The role of MeCP2 in CNS development and function

Physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated in underlying of ischemia/reperfusion injury in different organs

Ischemia-reperfusion (I/R) injury, as a pathological phenomenon, takes place when blood supply to an organ is disrupted and then aggravated during restoration of blood flow. Ischemic preconditioning (IPC) is a potent method for attenuating subsequent events of IR damage in numerous organs. IPC protocol is determined by a brief and sequential time periods of I/R before the main ischemia. MicroRNAs are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review introduces the physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated after I/R insult in different organs such as the liver, kidney, heart, brain, and intestine. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2023. Based on these literature studies, IPC/IR intervention can affect cellular mechanisms including oxidative stress, apoptosis, angiogenesis, and inflammation through up-regulation or down-regulation of multiple microRNAs and their target genes.

Methyl-CpG-Binding Protein 2 Emerges as a Central Player in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

MECP2 and its product methyl-CpG binding protein 2 (MeCP2) are associated with multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), which are inflammatory, autoimmune, and demyelinating disorders of the central nervous system (CNS). However, the mechanisms and pathways regulated by MeCP2 in immune activation in favor of MS and NMOSD are not fully understood. We summarize findings that use the binding properties of MeCP2 to identify its targets, particularly the genes recognized by MeCP2 and associated with several neurological disorders. MeCP2 regulates gene expression in neurons, immune cells and during development by modulating various mechanisms and pathways. Dysregulation of the MeCP2 signaling pathway has been associated with several disorders, including neurological and autoimmune diseases. A thorough understanding of the molecular mechanisms underlying MeCP2 function can provide new therapeutic strategies for these conditions. The nervous system is the primary system affected in MeCP2-associated disorders, and other systems may also contribute to MeCP2 action through its target genes. MeCP2 signaling pathways provide promise as potential therapeutic targets in progressive MS and NMOSD. MeCP2 not only increases susceptibility and induces anti-inflammatory responses in immune sites but also leads to a chronic increase in pro-inflammatory cytokines gene expression (IFN-γ, TNF-α, and IL-1β) and downregulates the genes involved in immune regulation (IL-10, FoxP3, and CX3CR1). MeCP2 may modulate similar mechanisms in different pathologies and suggest that treatments for MS and NMOSD disorders may be effective in treating related disorders. MeCP2 regulates gene expression in MS and NMOSD. However, dysregulation of the MeCP2 signaling pathway is implicated in these disorders. MeCP2 plays a role as a therapeutic target for MS and NMOSD and provides pathways and mechanisms that are modulated by MeCP2 in the regulation of gene expression.

Maternal Diabetes Deregulates the Expression of Mecp2 via miR-26b-5p in Mouse Embryonic Neural Stem Cells

Maternal diabetes has been associated with a greater risk of neurodevelopmental disorders in offspring. It has been established that hyperglycemia alters the expression of genes and microRNAs (miRNAs) regulating the fate of neural stem cells (NSCs) during brain development. In this study, the expression of methyl-CpG-binding protein-2 (Mecp2), a global chromatin organizer and a crucial regulator of synaptic proteins, was analyzed in NSCs obtained from the forebrain of embryos of diabetic mice. Mecp2 was significantly downregulated in NSCs derived from embryos of diabetic mice when compared to controls. miRNA target prediction revealed that the miR-26 family could regulate the expression of Mecp2, and further validation confirmed that Mecp2 is a target of miR-26b-5p. Knockdown of Mecp2 or overexpression of miR-26b-5p altered the expression of tau protein and other synaptic proteins, suggesting that miR-26b-5p alters neurite outgrowth and synaptogenesis via Mecp2. This study revealed that maternal diabetes upregulates the expression of miR-26b-5p in NSCs, resulting in downregulation of its target, Mecp2, which in turn perturbs neurite outgrowth and expression of synaptic proteins. Overall, hyperglycemia dysregulates synaptogenesis that may manifest as neurodevelopmental disorders in offspring from diabetic pregnancy.

MeCP2 Is an Epigenetic Factor That Links DNA Methylation with Brain Metabolism

DNA methylation, one of the most well-studied epigenetic modifications, is involved in a wide spectrum of biological processes. Epigenetic mechanisms control cellular morphology and function. Such regulatory mechanisms involve histone modifications, chromatin remodeling, DNA methylation, non-coding regulatory RNA molecules, and RNA modifications. One of the most well-studied epigenetic modifications is DNA methylation that plays key roles in development, health, and disease. Our brain is probably the most complex part of our body, with a high level of DNA methylation. A key protein that binds to different types of methylated DNA in the brain is the methyl-CpG binding protein 2 (MeCP2). MeCP2 acts in a dose-dependent manner and its abnormally high or low expression level, deregulation, and/or genetic mutations lead to neurodevelopmental disorders and aberrant brain function. Recently, some of MeCP2-associated neurodevelopmental disorders have emerged as neurometabolic disorders, suggesting a role for MeCP2 in brain metabolism. Of note, MECP2 loss-of-function mutation in Rett Syndrome is reported to cause impairment of glucose and cholesterol metabolism in human patients and/or mouse models of disease. The purpose of this review is to outline the metabolic abnormalities in MeCP2-associated neurodevelopmental disorders that currently have no available cure. We aim to provide an updated overview into the role of metabolic defects associated with MeCP2-mediated cellular function for consideration of future therapeutic strategies.

