Neuron-restrictive silencer factor/repressor element 1-silencing transcription factor (NRSF/REST) controls spatial K+ buffering in primary cortical astrocytes

Neuron-restrictive silencer factor/repressor element 1 (RE1)-silencing transcription factor (NRSF/REST) is a transcriptional repressor of a large cluster of neural genes containing RE1 motifs in their promoter region. NRSF/REST is ubiquitously expressed in non-neuronal cells, including astrocytes, while it is down-regulated during neuronal differentiation. While neuronal NRSF/REST homeostatically regulates intrinsic excitability and synaptic transmission, the role of the high NRSF/REST expression levels in the homeostatic functions of astrocytes is poorly understood. Here, we investigated the functional consequences of NRSF/REST deletion in primary cortical astrocytes derived from NRSF/REST conditional knockout mice (KO). We found that NRSF/REST KO astrocyte displayed a markedly reduced activity of inward rectifying K⁺ channels subtype 4.1 (Kir4.1) underlying spatial K⁺ buffering that was associated with a decreased expression and activity of the glutamate transporter-1 (GLT-1) responsible for glutamate uptake by astrocytes. The effects of the impaired astrocyte homeostatic functions on neuronal activity were investigated by co-culturing wild-type hippocampal neurons with NRSF/REST KO astrocytes. Interestingly, neurons experienced increased neuronal excitability at high firing rates associated with decrease after hyperpolarization and increased amplitude of excitatory postsynaptic currents. The data indicate that astrocytic NRSF/REST directly participates in neural circuit homeostasis by regulating intrinsic excitability and excitatory transmission and that dysfunctions of NRSF/REST expression in astrocytes may contribute to the pathogenesis of neurological disorders.

Increased NRSF/REST in anterior cingulate cortex contributes to diabetes-related neuropathic pain

Diabetic neuropathic pain is one of the most common complications of diabetes. Mechanisms underlying the central modulation are still unclear. Here, we investigated the role of the neuron-restricted silencing factor (NRSF/REST) in diabetic-related neuropathic pain. Mechanical allodynia and thermal hyperalgesia were assessed to evaluate painful behaviors. Our results found that in the anterior cingulate cortex (ACC) of db/db mice, NRSF/REST levels increased significantly. Reduction of NRSF/REST improved the painful sensation. Meanwhile, in vitro study found that high glucose and high palmitic acid treatment induced elevation of NRSF/REST and its cofactors (mSin3A, CoREST and HDAC1), whereas downregulation of GluR2 and NMDAR2B. Knockdown of NRSF/REST could attenuate the LDH release and partially reversed the expression changes of HDAC1 and NMDAR2B. Our results suggested that the elevation of NRSF/REST in the ACC area of db/db mice is one of the key mediators of diabetic neuropathic pain.

Brain-specific NRSF deficiency aggravates dopaminergic neurodegeneration and impairs neurogenesis in the MPTP mouse model of Parkinson's disease

Degeneration of the dopaminergic neurons in the substantia nigra and the resultant dopamine depletion from the striatum are the hallmarks of Parkinson's disease (PD) and are responsible for the disease's cardinal motor symptoms. The transcriptional repressor Neuron-Restrictive Silencer Factor (NRSF), also known as RE1-Silencing Transcription Factor (REST), was originally identified as a negative regulator of neuron-specific genes in non-neuronal cells. Our previous study showed that mice deficient in neuronal NRSF/REST expression were more vulnerable to the noxious effects of the dopaminergic neurotoxin MPTP. Here, we found that brain-specific deletion of NRSF/REST led to more severe damages to the nigrostriatal pathway and long-lasting behavioral impairments in mice challenged with MPTP. Moreover, compared to wild-type controls, these mice showed increased neurogenesis shortly after MPTP exposure, but reduced neurogenesis later on. These results suggest that NRSF/REST acts as a negative modulator of neurogenesis and a pro-survival factor of neural stem cells under both normal conditions and during the course of PD.

A mimetic of the mSin3-binding helix of NRSF/REST ameliorates abnormal pain behavior in chronic pain models

The neuron-restrictive silencing factor NRSF/REST binds to neuron-restrictive silencing elements in neuronal genes and recruits corepressors such as mSin3 to inhibit epigenetically neuronal gene expression. Because dysregulation of NRSF/REST is related to neuropathic pain, here, we have designed compounds to target neuropathic pain based on the mSin3-binding helix structure of NRSF/REST and examined their ability to bind to mSin3 by NMR. One compound, mS-11, binds strongly to mSin3 with a binding mode similar to that of NRSF/REST. In a mouse model of neuropathic pain, mS-11 was found to ameliorate abnormal pain behavior and to reverse lost peripheral morphine analgesia. Furthermore, even in the less well epigenetically defined case of fibromyalgia, mS-11 ameliorated symptoms in a mouse model, suggesting that fibromyalgia is related to the dysfunction of NRSF/REST. Taken together, these findings show that the chemically optimized mimetic mS-11 can inhibit mSin3-NRSF/REST binding and successfully reverse lost peripheral and central morphine analgesia in mouse models of pain.

