microRNA-132 regulates dendritic growth and arborization of newborn neurons in the adult hippocampus

Downregulation of miR-132/212 impairs S-nitrosylation balance and induces tau phosphorylation in Alzheimer's disease

MicroRNA-132 is markedly downregulated in Alzheimer's disease (AD) and related tauopathies, and its levels are closely associated with tau pathology in AD. Whether and how miR-132 contributes to pathology in these neurodegenerative diseases remains unclear. Here, we show that miR-132 and its paralogue miR-212 directly regulate the expression of neuronal nitric oxide synthase (NOS1) through the primate-specific binding site. Inhibition of miR-132 in primary human neurons and neural cells leads to increased NOS1 levels and triggers excessive production of nitric oxide, followed by aberrant S-nitrosylation (SNO) of specific proteins associated with neurodegeneration and tau pathology, such as cyclin-dependent kinase 5, dynamin-related protein 1, and glyceraldehyde-3-phosphate dehydrogenase. This, in turn, increases tau phosphorylation at disease associated Ser396, Ser404, and Ser202 sites, and impairs neural viability. Our findings indicate that downregulation of miR-132/212 disturbs the balance of S-nitrosylation and induces tau phosphorylation in a NOS1-dependent way, and thereby may contribute to the pathogenesis of AD and other tauopathies.

A role for miR-19 in the migration of adult-born neurons and schizophrenia

The latest miRNA database (Release 21) annotated 2588 and 1915 miRNAs in the human and mouse genomes, respectively.¹ However, the biological roles of miRNAs in vivo remain largely unknown. In particular, the physiological and pathological roles of individual microRNAs in the brain have not been investigated extensively although expression profiles of microRNAs have been reported in many given conditions. In a recent study,² we identified miR-19, which is enriched in adult hippocampal neural progenitor cells (NPCs), as a key regulator for adult hippocampal neurogenesis. miR-19 is an intrinsic factor regulating the migration of newborn neurons by modulating expression level of RAPGEF2. After observing the abnormal expression patterns of miR-19 and RAPGEF2 in NPCs derived from induced pluripotent stem cells of schizophrenic patients, which display aberrant cell migration, we proposed miR-19 as a molecule associated with schizophrenia. The results illustrate that a single microRNA has the potential to impact the functions of the brain. Identifying miRNA-mediated posttranscriptional gene regulation in the brain will expand our understanding of brain development and functions and the etiologies of several brain disorders.

microRNAs and the adolescent brain: Filling the knowledge gap

Over two decades ago the discovery of microRNAs (miRNA) broadened our understanding of the diverse molecular pathways mediating post-transcriptional control over gene expression. These small non-coding RNAs dynamically fluctuate, temporally and spatially, throughout the lifespan of all organisms. The fundamental role that miRNAs have in shaping embryonic neurodevelopment provides strong evidence that adolescent brain remodeling could be rooted in the changing miRNA landscape of the cell. Few studies have directly measured miRNA gene expression changes in the brain across pubertal development, and even less is known about the functional impact of those miRNAs on the maturational processes that occur in the developing adolescent brain. This review summarizes miRNA biogenesis and function in the brain in the context of normal (i.e. not diseased) physiology. These landmark studies can guide predictions about the role of miRNAs in facilitating maturation of the adolescent brain. However, there are clear indicators that adolescence/puberty is a unique life stage, suggesting miRNA function during adolescence is distinct from those in any other previously described system.

What we know about TMEM106B in neurodegeneration

Frontotemporal lobar degeneration is a neurodegenerative disorder affecting over 50,000 people in the United States alone. The most common pathological subtype of FTLD is the presence of ubiquitinated TAR DNA binding protein 43 (TDP-43) accumulations in frontal and temporal brain regions at autopsy. While some cases of FTLD-TDP can be attributed to the inheritance of disease-causing mutations, the majority of cases arise with no known genetic cause. In 2010, the first genome-wide association study was conducted in patients with FTLD-TDP to determine potential genetic risk factors for this homogenous subgroup of dementia patients, leading to the identification of the TMEM106B locus on chromosome 7. In this manuscript, we review the initial discovery and replication studies describing TMEM106B variants as disease risk factors and modifiers in TDP-43 proteinopathies, such as FTLD-TDP caused by progranulin (GRN) or chromosome 9 open reading frame 72 (C9orf72) mutations, as well as Alzheimer's disease and hippocampal sclerosis. We further summarize what is currently known about the previously uncharacterized TMEM106B protein and its role as a potential regulator of lysosomal function, and we discuss how modifying TMEM106B levels might uncover promising therapeutic strategies for individuals suffering from TDP-43 proteinopathy.

The miRNome of Alzheimer's disease: consistent downregulation of the miR-132/212 cluster

MicroRNAs (miRNAs) are small noncoding RNA molecules, with essential functions in RNA silencing and post-transcriptional regulation of gene expression. miRNAs appear to regulate the development and function of the nervous system. Alterations of miRNA expression have been associated with Alzheimer's disease (AD). To characterize the AD miRNA signature, we examined genome-wide miRNA and mRNA expression patterns in the temporal cortex of AD and control samples. We validated our miRNA results by semiquantitative real-time polymerase chain reaction (PCR) in independent prefrontal cortex. Furthermore, we separated gray and white matter brain sections to identify the cellular origin of the altered miRNA expression. We observed genome-wide downregulation of hsa-miR-132-3p and hsa-miR-212-3p in AD with a stronger decrease in gray matter AD samples. We further identified 10 differently expressed transcripts achieving genome-wide levels of significance. Significantly deregulated miRNAs and mRNAs were correlated and examined for potential binding sites (in silico). This miRNome-wide study in AD provides supportive evidence and corroborates an important contribution of miR-132/212 and corresponding target mRNAs to the pathogenesis of AD.

[Effect of a microRNA-132 antagonist on pilocarpine-induced status epilepticus in young rats]

OBJECTIVE

To study the effect of a microRNA-132 antagonist on lithium-pilocarpine-induced status epilepticus (SE) in young Sprague-Dawley (SD) rats.

METHODS

Forty-five 3-week-old SD rats were randomly and equally divided into epilepticus model group, microRNA-132 antagonist group, and microRNA-132 antagonist negative control group. The young SD rat model of SE was established using lithium-pilocarpine. For the microRNA-132 antagonist group and the negative control group, pretreatment was performed 24 hours before the model establishment. Behavioral observation was performed to assess the latency of SE and success rate of induction of SE. The scale of Lado was used to evaluate the seizure severity. Electroencephalography (EEG) was used to assess the frequency and amplitude of epileptiform discharges. The mortality rate was calculated in each group.

RESULTS

There was no significant difference in the success rate of induction of SE between the three groups (P>0.05). Compared with the microRNA-132 negative control group and the epilepticus model group, the microRNA-132 antagonist group had significantly prolonged SE latency after model establishment (P<0.05), a significantly lower Lado score of seizure (P<0.05), significantly lower frequency and amplitude of epileptiform discharges on EEG (P<0.05), and a slightly reduced mortality rate.

CONCLUSIONS

The treatment with the microRNA-132 antagonist shows an inhibitory effect on the development and progression of lithium-pilocarpine-induced SE in young SD rats. The inhibition of microRNA-132 is likely to be a potential target or direction for drug treatment of SE.

