation analysis showed increased PASMCs proliferation in MCT-induced PH, an effect relied on CREB-mediated transcriptional activity. Further analysis revealed the raised intracellular labile zinc possibly from ZIP12 was associated with reduced phosphatases, increased CREB-mediated transcriptional activity and PASMCs proliferation.

CONCLUSIONS

CREB pathway was overactivated in the development of PH and contributed to PASMCs proliferation, which was associated with multiple protein kinases and/or reduced CREB phosphatases and raised intracellular zinc. Thus, this study may provide a novel insight into the CREB pathway in the pathogenesis of PH. Video abstract.

Cyclic AMP response element-binding protein is required in excitatory neurons in the forebrain to sustain wakefulness

The molecular and intracellular signaling processes that control sleep and wake states remain largely unknown. A consistent observation is that the cyclic adenosine monophosphate (AMP) response element-binding protein (CREB), an activity-dependent transcription factor, is differentially activated during sleep and wakefulness. CREB is phosphorylated by the cyclic AMP/protein kinase A (cAMP/PKA) signaling pathway as well as other kinases, and phosphorylated CREB promotes the transcription of target genes. Genetic studies in flies and mice suggest that CREB signaling influences sleep/wake states by promoting and stabilizing wakefulness. However, it remains unclear where in the brain CREB is required to drive wakefulness. In rats, CREB phosphorylation increases in the cerebral cortex during wakefulness and decreases during sleep, but it is not known if this change is functionally relevant to the maintenance of wakefulness. Here, we used the Cre/lox system to conditionally delete CREB in the forebrain (FB) and in the locus coeruleus (LC), two regions known to be important for the production of arousal and wakefulness. We used polysomnography to measure sleep/wake levels and sleep architecture in conditional CREB mutant mice and control littermates. We found that FB-specific deletion of CREB decreased wakefulness and increased non-rapid eye movement sleep. Mice lacking CREB in the FB were unable to sustain normal periods of wakefulness. On the other hand, deletion of CREB from LC neurons did not change sleep/wake levels or sleep/wake architecture. Taken together, these results suggest that CREB is required in neurons within the FB but not in the LC to promote and stabilize wakefulness.

Recovery of post-stroke cognitive and motor deficiencies by Shuxuening injection via regulating hippocampal BDNF-mediated Neurotrophin/Trk Signaling

A mild ischemic stroke may cause both debilitating locomotor and cognitive decline, for which the mechanism is not fully understood, and no therapies are currently available. In this study, a nonfatal stroke model was constructed in mice by a modified middle cerebral artery occlusion (MCAO) procedure, allowing an extended recovery period up to 28 days. The extended MCAO model successfully mimicked phenotypes of a recovery phase post-stroke, including locomotor motor and cognitive deficiencies, which were effectively improved after Shuxuening injection (SXNI) treatment. Tissue slices staining showed that SXNI repaired brain injury and reduced neuronal apoptosis, especially in the hippocampus CA3 region. Transcriptomics sequencing study revealed 565 differentially expressed genes (DEGs) in the ischemic brain after SXNI treatment. Integrated network pharmacological analysis identified Neurotrophin/Trk Signaling was the most relevant pathway, which involves 15 key genes. Related DEGs were further validated by RT-PCR. Western-blot analysis showed that SXNI reversed the abnormal expression of BDNF, TrkB, Mek3 and Jnk1after stroke. ELISA found that SXNI increased brain level of p-Erk and Creb. At sub-brain level, the expression of BDNF and TrkB was decreased and GFAP was increased on the hippocampal CA3 region in the post-stroke recovery phase and this abnormality was improved by SXNI. In vitro experiments also found that oxygen glucose deprivation reduced the expression of BDNF and TrkB, which was reversed by SXNI. In summary, we conclude that SXNI facilitates the recovery of cognitive and locomotor dysfunction by modulating Neurotrophin/Trk Signaling in a mouse model for the recovery phase of post-ischemic stroke.

cAMP Response Element-Binding Protein (CREB): A Possible Signaling Molecule Link in the Pathophysiology of Schizophrenia

Dopamine is a brain neurotransmitter involved in the pathology of schizophrenia. The dopamine hypothesis states that, in schizophrenia, dopaminergic signal transduction is hyperactive. The cAMP-response element binding protein (CREB) is an intracellular protein that regulates the expression of genes that are important in dopaminergic neurons. Dopamine affects the phosphorylation of CREB via G protein-coupled receptors. Neurotrophins, such as brain derived growth factor (BDNF), are critical regulators during neurodevelopment and synaptic plasticity. The CREB is one of the major regulators of neurotrophin responses since phosphorylated CREB binds to a specific sequence in the promoter of BDNF and regulates its transcription. Moreover, susceptibility genes associated with schizophrenia also target and stimulate the activity of CREB. Abnormalities of CREB expression is observed in the brain of individuals suffering from schizophrenia, and two variants (-933T to C and -413G to A) were found only in schizophrenic patients. The CREB was also involved in the therapy of animal models of schizophrenia. Collectively, these findings suggest a link between CREB and the pathophysiology of schizophrenia. This review provides an overview of CREB structure, expression, and biological functions in the brain and its interaction with dopamine signaling, neurotrophins, and susceptibility genes for schizophrenia. Animal models in which CREB function is modulated, by either overexpression of the protein or knocked down through gene deletion/mutation, implicating CREB in schizophrenia and antipsychotic drugs efficacy are also discussed. Targeting research and drug development on CREB could potentially accelerate the development of novel medications against schizophrenia.

Acute Stress Enhances Epigenetic Modifications But Does Not Affect the Constitutive Binding of pCREB to Immediate-Early Gene Promoters in the Rat Hippocampus

The immediate early genes (IEGs) c-Fos and Egr-1 are rapidly and transiently induced in sparse neurons within the hippocampus after exposure to an acute stressor. The induction of these genes is a critical part of the molecular mechanisms underlying successful behavioral adaptation to stress. Our previous work has shown that transcriptional activation of c-Fos and Egr-1 in the hippocampus requires formation of a dual histone mark within their promoter regions, the phosphorylation of serine 10 and acetylation of lysine 9/14 of histone H3. In the present study, using chromatin immuno-precipitation (ChIP), we found that an increase in the formation of H3K9ac-S10p occurs within the c-Fos and Egr-1 promoters after FS stress in vivo and that these histone modifications were located to promoter regions containing cAMP Responsive Elements (CREs), but not in neighboring regions containing only Serum Responsive Elements (SREs). Surprisingly, however, subsequent ChIP analyses showed no changes in the binding of pCREB or CREB-binding protein (CBP) to the CREs after FS. In fact, pCREB binding to the c-Fos and Egr-1 promoters was already highly enriched under baseline conditions and did not increase further after stress. We suggest that constitutive pCREB binding may keep c-Fos and Egr-1 in a poised state for activation. Possibly, the formation of H3K9ac-S10p in the vicinity of CRE sites may participate in unblocking transcriptional elongation through recruitment of additional epigenetic factors.