Role of primary aging hallmarks in Alzheimer´s disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, which severely threatens the health of the elderly and causes significant economic and social burdens. The causes of AD are complex and include heritable but mostly aging-related factors. The primary aging hallmarks include genomic instability, telomere wear, epigenetic changes, and loss of protein stability, which play a dominant role in the aging process. Although AD is closely associated with the aging process, the underlying mechanisms involved in AD pathogenesis have not been well characterized. This review summarizes the available literature about primary aging hallmarks and their roles in AD pathogenesis. By analyzing published literature, we attempted to uncover the possible mechanisms of aberrant epigenetic markers with related enzymes, transcription factors, and loss of proteostasis in AD. In particular, the importance of oxidative stress-induced DNA methylation and DNA methylation-directed histone modifications and proteostasis are highlighted. A molecular network of gene regulatory elements that undergoes a dynamic change with age may underlie age-dependent AD pathogenesis, and can be used as a new drug target to treat AD.

The role of DNA methylation in progression of neurological disorders and neurodegenerative diseases as well as the prospect of using DNA methylation inhibitors as therapeutic agents for such disorders

Genome-wide studies related to neurological disorders and neurodegenerative diseases have pointed to the role of epigenetic changes such as DNA methylation, histone modification, and noncoding RNAs. DNA methylation machinery controls the dynamic regulation of methylation patterns in discrete brain regions.

Objective

This review aims to describe the role of DNA methylation in inhibiting and progressing neurological and neurodegenerative disorders and therapeutic approaches.

Methods

A Systematic search of PubMed, Web of Science, and Cochrane Library was conducted for all qualified studies from 2000 to 2022.

Results

For the current need of time, we have focused on the DNA methylation role in neurological and neurodegenerative diseases and the expression of genes involved in neurodegeneration such as Alzheimer's, Depression, and Rett Syndrome. Finally, it appears that the various epigenetic changes do not occur separately and that DNA methylation and histone modification changes occur side by side and affect each other. We focused on the role of modification of DNA methylation in several genes associated with depression (NR3C1, NR3C2, CRHR1, SLC6A4, BDNF, and FKBP5), Rett syndrome (MECP2), Alzheimer's, depression (APP, BACE1, BIN1 or ANK1) and Parkinson's disease (SNCA), as well as the co-occurring modifications to histones and expression of non-coding RNAs. Understanding these epigenetic changes and their interactions will lead to better treatment strategies.

Conclusion

This review captures the state of understanding of the epigenetics of neurological and neurodegenerative diseases. With new epigenetic mechanisms and targets undoubtedly on the horizon, pharmacological modulation and regulation of epigenetic processes in the brain holds great promise for therapy.

Assessing Children with Poor Coordination Can Be Tricky - A Review on Ataxia and Ataxia Mimickers and a Study of Three Children with Severe Epilepsy

While ataxia is a relatively common presenting feature in pediatric patients, it represents only one possible cause of uncoordinated movements. Other possible causes of uncoordinated movements include ingestion of toxic substances, musculoskeletal diseases, psychogenic disorders, extrapyramidal movement disorders, peripheral neuropathies, spasticity from any cause, and epilepsy. Therefore, primary health care providers must recognize and exclude other etiologies of uncoordinated movements before attaching the label “ataxia” to any patient presenting with poor coordination. Once the presence of ataxia is confirmed, the cause should be investigated. As ataxia may be vestibular, sensory, or cerebellar in origin, medical practitioners must evaluate the diverse symptoms and signs to effectively differentiate the various types of ataxia. Three case studies are presented to illustrate the complexity associated with the assessment of ataxia. Each case will discuss a pediatric patient who displays cerebellar ataxia as a concurrent feature of a gene-specific developmental and epileptic encephalopathy. These cases will provide an example of how ataxia may be differentiated from other causes of uncoordinated movements related to epilepsy and anti-seizure medications, namely: nonconvulsive seizures, postictal state, and medication side effects or toxicity. The assessment of poor balance can be challenging at times; however, with knowledge of the differential diagnosis of poor balance, medical practitioners will be able to confidently determine the presence of true ataxia from various ataxia mimickers, thereby allowing for timely and accurate diagnosis, and appropriate management.