Prolonged ovarian hormone deprivation alters the effects of 17β-estradiol on microRNA expression in the aged female rat hypothalamus

Administration of 17β-estradiol (E₂) has beneficial effects on cognitive function in peri- but not post-menopausal women, yet the molecular mechanisms underlying age-related changes in E₂ action remain unclear. We propose that there is a biological switch in E₂ action that occurs coincident with age and length of time after ovarian hormone depletion, and we hypothesized that age-dependent regulation of microRNAs (miRNAs) could be the molecular basis for that switch. Previously we showed that miRNAs are regulated by E₂ in young compared to aged female rats. Here we tested whether increasing lengths of ovarian hormone deprivation in aged females altered E₂ regulation of these mature miRNAs. In addition, we determined where along the miRNA biogenesis pathway E₂ exerted its effects. Our results showed that age and increased lengths of ovarian hormone deprivation abolished the ability of E₂ to regulate mature miRNA expression in the brain. Further, we show that E₂ acted at specific points along the miRNA biogenesis pathway.

Preliminary examination of microRNA expression profiling in bipolar disorder I patients during antipsychotic treatment

Although major progress has been achieved in research and development of antipsychotic medications for bipolar disorder (BPD), knowledge of the molecular mechanisms underlying this disorder and the action of atypical antipsychotics remains incomplete. The levels of microRNAs (miRNAs)-small non-coding RNA molecules that regulate gene expression, including genes involved in neuronal function and plasticity-are frequently altered in psychiatric disorders. This study aimed to examine changes in miRNA expression in bipolar mania patients after treatment with asenapine and risperidone. Using a miRNA microarray, we analyzed miRNA expression in the blood of 10 bipolar mania patients following 12 weeks of treatment with asenapine or risperidone. Selected miRNAs were validated by using real-time PCR. A total of 16 miRNAs were differentially expressed after treatment in the asenapine group, 14 of which were significantly upregulated and the other two significantly downregulated. However, all three differentially expressed miRNAs in the risperidone group were downregulated. MiRNA target gene prediction and gene ontology analysis revealed significant enrichment for pathways associated with immune system response and regulation of programmed cell death and transcription. Our results suggest that candidate miRNAs may be involved in the mechanism of action of both antipsychotics in bipolar mania. © 2016 Wiley Periodicals, Inc.

Expressions of miR-132, miR-134, and miR-485 in rat primary motor cortex during transhemispheric functional reorganization after contralateral seventh cervical spinal nerve root transfer following brachial plexus avulsion injuries

The transfer of a contralateral healthy seventh cervical spinal nerve root (cC7) to the recipient nerve in the injured side is considered a promising procedure for restoration of the physiological functions of an injured hand after brachial plexus root avulsion injury (BPAI). Growing evidence shows that transhemispheric cortical reorganization plays an important role in the functional recovery of the injured arm after cC7 nerve transfer surgery. However, the molecular mechanism underlying the transhemispheric cortical reorganization after cC7 transfer remains elusive. In the present study, we investigated the expression of miR-132, miR-134, and miR-485 in the rat primary motor cortex after cC7 transfer following BPAI by quantitative PCR. The results demonstrated the dynamic alteration in the expression of miR-132, miR-134, and miR-485 in the primary motor cortex of rats after cC7 transfer following BPAI. It indicates that microRNAs are involved in the dynamic transhemispheric functional reorganization after cC7 root transfer following BPAI. Together, this study is the first to provide evidence for the involvement of microRNAs during dynamic transhemispheric functional reorganization after cC7 transfer following BPAI. The results are useful for understanding the mechanism underlying transhemispheric functional reorganization after contralateral seventh cervical spinal nerve root transfer following BPAI.

microRNA-132/212 deficiency enhances Aβ production and senile plaque deposition in Alzheimer's disease triple transgenic mice

The abnormal regulation of amyloid-β (Aβ) metabolism (e.g., production, cleavage, clearance) plays a central role in Alzheimer’s disease (AD). Among endogenous factors believed to participate in AD progression are the small regulatory non-coding microRNAs (miRs). In particular, the miR-132/212 cluster is severely reduced in the AD brain. In previous studies we have shown that miR-132/212 deficiency in mice leads to impaired memory and enhanced Tau pathology as seen in AD patients. Here we demonstrate that the genetic deletion of miR-132/212 promotes Aβ production and amyloid (senile) plaque formation in triple transgenic AD (3xTg-AD) mice. Using RNA-Seq and bioinformatics, we identified genes of the miR-132/212 network with documented roles in the regulation of Aβ metabolism, including Tau, Mapk, and Sirt1. Consistent with these findings, we show that the modulation of miR-132, or its target Sirt1, can directly regulate Aβ production in cells. Finally, both miR-132 and Sirt1 levels correlated with Aβ load in humans. Overall, our results support the hypothesis that the miR-132/212 network, including Sirt1 and likely other target genes, contributes to abnormal Aβ metabolism and senile plaque deposition in AD. This study strengthens the importance of miR-dependent networks in neurodegenerative disorders, and opens the door to multifactorial drug targets of AD by targeting Aβ and Tau.

Altered Levels of MicroRNA-9, -206, and -132 in Spinal Muscular Atrophy and Their Response to Antisense Oligonucleotide Therapy

The identification of noninvasive biomarkers to monitor the disease progression in spinal muscular atrophy (SMA) is becoming increasingly important. MicroRNAs (miRNAs) regulate gene expression and are implicated in the pathogenesis of neuromuscular diseases, including motor neuron degeneration. In this study, we selectively characterized the expression of miR-9, miR-206, and miR-132 in spinal cord, skeletal muscle, and serum from SMA transgenic mice, and in serum from SMA patients. A systematic analysis of miRNA expression was conducted in SMA mice with different disease severities (severe type I-like and mild type III-like) at different disease stages (pre-, mid-, and late-symptomatic stages), and in morpholino antisense oligonucleotide-treated mice. There was differential expression of all three miRNAs in spinal cord, skeletal muscle and serum samples in SMA mice. Serum miRNAs were altered prior to the changes in spinal cord and skeletal muscle at the presymptomatic stage. The altered miR-132 levels in spinal cord, muscle, and serum transiently reversed to normal level after a single-dose morpholino antisense oligomer PMO25 treatment in SMA mice. We also confirmed a significant alteration of miR-9 and miR-132 level in serum samples from SMA patients. Our study indicates the potential of developing miRNAs as noninvasive biomarkers in SMA.

Bidirectional Synaptic Structural Plasticity after Chronic Cocaine Administration Occurs through Rap1 Small GTPase Signaling

Dendritic spines are the sites of most excitatory synapses in the CNS, and opposing alterations in the synaptic structure of medium spiny neurons (MSNs) of the nucleus accumbens (NAc), a primary brain reward region, are seen at early versus late time points after cocaine administration. Here we investigate the time-dependent molecular and biochemical processes that regulate this bidirectional synaptic structural plasticity of NAc MSNs and associated changes in cocaine reward in response to chronic cocaine exposure. Our findings reveal key roles for the bidirectional synaptic expression of the Rap1b small GTPase and an associated local synaptic protein translation network in this process. The transcriptional mechanisms and pathway-specific inputs to NAc that regulate Rap1b expression are also characterized. Collectively, these findings provide a precise mechanism by which nuclear to synaptic interactions induce "metaplasticity" in NAc MSNs, and we reveal the specific effects of this plasticity on reward behavior in a brain circuit-specific manner.

Porphyromonas gingivalis-induced miR-132 regulates TNFα expression in THP-1 derived macrophages

Background

Periodontitis is a chronic inflammatory disease induced by periodontopathogens such as Porphyromonas gingivalis (P. gingivalis). MicroRNAs (miRNAs) are small single-stranded noncoding RNAs that regulate gene expression at the level of translation. MiRNAs have been reported to be involved in inflammatory processes. In this study, we examined the effects of P. gingivalis-induced inflammatory miRNAs expression on TNFα production in THP-1 derived macrophages.