Immunocytochemistry and fluorescence imaging efficiently identify individual neurons with CRISPR/Cas9-mediated gene disruption in primary cortical cultures

Background

CRISPR/Cas9 system is a powerful method to investigate the role of genes by introducing a mutation selectively and efficiently to specific genome positions in cell and animal lines. However, in primary neuron cultures, this method is affected by the issue that the effectiveness of CRISPR/Cas9 is different in each neuron. Here, we report an easy, quick and reliable method to identify mutants induced by the CRISPR/Cas9 system at a single neuron level, using immunocytochemistry (ICC) and fluorescence imaging.

Results

Dissociated cortical cells were transfected with CRISPR/Cas9 plasmids targeting the transcription factor cAMP-response element binding protein (CREB). Fluorescence ICC with CREB antibody and quantitative analysis of fluorescence intensity demonstrated that CREB expression disappeared in a fraction of the transfected neurons. The downstream FOS expression was also decreased in accordance with suppressed CREB expression. Moreover, dendritic arborization was decreased in the transfected neurons which lacked CREB immunoreactivity.

Conclusions

Detection of protein expression is efficient to identify individual postmitotic neurons with CRISPR/Cas9-mediated gene disruption in primary cortical cultures. The present method composed of CRISPR/Cas9 system, ICC and fluorescence imaging is applicable to study the function of various genes at a single-neuron level.

A role for cerebellum in the hereditary dystonia DYT1

DYT1 is a debilitating movement disorder caused by loss-of-function mutations in torsinA. How these mutations cause dystonia remains unknown. Mouse models which have embryonically targeted torsinA have failed to recapitulate the dystonia seen in patients, possibly due to differential developmental compensation between rodents and humans. To address this issue, torsinA was acutely knocked down in select brain regions of adult mice using shRNAs. TorsinA knockdown in the cerebellum, but not in the basal ganglia, was sufficient to induce dystonia. In agreement with a potential developmental compensation for loss of torsinA in rodents, torsinA knockdown in the immature cerebellum failed to produce dystonia. Abnormal motor symptoms in knockdown animals were associated with irregular cerebellar output caused by changes in the intrinsic activity of both Purkinje cells and neurons of the deep cerebellar nuclei. These data identify the cerebellum as the main site of dysfunction in DYT1, and offer new therapeutic targets.

DOI:http://dx.doi.org/10.7554/eLife.22775.001

Dystonia is the third most common type of movement disorder after Parkinson’s disease and tremor. Patients with dystonia experience prolonged involuntary contractions of their muscles, often causing uncontrollable postures or repetitive movements. Almost thirty years ago, genetic studies revealed that a mutation in the gene that encodes a protein called torsinA causes the most common type of dystonia, called DYT1.

Exactly how mutations that affect the torsinA protein give rise to DYT1 remains unclear, and there are still no effective treatments for the disorder. Part of the problem is that we do not fully understand how torsinA works, or which of its many proposed functions is relevant to dystonia. Moreover, attempts to study DYT1 using genetically modified mice have proved largely unsuccessful. This is because mice that simply express the same genetic mutations that cause dystonia in humans do not show the overt symptoms of dystonia.

Fremont, Tewari et al. have now generated a mouse ‘model’ that does show symptoms of dystonia, and used these model mice to investigate the role of torsinA in the disorder. Acutely reducing the amount of torsinA protein in a region of the brain called the cerebellum induced the symptoms of dystonia in the mice. Conversely, reducing the amount of torsinA in a different brain area known as the basal ganglia had no such effect, even though both the cerebellum and the basal ganglia contribute to movement. Furthermore, neither manipulation had any effect in juvenile mice, which suggests that, in contrast to humans, young mice can compensate for the loss of torsinA.

Fremont, Tewari et al. also found that the loss of torsinA causes the cerebellum to generate incorrect output signals, which in turn trigger the abnormal movements seen in dystonia. In the future, further studies of the model mice could identify the exact changes that occur in neurons following the loss of torsinA from the cerebellum. Understanding these changes could potentially pave the way for developing effective treatments for DYT1 and other dystonias.

DOI:http://dx.doi.org/10.7554/eLife.22775.002

Suppressing cAMP response element-binding protein transcription shortens the duration of status epilepticus and decreases the number of spontaneous seizures in the pilocarpine model of epilepsy

OBJECTIVE

Current epilepsy therapies directed at altering the function of neurotransmitter receptors or ion channels, or release of synaptic vesicles fail to prevent seizures in approximately 30% of patients. A better understanding of the molecular mechanism underlying epilepsy is needed to provide new therapeutic targets. The activity of cyclic AMP (cAMP) response element-binding protein (CREB), a major transcription factor promoting CRE-mediated transcription, increases following a prolonged seizure called status epilepticus. It is also increased in the seizure focus of patients with medically intractable focal epilepsy. Herein we explored the effect of acute suppression of CREB activity on status epilepticus and spontaneous seizures in a chronic epilepsy model.

METHODS

Pilocarpine chemoconvulsant was used to induce status epilepticus. To suppress CREB activity, a transgenic mouse line expressing an inducible dominant negative mutant of CREB (CREB(IR) ) with a serine to alanine 133 substitution was used. Status epilepticus and spontaneous seizures of transgenic and wild-type mice were analyzed using video-electroencephalography (EEG) to assess the effect of CREB suppression on seizures.

RESULTS

Our findings indicate that activation of CREB(IR) shortens the duration of status epilepticus. The frequency of spontaneous seizures decreased in mice with chronic epilepsy during CREB(IR) induction; however, the duration of the spontaneous seizures was unchanged. Of interest, we found significantly reduced levels of phospho-CREB Ser133 upon activation of CREB(IR) , supporting prior work suggesting that binding to the CRE site is important for CREB phosphorylation.