Perinatal exposure to high fat diet alters expression of MeCP2 in the hypothalamus

Obesity is a complex disease that is the result of a number of different factors including genetic, environmental, and endocrine abnormalities. Given that monogenic forms of obesity are rare, it is important to identify other mechanisms that contribute to its etiology. Methyl-Cp-G binding protein 2 (MeCP2) is a neuroepigenetic factor that binds to methylated regions of DNA to influence transcription. Past studies demonstrate that disruption in MeCP2 function produces obesity in mice. Using a diet-induced obesity mouse model, we show that perinatal exposure to high fat diet significantly decreases MeCP2 protein expression in the hypothalamus of female mice, effects not seen when high fat diet is given to mice during adulthood. Moreover, these effects are seen specifically in a subregion of the hypothalamus known as the arcuate nucleus with females having decreased MeCP2 expression in rostral areas and males having decreased MeCP2 expression in intermediate regions of the arcuate nucleus. Interestingly, mice gain more weight when exposed to high fat diet during adulthood relative to mice exposed to high fat diet perinatally, suggesting that perhaps high fat diet exposure during adulthood may be affecting mechanisms independent of MeCP2 function. Collectively, our data demonstrate that there are developmentally sensitive periods in which MeCP2 expression is influenced by high fat diet exposure and this occurs in a sexually dimorphic manner.

Sex-specific transgenerational effects of adolescent morphine exposure on short-term memory and anxiety behavior: Male linage

Current estimates indicate that opioid use and misuse are a rising epidemic, which presents a substantial socioeconomic burden around the world. Chronic opioid consumption, specifically during the critical period of adolescence, can lead to enduring effects not only in individuals but also in future generations. Utilizing rodent model, we have previously reported the impacts of paternal exposure to chronic morphine during adolescence on neurobehavioral features in progenies. Currently, the potential transgenerational effects of paternal morphine exposure during adolescence on anxiety-like behavior and short-term memory remains unknown. Male Wistar rats were exposed to increasing doses of morphine for ten days in adolescence (PND 30-39). Thereafter, following a 30-days drug-free period, the treated male rats mated with naïve females. The anxiety-like behavior and short-term memory performance were assessed in adult male and female offspring (PND 60) using open field and Y-maze tests. Both male and female progenies of morphine-treated sires revealed a significant reduction in the movement velocity compared to progenies of saline-treated sires as measured by open field test. Morphine-sired male but not female offspring also showed a non-significant large decreasing effect on time spent in the center and frequency of entries to the center of open field box. Moreover, a significant reduction in the number of entries and percent of time spent in the novel arm was observed in male and female morphine-sired offspring, as measured using Y-maze test. Growth outcomes also did not demonstrate any difference in the number of dam's fertility, pups birth, and death between morphine-sired and saline-sired groups in both sexes. Collectively, paternal exposure to morphine during adolescence induces sex-specific and selective disturbances in short-term memory while anxiety-like behavior was slightly disturbed.

DNA methylation and behavioral dysfunction in males with 47,XXY and 49,XXXXY: a pilot study

Background

Equal dosage of X-linked genes between males and females is maintained by the X-inactivation of the second X chromosome in females through epigenetic mechanisms. Boys with aneuploidy of the X chromosome exhibit a host of symptoms such as low fertility, musculoskeletal anomalies, and cognitive and behavioral deficits that are presumed to be caused by the abnormal dosage of these genes. The objective of this pilot study is to assess the relationship between CpG methylation, an epigenetic modification, at several genes on the X chromosome and behavioral dysfunction in boys with supernumerary X chromosomes.

Results

Two parental questionnaires, the Behavior Rating Inventory of Executive Function (BRIEF) and Child Behavior Checklist (CBCL), were analyzed, and they showed expected differences in both internal and external behaviors between neurotypical (46,XY) boys and boys with 49,XXXXY. There were several CpGs in AR and MAOA of boys with 49,XXXXY whose methylation levels were skewed from levels predicted from having one active (Xa) and three inactive (Xi) X chromosomes. Further, methylation levels of multiple CpGs in MAOA showed nominally significant association with externalizing behavior on the CBCL, and the methylation level of one CpG in AR showed nominally significant association with the BRIEF Regulation Index.

Conclusions

Boys with 49,XXXXY displayed higher levels of CpG methylation at regulatory intronic regions in X-linked genes encoding the androgen receptor (AR) and monoamine oxidase A (MAOA), compared to that in boys with 47,XXY and neurotypical boys. Our pilot study results suggest a link between CpG methylation levels and behavior in boys with 49,XXXXY.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01123-4.