Results

Porphyromonas gingivalis induced the expression of miR-132. P. gingivalis-induced miR-132 expression was significantly inhibited by TLR2/4 knock-down and NF-κB inhibitor. Additionally, miR-132 antagomir strongly repressed production of TNFα. The expression of NFE2L2 and NFAT5, the putative target genes of miR-132 involved in regulation of TNFα, decreased in response to P. gingivalis. Furthermore, miR-132 antagomir rescued P. gingivalis-induced suppression of NFE2L2 and NFAT5.

Conclusions

These results suggest that the induction of miR-132 by P. gingivalis can modulate the pathogenesis of periodontitis induced via regulatory expression of TNFα.

MicroRNA: Small RNA mediators of the brains genomic response to environmental stress

The developmental processes that establish the synaptic architecture of the brain while retaining capacity for activity-dependent remodeling, are complex and involve a combination of genetic and epigenetic influences. Dysregulation of these processes can lead to problems with neural circuitry which manifest in humans as a range of neurodevelopmental syndromes, such as schizophrenia, bipolar disorder and fragile X mental retardation. Recent studies suggest that prenatal, postnatal and intergenerational environmental factors play an important role in the aetiology of stress-related psychopathology. A number of these disorders have been shown to display epigenetic changes in the postmortem brain that reflect early life experience. These changes affect the regulation of gene expression though chromatin remodeling (transcriptional) and post-transcriptional influences, especially small noncoding microRNA (miRNA). These dynamic and influential molecules appear to play an important function in both brain development and its adaption to stress. In this review, we examine the role of miRNA in mediating the brain's response to both prenatal and postnatal environmental perturbations and explore how stress- induced alterations in miRNA expression can regulate the stress response via modulation of the immune system. Given the close relationship between environmental stress, miRNA, and brain development/function, we assert that miRNA hold a significant position at the molecular crossroads between neural development and adaptations to environmental stress. A greater understanding of the dynamics that mediate an individual's predisposition to stress-induced neuropathology has major human health benefits and is an important area of research.

MicroRNAs: Key Regulators in the Central Nervous System and Their Implication in Neurological Diseases

MicroRNAs (miRNAs) are a class of small, well-conserved noncoding RNAs that regulate gene expression post-transcriptionally. They have been demonstrated to regulate a lot of biological pathways and cellular functions. Many miRNAs are dynamically regulated during central nervous system (CNS) development and are spatially expressed in adult brain indicating their essential roles in neural development and function. In addition, accumulating evidence strongly suggests that dysfunction of miRNAs contributes to neurological diseases. These observations, together with their gene regulation property, implicated miRNAs to be the key regulators in the complex genetic network of the CNS. In this review, we first focus on the ways through which miRNAs exert the regulatory function and how miRNAs are regulated in the CNS. We then summarize recent findings that highlight the versatile roles of miRNAs in normal CNS physiology and their association with several types of neurological diseases. Subsequently we discuss the limitations of miRNAs research based on current studies as well as the potential therapeutic applications and challenges of miRNAs in neurological disorders. We endeavor to provide an updated description of the regulatory roles of miRNAs in normal CNS functions and pathogenesis of neurological diseases.

Fluorescence imaging of in vivo miR-124a-induced neurogenesis of neuronal progenitor cells using neuron-specific reporters

Background

Facilitation of the differentiation of the stem cells toward neuronal lineage is crucial for enhancing the differentiation efficacy of grafted stem cells for the possible treatment of neurodegenerative disorders. MicroRNA124a (miR-124a) has been considered as a neuronal lineage regulator, possessing the capability to activate neuronal differentiation. In this study, using a neuronal promoter-based reporter and live-cell fluorescence imaging, we visualized in vitro and in vivo the enhanced neuronal differentiation of neuronal progenitor cells with miR-124a overproduction.

Methods

The neuron specific alpha1 tubulin promoter-driven RFP reporter (pTa1-RFP) was used to trace the miR-124a-induced neuronal differentiation in live cell condition. MiR-124a or miR-scramble in 10 % glucose buffer was mixed with in vivo-jetPEITM and in vivo fluorescence images were obtained daily using Maestro spectral fluorescent imager.

Results

Neurite outgrowth was clearly seen in F11 cells after miR-124a transfection, and immunofluorescence staining showed increase of Tuj1 and NF at 48 hours. When pTa1-RFP-transfected F11 cells were implanted simultaneously with miR-124a into the nude mice, gradually increasing reporter signals and morphological changes indicated neuronal differentiation for 48 hours in live cells in vitro. The miR-124a-treated F11 cells showed higher reporter signals on in vivo fluorescence imaging than miR-scramble-treated cells, which were verified by ex vivo confirmation of Tuj1 and NF expression.

Conclusions

These results indicated that neuronal reporter-based neurogenesis imaging can be used for monitoring miR-124a acting as neuronal activator when miRNA was injected in in vivo PEI-coated form for miRNA-mediated regenerative therapy.

MiR-132 Is Upregulated by Ischemic Preconditioning of Cultured Hippocampal Neurons and Protects them from Subsequent OGD Toxicity

We explored the response of a panel of selected microRNAs (miRNAs) in neuroprotection produced by ischemic preconditioning. Hippocampal neuronal cultures were exposed to a 30-min oxygen-glucose deprivation (OGD). In our hands, this duration of OGD does not result in neuronal loss in vitro but significantly reduces neuronal death from a subsequent 'lethal' OGD insult. RT-qPCR was used to determine the expression of 16 miRNAs of interest at 1 and 24-h post-OGD. One miRNA (miR-98) was significantly decreased at 1-h post-OGD. Ten miRNAs (miR-9, miR-21, miR-29b, miR-30e, miR-101a, miR-101b, miR-124a, miR-132, miR-153, miR-204) were increased significantly at 24-h post-OGD. No miRNAs were decreased at 24-h. The increases observed in the 24-h group suggested that these miRNAs might play a role in preconditioning-induced neuroprotection. We selected the widely studied miR-132, a brain enriched, CREB regulated miRNA, to explore its role in simulated ischemic insults. We found that hippocampal neurons transduced with lentiviral vectors expressing miR-132 were protected from OGD and NMDA treatment, but not hydrogen peroxide. These findings add to the growing literature that targeting neuroprotective pathways controlled by miRNAs may represent a therapeutic strategy for the treatment of ischemic brain injury.

CREB-regulated transcription coactivator 1 enhances CREB-dependent gene expression in spinal cord to maintain the bone cancer pain in mice

Background

cAMP response element binding protein (CREB)-dependent gene expression plays an important role in central sensitization. CREB-regulated transcription coactivator 1 (CRTC1) dramatically increases CREB-mediated transcriptional activity. Brain-derived neurotrophic factor, N-methyl-d-aspartate receptor subunit 2B, and miRNA-212/132, which are highly CREB responsive, function downstream from CREB/CRTC1 to mediate activity-dependent synaptic plasticity and in turn loops back to amplify CREB/CRTC1 signaling. This study aimed to investigate the role of spinal CRTC1 in the maintenance of bone cancer pain using an RNA interference method.

Results

Osteosarcoma cells were implanted into the intramedullary space of the right femurs of C3H/HeNCrlVr mice to induce bone cancer pain. Western blotting was applied to examine the expression of spinal phospho-Ser133 CREB and CRTC1. We further investigated effects of repeated intrathecal administration with Adenoviruses expressing CRTC1-small interfering RNA (siRNA) on nociceptive behaviors and on the upregulation of CREB/CRTC1-target genes associated with bone cancer pain. Inoculation of osteosarcoma cells induced progressive mechanical allodynia and spontaneous pain, and resulted in upregulation of spinal p-CREB and CRTC1. Repeated intrathecal administration with Adenoviruses expressing CRTC1-siRNA attenuated bone cancer–evoked pain behaviors, and reduced CREB/CRTC1-target genes expression in spinal cord, including BDNF, NR2B, and miR-212/132.