SIGNIFICANCE

Our results suggest that CRE transcription supports seizure activity both during status epilepticus and in spontaneous seizures. Thus, blocking of CRE transcription is a novel target for the treatment of epilepsy.

Serine 133 phosphorylation is not required for hippocampal CREB-mediated transcription and behavior

The cAMP response element (CRE)-binding protein, CREB, is a transcription factor whose activity in the brain is critical for long-term memory formation. Phosphorylation of Ser133 in the kinase-inducible domain (KID), that in turn leads to the recruitment of the transcriptional coactivator CREB-binding protein (CBP), is thought to mediate the activation of CREB. However, the importance of phosphorylation for CREB binding to DNA and subsequent gene transcription in vivo is controversial. To definitively address the role of CREB phosphorylation in gene transcription and learning and memory, we derived mutant mice lacking the Ser133 phosphorylation site. These mice exhibit normal CREB-mediated gene transcription for a number of genes implicated in learning and memory processes. Furthermore these mice have no deficits in hippocampus- or striatum-dependent learning. Strikingly, our findings show that CREB phosphorylation at Ser133 is not necessary for CREB binding to CRE sites, CREB-mediated transcription, or CREB-mediated behavioral phenotypes associated with learning and memory.

Inducible forebrain-specific ablation of the transcription factor Creb during adulthood induces anxiety but no spatial/contextual learning deficits

The cyclic AMP (cAMP)-response element binding protein (CREB) is an activity-dependent transcription factor playing a role in synaptic plasticity, learning and memory, and emotional behavior. However, the impact of Creb ablation on rodent behavior is vague as e.g., memory performance of different Creb mutant mice depends on the specific type of mutation per se but additionally on the background and learning protocol differences. Here we present the first targeted ablation of CREB induced during adulthood selectively in principal forebrain neurons in a pure background strain of C57BL/6 mice. All hippocampal principal neurons exhibited lack of CREB expression. Mutant mice showed a severe anxiety phenotype in the openfield and novel object exploration test as well as in the Dark-Light Box Test, but unaltered hippocampus-dependent long-term memory in the Morris water maze and in context dependent fear conditioning. On the molecular level, CREB ablation led to CREM up regulation in the hippocampus and frontal cortex which may at least in part compensate for the loss of CREB. BDNF, a postulated CREB target gene, was down regulated in the frontal lobe but not in the hippocampus; neurogenesis remained unaltered. Our data indicate that in the adult mouse forebrain the late onset of CREB ablation can, in case of memory functionality, be compensated for and is not essential for memory consolidation and retrieval during adulthood. In contrast, the presence of CREB protein during adulthood seems to be pivotal for the regulation of emotional behavior.

CREB mediates the insulinotropic and anti-apoptotic effects of GLP-1 signaling in adult mouse β-cells

Objective

Glucagon-like peptide-1 (GLP-1) plays a major role in pancreatic β-cell function and survival by increasing cytoplasmic cAMP levels, which are thought to affect transcription through activation of the basic leucine zipper (bZIP) transcription factor CREB. Here, we test CREB function in the adult β-cell through inducible gene deletion.

Methods

We employed cell type-specific and inducible gene ablation to determine CREB function in pancreatic β-cells in mice.

Results

By ablating CREB acutely in mature β-cells in tamoxifen-treated Creb^loxP/loxP;Pdx1-CreERT2 mice, we show that CREB has little impact on β-cell turnover, in contrast to what had been postulated previously. Rather, CREB is required for GLP-1 to elicit its full effects on stimulating glucose-induced insulin secretion and protection from cytokine-induced apoptosis. Mechanistically, we find that CREB regulates expression of the pro-apoptotic gene p21 (Cdkn1a) in β-cells, thus demonstrating that CREB is essential to mediating this critical aspect of GLP-1 receptor signaling.

Conclusions

In sum, our studies using conditional gene deletion put into question current notions about the importance of CREB in regulating β-cell function and mass. However, we reveal an important role for CREB in the β-cell response to GLP-1 receptor signaling, further validating CREB as a therapeutic target for diabetes.

The neuronal activity-driven transcriptome

Activity-driven transcription is a key event associated with long-lasting forms of neuronal plasticity. Despite the efforts to investigate the regulatory mechanisms that control this complex process and the important advances in the knowledge of the function of many activity-induced genes in neurons, as well as the specific contribution of activity-regulated transcription factors, our understanding of how activity-driven transcription operates at the systems biology level is still very limited. This review focuses on the research of neuronal activity-driven transcription from an "omics" perspective. We will discuss the different high-throughput approaches undertaken to characterize the gene programs downstream of specific activity-regulated transcription factors, including CREB, SRF, MeCP2, Fos, Npas4, and others, and the interplay between epigenetic and transcriptional mechanisms underlying neuronal plasticity changes. Although basic questions remain unanswered and important challenges still lie ahead, the refinement of genome-wide techniques for investigating the neuronal transcriptome and epigenome promises great advances.

Genome-wide map of nuclear protein degradation shows NCoR1 turnover as a key to mitochondrial gene regulation

Transcription factor activity and turnover are functionally linked, but the global patterns by which DNA-bound regulators are eliminated remain poorly understood. We established an assay to define the chromosomal location of DNA-associated proteins that are slated for degradation by the ubiquitin-proteasome system. The genome-wide map described here ties proteolysis in mammalian cells to active enhancers and to promoters of specific gene families. Nuclear-encoded mitochondrial genes in particular correlate with protein elimination, which positively affects their transcription. We show that the nuclear receptor corepressor NCoR1 is a key target of proteolysis and physically interacts with the transcription factor CREB. Proteasome inhibition stabilizes NCoR1 in a site-specific manner and restrains mitochondrial activity by repressing CREB-sensitive genes. In conclusion, this functional map of nuclear proteolysis links chromatin architecture with local protein stability and identifies proteolytic derepression as highly dynamic in regulating the transcription of genes involved in energy metabolism.