MeCP2 deficiency exacerbates the neuroinflammatory setting and autoreactive response during an autoimmune challenge

Rett syndrome is a severe and progressive neurological disorder linked to mutations in the MeCP2 gene. It has been suggested that immune alterations may play an active role in the generation and/or maintenance of RTT phenotypes. However, there is no clear consensus about which pathways are regulated in vivo by MeCP2 in the context of immune activation. In the present work we set to characterize the role of MeCP2 during the progression of Experimental Autoimmune Encephalomyelitis (EAE) using the MeCP2308/y mouse model (MUT), which represents a condition of "MeCP2 function deficiency". Our results showed that MeCP2 deficiency increased the susceptibility to develop EAE, along with a defective induction of anti-inflammatory responses and an exacerbated MOG-specific IFNγ expression in immune sites. In MUT-EAE spinal cord, we found a chronic increase in pro-inflammatory cytokines gene expression (IFNγ, TNFα and IL-1β) and downregulation of genes involved in immune regulation (IL-10, FoxP3 and CX3CR1). Moreover, our results indicate that MeCP2 acts intrinsically upon immune activation, affecting neuroimmune homeostasis by regulating the pro-inflammatory/anti-inflammatory balance in vivo. These results are relevant to identify the potential consequences of MeCP2 mutations on immune homeostasis and to explore novel therapeutic strategies for MeCP2-related disorders.

Methylation Analysis in Monozygotic Twins With Treatment-Resistant Schizophrenia and Discordant Responses to Clozapine

Schizophrenia is a mental illness that involves both genetic and environmental factors. Clozapine, an atypical antipsychotic, is a well-established therapy for treatment-resistant schizophrenia. In this study, we focused on a set of monozygotic twins with treatment-resistant schizophrenia in which one twin effectively responded to clozapine treatment and the other did not. Our previous study generated neurons from induced pluripotent stem (iPS) cells derived from these patients and compared the transcriptome profiles between mock- and clozapine-treated neurons. In this study, we performed genome-wide DNA methylation profiling to investigate the mechanisms underlying gene expression changes. First, we extracted the differentially methylated sites from each twin based on statistical analysis. Then, we combined the DNA methylation profiling with transcriptome profiling from our previous RNA-seq data. Among the genes with altered methylation and expression, we found the different proportions of the genes related to neuronal and synaptic functions between the clozapine responder and non-responder (35.7 and 6.7%, respectively). This trend was observed even when the basal differences between the responder and non-responder was excluded. These results suggest that effective clozapine action may correct the abnormalities of neuronal and synapse functions in schizophrenia via changes in methylation.

Neurogenesis From Neural Crest Cells: Molecular Mechanisms in the Formation of Cranial Nerves and Ganglia

The neural crest (NC) is a transient multipotent cell population that originates in the dorsal neural tube. Cells of the NC are highly migratory, as they travel considerable distances through the body to reach their final sites. Derivatives of the NC are neurons and glia of the peripheral nervous system (PNS) and the enteric nervous system as well as non-neural cells. Different signaling pathways triggered by Bone Morphogenetic Proteins (BMPs), Fibroblast Growth Factors (FGFs), Wnt proteins, Notch ligands, retinoic acid (RA), and Receptor Tyrosine Kinases (RTKs) participate in the processes of induction, specification, cell migration and neural differentiation of the NC. A specific set of signaling pathways and transcription factors are initially expressed in the neural plate border and then in the NC cell precursors to the formation of cranial nerves. The molecular mechanisms of control during embryonic development have been gradually elucidated, pointing to an important role of transcriptional regulators when neural differentiation occurs. However, some of these proteins have an important participation in malformations of the cranial portion and their mutation results in aberrant neurogenesis. This review aims to give an overview of the role of cell signaling and of the function of transcription factors involved in the specification of ganglia precursors and neurogenesis to form the NC-derived cranial nerves during organogenesis.

MeCP2 mediates transgenerational transmission of chronic pain

Pain symptoms can be transmitted across generations, but the mechanisms underlying these outcomes remain poorly understood. Here, we identified an essential role for primary somatosensory cortical (S1) glutamate neuronal DNA methyl-CpG binding protein 2 (MeCP2) in the transgenerational transmission of pain. In a female mouse chronic pain model, the offspring displayed significant pain sensitization. In these mice, MeCP2 expression was increased in S1 glutamate (Glu^S1) neurons, correlating with increased neuronal activity. Downregulation of Glu^S1 neuronal MeCP2 in maternal mice with pain abolished offspring pain sensitization, whereas overexpression of MeCP2 in naïve maternal mice induced pain sensitization in offspring. Notably, single-cell sequencing and chromatin immunoprecipitation analysis showed that the expression of a wide range of genes was changed in offspring and maternal Glu^S1 neurons, some of which were regulated by MeCP2. These results collectively demonstrate the putative importance of MeCP2 as a key regulator in pain transgenerational transmission through actions on Glu^S1 neuronal maladaptation.

Two Thalamic Regions Screened Using Laser Capture Microdissection with Whole Human Genome Microarray in Schizophrenia Postmortem Samples

We used whole human genome microarray screening of highly enriched neuronal populations from two thalamic regions in postmortem samples from subjects with schizophrenia and controls to identify brain region-specific gene expression changes and possible transcriptional targets. The thalamic anterior nucleus is reciprocally connected to anterior cingulate, a schizophrenia-affected cortical region, and is also thought to be schizophrenia affected; the other thalamic region is not. Using two regions in the same subject to identify disease-relevant gene expression differences was novel and reduced intersubject heterogeneity of findings. We found gene expression differences related to miRNA-137 and other SZ-associated microRNAs, ELAVL1, BDNF, DISC-1, MECP2 and YWHAG associated findings, synapses, and receptors. Manual curation of our data may support transcription repression.