Conclusions

Upregulation of CRTC1 enhancing CREB-dependent gene transcription in spinal cord may play an important role in bone cancer pain. Inhibition of spinal CRTC1 expression reduced bone cancer pain. Interruption to the positive feedback circuit between CREB/CRTC1 and its targets may contribute to the analgesic effects. These findings may provide further insight into the mechanisms and treatment of bone cancer pain.

Non-coding RNAs as Emerging Regulators of Neural Injury Responses and Regeneration

Non-coding RNAs (ncRNAs) are a large cluster of RNAs that do not encode proteins, but have multiple functions in diverse cellular processes. Mounting evidence indicates the involvement of ncRNAs in the physiology and pathophysiology of the central and peripheral nervous systems. It has been shown that numerous ncRNAs, especially microRNAs and long non-coding RNAs, are differentially expressed after insults such as acquired brain injury, spinal cord injury, and peripheral nerve injury. These ncRNAs affect neuronal survival, neurite regrowth, and glial phenotype primarily by targeting specific mRNAs, resulting in translation repression or degradation of the mRNAs. An increasing number of studies have investigated the regulatory roles of microRNAs and long non-coding RNAs in neural injury and regeneration, and thus a new research field is emerging. In this review, we highlight current progress in the field in an attempt to provide further insight into post-transcriptional changes occurring after neural injury, and to facilitate the potential use of ncRNAs for improving neural regeneration. We also suggest potential directions for future studies.

Phosphorylation of Ago2 and Subsequent Inactivation of let-7a RNP-Specific MicroRNAs Control Differentiation of Mammalian Sympathetic Neurons

MicroRNAs (miRNAs) are small regulatory RNAs that regulate gene expression posttranscriptionally by base pairing to the target mRNAs in animal cells. KRas, an oncogene known to be repressed by let-7a miRNAs, is expressed and needed for the differentiation of mammalian sympathetic neurons and PC12 cells. We documented a loss of let-7a activity during this differentiation process without any significant change in the cellular level of let-7a miRNA. However, the level of Ago2, an essential component that is associated with miRNAs to form RNP-specific miRNA (miRNP) complexes, shows an increase with neuronal differentiation. In this study, differentiation-induced phosphorylation and the subsequent loss of miRNA from Ago2 were noted, and these accounted for the loss of miRNA activity in differentiating neurons. Neuronal differentiation induces the phosphorylation of mitogen-activated protein kinase p38 and the downstream kinase mitogen- and stress-activated protein kinase 1 (MSK1). This in turn upregulates the phosphorylation of Ago2 and ensures the dissociation of miRNA from Ago2 in neuronal cells. MSK1-mediated miRNP inactivation is a prerequisite for the differentiation of neuronal cells, where let-7a miRNA gets unloaded from Ago2 to ensure the upregulation of KRas, a target of let-7a. We noted that the inactivation of let-7a is both necessary and sufficient for the differentiation of sympathetic neurons.

miR-132 targeting E2F5 suppresses cell proliferation, invasion, migration in ovarian cancer cells

Accumulating evidence showed that microRNA-132 (miR-132) are involved in development and progression of several types of cancers, however, the function and underlying molecular mechanism of miR-132 in ovarian cancer remains unclear. In this study we investigated the biological roles and molecular mechanism of miR-132 in ovarian cancer. Here, we found that that the expression levels of miR-132 were dramatically decreased in ovarian cancer cell lines and clinical ovarian cancer tissue samples. Then, we found that introduction of miR-132 significantly suppressed the proliferation, colony formation, migration and invasion of ovarian cancer cells. Mechanism investigation revealed that miR-132 inhibited the expression of transcription factor E2F5 by specifically targeting its mRNA 3'UTR. Moreover, the expression level of E2F5 was significantly increased in ovarian cancer tissues than in the adjacent normal tissues, and its expression was inversely correlated with miR-132 expression in clinical ovarian cancer tissues. Additionally, silencing E2F5 was able to inhibit the proliferation, colony formation, migration and invasion of ovarian cancer cells, parallel to the effect of miR-132 overexpression on the ovarian cancer cells. Meanwhile, overexpression of E2F5 reversed the inhibition effect mediated by miR-132 overexpression. These results indicate that miR-132 suppresses the cell proliferation, invasion, migration in ovarian cancer cells by targeting E2F5.

Role of MicroRNA in Governing Synaptic Plasticity

Although synaptic plasticity in neural circuits is orchestrated by an ocean of genes, molecules, and proteins, the underlying mechanisms remain poorly understood. Recently, it is well acknowledged that miRNA exerts widespread regulation over the translation and degradation of target gene in nervous system. Increasing evidence suggests that quite a few specific miRNAs play important roles in various respects of synaptic plasticity including synaptogenesis, synaptic morphology alteration, and synaptic function modification. More importantly, the miRNA-mediated regulation of synaptic plasticity is not only responsible for synapse development and function but also involved in the pathophysiology of plasticity-related diseases. A review is made here on the function of miRNAs in governing synaptic plasticity, emphasizing the emerging regulatory role of individual miRNAs in synaptic morphological and functional plasticity, as well as their implications in neurological disorders. Understanding of the way in which miRNAs contribute to synaptic plasticity provides rational clues in establishing the novel therapeutic strategy for plasticity-related diseases.

The loop structure and the RNA helicase p72/DDX17 influence the processing efficiency of the mice miR-132

miRNAs are small RNAs that are key regulators of gene expression in eukaryotic organisms. The processing of miRNAs is regulated by structural characteristics of the RNA and is also tightly controlled by auxiliary protein factors. Among them, RNA binding proteins play crucial roles to facilitate or inhibit miRNA maturation and can be controlled in a cell, tissue and species-specific manners or in response to environmental stimuli. In this study we dissect the molecular mechanism that promotes the overexpression of miR-132 in mice over its related, co-transcribed and co-regulated miRNA, miR-212. We have shown that the loop structure of miR-132 is a key determinant for its efficient processing in cells. We have also identified a range of RNA binding proteins that recognize the loop of miR-132 and influence both miR-132 and miR-212 processing. The DEAD box helicase p72/DDX17 was identified as a factor that facilitates the specific processing of miR-132.

Positive feedback regulation between microRNA-132 and CREB in spinal cord contributes to bone cancer pain in mice

BACKGROUND

cAMP response element-binding protein (CREB)-dependent gene expression plays an important role in central sensitization. CREB-regulated transcription coactivator 1 (CRTC1) dramatically increase CREB-mediated transcriptional activity. microRNA-132 (miR-132), which is highly CREB-responsive, functions downstream from CREB/CRTC1 to mediate activity-dependent synaptic plasticity and in turn loops back to amplify CREB/CRTC1 signalling. This study aimed to investigate the positive feedback regulation between miR-132 and CREB in spinal cord in the maintenance of bone cancer pain.

METHODS

Osteosarcoma cells were implanted into the intramedullary space of the right femurs of C3H/HeNCrlVr mice to induce bone cancer pain. We further investigated effects of repeated intrathecal administration with Adenoviruses expressing CREB-siRNA or miR-132 antisense locked nucleic acid (LNA), respectively, on nociceptive behaviours and on the activity of CREB/CRTC1 signalling.

RESULTS

Intramedullary inoculation of osteosarcoma cells resulted in up-regulation of spinal p-CREB, CRTC1 and CREB-target genes (NR2B and miR-132). Repeated intrathecal administration with Adenoviruses expressing CREB-siRNA or miR-132 LNA-AS, respectively, attenuated bone cancer-evoked pain behaviours, reduced the activity of CREB/CRTC1 signalling and down-regulated CREB-target gene NR2B expression in spinal cord.