The α and Δ isoforms of CREB1 are required to maintain normal pulmonary vascular resistance

Chronic hypoxia causes pulmonary hypertension associated with structural alterations in pulmonary vessels and sustained vasoconstriction. The transcriptional mechanisms responsible for these distinctive changes are unclear. We have previously reported that CREB1 is activated in the lung in response to alveolar hypoxia but not in other organs. To directly investigate the role of α and Δ isoforms of CREB1 in the regulation of pulmonary vascular resistance we examined the responses of mice in which these isoforms of CREB1 had been inactivated by gene mutation, leaving only the β isoform intact (CREB(αΔ) mice). Here we report that expression of CREB regulated genes was altered in the lungs of CREB(αΔ) mice. CREB(αΔ) mice had greater pulmonary vascular resistance than wild types, both basally in normoxia and following exposure to hypoxic conditions for three weeks. There was no difference in rho kinase mediated vasoconstriction between CREB(αΔ) and wild type mice. Stereological analysis of pulmonary vascular structure showed characteristic wall thickening and lumen reduction in hypoxic wild-type mice, with similar changes observed in CREB(αΔ). CREB(αΔ) mice had larger lungs with reduced epithelial surface density suggesting increased pulmonary compliance. These findings show that α and Δ isoforms of CREB1 regulate homeostatic gene expression in the lung and that normal activity of these isoforms is essential to maintain low pulmonary vascular resistance in both normoxic and hypoxic conditions and to maintain the normal alveolar structure. Interventions that enhance the actions of α and Δ isoforms of CREB1 warrant further investigation in hypoxic lung diseases.

Not all stress is equal: CREB is not necessary for restraint stress reinstatement of cocaine-conditioned reward

Stress elicits relapse to cocaine seeking in humans and in animal models. Cyclic AMP response element binding protein (CREB) is required for swim stress-induced reinstatement of cocaine conditioned place preference. However, the role of CREB in other stress-induced reinstatement models has not been examined. To determine whether CREB is required across different stressors we examined the ability of restraint to elicit reinstatement of cocaine-conditioned place preference in wild-type and CREBαΔ mutant mice. In contrast to previously published differences in swim stress-induced reinstatement, both wild-type and CREBαΔ mutant mice demonstrated restraint stress elicited reinstatement of cocaine-conditioned reward. While CREB is necessary for swim stress-elicited zif268 expression within the nucleus accubmens (NAc) shell and prelimbic cortex (PrL), restraint-stress-elicited comparable increases in zif268 expression within these regions in both wild-type and CREBαΔ mutant mice. Our findings suggest that not all stressors engage the same circuits or molecular mechanisms to elicit reinstatement behavior.

Alterations in phosphorylated CREB expression in different brain regions following short- and long-term morphine exposure: relationship to food intake

BACKGROUND

Activation of the cyclic adenosine monophosphate (cAMP)/phosphorylated CREB (P-CREB) system in different brain regions has been implicated in mediating opioid tolerance and dependence, while alteration of this system in the lateral hypothalamus (LH) has been suggested to have a role in food intake and body weight.

METHODS

Given that opioids regulate food intake, we measured P-CREB in different brain regions in mice exposed to morphine treatments designed to induce different degrees of tolerance and dependence.

RESULTS

We found that a single morphine injection or daily morphine injections for 8 days did not influence P-CREB levels, while the escalating dose of morphine regimen raised P-CREB levels only in the ventral tegmental area (VTA). Chronic morphine pellet implantation for 7 days raised P-CREB levels in the LH, VTA, and dorsomedial nucleus of the hypothalamus (DM) but not in the nucleus accumbens and amygdala. Increased P-CREB levels in LH, VTA, and DM following 7-day treatment with morphine pellets and increased P-CREB levels in the VTA following escalating doses of morphine were associated with decreased food intake and body weight.

CONCLUSION

The morphine regulation of P-CREB may explain some of the physiological sequelae of opioid exposure including altered food intake and body weight.

Clenbuterol upregulates histone demethylase JHDM2a via the β2-adrenoceptor/cAMP/PKA/p-CREB signaling pathway

BACKGROUND

β(2)-Adrenergic receptor (β(2)-AR) signaling activated by the agonist clenbuterol is important in the metabolism of muscle and adipose cells. Additionally, the significant role of histone demethylase JHDM2a in regulating metabolic gene expression was also recently demonstrated in Jhdm2a(-/-) mice. To elucidate the molecular mechanism involved in clenbuterol-induced adipocyte reduction from an epigenetic perspective, this study focused on cAMP-responsive element binding protein (CREB) to determine whether JHDM2a is regulated by the β(2)-AR/cAMP/protein kinase A (PKA) signaling pathway.

RESULTS

In porcine tissues treated with clenbuterol, JHDM2a expression was upregulated, and in porcine cells, expression of exogenous CREB led to increased JHDM2a expression. In addition, changes in JHDM2a expression were coincident with variations in the phosphorylation of CREB and p-CREB/CBP interaction in porcine and human cells treated with drugs known to modify the β(2)-AR/cAMP/PKA pathway. Finally, binding assays demonstrated that CREB regulated JHDM2a by binding directly to the CRE site nearest to the transcription start site.

CONCLUSION

Our results reveal that clenbuterol activates the β(2)-AR signaling pathway upstream of JHDM2a and that CREB acts as an intermediate link regulated by cAMP-PKA to induce activity of the JHDM2a promoter. These findings suggest that clenbuterol decreases adipose cell size and increases muscle fiber size in porcine tissues by virtue of JHDM2a-mediated demethylation, which regulates downstream metabolic and related genes.

CREB signalling in neural stem/progenitor cells: recent developments and the implications for brain tumour biology

This paper discusses the evidence for the role of CREB in neural stem/progenitor cell (NSPC) function and oncogenesis and how these functions may be important for the development and growth of brain tumours. The cyclic-AMP response element binding (CREB) protein has many roles in neurons, ranging from neuronal survival to higher order brain functions such as memory and drug addiction behaviours. Recent studies have revealed that CREB also has a role in NSPC survival, differentiation and proliferation. Recent work has shown that over-expression of CREB in transgenic animals can impart oncogenic properties on cells in various tissues and that aberrant CREB expression is associated with tumours in patients. It is the central position of CREB, downstream of key developmental and growth signalling pathways, which give CREB the ability to influence a spectrum of cell activities, such as cell survival, growth and differentiation in both normal and cancer cells.

CREB1 and CREB-binding protein in striatal medium spiny neurons regulate behavioural responses to psychostimulants

RATIONALE

The transcription factor cAMP responsive element-binding protein 1 (CREB1) has a complex influence on behavioural responses to drugs of abuse which varies depending on the brain region in which it is expressed. In response to drug exposure, CREB1 is phosphorylated in the striatum, a structure that is critically involved in reward-related learning.