Animal Models of Maternal Immune Activation in Depression Research

Abstract: Background

Depression and schizophrenia are debilitating mental illnesses with significant socio-economic impact. The high degree of comorbidity between the two disorders, and shared symptoms and risk factors, suggest partly common pathogenic mechanisms. Supported by human and animal studies, maternal immune activation (MIA) has been intimately associated with the development of schizophrenia. However, the link between MIA and depression has remained less clear, in part due to the lack of appropriate animal models.

Objective

Here we aim to summarize findings obtained from studies using MIA animal models and discuss their relevance for preclinical depression research.

Methods

Results on molecular, cellular and behavioral phenotypes in MIA animal models were collected by literature search (PubMed) and evaluated for their significance for depression.

Results

Several reports on offspring depression-related behavioral alterations indicate an involvement of MIA in the development of depression later in life. Depression-related behavioral phenotypes were frequently paralleled by neurogenic and neurotrophic deficits and modulated by several genetic and environmental factors.

Conclusion

Literature evidence analyzed in this review supports a relevance of MIA as animal model for a specific early life adversity, which may prime an individual for the development of distinct psychopathologies later life. MIA animal models may present a unique tool for the identification of additional exogenous and endogenous factors, which are required for the manifestation of a specific neuropsychiatric disorder, such as depression, later in life. Hereby, novel insights into the molecular mechanisms involved in the pathophysiology of depression may be obtained, supporting the identification of alternative therapeutic strategies.

Expression of Phospho-MeCP2s in the Developing Rat Brain and Function of Postnatal MeCP2 in Cerebellar Neural Cell Development

Abnormal expression and dysfunction of methyl-CpG binding protein 2 (MeCP2) cause Rett syndrome (RTT). The diverse phosphorylation modifications modulate MeCP2 function in neural cells. Using western blot and immunohistochemistry, we examined the expression patterns of MeCP2 and three phospho-MeCP2s (pMeCP2s) in the developing rat brain. The expression of MeCP2 and phospho-S80 (pS80) MeCP2 increased while pS421 MeCP2 and pS292 MeCP2 decreased with brain maturation. In contrast to the nuclear localization of MeCP2 and pS80 MeCP2, pS421 MeCP2 and pS292 MeCP2 were mainly expressed in the cytoplasmic compartment. Apart from their distribution in neurons, they were also detected at a low level in astrocytes. Postnatally-initiated MeCP2 deficiency affected cerebellar neural cell development, as determined by the abnormal expression of GFAP, DCX, Tuj1, MAP-2, and calbindin-D28k. Together, these results demonstrate that MeCP2 and diverse pMeCP2s have distinct features of spatio-temporal expression in the rat brain, and that the precise levels of MeCP2 in the postnatal period are vital to cerebellar neural cell development.

Enhancement of postsynaptic GABAA and extrasynaptic NMDA receptor-mediated responses in the barrel cortex of Mecp2-null mice

Rett syndrome (RTT) is a neurodevelopmental disorder that results from mutations in the X-linked gene for methyl-CpG-binding protein 2 (MECP2). The underlying cellular mechanism for the sensory deficits in patients with RTT is largely unknown. This study used the Bird mouse model of RTT to investigate sensory thalamocortical synaptic transmission in the barrel cortex of Mecp2-null mice. Electrophysiological results showed an excitation/inhibition imbalance, biased toward inhibition, due to an increase in efficacy of postsynaptic GABAA receptors rather than alterations in inhibitory network and presynaptic release properties. Enhanced inhibition impaired the transmission of tonic sensory signals from the thalamus to the somatosensory cortex. Previous morphological studies showed an upregulation of NMDA receptors in the neocortex of both RTT patients and Mecp2-null mice at early ages [Blue ME, Naidu S, Johnston MV. Ann Neurol 45: 541-545, 1999; Blue ME, Kaufmann WE, Bressler J, Eyring C, O'Driscoll C, Naidu S, Johnston MV. Anat Rec (Hoboken) 294: 1624-1634, 2011]. Although AMPA and NMDA receptor-mediated excitatory synaptic transmission was not altered in the barrel cortex of Mecp2-null mice, extrasynaptic NMDA receptor-mediated responses increased markedly. These responses were blocked by memantine, suggesting that extrasynaptic NMDA receptors play an important role in the pathogenesis of RTT. The results suggest that enhancement of postsynaptic GABAA and extrasynaptic NMDA receptor-mediated responses may underlie impaired somatosensation and that pharmacological blockade of extrasynaptic NMDA receptors may have therapeutic value for RTT.