CONCLUSIONS

These findings suggest that activation of spinal CREB/CRTC1 signalling may play an important role in bone cancer pain. Interruption to the positive feedback regulation between CREB/CRTC1 and its target gene miR-132 can effectively relieved the bone cancer-induced mechanical allodynia and spontaneous pain. WHAT DOES THIS STUDY ADD?: The positive feedback regulation between CREB/CRTC1 and its target gene miR-132 in spinal cord plays an important role in bone cancer pain.

Decoding the ubiquitous role of microRNAs in neurogenesis

Neurogenesis generates fledgling neurons that mature to form an intricate neuronal circuitry. The delusion on adult neurogenesis was far resolved in the past decade and became one of the largely explored domains to identify multifaceted mechanisms bridging neurodevelopment and neuropathology. Neurogenesis encompasses multiple processes including neural stem cell proliferation, neuronal differentiation, and cell fate determination. Each neurogenic process is specifically governed by manifold signaling pathways, several growth factors, coding, and non-coding RNAs. A class of small non-coding RNAs, microRNAs (miRNAs), is ubiquitously expressed in the brain and has emerged to be potent regulators of neurogenesis. It functions by fine-tuning the expression of specific neurogenic gene targets at the post-transcriptional level and modulates the development of mature neurons from neural progenitor cells. Besides the commonly discussed intrinsic factors, the neuronal morphogenesis is also under the control of several extrinsic temporal cues, which in turn are regulated by miRNAs. This review enlightens on dicer controlled switch from neurogenesis to gliogenesis, miRNA regulation of neuronal maturation and the differential expression of miRNAs in response to various extrinsic cues affecting neurogenesis.

Reciprocal regulation of autism-related genes MeCP2 and PTEN via microRNAs

MeCP2 encodes a methyl-CpG-binding protein that plays a critical role in repressing gene expression, mutations of which lead to Rett syndrome and autism. PTEN is a critical tumor suppressor gene that is frequently mutated in human cancers and autism spectrum disorders. Various studies have shown that both MeCP2 and PTEN proteins play important roles in brain development. Here we find that MeCP2 and PTEN reciprocally regulate expression of each other via microRNAs. Knockdown of MeCP2 leads to upregulation of microRNA-137, which in turn represses expression of PTEN, thus PTEN would be down-regulated when MeCP2 is knockdown. Furthermore, we find that deletion of PTEN leads to phosphorylation of Serine 133 of CREB, then increases the expression of microRNA-132. miR-132 inhibits the expression of MeCP2 by targeting on the 3'UTR of MeCP2 mRNA. Our work shows that two critical disorders-related gene MeCP2 and PTEN reciprocally regulate expression of each other by distinct mechanisms, suggesting that rare mutations in various disorders may lead to dysregulation of other critical genes and yield unexpected consequences.

The Ever-Changing Morphology of Hippocampal Granule Neurons in Physiology and Pathology

Newborn neurons are continuously added to the hippocampal dentate gyrus throughout adulthood. In this review, we analyze the maturational stages that newborn granule neurons go through, with a focus on their unique morphological features during each stage under both physiological and pathological circumstances. In addition, the influence of deleterious (such as schizophrenia, stress, Alzheimer's disease, seizures, stroke, inflammation, dietary deficiencies, or the consumption of drugs of abuse or toxic substances) and neuroprotective (physical exercise and environmental enrichment) stimuli on the maturation of these cells will be examined. Finally, the regulation of this process by proteins involved in neurodegenerative and neurological disorders such as Glycogen synthase kinase 3β, Disrupted in Schizophrenia 1 (DISC-1), Glucocorticoid receptor, pro-inflammatory mediators, Presenilin-1, Amyloid precursor protein, Cyclin-dependent kinase 5 (CDK5), among others, will be evaluated. Given the recently acquired relevance of the dendritic branch as a functional synaptic unit required for memory storage, a full understanding of the morphological alterations observed in newborn neurons may have important consequences for the prevention and treatment of the cognitive and affective alterations that evolve in conjunction with impaired adult hippocampal neurogenesis.

Targeted deletion of miR-132/-212 impairs memory and alters the hippocampal transcriptome

miR-132 and miR-212 are structurally related microRNAs that have been found to exert powerful modulatory effects within the central nervous system (CNS). Notably, these microRNAs are tandomly processed from the same noncoding transcript, and share a common seed sequence: thus it has been difficult to assess the distinct contribution of each microRNA to gene expression within the CNS. Here, we employed a combination of conditional knockout and transgenic mouse models to examine the contribution of the miR-132/-212 gene locus to learning and memory, and then to assess the distinct effects that each microRNA has on hippocampal gene expression. Using a conditional deletion approach, we show that miR-132/-212 double-knockout mice exhibit significant cognitive deficits in spatial memory, recognition memory, and in tests of novel object recognition. Next, we utilized transgenic miR-132 and miR-212 overexpression mouse lines and the miR-132/-212 double-knockout line to explore the distinct effects of these two miRNAs on the transcriptional profile of the hippocampus. Illumina sequencing revealed that miR-132/-212 deletion increased the expression of 1138 genes; Venn analysis showed that 96 of these genes were also downregulated in mice overexpressing miR-132. Of the 58 genes that were decreased in animals overexpressing miR-212, only four of them were also increased in the knockout line. Functional gene ontology analysis of downregulated genes revealed significant enrichment of genes related to synaptic transmission, neuronal proliferation, and morphogenesis, processes known for their roles in learning, and memory formation. These data, coupled with previous studies, firmly establish a role for the miR-132/-212 gene locus as a key regulator of cognitive capacity. Further, although miR-132 and miR-212 share a seed sequence, these data indicate that these miRNAs do not exhibit strongly overlapping mRNA targeting profiles, thus indicating that these two genes may function in a complex, nonredundant manner to shape the transcriptional profile of the CNS. The dysregulation of miR-132/-212 expression could contribute to signaling mechanisms that are involved in an array of cognitive disorders.

The Ins and Outs of miRNA-Mediated Gene Silencing during Neuronal Synaptic Plasticity

Neuronal connections through specialized junctions, known as synapses, create circuits that underlie brain function. Synaptic plasticity, i.e., structural and functional changes to synapses, occurs in response to neuronal activity and is a critical regulator of various nervous system functions, including long-term memory formation. The discovery of mRNAs, miRNAs, ncRNAs, ribosomes, translational repressors, and other RNA binding proteins in dendritic spines allows individual synapses to alter their synaptic strength rapidly through regulation of local protein synthesis in response to different physiological stimuli. In this review, we discuss our understanding of a number of miRNAs, ncRNAs, and RNA binding proteins that are emerging as important regulators of synaptic plasticity, which play a critical role in memory, learning, and diseases that arise when neuronal circuits are impaired.

The miR-132/212 locus: a complex regulator of neuronal plasticity, gene expression and cognition

The microRNA (miRNA) class of small (typically 22-24 nt) non-coding RNA affects a wide range of physiological processes in the mammalian central nervous system (CNS). By acting as potent regulators of mRNA translation and stability, miRNAs fine-tune the expression of a multitude of genes that play critical roles in complex cognitive processes, including learning and memory. Of note, within the CNS, miRNAs can be expressed in an inducible, and cell-type specific manner. Here, we provide a brief overview of the expression and functional effects of the miR-132/212 gene locus in forebrain circuits of the CNS, and then discuss a recent publication that explored the contributions of miR-132 and miR-212 to cognition and to transcriptome regulation. We also discuss mechanisms by which synaptic activity regulates miR-132/212 expression, how miR-132 and miR-212 affect neuronal plasticity, and how the dysregulation of these two miRNAs could contribute to the development of cognitive impairments.