OBJECTIVE

The present study assessed the role of striatal CREB1 and its coactivator CREB-binding protein (CBP) in behavioural responses to psychostimulants.

METHODS

Using the 'cre/lox' recombination system, we generated mice with a postnatal deletion of CREB1 or CBP directed to medium spiny neurons of the striatum. qRT-PCR and immunohistochemistry were used to confirm the deletion, and mice were assessed with respect to their locomotor response to acute cocaine (20 mg/kg), cocaine sensitization (10 mg/kg), amphetamine-induced stereotypies (10 mg/kg) and ethanol-induced hypnosis (3.5 g/kg).

RESULTS

Here we show that CREB1 mutant mice have increased sensitivity to psychostimulants, an effect that does not generalise to ethanol-induced hypnosis. Furthermore, in the absence of CREB1, there is rapid postnatal upregulation of the related transcription factor CREM, indicating possible redundancy amongst this family of transcription factors. Finally striatal deletion of CBP, a coactivator for the CREB1/CREM signalling pathway, results in an even more increased sensitivity to psychostimulants.

CONCLUSIONS

These data suggest that striatal CREB1 regulates sensitivity to psychostimulants and that CREM acting via CBP is able to partially compensate in the absence of CREB1 signalling.

Decreased CREB levels suppress epilepsy

Epilepsy is a common neurologic disorder yet no treatments aimed at preventing epilepsy have been developed. Several molecules including genes containing cAMP response elements (CREs) in their promoters have been identified that contribute to the development of epilepsy, a process called epileptogenesis. When phosphorylated cAMP response element binding protein (CREB) increases transcription from CRE regulated promoters. CREB phosphorylation is increased in rodent epilepsy models, and in the seizure onset region of humans with medically intractable epilepsy (Rakhade et al., 2005; Lee et al., 2007; Lund et al., 2008). Here we show that mice with decreased CREB levels (CREB(α∆) mutants) have a ~50% reduction in spontaneous seizures following pilocarpine induced status epilepticus (SE) and require more stimulation to electrically kindle. Following SE, brain derived neurotrophic factor (BDNF) and inducible cAMP early repressor (ICER) mRNAs are differentially up-regulated in the hippocampus and cortex of the CREB(α∆) mutants compared to wild-type mice, which may be contributing to differences in the severity of epilepsy. In contrast, we found no difference in KCC2 mRNA levels between the CREB(α∆) and wild-type mice after SE. The mechanism by which BDNF and ICER mRNAs increase specifically in the CREB(α∆) compared to wild-type mice following SE is not known. We did, however, find an increase in specific cAMP response element modulator (CREM) mRNA transcripts in the CREB(α∆) mutants that might be responsible for the differential regulation of BDNF and ICER after SE. Altering CREB activity following a neurologic insult provides a therapeutic strategy for modifying epileptogenesis.

Genetic approaches to investigate the role of CREB in neuronal plasticity and memory

In neurons, the convergence of multiple intracellular signaling cascades leading to cAMP-responsive element-binding protein (CREB) activation suggests that this transcription factor plays a critical role in integrating different inputs and mediating appropriate neuronal responses. The nature of this transcriptional response depends on both the type and strength of the stimulus and the cellular context. CREB-dependent gene expression has been involved in many different aspects of nervous system function, from embryonic development to neuronal survival, and synaptic, structural, and intrinsic plasticity. Here, we first review the different methodological approaches used to genetically manipulate CREB activity and levels in neurons in vivo in the adult brain, including recombinant viral vectors, mouse transgenesis, and gene-targeting techniques. We then discuss the impact of these approaches on our understanding of CREB's roles in neuronal plasticity and memory in rodents. Studies combining these genetic approaches with electrophysiology and behavior provide strong evidence that CREB is critically involved in the regulation of synaptic plasticity, intrinsic excitability, and long-term memory formation. These findings pave the way for the development of novel therapeutic strategies to treat memory disorders.

CREB-mediated alterations in the amygdala transcriptome: coordinated regulation of immune response genes following cocaine

The neuronal circuitry underlying stress- and drug-induced reinstatement of cocaine-seeking has been relatively well characterized; however, less is known regarding the long-term molecular changes following cocaine administration that may promote future reinstatement. The transcription factor cAMP response element-binding protein (CREB) is necessary for stress- but not cocaine-induced reinstatement of conditioned reward, suggesting that different molecular mechanisms may underlie these two types of reinstatement. To explore the relationship between this transcription factor and reinstatement, we utilized the place-conditioning paradigm to examine alterations in gene expression in the amygdala, a neural substrate critically involved in stress-induced reinstatement, following the development of cocaine reward and subsequent extinction. Our findings demonstrate that the amygdala transcriptome was altered by CREB deficiency more than by previous cocaine experience, with an over-representation of genes involved in the immune response. However, a subset of genes involved in stress and immune response demonstrated a drug×genotype interaction, indicating that cocaine produces different long-term alterations in gene expression depending on the presence or absence of CREB. This profile of gene expression in the context of addiction enhances our understanding of the long-term molecular changes that occur throughout the addiction cycle and identifies novel genes and pathways that might lead to the creation of better therapeutic agents.

Calcium signaling in cognition and aging-dependent cognitive decline

Calcium-dependent signals are key triggers of the molecular mechanisms underlying learning and memory and dysregulation of calcium homeostasis in the aging brain has been proposed to underlie aging-dependent cognitive decline. Mechanisms triggered by calcium in neurons include activity-dependent activation of transcription responsible for the synthesis of molecules underlying the long-term changes of neuronal function. Effectors of calcium signaling with a primordial role in transcription regulation are calcium signal-regulated transcription factors. In this review, we summarize the current knowledge of the contribution of key calcium signal-regulated transcription factors, namely CREB, NFAT, and DREAM, to memory formation. We further describe evidence for dysregulation of the activity of these factors during aging.

