Neural restrictive silencer factor and choline acetyltransferase expression in cerebral tissue of Alzheimer's Disease patients: A pilot study

NRSF regulates age-dependently cognitive ability and its conditional knockout in APP/PS1 mice moderately alters AD-like pathology

NRSF/REST (neuron-restrictive silencer element, also known as repressor element 1-silencing transcription factor), plays a key role in neuronal homeostasis as a transcriptional repressor of neuronal genes. NRSF/REST relates to cognitive preservation and longevity of humans, but its specific functions in age-dependent and Alzheimer's disease (AD)-related memory deficits remain unclear. Here, we show that conditional NRSF/REST knockout either in the dorsal telencephalon or specially in neurons induced an age-dependently diminished retrieval performance in spatial or fear conditioning memory tasks and altered hippocampal synaptic transmission and activity-dependent synaptic plasticity. The NRSF/REST deficient mice were also characterized by an increase of activated glial cells, complement C3 protein and the transcription factor C/EBPβ in the cortex and hippocampus. Reduction of NRSF/REST by conditional depletion upregulated the activation of astrocytes in APP/PS1 mice, and increased the C3-positive glial cells, but did not alter the Aβ loads and memory retrieval performances of 6- and 12-month-old APP/PS1 mice. Simultaneously, overexpression of NRSF/REST improved cognitive abilities of aged wild type, but not in AD mice. These findings demonstrated that NRSF/REST is essential for the preservation of memory performance and activity-dependent synaptic plasticity during aging and takes potential roles in the onset of age-related memory impairments. However, while altering the glial activation, NRSF/REST deficiency does not interfere with the Aβ deposits and the electrophysiological and cognitive AD-like pathologies.

The non-coding genome in Autism Spectrum Disorders

Autism Spectrum Disorders (ASD) are a group of neurodevelopmental disorders (NDDs) characterized by difficulties in social interaction and communication, repetitive behavior, and restricted interests. While ASD have been proven to have a strong genetic component, current research largely focuses on coding regions of the genome. However, non-coding DNA, which makes up for ∼99% of the human genome, has recently been recognized as an important contributor to the high heritability of ASD, and novel sequencing technologies have been a milestone in opening up new directions for the study of the gene regulatory networks embedded within the non-coding regions. Here, we summarize current progress on the contribution of non-coding alterations to the pathogenesis of ASD and provide an overview of existing methods allowing for the study of their functional relevance, discussing potential ways of unraveling ASD's "missing heritability".

A Mixture of Artemisia argyi and Saururus chinensis Improves PM2.5-Induced Cognitive Dysfunction by Regulating Oxidative Stress and Inflammatory Response in the Lung and Brain

This study was performed to investigate the improving effect of a mixture of Artemisia argyi and Saururus chinensis (AASC) on cognitive dysfunction in mice with long-term exposure to fine particles (particulate matter smaller than 2.5 µm: PM_2.5). The main compounds of AASC were identified as dicaffeoylquinic acid isomers of A. argyi and a quercetin-3-glucoside of S. chinesis. As a result of behavioral tests for the evaluation of cognitive function, it was confirmed that cognitive dysfunction was induced in the PM_2.5 exposure group, and a tendency to improve in the AASC group was confirmed. Increased oxidative stress and inflammatory response and mitochondrial dysfunction were observed in the brain and lung tissues of the PM group. Damage to the brain and lung affected the accumulation of amyloid beta (Aβ) in the brain. It increased Aβ and induced the cholinergic dysfunction, hyperphosphorylation of the tau protein, and activation of apoptosis, leading to cognitive impairment. However, AASC suppressed brain and lung oxidative stress and inflammation, thereby suppressing brain Aβ expression. Consequently, this study shows the potential that a steady intake of plant resources with antioxidant and anti-inflammatory activity could prevent cognitive impairment caused by PM_2.5.