Circulating microRNA 132-3p and 324-3p Profiles in Patients after Acute Aneurysmal Subarachnoid Hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (SAH) is a highly morbid and fatal condition with high rate of cognitive impairment and negative impact in quality of life among survivors. Delayed cerebral infarction (DCI) is one the major factors for these negative outcomes. In this study we compared the circulating microRNA profiles of SAH patients and healthy individuals, and the circulating microRNA profiles of SAH patients with and without DCI.

Methods

Peripheral blood samples on Day 7 after the onset of SAH were subjected to microarray analysis with Affymetrix miRNA 3.0 array and quantitative PCR analysis. SAH patients with (N = 20) and without DCI (N = 20) and Healthy controls (N = 20) were included for analyses.

Results

We demonstrated that 99 miRNAs were found to be dysregulated in the SAH patient group with DCI. 81 miRNAs were upregulated and 18 were downregulated. Findings from KEGG pathway analysis showed that miRNAs and target genes for axon guidance and TGF-beta signaling were involved, implying that the resulted differential miRNA expression pattern reflect the results of SAH instead of etiology of the disease. miR-132-3p and miR-324-3p showed distinctive upregulations in qPCR [miR-132: 9.5 fold (95%CI: 2.3 to 16.7) in DCI group and 3.4 fold (95%CI: 1.0 to 5.8) in Non-DCI group; miR-324: 4924 fold (95%CI: 2620 to 7228) in DCI group and 4545 fold (95%CI: 2408 to 6683) in non-DCI group]. However, there were no significant differences in fold changes between SAH patients with and without DCI [fold change ratios (mean+/-SD): 2.7+/-4.2 and 1.1+/-1.1 for miRNA-132 and miRNA-324].

Conclusion

Our study demonstrated that as compared to healthy control, miR-132 and miR-324 showed a upregulation in both SAH DCI and Non-DCI groups. However, the differences between the SAH DCI and non-DCI groups were not statistically significant.

MicroRNA abundance is altered in synaptoneurosomes during prion disease

Discrepancy in synaptic structural plasticity is one of the earliest manifestations of the neurodegenerative state. In prion diseases, a reduction in synapses and dendritic spine densities is observed during preclinical disease in neurons of the cortex and hippocampus. The underlying molecular mechanisms of these alterations have not been identified but microRNAs (miRNAs), many of which are enriched at the synapse, likely regulate local protein synthesis in rapid response to stressors such as replicating prions. MiRNAs are therefore candidate regulators of these early neurodegenerative changes and may provide clues as to the molecular pathways involved. We therefore determined changes in mature miRNA abundance within synaptoneurosomes isolated from prion-infected, as compared to mock-infected animals, at asymptomatic and symptomatic stages of disease. During preclinical disease, miRNAs that are enriched in neurons including miR-124a-3p, miR-136-5p and miR-376a-3p were elevated. At later stages of disease we found increases in miRNAs that have previously been identified as deregulated in brain tissues of prion infected mice, as well as in Alzheimer's disease (AD) models. These include miR-146a-5p, miR-142-3p, miR-143-3p, miR-145a-5p, miR-451a, miR-let-7b, miR-320 and miR-150-5p. A number of miRNAs also decreased in abundance during clinical disease. These included almost all members of the related miR-200 family (miR-200a-3p, miR-200b-3p, miR-200c-3p, miR-141-3p, and miR-429-3p) and the 182 cluster (miR-182-5p and miR-183-5p).

miR-132/212 deficiency impairs tau metabolism and promotes pathological aggregation in vivo

Alzheimer's disease (AD) and related tauopathies comprise a large group of neurodegenerative diseases associated with the pathological aggregation of tau protein. While much effort has focused on understanding the function of tau, little is known about the endogenous mechanisms regulating tau metabolism in vivo and how these contribute to disease. Previously, we have shown that the microRNA (miRNA) cluster miR-132/212 is downregulated in tauopathies such as AD. Here, we report that miR-132/212 deficiency in mice leads to increased tau expression, phosphorylation and aggregation. Using reporter assays and cell-based studies, we demonstrate that miR-132 directly targets tau mRNA to regulate its expression. We identified GSK-3β and PP2B as effectors of abnormal tau phosphorylation in vivo. Deletion of miR-132/212 induced tau aggregation in mice expressing endogenous or human mutant tau, an effect associated with autophagy dysfunction. Conversely, treatment of AD mice with miR-132 mimics restored in part memory function and tau metabolism. Finally, miR-132 and miR-212 levels correlated with insoluble tau and cognitive impairment in humans. These findings support a role for miR-132/212 in the regulation of tau pathology in mice and humans and provide new alternatives for therapeutic development.

Micro-RNAs in cognition and cognitive disorders: Potential for novel biomarkers and therapeutics

Micro-RNAs (miRNAs) are small regulatory non-coding RNAs involved in the regulation of many biological functions. In the brain, they have distinct expression patterns depending on region, cell-type and developmental stage. Their expression profile is altered by neuronal activation in response to behavioral training or chemical/electrical stimulation. The dynamic changes in miRNA level regulate the expression of genes required for cognitive processes such as learning and memory. In addition, in cognitive dysfunctions such as dementias, expression levels of many miRNAs are perturbed, not only in brain areas affected by the pathology, but also in peripheral body fluids such as serum and cerebrospinal fluid. This presents an opportunity to utilize miRNAs as biomarkers for early detection and assessment of cognitive dysfunctions. Further, since miRNAs target many genes and pathways, they may represent key molecular signatures that can help understand the mechanisms of cognitive disorders and the development of potential therapeutic agents.

MicroRNAs: Not "Fine-Tuners" but Key Regulators of Neuronal Development and Function

MicroRNAs (miRNAs) are a class of short non-coding RNAs that operate as prominent post-transcriptional regulators of eukaryotic gene expression. miRNAs are abundantly expressed in the brain of most animals and exert diverse roles. The anatomical and functional complexity of the brain requires the precise coordination of multilayered gene regulatory networks. The flexibility, speed, and reversibility of miRNA function provide precise temporal and spatial gene regulatory capabilities that are crucial for the correct functioning of the brain. Studies have shown that the underlying molecular mechanisms controlled by miRNAs in the nervous systems of invertebrate and vertebrate models are remarkably conserved in humans. We endeavor to provide insight into the roles of miRNAs in the nervous systems of these model organisms and discuss how such information may be used to inform regarding diseases of the human brain.

MicroRNAs 99b-5p/100-5p Regulated by Endoplasmic Reticulum Stress are Involved in Abeta-Induced Pathologies

Alzheimer's disease (AD) is the most common cause of dementia. Amyloid β (Abeta, Aβ) deposition and intracellular tangles are the pathological hallmarks of AD. MicroRNAs (miRNAs) are small non-coding RNAs, which have been found to play very important roles, and have the potential to serve as diagnostic markers during neuronal pathogenesis. In this study, we aimed to determine the roles of miR-99b-5p and miR-100-5p in Aβ-induced neuronal pathologies. We detected the expression levels of miR-99b-5p and miR-100-5p in the brains of APPswe/PS1ΔE9 double-transgenic mice (APP/PS1 mice) at different age stages and found that both miRNAs were decreased at early stages while increased at late stages of APP/PS1 mice when compared with the age-matched wild type (WT) mice. Similar phenomenon was also observed in Aβ-treated cultured cells. We also confirmed that mammalian target of rapamycin (mTOR) is one of the targets of miR-99b-5p/100-5p, which is consistent with previous studies in cancer. MiR-99b-5p/100-5p has been found to promote cell apoptosis with the Aβ treatment. This effect may be induced via the mTOR pathway. In our study, we find both miR-99b-5p and miR-100-5p affect neuron survival by targeting mTOR. We also speculate that dynamic change of miR-99b-5p/100-5p levels during Aβ-associated pathologies might be attributed to Aβ-induced endoplasmic reticulum stress (ER stress), suggesting the potential role of the "ER stress-miRNAs-mTOR" axis in Aβ-related AD pathogenesis.