Lack of cAMP-response element-binding protein 1 in the hypothalamus causes obesity

The melanocortin system in the hypothalamus controls food intake and energy expenditure. Its disruption causes severe obesity in mice and humans. cAMP-response element-binding protein 1 (CREB1) has been postulated to play an important role downstream of the melanocortin-4 receptor (MC4R), but this hypothesis has never been confirmed in vivo. To test this, we generated mice that lack CREB1 in SIM1-expressing neurons, of the paraventricular nucleus (PVN), which are known to be MC4R-positive. Interestingly, CREB1(ΔSIM1) mice developed obesity as a result of decreased energy expenditure and impairment in maintaining their core body temperature and not because of hyperphagia, defining a new role for CREB1 in the PVN. In addition, the lack of CREB1 in the PVN caused a reduction in vasopressin expression but did not affect adrenal or thyroid function. Surprisingly, MC4R function tested pharmacologically was normal in CREB1(ΔSIM1) mice, suggesting that CREB1 is not required for intact MC4R signaling. Thus CREB1 may affect other pathways that are implicated in the regulation of body weight.

CREB: a multifaceted regulator of neuronal plasticity and protection

Since its initial characterization over 20 years ago, there has been intense and unwavering interest in understanding the role of the transcription factor cAMP-responsive element binding protein (CREB) in nervous system physiology. Through an array of experimental approaches and model systems, researchers have begun to unravel the complex and multifaceted role of this transcription factor in such diverse processes as neurodevelopment, synaptic plasticity, and neuroprotection. Here we discuss current insights into the molecular mechanisms by which CREB couples synaptic activity to long-term changes in neuronal plasticity, which is thought to underlie learning and memory. We also discuss work showing that CREB is a critical component of the neuroprotective transcriptional network, and data indicating that CREB dysregulation contributes to an array of neuropathological conditions.

Effects of the cell type-specific ablation of the cAMP-responsive transcription factor in noradrenergic neurons on locus coeruleus firing and withdrawal behavior after chronic exposure to morphine

Repeated exposure to opiates leads to cellular and molecular changes and behavioral alterations reflecting a state of dependence. In noradrenergic neurons, cyclic AMP (cAMP)-dependent pathways are activated during opiate withdrawal, but their contribution to the activity of locus coeruleus noradrenergic neurons and behavioral manifestations remains controversial. Here, we test whether the cAMP-dependent transcription factors cAMP responsive element binding protein (CREB) and cAMP-responsive element modulator (CREM) in noradrenergic neurons control the cellular markers and the physical signs of morphine withdrawal in mice. Using the Cre/loxP system we ablated the Creb1 gene in noradrenergic neurons. To avoid adaptive effects because of compensatory up-regulation of CREM, we crossed the conditional Creb1 mutant mice with a Crem-/- line. We found that the enhanced expression of tyrosine hydroxylase normally observed during withdrawal was attenuated in CREB/CREM mutants. Moreover, the withdrawal-associated cellular hyperactivity and c-fos expression was blunted. In contrast, naloxone-precipitated withdrawal signs, such as jumping, paw tremor, tremor and mastication were preserved. We conclude by a specific genetic approach that the withdrawal-associated hyperexcitability of noradrenergic neurons depends on CREB/CREM activity in these neurons, but does not mediate several behavioral signs of morphine withdrawal.

CREB expression in the brains of two closely related parasitic wasp species that differ in long-term memory formation

The cAMP/PKA signalling pathway and transcription factor cAMP response element-binding protein (CREB) play key roles in long-term memory (LTM) formation. We used two closely related parasitic wasp species, Cotesia glomerata and Cotesia rubecula, which were previously shown to be different in LTM formation, and sequenced at least nine different CREB transcripts in both wasp species. The splicing patterns, functional domains and amino acid sequences were similar to those found in the CREB genes of other organisms. The predicted amino acid sequences of the CREB isoforms were identical in both wasp species. Using real-time quantitative PCR we found that two low abundant CREB transcripts are differentially expressed in the two wasps, whereas the expression levels of high abundant transcripts are similar.

Generation of a conditional CREB Ser133Ala knockin mouse

Phosphorylation of Ser133 in the transcription factor CREB is an important mechanism for regulating its transcriptional activity, however recent work has suggested significant roles for other regulatory inputs into CREB. To allow study of this in vivo, we have generated a Ser133 to alanine knockin mutation in the mouse CREB locus. As CREB knockout is perinatal lethal, a minigene strategy was used to allow conditional knockin of the Ser133Ala mutation in adult mice using Cre recombinase. While some expression of the mutated protein was observed prior to Cre expression, following Cre expression in either T cells or neurons only the mutated CREB protein was detected.

Blockade of serotonin 2A receptors prevents PCP-induced attentional performance deficit and CREB phosphorylation in the dorsal striatum of DBA/2 mice

RATIONAL AND OBJECTIVE

Functional opposition between N-methyl-D-aspartate and 5-HT(2A) receptors may be a neural mechanism supporting cognitive functions. These systems converge on an intracellular signaling pathway that involves protein kinase A-dependent phosphorylation of different proteins including cyclic adenosine monophosphate response element binding (CREB). Thus, we tested whether selective 5-HT(2A) receptor antagonist, M100907, might abolish phencyclidine (PCP)-induced attentional performance deficit by preventing its effects on transduction mechanisms leading to CREB phosphorylation.

METHODS

Using the five-choice serial reaction time task, the ability of subcutaneous injections of 2.5 and 10 microg/kg of M100907 to abolish the effects of an intraperitoneal injection of 1.5 mg/kg PCP on attentional performance as measured by accuracy (percentage of correct responses) and anticipatory and perseverative responding was assessed in DBA/2 mice. The effects of PCP, M100907, and their combination on S(133)-CREB and T(34)-DARPP32 phosphorylation in the dorsal striatum and prefrontal cortex (PFC) of behaviorally naïve mice were examined using Western blotting technique.

RESULTS

PCP reduced accuracy and increased anticipatory and perseverative responses as well as it increased S(133)-CREB phosphorylation in the dorsal striatum but not in the PFC. Ten microg/kg M100907 abolished the PCP-induced attentional performance deficits and the increase in S(133)-CREB but not T(34)-DARPP32 phosphorylation. By itself, M100907 had no effect on attentional performance or phospho-S(133)-CREB and phospho-T(34)-DARPP32. Interestingly, the effect of PCP on phospho-S(133)-CREB but not on phospho-T(34)-DARPP32 was dependent on endogenous 5-HT.

CONCLUSIONS

The data indicate that blockade of 5-HT(2A) receptors may exert beneficial effects on cognitive deficits through a mechanism linked to striatal S(133)-CREB phosphorylation.