Overexpression of REST Causes Neuronal Injury and Decreases Cofilin Phosphorylation in Mice

Background: RE1-silencing transcription factor (REST) is known to silence target genes involved in synaptic plasticity and neuronal differentiation. Although previous studies implicate REST in neurodegenerative diseases, its function in the progression of Alzheimer’s disease (AD) is uncertain. Objective: The aim of the present work was to explore the mechanisms of AD and determine whether and how REST was involved in the pathogenesis of AD. Methods: We investigated the differentially expressed genes and key transcription factors in AD using bioinformatics analysis. In addition, we assessed the expression of REST under the influence of AD-related factors. Mice overexpressing REST were generated and analyzed by proteomics analysis. We used transmission electron microscopy, Golgi-cox staining, immunohistochemistry, and western blotting to examine the impact of REST on neurons. Results: The results of bioinformatics analysis revealed REST as a hub transcriptional regulator in AD. We demonstrate that the mRNA expression of REST was significantly upregulated compared with that in the control groups, not only in AD patients but also in APP/PS1 transgenic mice, lipopolysaccharide-induced neuroinflammatory mice, and oxidative and glutamate stressed neurons. Using proteomics analysis, we showed that the upregulation of REST increased the expression of genes involved in apoptotic and mitochondrial pathways. Long-term overexpression of REST significantly reduced the number of dendritic spines and increased the mitochondrial defect and apoptosis. Reduction of the cofilin phosphorylation may be one of its mechanisms, and cofilin activity could be affected through the P38 MAPK/CREB signaling pathway. Conclusion: These results demonstrated the possible mechanism underlying AD and indicated REST as a potential therapeutic target for AD.

Induced genetic ablation of Rest leads to the alteration of stimulus-induced response of the vagal nerve

Rest (RE1-silencing transcription factor, also called Nrsf) is involved in the maintenance of the undifferentiated state of neuronal stem/progenitor cells by preventing precocious expression of neuronal genes. In order to further investigate the function of Rest in neurons, we generated and examined mice evoking genetic ablation of Rest specifically in neural tissues by generating Rest conditional knockout mice. As the Rest knockout mice are embryonically lethal, we used a Sox1-Cre allele to excise the floxed Rest gene from the early stage of nerve cell differentiation including neural crest-derived nerve cells. Using this conditional Rest knockout Sox1-Cre; Restflox/flox mice, we have revealed the role of Rest in the parasympathetic nervous system in the stomach and heart.

Influence of a genetic variant of CHAT gene over the profile of plasma soluble ChAT in Alzheimer disease

The choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) are fundamental to neurophysiological functions of the central cholinergic system. We confirmed and quantified the presence of extracellular ChAT protein in human plasma and also characterized ChAT and VAChT polymorphisms, protein and activity levels in plasma of Alzheimer's disease patients (AD; N = 112) and in cognitively healthy controls (EC; N = 118). We found no significant differences in plasma levels of ChAT activity and protein between AD and EC groups. Although no differences were observed in plasma ChAT activity and protein concentration among ChEI-treated and untreated AD patients, ChAT activity and protein levels variance in plasma were higher among the rivastigmine-treated group (ChAT protein: p = 0.005; ChAT activity: p = 0.0002). Moreover, AD patients homozygous for SNP rs1880676 A allele exhibited higher levels of ChAT activity. Considering this is the first study to report the influence of genetic variability of CHAT locus over ChAT activity in AD patients plasma, it opens a new set of important questions on peripheral cholinergic signaling in AD.

Effect of 9 - PAHSA on cognitive dysfunction in diabetic mice and its possible mechanism

Diabetes mellitus (DM) is currently a major global health problem, which is associated with the development of cognitive dysfunction. However, although numerous clinical drugs for hyperglycemia have been used at present, safer and more effective therapeutic intervention strategies for diabetic cognitive impairments are still a huge challenge. Recently, several studies have indicated that a novel class of branched palmitic acid esters of hydroxyl stearic acids (PAHSAs) may have anti-diabetes and anti-inflammatory effects in insulin-resistant mice. Herein, whether the 9-PAHSA that one of the PAHSAs can attenuates DM-associated cognitive impairment in a mouse model of type 2 diabetes has been investigated. Our results showed that 9-PAHSA mildly prevented deficits of spatial working memory in Y-maze test while reversed the preference bias toward novel mice in Social choice test. Furthermore, the effect of REST on cognitive impairment of diabetes was explored for the first time. It was found that the expression of REST in diabetic mice increased, and the expression of target protein BDNF (Brain-derived neurotrophic factor) was decreased. After administration of 9-PAHSA, the situation was reversed. In summary, we conclude that exogenous supplement of 9-PAHSA can improve DM-related cognitive impairment to some extent, and the protective effect may be associated with decreased REST/NRSF (repressor element-1 silencing transcription factor/neuron-restrictive silence factor) and upregulated BDNF expression in frontal cortex.