Signal transduction of the physical environment in the neural differentiation of stem cells

Neural differentiation is largely dependent on extracellular signals within the cell microenvironment. These extracellular signals are mainly in the form of soluble factors that activate intracellular signaling cascades that drive changes in the cell nucleus. However, it is becoming increasingly apparent that the physical microenvironment provides signals that can also influence lineage commitment and very low modulus surfaces has been repeatedly demonstrated to promote neurogenesis. The molecular mechanisms governing mechano-induced neural differentiation are still largely uncharacterized; however, a growing body of evidence indicates that physical stimuli can regulate known signaling cascades and transcription factors involved in neural differentiation. Understanding how the physical environment affects neural differentiation at the molecular level will enable research and design of materials that will eventually enhance neural stem cell (NSC) differentiation, homogeneity and specificity.

NRSF and BDNF polymorphisms as biomarkers of cognitive dysfunction in adults with newly diagnosed epilepsy

Cognitive dysfunction is a common comorbidity in people with epilepsy, but its causes remain unclear. It may be related to the etiology of the disorder, the consequences of seizures, or the effects of antiepileptic drug treatment. Genetics may also play a contributory role. We investigated the influence of variants in the genes encoding neuron-restrictive silencer factor (NRSF) and brain-derived neurotrophic factor (BDNF), proteins previously associated with cognition and epilepsy, on cognitive function in people with newly diagnosed epilepsy. A total of 82 patients who had previously undergone detailed neuropsychological assessment were genotyped for single nucleotide polymorphisms (SNPs) across the NRSF and BDNF genes. Putatively functional SNPs were included in a genetic association analysis with specific cognitive domains, including memory, psychomotor speed, and information processing. Cross-sectional and longitudinal designs were used to explore genetic influences on baseline cognition at diagnosis and change from baseline over the first year since diagnosis, respectively. We found a statistically significant association between genotypic variation and memory function at both baseline (NRSF: rs1105434, rs2227902 and BDNF: rs1491850, rs2030324, rs11030094) and in our longitudinal analysis (NRSF: rs2227902 and BDNF: rs12273363). Psychomotor speed was also associated with genotype (NRSF rs3796529) in the longitudinal assessment. In line with our previous work on general cognitive function in the healthy aging population, we observed an additive interaction between risk alleles for the NRSF rs2227902 (G) and BDNF rs6265 (A) polymorphisms which was again consistent with a significantly greater decline in delayed recall over the first year since diagnosis. These findings support a role for the NRSF-BDNF pathway in the modulation of cognitive function in patients with newly diagnosed epilepsy.

Selective repression of gene expression in neuropathic pain by the neuron-restrictive silencing factor/repressor element-1 silencing transcription (NRSF/REST)

Neuropathic pain often develops following nerve injury as a result of maladaptive changes that occur in the injured nerve and along the nociceptive pathways of the peripheral and central nervous systems. Multiple cellular and molecular mechanisms likely account for these changes; however, the exact nature of these mechanisms remain largely unknown. A growing number of studies suggest that alteration in gene expression is an important step in the progression from acute to chronic pain states and epigenetic regulation has been proposed to drive this change in gene expression. In this review, we discuss recent evidence that the DNA-binding protein neuron-restrictive silencing factor/repressor element-1 silencing transcription factor (NRSF/REST) is an important component in the development and maintenance of neuropathic pain through its role as a transcriptional regulator for a select subset of genes that it normally represses during development.

The many faces of neuroendocrine differentiation in prostate cancer progression

In normal prostate, neuroendocrine (NE) cells are rare and interspersed among the epithelium. These cells are believed to provide trophic signals to epithelial cell populations through the secretion of an abundance of neuropeptides that can diffuse to influence surrounding cells. In the setting of prostate cancer (PC), NE cells can also stimulate surrounding prostate adenocarcinoma cell growth, but in some cases adenocarcinoma cells themselves acquire NE characteristics. This epithelial plasticity is associated with decreased androgen receptor (AR) signaling and the accumulation of neuronal and stem cell characteristics. Transformation to an NE phenotype is one proposed mechanism of resistance to contemporary AR-targeted treatments, is associated with poor prognosis, and thought to represent up to 25% of lethal PCs. Importantly, the advent of high-throughput technologies has started to provide clues for understanding the complex molecular profiles of tumors exhibiting NE differentiation. Here, we discuss these recent advances, the multifaceted manner by which an NE-like state may arise during the different stages of disease progression, and the potential benefit of this knowledge for the management of patients with advanced PC.

A C-terminal truncated mutation of spr-3 gene extends lifespan in Caenorhabditis elegans

The lifespan of Caenorhabditis elegans is determined by various genetic and environmental factors. In this paper, spr-3, a C. elegans homologous gene of the mammalian neural restrictive silencing factor (NRSF/REST), is reported to be an important gene regulating lifespan of C. elegans. A deletion mutation of spr-3, spr-3(ok2525), or RNAi inhibition of spr-3 expression led to the short lifespan phenotype in C. elegans. However, a nonsense mutation of spr-3, spr-3(by108), increased the lifespan by 26% when compared with that of wild-type nematode. The spr-3(by108) also showed increased resistance to environmental stress. The spr-3(by108) mutated gene encodes a C-terminal truncated protein with a structure comparable with the REST4, a splice variant of the NRSF/REST in mammalian. The long lifespan phenotype of spr-3(by108) mutant is confirmed as a gain of function and dependent on normal functions of daf-16 and glp-1. The lifespan of the spr-3(by108) can be synergistically enhanced by inducing a mutation in daf-2. Quantitative polymerase chain reaction results showed that the expression of daf-16 as well as its target gene sod-3, mtl-1, and sip-1 was up-regulated in the spr-3(by108) mutant. These results would be helpful to further understand the complex function of NRSF/REST gene in mammalian, especially in the aging process and longevity determination.