Melatonin treatment during the incubation of sensitization attenuates methamphetamine-induced locomotor sensitization and MeCP2 expression

Behavior sensitization is a long-lasting enhancement of locomotor activity after exposure to psychostimulants. Incubation of sensitization is a phenomenon of remarkable augmentation of locomotor response after withdrawal and reflects certain aspects of compulsive drug craving. However, the mechanisms underlying these phenomena remain elusive. Here we pay special attention to the incubation of sensitization and suppose that the intervention of this procedure will finally decrease the expression of sensitization. Melatonin is an endogenous hormone secreted mainly by the pineal gland. It is effective in treating sleep disorder, which turns out to be one of the major withdrawal symptoms of methamphetamine (MA) addiction. Furthermore, melatonin can also protect neuronal cells against MA-induced neurotoxicity. In the present experiment, we treated mice with low dose (10mg/kg) of melatonin for 14 consecutive days during the incubation of sensitization. We found that melatonin significantly attenuated the expression of sensitization. In contrast, the vehicle treated mice showed prominent enhancement of locomotor activity after incubation. MeCP2 expression was also elevated in the vehicle treated mice and melatonin attenuated its expression. Surprisingly, correlation analysis suggested significant correlation between MeCP2 expression in the nucleus accumbens (NAc) and locomotion in both saline control and vehicle treated mice, but not in melatonin treated ones. MA also induced MeCP2 over-expression in PC12 cells. However, melatonin failed to reduce MeCP2 expression in vitro. Our results suggest that melatonin treatment during the incubation of sensitization attenuates MA-induced expression of sensitization and decreases MeCP2 expression in vivo.

MicroRNAs downregulated in neuropathic pain regulate MeCP2 and BDNF related to pain sensitivity

Nerve injury induces chronic pain and dysregulation of microRNAs in dorsal root ganglia (DRG). Several downregulated microRNAs are predicted to target Mecp2. MECP2 mutations cause Rett syndrome and these patients report decreased pain perception. We confirmed MeCP2 upregulation in DRG following nerve injury and repression of MeCP2 by miRNAs in vitro. MeCP2 regulates brain-derived neurotrophic factor (BDNF) and downregulation of MeCP2 by microRNAs decreased Bdnf in vitro. MeCP2 T158A mice exhibited reduced mechanical sensitivity and Mecp2-null and MeCP2 T158A mice have decreased Bdnf in DRG. MeCP2-mediated regulation of Bdnf in the DRG could contribute to altered pain sensitivity.

Decreasing-Rate Pruning Optimizes the Construction of Efficient and Robust Distributed Networks

Robust, efficient, and low-cost networks are advantageous in both biological and engineered systems. During neural network development in the brain, synapses are massively over-produced and then pruned-back over time. This strategy is not commonly used when designing engineered networks, since adding connections that will soon be removed is considered wasteful. Here, we show that for large distributed routing networks, network function is markedly enhanced by hyper-connectivity followed by aggressive pruning and that the global rate of pruning, a developmental parameter not previously studied by experimentalists, plays a critical role in optimizing network structure. We first used high-throughput image analysis techniques to quantify the rate of pruning in the mammalian neocortex across a broad developmental time window and found that the rate is decreasing over time. Based on these results, we analyzed a model of computational routing networks and show using both theoretical analysis and simulations that decreasing rates lead to more robust and efficient networks compared to other rates. We also present an application of this strategy to improve the distributed design of airline networks. Thus, inspiration from neural network formation suggests effective ways to design distributed networks across several domains.

Methyl CpG Binding Protein 2 Gene Disruption Augments Tonic Currents of γ-Aminobutyric Acid Receptors in Locus Coeruleus Neurons: IMPACT ON NEURONAL EXCITABILITY AND BREATHING

People with Rett syndrome and mouse models show autonomic dysfunction involving the brain stem locus coeruleus (LC). Neurons in the LC of Mecp2-null mice are overly excited, likely resulting from a defect in neuronal intrinsic membrane properties and a deficiency in GABA synaptic inhibition. In addition to the synaptic GABA receptors, there is a group of GABAA receptors (GABAARs) that is located extrasynaptically and mediates tonic inhibition. Here we show evidence for augmentation of the extrasynaptic GABAARs in Mecp2-null mice. In brain slices, exposure of LC neurons to GABAAR agonists increased tonic currents that were blocked by GABAAR antagonists. With 10 μm GABA, the bicuculline-sensitive tonic currents were ∼4-fold larger in Mecp2-null LC neurons than in the WT. Single-cell PCR analysis showed that the δ subunit, the principal subunit of extrasynaptic GABAARs, was present in LC neurons. Expression levels of the δ subunit were ∼50% higher in Mecp2-null neurons than in the WT. Also increased in expression in Mecp2-null mice was another extrasynaptic GABAAR subunit, α6, by ∼4-fold. The δ subunit-selective agonists 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol hydrochloride and 4-chloro-N-[2-(2-thienyl)imidazo[1,2-a]pyridin-3-yl]]benzamide activated the tonic GABAA currents in LC neurons and reduced neuronal excitability to a greater degree in Mecp2-null mice than in the WT. Consistent with these findings, in vivo application of 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol hydrochloride alleviated breathing abnormalities of conscious Mecp2-null mice. These results suggest that extrasynaptic GABAARs seem to be augmented with Mecp2 disruption, which may be a compensatory response to the deficiency in GABAergic synaptic inhibition and allows control of neuronal excitability and breathing abnormalities.