The function of activity-regulated genes in the nervous system

The mammalian brain is plastic in the sense that it shows a remarkable capacity for change throughout life. The contribution of neuronal activity to brain plasticity was first recognized in relation to critical periods of development, when manipulating the sensory environment was found to profoundly affect neuronal morphology and receptive field properties. Since then, a growing body of evidence has established that brain plasticity extends beyond development and is an inherent feature of adult brain function, spanning multiple domains, from learning and memory to adaptability of primary sensory maps. Here we discuss evolution of the current view that plasticity of the adult brain derives from dynamic tuning of transcriptional control mechanisms at the neuronal level, in response to external and internal stimuli. We then review the identification of "plasticity genes" regulated by changes in the levels of electrical activity, and how elucidating their cellular functions has revealed the intimate role transcriptional regulation plays in fundamental aspects of synaptic transmission and circuit plasticity that occur in the brain on an every day basis.

Inducible cAMP early repressor (ICER) and brain functions

The inducible cAMP early repressor (ICER) is an endogenous repressor of cAMP-responsive element (CRE)-mediated gene transcription and belongs to the CRE-binding protein (CREB)/CRE modulator (CREM)/activating transcription factor 1 (ATF-1) gene family. ICER plays an important role in regulating the neuroendocrine system and the circadian rhythm. Other aspects of ICER function have recently attracted heightened attention. Being a natural inducible CREB antagonist, and more broadly, an inducible repressor of CRE-mediated gene transcription, ICER regulates long-lasting plastic changes that occur in the brain in response to incoming stimulation. This review will bring together data on ICER and its functions in the brain, with a special emphasis on recent findings highlighting the involvement of ICER in the regulation of long-term plasticity underlying learning and memory.

Inhibition of CREB function in mouse epidermis reduces papilloma formation

We used a double transgenic tetracycline system to conditionally express A-CREB, a dominant negative protein that prevents the DNA binding and function of cAMP-responsive element binding protein (CREB) family members, in mouse basal epidermis using the keratin 5 promoter. There was no phenotype in the adult. However, following a 7,12-dimethylbenz(a)anthracene (DMBA)/phorbol-12-myristate-13-acetate two-stage skin carcinogenesis experiment, A-CREB-expressing epidermis develop 5-fold fewer papillomas than wild-type controls. However, A-CREB expression one month after DMBA treatment does not prevent papilloma formation, suggesting that CREB functions at an early stage of papilloma formation. Oncogenic H-Ras genes with A-->T mutations in codon 61 were found in wild-type skin but not in A-CREB-expressing skin 2 days after DMBA treatment, suggesting that A-CREB either prevents DMBA mutagenesis or kills oncogenic H-Ras cells. In primary keratinocyte cultures, A-CREB expression induced apoptosis of v-Ras(Ha)-infected cells and suppressed the expression of cell cycle proteins cyclin B1 and cyclin D1. These results suggest that inhibiting CREB function is a valuable cancer prevention strategy.

Chronic enhancement of CREB activity in the hippocampus interferes with the retrieval of spatial information

The activation of cAMP-responsive element-binding protein (CREB)-dependent gene expression is thought to be critical for the formation of different types of long-term memory. To explore the consequences of chronic enhancement of CREB function on spatial memory in mammals, we examined spatial navigation in bitransgenic mice that express in a regulated and restricted manner a constitutively active form of CREB, VP16-CREB, in forebrain neurons. We found that chronic enhancement of CREB activity delayed the acquisition of an allocentric strategy to solve the hidden platform task. The ability to turn on and off transgene expression allowed us to dissect the role of CREB in dissociable memory processes. In mice in which transgene expression was turned on during memory acquisition, turning off the transgene re-established the access to the memory trace, whereas in mice in which transgene expression was turned off during acquisition, turning on the transgene impaired memory expression in a reversible manner, indicating that CREB enhancement specifically interfered with the retrieval of spatial information. The defects on spatial navigation in mice with chronic enhancement of CREB function were not corrected by conditions that increased further CREB-dependent activation of hippocampal memory systems, such as housing in an enriched environment. These results along with previous findings in CREB-deficient mutants indicate that the relationship of CREB-mediated plasticity to spatial memory is an inverted-U function, and that optimal learning in the water maze requires accurate regulation of this pathway.

Inhibition of cAMP response element-binding protein reduces neuronal excitability and plasticity, and triggers neurodegeneration

The cAMP-responsive element-binding protein (CREB) pathway has been involved in 2 major cascades of gene expression regulating neuronal function. The first one presents CREB as a critical component of the molecular switch that controls long-lasting forms of neuronal plasticity and learning. The second one relates CREB to neuronal survival and protection. To investigate the role of CREB-dependent gene expression in neuronal plasticity and survival in vivo, we generated bitransgenic mice expressing A-CREB, an artificial peptide with strong and broad inhibitory effect on the CREB family, in forebrain neurons in a regulatable manner. The expression of A-CREB in hippocampal neurons impaired L-LTP, reduced intrinsic excitability and the susceptibility to induced seizures, and altered both basal and activity-driven gene expression. In the long-term, the chronic inhibition of CREB function caused severe loss of neurons in the CA1 subfield as well as in other brain regions. Our experiments confirmed previous findings in CREB-deficient mutants and revealed new aspects of CREB-dependent gene expression in the hippocampus supporting a dual role for CREB-dependent gene expression regulating intrinsic and synaptic plasticity and promoting neuronal survival.

Allegro: analyzing expression and sequence in concert to discover regulatory programs

A major goal of system biology is the characterization of transcription factors and microRNAs (miRNAs) and the transcriptional programs they regulate. We present Allegro, a method for de-novo discovery of cis-regulatory transcriptional programs through joint analysis of genome-wide expression data and promoter or 3' UTR sequences. The algorithm uses a novel log-likelihood-based, non-parametric model to describe the expression pattern shared by a group of co-regulated genes. We show that Allegro is more accurate and sensitive than existing techniques, and can simultaneously analyze multiple expression datasets with more than 100 conditions. We apply Allegro on datasets from several species and report on the transcriptional modules it uncovers. Our analysis reveals a novel motif over-represented in the promoters of genes highly expressed in murine oocytes, and several new motifs related to fly development. Finally, using stem-cell expression profiles, we identify three miRNA families with pivotal roles in human embryogenesis.