RE1-silencing transcription factor controls the acute-to-chronic neuropathic pain transition and Chrm2 receptor gene expression in primary sensory neurons

Neuropathic pain is associated with persistent changes in gene expression in primary sensory neurons, but the underlying epigenetic mechanisms that cause these changes remain unclear. The muscarinic cholinergic receptors (mAChRs), particularly the M2 subtype (encoded by the cholinergic receptor muscarinic 2 (Chrm2) gene), are critically involved in the regulation of spinal nociceptive transmission. However, little is known about how Chrm2 expression is transcriptionally regulated. Here we show that nerve injury persistently increased the expression of RE1-silencing transcription factor (REST, also known as neuron-restrictive silencing factor [NRSF]), a gene-silencing transcription factor, in the dorsal root ganglion (DRG). Remarkably, nerve injury-induced chronic but not acute pain hypersensitivity was attenuated in mice with Rest knockout in DRG neurons. Also, siRNA-mediated Rest knockdown reversed nerve injury-induced chronic pain hypersensitivity in rats. Nerve injury persistently reduced Chrm2 expression in the DRG and diminished the analgesic effect of muscarine. The RE1 binding site on the Chrm2 promoter is required for REST-mediated Chrm2 repression, and nerve injury increased the enrichment of REST in the Chrm2 promoter in the DRG. Furthermore, Rest knockdown or genetic ablation in DRG neurons normalized Chrm2 expression and augmented muscarine's analgesic effect on neuropathic pain and fully reversed the nerve injury-induced reduction in the inhibitory effect of muscarine on glutamatergic input to spinal dorsal horn neurons. Our findings indicate that nerve injury-induced REST up-regulation in DRG neurons plays an important role in the acute-to-chronic pain transition and is essential for the transcriptional repression of Chrm2 in neuropathic pain.

The Stress-Responding miR-132-3p Shows Evolutionarily Conserved Pathway Interactions

MicroRNAs (miRNAs) are small non-coding RNA chains that can each interact with the 3′-untranslated region of multiple target transcripts in various organisms, humans included. MiRNAs tune entire biological pathways, spanning stress reactions, by regulating the stability and/or translation of their targets. MiRNA genes are often subject to co-evolutionary changes together with their target transcripts, which may be reflected by differences between paralog mouse and primate miRNA/mRNA pairs. However, whether such evolution occurred in stress-related miRNAs remained largely unknown. Here, we report that the stress-induced evolutionarily conserved miR-132-3p, its target transcripts and its regulated pathways provide an intriguing example to exceptionally robust conservation. Mice and human miR-132-3p share six experimentally validated targets and 18 predicted targets with a common miRNA response element. Enrichment analysis and mining in-house and web-available experimental data identified co-regulation by miR-132 in mice and humans of stress-related, inflammatory, metabolic, and neuronal growth pathways. Our findings demonstrate pan-mammalian preservation of miR-132′s neuronal roles, and call for further exploring the corresponding stress-related implications.

The memory enhancement effect of Kai Xin San on cognitive deficit induced by simulated weightlessness in rats

ETHNOPHARMACOLOGICAL RELEVANCE

It is vital for astronauts to develop effective countermeasures to prevent their decline of cognitive performance in microgravity to make space-flight missions successful. The traditional Chinese herbal formula Kai Xin San (KXS) has been used to treat amnesia for thousands years. It is a traditional complex prescription comprising of ginseng (Panax ginseng C. A. Meyer), hoelen (Poria cocos (Schw.) Wolf), polygala (Polygala tenaifolia Willd), and acorus (Acorus tatarinowii Schott). Previous study showed KXS could improve CMS-induced memory impairment in rats.