Transdifferentiation of periodontal ligament-derived stem cells into retinal ganglion-like cells and its microRNA signature

Retinal diseases are the leading causes of irreversible visual impairment and blindness in the developed countries. Human retina has limited regenerative power to replace cell loss. Stem cell replacement therapy has been proposed as a viable option. Previously, we have induced human adult periodontal ligament stem cells (PDLSCs) to the retinal lineage. In this study, we modified our induction protocol to direct human adult PDLSCs into retinal ganglion-like cells and determined the microRNA (miRNA) signature of this transdifferentiation process. The differentiated PDLSCs demonstrated the characteristics of functional neurons as they expressed neuronal and retinal ganglion cell markers (ATOH7, POU4F2, β-III tubulin, MAP2, TAU, NEUROD1 and SIX3), formed synapses and showed glutamate-induced calcium responses as well as spontaneous electrical activities. The global miRNA expression profiling identified 44 upregulated and 27 downregulated human miRNAs after retinal induction. Gene ontology analysis of the predicted miRNA target genes confirmed the transdifferentiation is closely related to neuronal differentiation processes. Furthermore, the expressions of 2 miRNA-targeted candidates, VEGF and PTEN, were significantly upregulated during the induction process. This study identified the transdifferentiation process of human adult stem cells into retinal ganglion-like cells and revealed the involvement of both genetic and miRNA regulatory mechanisms.

Network analysis of microRNA and mRNA seasonal dynamics in a highly plastic sensorimotor neural circuit

Background

Adult neurogenesis and the incorporation of adult-born neurons into functional circuits requires precise spatiotemporal coordination across molecular networks regulating a wide array of processes, including cell proliferation, apoptosis, neurotrophin signaling, and electrical activity. MicroRNAs (miRs) - short, non-coding RNA sequences that alter gene expression by post-transcriptional inhibition or degradation of mRNA sequences - may be involved in the global coordination of such diverse biological processes. To test the hypothesis that miRs related to adult neurogenesis and related cellular processes are functionally regulated in the nuclei of the avian song control circuit, we used microarray analyses to quantify changes in expression of miRs and predicted target mRNAs in the telencephalic nuclei HVC, the robust nucleus of arcopallium (RA), and the basal ganglia homologue Area X in breeding and nonbreeding Gambel’s white-crowned sparrows (Zonotrichia leucophrys gambelli).

Results

We identified 46 different miRs that were differentially expressed across seasons in the song nuclei. miR-132 and miR-210 showed the highest differential expression in HVC and Area X, respectively. Analyzing predicted mRNA targets of miR-132 identified 33 candidate target genes that regulate processes including cell cycle control, calcium signaling, and neuregulin signaling in HVC. Likewise, miR-210 was predicted to target 14 mRNAs differentially expressed across seasons that regulate serotonin, GABA, and dopamine receptor signaling and inflammation.

Conclusions

Our results identify potential miR–mRNA regulatory networks related to adult neurogenesis and provide opportunities to discover novel genetic control of the diverse biological processes and factors related to the functional incorporation of new neurons to the adult brain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2175-z) contains supplementary material, which is available to authorized users.

Evidence for a neuroprotective microRNA pathway in amnestic mild cognitive impairment

MicroRNAs (miRNAs) that regulate mRNA stability have been linked to amyloid production, tau phosphorylation, and inflammation in Alzheimer's disease (AD). However, whether cerebral miRNA networks are dysregulated during the earliest stages of AD remains underexplored. We performed miRNA expression analysis using frontal cortex tissue harvested from subjects who died with a clinical diagnosis of no cognitive impairment (NCI), amnestic mild cognitive impairment (aMCI, a putative prodromal AD stage), or mild AD. Analysis revealed that the miRNA clusters miR-212/132 and miR-23a/23b were down-regulated in the frontal cortex of aMCI subjects. Both miR-212/132 and miR23a/b are predicted to destabilize the message for sirtuin 1 (sirt1); hence, down-regulation of either miR-212/132 or miR-23a/b in frontal cortex should promote sirt1 mRNA expression in this region. qPCR studies revealed that frontal cortex levels of sirt1 were increased in aMCI. Given the ability of frontal cortex to respond to the onset of dementia by neuronal reorganization, these data suggest that miRNA-mediated up-regulation of the sirt1 pathway represents a compensatory response to the onset of the disease. By contrast, qPCR analysis of inferior temporal cortex, an area affected early in the progression of AD, showed no changes in miR-212/132, miR-23a/b, or sirt1 transcripts in the same aMCI subjects. In vitro mechanistic studies showed that coordinated down-regulation of miR-212 and miR-23a increased sirt1 protein expression and provided neuroprotection from β-amyloid toxicity in human neuronal cells. Taken together, these data suggest a novel miRNA-mediated neuroprotective pathway activated during the progression of AD that may be amenable to therapeutic manipulation.

miRNAs: biological and clinical determinants in epilepsy

Recently, microRNAs (miRNAs) are reported to be crucial modulators in the pathogenesis and potential treatment of epilepsies. To date, several miRNAs have been demonstrated to be significantly expressed in the epileptic tissues and strongly associated with the development of epilepsy. Specifically, miRNAs regulate synaptic strength, inflammation, neuronal and glial function, ion channels, and apoptosis. Furthermore, peripheral blood miRNAs can also be utilized as diagnostic biomarkers to assess disease risk and treatment responses. Here, we will summarize the recent available literature regarding the role of miRNAs in the pathogenesis and treatment of epilepsy. Moreover, we will provide brief insight into the potential of miRNA as diagnostic biomarkers for early diagnosis and prognosis of epilepsy.

Neonatal Irradiation Leads to Persistent Proteome Alterations Involved in Synaptic Plasticity in the Mouse Hippocampus and Cortex

Recent epidemiological data indicate that radiation doses as low as those used in computer tomography may result in long-term neurocognitive side effects. The aim of this study was to elucidate long-term molecular alterations related to memory formation in the brain after low and moderate doses of γ radiation. Female C57BL/6J mice were irradiated on postnatal day 10 with total body doses of 0.1, 0.5, or 2.0 Gy; the control group was sham-irradiated. The proteome analysis of hippocampus, cortex, and synaptosomes isolated from these brain regions indicated changes in ephrin-related, RhoGDI, and axonal guidance signaling. Immunoblotting and miRNA-quantification demonstrated an imbalance in the synapse morphology-related Rac1-Cofilin pathway and long-term potentiation-related cAMP response element-binding protein (CREB) signaling. Proteome profiling also showed impaired oxidative phosphorylation, especially in the synaptic mitochondria. This was accompanied by an early (4 weeks) reduction of mitochondrial respiration capacity in the hippocampus. Although the respiratory capacity was restored by 24 weeks, the number of deregulated mitochondrial complex proteins was increased at this time. All observed changes were significant at doses of 0.5 and 2.0 Gy but not at 0.1 Gy. This study strongly suggests that ionizing radiation at the neonatal state triggers persistent proteomic alterations associated with synaptic impairment.