Genetic dissection of neural circuits and behavior in Mus musculus

One of the major challenges in the field of neurobiology is to elucidate the molecular machinery that underlies the formation and storage of memories. For many decades, genetic studies in the fruit fly (Drosophila melanogaster) have provided insight into the role of specific genes underlying memory storage. Although these pioneering studies were groundbreaking, a transition to a mammalian system more closely resembling the human brain is critical for the translation of basic research findings into therapeutic strategies in humans. Because the mouse (Mus musculus) shares the complex genomic and neuroanatomical organization of mammals and there is a wealth of molecular tools that are available to manipulate gene function in mice, the mouse has become the primary model for research into the genetic basis of mammalian memory. Another major advantage of mouse research is the ability to examine in vivo electrophysiological processes, such as synaptic plasticity and neuronal firing patterns during behavior (e.g., the analysis of place cell activity). The focus on mouse models for memory research has led to the development of sophisticated behavioral protocols capable of exploring the role of particular genes in distinct phases of learning and memory formation, which is one of the major accomplishments of the past decade. In this chapter, we will give an overview of several state of the art genetic approaches to study gene function in the mouse brain in a spatially and temporally restricted fashion.

Germ cell nuclear factor directly represses the transcription of peroxisome proliferator-activated receptor delta gene

Germ cell nuclear factor (GCNF) is a transcription factor that can repress gene transcription and plays an important role during spermatogenesis. Peroxisome proliferator-activated receptor delta (PPARdelta) is a nuclear hormone receptor belonging to the steroid receptor superfamily. It can activate the expression of many genes, including those involved in lipid metabolism. In this report, we showed that GCNF specifically interacts with PPARdelta promoter. Overexpression of GCNF in African green monkey SV40-transformed kidney fibroblast COS7 cells and mouse embryo fibroblast NIH 3T3 cells represses the activity of PPARdelta promoter. The mutation of GCNF response element in PPARdelta promoter relieves the repression in NIH 3T3 cells and mouse testis. Moreover, we showed that GCNF in nuclear extracts of mouse testis is able to bind to PPARdelta promoter directly. We also found that GCNF and PPARdelta mRNA were expressed with different patterns in mouse testis by in situ hybridization. These results suggested that GCNF might be a negative regulator of PPARdelta gene expression through its direct interaction with PPARdelta promoter in mouse testis.

Intra-axonal translation and retrograde trafficking of CREB promotes neuronal survival

During development of the nervous system, axons and growth cones contain mRNAs such as beta-actin, cofilin and RhoA, which are locally translated in response to guidance cues. Intra-axonal translation of these mRNAs results in local morphological responses; however, other functions of intra-axonal mRNA translation remain unknown. Here, we show that axons of developing mammalian neurons contain mRNA encoding the cAMP-responsive element (CRE)-binding protein (CREB). CREB is translated within axons in response to nerve growth factor (NGF) and is retrogradely trafficked to the cell body. In neurons that are selectively deficient in axonal CREB transcripts, increases in nuclear pCREB, CRE-mediated transcription and neuronal survival elicited by axonal application of NGF are abolished, indicating a signalling function for axonally synthesized CREB. These studies identify a signalling role for axonally derived CREB, and indicate that signal-dependent synthesis and retrograde trafficking of transcription factors enables specific transcriptional responses to signalling events at distal axons.

NSSR1 is regulated in testes development and cryptorchidism and promotes the exon 5-included splicing of CREB transcripts

Neural salient serine/arginine rich protein 1 (NSSR1, alternatively SRp38) is a newly identified splicing factor that is highly expressed in neural and reproductive tissues. We showed that the expression of testicular NSSR1 increased significantly during mouse testes development. NSSR1 was mainly expressed in germ cells, but barely detected in Sertoli cells. Testicular NSSR1 was mostly phosphorylated and cytosolic in germ cells. In comparison, pituitary NSSR1 was mostly dephosphorylated and nuclear. In the cryptorchid testes, the dephosphorylated NSSR1 was significantly increased. RT-PCR analysis demonstrated that the alternative splicing of CREB and CREM genes was altered in the cryptorchid testes. In addition, CREB transcripts were associated with NSSR1 either in testes tissues or cultured GC-1 cells. Moreover, the studies with NSSR1 over-expression or silence demonstrated that NSSR1 promoted the exon 5 inclusion of CREB, indicating that NSSR1 is a new factor that regulates the alternative exon 5 inclusion of CREB transcripts. The findings for the first time provide the evidence indicating the potential importance of NSSR1 in testes development, spermatogenesis and cryptorchidism.

Gdnf upregulates c-Fos transcription via the Ras/Erk1/2 pathway to promote mouse spermatogonial stem cell proliferation

Glial cell line-derived neurotrophic factor (GDNF) plays a crucial role in regulating the proliferation of spermatogonial stem cells (SSC). The signaling pathways mediating the function of GDNF in SSC remain unclear. This study was designed to determine whether GDNF signals via the Ras/ERK1/2 pathway in the C18-4 cells, a mouse SSC line. The identity of this cell line was confirmed by the expression of various markers for germ cells, proliferating spermatogonia, and SSC, including GCNA1, Vasa, Dazl, PCNA, Oct-4, GFRalpha1, Ret, and Plzf. Western blot analysis revealed that GDNF activated Ret tyrosine phosphorylation. All 3 isoforms of Shc were phosphorylated upon GDNF stimulation, and GDNF induced the binding of the phosphorylated Ret to Shc and Grb2 as indicated by immunoprecipitation and Western blotting. The active Ras was induced by GDNF, which further activated ERK1/2 phosphorylation. GDNF stimulated the phosphorylation of CREB-1, ATF-1, and CREM-1, and c-fos transcription. Notably, the increase in ERK1/2 phosphorylation, c-fos transcription, bromodeoxyuridine incorporation, and metaphase counts induced by GDNF, was completely blocked by pretreatment with PD98059, a specific inhibitor for MEK1, the upstream regulator of ERK1/2. GDNF stimulation eventually upregulated cyclin A and CDK2 expression. Together, these data suggest that GDNF induces CREB/ATF-1 family member phosphorylation and c-fos transcription via the Ras/ERK1/2 pathway to promote the proliferation of SSC. Unveiling GDNF signaling cascades in SSC has important implications in providing attractive targets for male contraception as well as for the regulation of stem cell renewal vs. differentiation.