MATERIAL AND METHODS

In this paper, a unique environmental factor-microgravity (weightlessness) was simulated as hindlimb suspension (HLS) by tail in rats for two weeks as the HLS animal model. The KXS at the doses of 0.3 or 0.6g/kg p.o. daily was administrated to HLS rats for two weeks at the same time of HLS, the memory behavior tests were investigated with Morris water maze (MWM) and Shuttle Box (SB) test. The levels of ROS, 8-OHdG and 3-nitrotyrosine (3-NT) in the serum, and AChE and ChAT activity in the brain of rats were determined by ELISA or biochemical analysis.

RESULTS

After HLS for two weeks, the escape latency and the swimming distance were significantly increased in the MWM test in rats in the HLS group, compared with control group. The percent of swimming distance in target quadrant and the number of target crossing was significantly decreased in rats in the HLS group compared with the control group. Performance in the SB test showed, the numbers and the distance of active avoidance was decreased from day 4 to day 7, the time spent in electric area was increased in rats in the HLS group compared with the control group. Administration of KXS 0.3 or 0.6g/kg to the HLS rats for two weeks significantly reduced the escape latency and the swimming distance, increased the percentage of swimming distance in target quadrant and the number of target crossings (P<0.01, compared with the HLS group) in the MWM test. Similar treatment with KXS increased the numbers and the distance of active avoidance (P<0.01, compared with the HLS group) and reduced the time spent in electric area after training 3 days in the SB test (P<0.01, compared with the HLS group). The HLS induced the increase of the ROS, 8-OHdG and 3-NT in the serum of rats, but has little influence on the AChE, ChAT activity in the brain. Only the AChE activity in the cortex and the ChAT activity in the hippocampus had some changes in rats in the HLS model group. After administration of KXS 0.6g/kg for two weeks, the abnormal levels of ROS, 8-OHdG, 3-NT were found reversed in the serum of rats (P<0.05, compared with HLS model group). And KXS 0.3g/kg was found reversed the increased AChE activity in the cortex.

CONCLUSIONS

Experimental results from this study show that KXS may improve memory deficiency induced by HLS, its mechanisms are major related to antioxidant activities, rather than the central cholinergic system.

Downregulation of the sodium channel Nav1.6 by potential transcriptomic deregulation may explain sensory deficits in critical illness neuropathy

AIMS

Sepsis patients and other patients in the critical care settings are at very high risk of mortality due to the primary illness. However, a fraction of patients, even after showing initial clinical improvement, deteriorates relentlessly at later stages. Increasingly, it is being identified that this is mostly due to dysfunction of the neurological system.

MAIN METHODS

We obtained peripheral nerve biopsies from the sural nerve from ICU patients. Nav1.6 expression was significantly diminished. The expression of cellular membrane anchoring protein for Nav1.6, ankyrin, remained unaffected, suggesting that genomic repression may be responsible for the diminished expression of the sodium channels. We examined the expression of two regulatory transcription factors: (a) a positive regulator YY1 that binds to the promoter region of sodium channels and (b) an upstream negative neuronal regulator REST.

KEY FINDINGS

REST expression was significantly elevated, while YY1 expression was diminished. Finally, we also observed that the cholinergic synthetic enzyme acyltransferase was also significantly diminished in sensory nerve lysates. Finally, circulating antibodies was detected in the peripheral blood against all the major sodium channels Nav1.6, 1.8 and 1.9, which contribute to the development and propagation of action potentials.

SIGNIFICANCE

This may potentially explain why its dysfunction affects neurological functions across all systems of the body during critical illness. The underlying mechanism of why the expression of the REST transcriptional factor is affected in critical illnesses remains our future goals of investigation.