Role of mecp2 in experience-dependent epigenetic programming

Mutations in the X-linked gene MECP2, the founding member of a family of proteins recognizing and binding to methylated DNA, are the genetic cause of a devastating neurodevelopmental disorder in humans, called Rett syndrome. Available evidence suggests that MECP2 protein has a critical role in activity-dependent neuronal plasticity and transcription during brain development. Moreover, recent studies in mice show that various posttranslational modifications, notably phosphorylation, regulate Mecp2’s functions in learning and memory, drug addiction, depression-like behavior, and the response to antidepressant treatment. The hypothalamic-pituitary-adrenal (HPA) axis drives the stress response and its deregulation increases the risk for a variety of mental disorders. Early-life stress (ELS) typically results in sustained HPA-axis deregulation and is a major risk factor for stress related diseases, in particular major depression. Interestingly, Mecp2 protein has been shown to contribute to ELS-dependent epigenetic programming of Crh, Avp, and Pomc, all of these genes enhance HPA-axis activity. Hereby ELS regulates Mecp2 phosphorylation, DNA binding, and transcriptional activities in a tissue-specific and temporospatial manner. Overall, these findings suggest MECP2 proteins are so far underestimated and have a more dynamic role in the mediation of the gene-environment dialog and epigenetic programming of the neuroendocrine stress system in health and disease.

Transcriptional Regulation of Brain-Derived Neurotrophic Factor (BDNF) by Methyl CpG Binding Protein 2 (MeCP2): a Novel Mechanism for Re-Myelination and/or Myelin Repair Involved in the Treatment of Multiple Sclerosis (MS)

Multiple sclerosis (MS) is a chronic progressive, neurological disease characterized by the targeted immune system-mediated destruction of central nervous system (CNS) myelin. Autoreactive CD4+ T helper cells have a key role in orchestrating MS-induced myelin damage. Once activated, circulating Th1-cells secrete a variety of inflammatory cytokines that foster the breakdown of blood-brain barrier (BBB) eventually infiltrating into the CNS. Inside the CNS, they become reactivated upon exposure to the myelin structural proteins and continue to produce inflammatory cytokines such as tumor necrosis factor α (TNFα) that leads to direct activation of antibodies and macrophages that are involved in the phagocytosis of myelin. Proliferating oligodendrocyte precursors (OPs) migrating to the lesion sites are capable of acute remyelination but unable to completely repair or restore the immune system-mediated myelin damage. This results in various permanent clinical neurological disabilities such as cognitive dysfunction, fatigue, bowel/bladder abnormalities, and neuropathic pain. At present, there is no cure for MS. Recent remyelination and/or myelin repair strategies have focused on the role of the neurotrophin brain-derived neurotrophic factor (BDNF) and its upstream transcriptional repressor methyl CpG binding protein (MeCP2). Research in the field of epigenetic therapeutics involving histone deacetylase (HDAC) inhibitors and lysine acetyl transferase (KAT) inhibitors is being explored to repress the detrimental effects of MeCP2. This review will address the role of MeCP2 and BDNF in remyelination and/or myelin repair and the potential of HDAC and KAT inhibitors as novel therapeutic interventions for MS.

Vulnerability to opiate intake in maternally deprived rats: implication of MeCP2 and of histone acetylation

We previously showed that maternal deprivation predisposes male rats to anxiety, accompanied with an increase in their opiate consumption. In the present report, we searched for brain epigenetic mechanisms that possibly underlie this increase. For that, we examined the expression of the methyl-CpG-binding protein MeCP2 and of the histone deacetylases HDAC2 and HDAC3, as well as the acetylation status of histone H3 and H4 in mesolimbic structures of adult maternally deprived rats, using immunohistochemistry and Western blot analysis. A long-lasting increase in MeCP2 expression was found throughout the striatum of deprived rats. Enhanced HDAC2 expression and increased nuclear HDAC activity in the nucleus accumbens of deprived rats were associated with lower acetylation levels of histone H3 and H4. Treatment for 3 weeks with the HDAC inhibitor sodium valproate abolished HDAC activation together with the decrease in the acetylation levels of histone H4, and was accompanied with normalized oral morphine consumption. The data indicate that epigenetic mechanisms induced by early adverse environment memorize life experience to trigger greater opiate vulnerability during adult life. They suggest that sodium valproate may lessen vulnerability to opiate intake, particularly in subgroups of individuals subjected to adverse postnatal environments.