RNA-Binding Proteins in the Regulation of miRNA Activity: A Focus on Neuronal Functions

Posttranscriptional modifications of messenger RNAs (mRNAs) are key processes in the fine-tuning of cellular homeostasis. Two major actors in this scenario are RNA binding proteins (RBPs) and microRNAs (miRNAs) that together play important roles in the biogenesis, turnover, translation and localization of mRNAs. This review will highlight recent advances in the understanding of the role of RBPs in the regulation of the maturation and the function of miRNAs. The interplay between miRNAs and RBPs is discussed specifically in the context of neuronal development and function.

miR-132 Regulates Dendritic Spine Structure by Direct Targeting of Matrix Metalloproteinase 9 mRNA

Mir-132 is a neuronal activity-regulated microRNA that controls the morphology of dendritic spines and neuronal transmission. Similar activities have recently been attributed to matrix metalloproteinase-9 (MMP-9), an extrasynaptic protease. In the present study, we provide evidence that miR-132 directly regulates MMP-9 mRNA in neurons to modulate synaptic plasticity. With the use of luciferase reporter system, we show that miR-132 binds to the 3’UTR of MMP-9 mRNA to regulate its expression in neurons. The overexpression of miR-132 in neurons reduces the level of endogenous MMP-9 protein secretion. In synaptoneurosomes, metabotropic glutamate receptor (mGluR)-induced signaling stimulates the dissociation of miR-132 from polyribosomal fractions and shifts it towards the messenger ribonucleoprotein (mRNP)-containing fraction. Furthermore, we demonstrate that the overexpression of miR-132 in the cultured hippocampal neurons from Fmr1 KO mice that have increased synaptic MMP-9 level provokes enlargement of the dendritic spine heads, a process previously implicated in enhanced synaptic plasticity. We propose that activity-dependent miR-132 regulates structural plasticity of dendritic spines through matrix metalloproteinase 9.

MicroRNA-132 promotes estradiol synthesis in ovarian granulosa cells via translational repression of Nurr1

BACKGROUND

Estrogen synthesis is an important function of the mammalian ovary. Estrogen plays important roles in many biological processes, including follicular development, oocyte maturation and endometrial proliferation, and dysfunctions in estrogen synthesis contribute to the development of polycystic ovary syndrome and premature ovarian failure. Classical signaling cascades triggered by follicle-stimulating hormone induce estrogen synthesis via the upregulation of Cyp19a1 in granulosa cells (GCs). This study aimed to determine the effect of microRNA-132 (miR-132) on estradiol synthesis in GCs.

METHODS

Primary mouse GCs were collected from ovaries of 21-day-old immature ICR mice through follicle puncture. GCs were cultured and treated with the stable cyclic adenosine monophosphate analog 8-Br-cAMP or transfected with miR-132 mimics, Nurr1-specific small interfering RNA oligonucleotides and Flag-Nurr1 plasmids. Concentrations of estradiol and progesterone in culture medium were determined by an automated chemiluminescence-based assay. Quantitative real time PCR and western blot were performed to identify the effect of miR-132 on Cyp19a1, Cyp11a1 and an orphan nuclear receptor-Nurr1 expression in GCs. Direct suppression of Nurr1 via its 3'-untranslated region by miR-132 were further verified using luciferase reporter assays.

RESULTS

The expression level of miR-132 in cultured mouse GCs was significantly elevated during 48 h of treatment with 8-Br-cAMP. The synthesis of estradiol increased after the overexpression of miR-132 in mouse GCs. The real-time PCR results demonstrated that miR-132 induced the expression of Cyp19a1 significantly. Nurr1, an orphan nuclear receptor that suppresses Cyp19a1 expression, was found to be a direct target of miR-132. Nurr1 was suppressed by miR-132, as indicated by a luciferase assay and Western blotting. The knockdown of Nurr1 primarily elevated the synthesis of estradiol and partially attenuated the miR-132-induced estradiol elevation, and the ectopic expression of Flag-Nurr1 abrogated the stimulatory effect of miR-132 on estradiol synthesis in mouse GCs.

CONCLUSIONS

Our findings suggest that miR-132 is involved in the cAMP signaling pathway and promotes estradiol synthesis via the translational repression of Nurr1 in ovarian GCs.

Differential effects of social and physical environmental enrichment on brain plasticity, cognition, and ultrasonic communication in rats

Environmental enrichment (EE) exerts beneficial effects on brain plasticity, cognition, and anxiety/depression, leading to a brain that can counteract deficits underlying various brain disorders. Because the complexity of the EE commonly used makes it difficult to identify causal aspects, we examined possible factors using a 2 × 2 design with social EE (two vs. six rats) and physical EE (physically enriched vs. nonenriched). For the first time, we demonstrate that social and physical EE have differential effects on brain plasticity, cognition, and ultrasonic communication. Expectedly, physical EE promoted neurogenesis in the dentate gyrus of the hippocampal formation, but not in the subventricular zone, and, as a novel finding, affected microRNA expression levels, with the activity-dependent miR-124 and miR-132 being upregulated. Concomitant improvements in cognition were observed, yet social deficits were seen in the emission of prosocial 50-kHz ultrasonic vocalizations (USV) paralleled by a lack of social approach in response to them, consistent with the intense world syndrome/theory of autism. In contrast, social EE had only minor effects on brain plasticity and cognition, but led to increased prosocial 50-kHz USV emission rates and enhanced social approach behavior. Importantly, social deficits following physical EE were prevented by additional social EE. The finding that social EE has positive whereas physical EE has negative effects on social behavior indicates that preclinical studies focusing on EE as a potential treatment in models for neuropsychiatric disorders characterized by social deficits, such as autism, should include social EE in addition to physical EE, because its lack might worsen social deficits.

MicroRNA-132 aggravates epileptiform discharges via suppression of BDNF/TrkB signaling in cultured hippocampal neurons

MicroRNAs (miRs) are increasingly recognized as targets to prevent or disrupt epilepsy as well as serve as diagnostic biomarkers of epileptogenesis. Brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin related kinase type B (TrkB) also contribute to the pathophysiology of epilepsy. However, the possible involvement of miRs in BDNF-mediated molecular basis for epileptogenesis is less understood. In the present study, we found a dramatic upregulation of miR-132 and BDNF mRNA in the hippocampal neuronal culture model of status epilepticus (SE) obtained by Mg(2+)-free treatment. To investigate the role of miR-132 in the pathogenesis of epilepsy mediated by BDNF/TrkB signaling, we used a transfection approach to overexpress miR-132, and then detected a consequential decrease in BDNF mRNA and BDNF-dependent full-length TrkB receptor (TrkB.FL) signaling activity in the epileptic neurons. We investigated the alterations of epileptiform discharges in the hippocampal neuronal culture model of SE using the whole-cell patch-clamp technique. Activation of TrkB.FL by pretreatment with BDNF partly inhibited the Mg(2+)-free induced continuous high-frequency epileptiform discharges, while overexpression of miR-132 exacerbated epileptiform discharges. MiR-132 was also implicated in the postepileptic enhancement of high voltage dependent calcium channel. These results suggest that miR-132 promotes epileptogenesis through regulating BDNF/TrkB signaling in the hippocampal neuronal culture model of SE.

A large-scale functional screen identifies Nova1 and Ncoa3 as regulators of neuronal miRNA function

MicroRNAs (miRNAs) are important regulators of neuronal development, network connectivity, and synaptic plasticity. While many neuronal miRNAs were previously shown to modulate neuronal morphogenesis, little is known regarding the regulation of miRNA function. In a large-scale functional screen, we identified two novel regulators of neuronal miRNA function, Nova1 and Ncoa3. Both proteins are expressed in the nucleus and the cytoplasm of developing hippocampal neurons. We found that Nova1 and Ncoa3 stimulate miRNA function by different mechanisms that converge on Argonaute (Ago) proteins, core components of the miRNA-induced silencing complex (miRISC). While Nova1 physically interacts with Ago proteins, Ncoa3 selectively promotes the expression of Ago2 at the transcriptional level. We further show that Ncoa3 regulates dendritic complexity and dendritic spine maturation of hippocampal neurons in a miRNA-dependent fashion. Importantly, both the loss of miRNA activity and increased dendrite complexity upon Ncoa3 knockdown were rescued by Ago2 overexpression. Together, we uncovered two novel factors that control neuronal miRISC function at the level of Ago proteins, with possible implications for the regulation of synapse development and plasticity.