The Transcription Repressor REST in Adult Neurons: Physiology, Pathology, and Diseases

REST [RE1-silencing transcription factor (also called neuron-restrictive silencer factor)] is known to repress thousands of possible target genes, many of which are neuron specific. To date, REST repression has been investigated mostly in stem cells and differentiating neurons. Current evidence demonstrates its importance in adult neurons as well. Low levels of REST, which are acquired during differentiation, govern the expression of specific neuronal phenotypes. REST-dependent genes encode important targets, including transcription factors, transmitter release proteins, voltage-dependent and receptor channels, and signaling proteins. Additional neuronal properties depend on miRNAs expressed reciprocally to REST and on specific splicing factors. In adult neurons, REST levels are not always low. Increases occur during aging in healthy humans. Moreover, extensive evidence demonstrates that prolonged stimulation with various agents induces REST increases, which are associated with the repression of neuron-specific genes with appropriate, intermediate REST binding affinity. Whether neuronal increases in REST are protective or detrimental remains a subject of debate. Examples of CA1 hippocampal neuron protection upon depolarization, and of neurodegeneration upon glutamate treatment and hypoxia have been reported. REST participation in psychiatric and neurological diseases has been shown, especially in Alzheimer’s disease and Huntington’s disease, as well as epilepsy. Distinct, complex roles of the repressor in these different diseases have emerged. In conclusion, REST is certainly very important in a large number of conditions. We suggest that the conflicting results reported for the role of REST in physiology, pathology, and disease depend on its complex, direct, and indirect actions on many gene targets and on the diverse approaches used during the investigations.

Molecular mechanisms regulating the defects in fragile X syndrome neurons derived from human pluripotent stem cells

Fragile X syndrome (FXS) is caused by the absence of the fragile X mental retardation protein (FMRP). We have previously generated FXS-induced pluripotent stem cells (iPSCs) from patients' fibroblasts. In this study, we aimed at unraveling the molecular phenotype of the disease. Our data revealed aberrant regulation of neural differentiation and axon guidance genes in FXS-derived neurons, which are regulated by the RE-1 silencing transcription factor (REST). Moreover, we found REST to be elevated in FXS-derived neurons. As FMRP is involved in the microRNA (miRNA) pathway, we employed miRNA-array analyses and uncovered several miRNAs dysregulated in FXS-derived neurons. We found hsa-mir-382 to be downregulated in FXS-derived neurons, and introduction of mimic-mir-382 into these neurons was sufficient to repress REST and upregulate its axon guidance target genes. Our data link FMRP and REST through the miRNA pathway and show a new aspect in the development of FXS.

ChIP-Seq Data Mining: Remarkable Differences in NRSF/REST Target Genes between Human ESC and ESC-Derived Neurons

The neuron-restrictive silencer factor (NRSF) is a zinc finger transcription factor that represses neuronal gene transcription in non-neuronal cells by binding to the consensus repressor element-1 (RE1) located in regulatory regions of target genes. NRSF silences the expression of a wide range of target genes involved in neuron-specific functions. Previous studies showed that aberrant regulation of NRSF plays a key role in the pathological process of human neurodegenerative diseases. However, a comprehensive set of NRSF target genes relevant to human neuronal functions has not yet been characterized. We performed genome-wide data mining from chromatin immunoprecipitation followed by deep sequencing (ChIP-Seq) datasets of NRSF binding sites in human embryonic stem cells (ESC) and the corresponding ESC-derived neurons, retrieved from the database of the ENCODE/HAIB project. Using bioinformatics tools such as Avadis NGS and MACS, we identified 2,172 NRSF target genes in ESC and 308 genes in ESC-derived neurons based on stringent criteria. Only 40 NRSF target genes overlapped between both data sets. According to motif analysis, binding regions showed an enrichment of the consensus RE1 sites in ESC, whereas they were mainly located in poorly defined non-RE1 sites in ESC-derived neurons. Molecular pathways of NRSF target genes were linked with various neuronal functions in ESC, such as neuroactive ligand-receptor interaction, CREB signaling, and axonal guidance signaling, while they were not directed to neuron-specific functions in ESC-derived neurons. Remarkable differences in ChIP-Seq-based NRSF target genes and pathways between ESC and ESC-derived neurons suggested that NRSF-mediated silencing of target genes is highly effective in human ESC but not in ESC-derived neurons.