Astrocyte-specific regulation of hMeCP2 expression in Drosophila

Alterations in the expression of Methyl-CpG-binding protein 2 (MeCP2) either by mutations or gene duplication leads to a wide spectrum of neurodevelopmental disorders including Rett Syndrome and MeCP2 duplication disorder. Common features of Rett Syndrome (RTT), MeCP2 duplication disorder, and neuropsychiatric disorders indicate that even moderate changes in MeCP2 protein levels result in functional and structural cell abnormalities. In this study, we investigated two areas of MeCP2 pathophysiology using Drosophila as a model system: the effects of MeCP2 glial gain-of-function activity on circuits controlling sleep behavior, and the cell-type specific regulation of MeCP2 expression. In this study, we first examined the effects of elevated MeCP2 levels on microcircuits by expressing human MeCP2 (hMeCP2) in astrocytes and distinct subsets of amine neurons including dopamine and octopamine (OA) neurons. Depending on the cell-type, hMeCP2 expression reduced sleep levels, altered daytime/nighttime sleep patterns, and generated sleep maintenance deficits. Second, we identified a 498 base pair region of the MeCP2e2 isoform that is targeted for regulation in distinct subsets of astrocytes. Levels of the full-length hMeCP2e2 and mutant RTT R106W protein decreased in astrocytes in a temporally and spatially regulated manner. In contrast, expression of the deletion Δ166 hMeCP2 protein was not altered in the entire astrocyte population. qPCR experiments revealed a reduction in full-length hMeCP2e2 transcript levels suggesting transgenic hMeCP2 expression is regulated at the transcriptional level. Given the phenotypic complexities that are caused by alterations in MeCP2 levels, our results provide insight into distinct cellular mechanisms that control MeCP2 expression and link microcircuit abnormalities with defined behavioral deficits.

MicroRNA-132, -134, and -138: a microRNA troika rules in neuronal dendrites

Dendritic mRNA transport and local translation in the postsynaptic compartment play an important role in synaptic plasticity, learning and memory. Local protein synthesis at the synapse has to be precisely orchestrated by a plethora of factors including RNA binding proteins as well as microRNAs, an extensive class of small non-coding RNAs. By binding to complementary sequences in target mRNAs, microRNAs fine-tune protein synthesis and thereby represent critical regulators of gene expression at the post-transcriptional level. Research over the last years identified an entire network of dendritic microRNAs that fulfills an essential role in synapse development and physiology. Recent studies provide evidence that these small regulatory molecules are highly regulated themselves, at the level of expression as well as function. The importance of microRNAs for correct function of the nervous system is reflected by an increasing number of studies linking dysregulation of microRNA pathways to neurological disorders. By focusing on three extensively studied examples (miR-132, miR-134, miR-138), this review will attempt to illustrate the complex regulatory roles of dendritic microRNAs at the synapse and their implications for pathological conditions.

The miRNA-mediated cross-talk between transcripts provides a novel layer of posttranscriptional regulation

Endogenously expressed transcripts that are posttranscriptionally regulated by the same microRNAs (miRNAs) will, in principle, compete for the binding of their shared small noncoding RNA regulators and modulate each other's abundance. Recently, the levels of some coding as well as noncoding transcripts have indeed been found to be regulated in this way. Transcripts that engage in such regulatory interactions are referred to as competitive endogenous RNAs (ceRNAs). This novel layer of posttranscriptional regulation has been shown to contribute to diverse aspects of organismal and cellular biology, despite the number of functionally characterized ceRNAs being as yet relatively low. Importantly, increasing evidence suggests that the dysregulation of some ceRNA interactions is associated with disease etiology, most preeminently with cancer. Here we review how posttranscriptional regulation by miRNAs contributes to the cross-talk between transcripts and review examples of known ceRNAs by highlighting the features underlying their interactions and what might be their biological relevance.

A high-throughput framework to detect synapses in electron microscopy images

Motivation: Synaptic connections underlie learning and memory in the brain and are dynamically formed and eliminated during development and in response to stimuli. Quantifying changes in overall density and strength of synapses is an important pre-requisite for studying connectivity and plasticity in these cases or in diseased conditions. Unfortunately, most techniques to detect such changes are either low-throughput (e.g. electrophysiology), prone to error and difficult to automate (e.g. standard electron microscopy) or too coarse (e.g. magnetic resonance imaging) to provide accurate and large-scale measurements.

Results: To facilitate high-throughput analyses, we used a 50-year-old experimental technique to selectively stain for synapses in electron microscopy images, and we developed a machine-learning framework to automatically detect synapses in these images. To validate our method, we experimentally imaged brain tissue of the somatosensory cortex in six mice. We detected thousands of synapses in these images and demonstrate the accuracy of our approach using cross-validation with manually labeled data and by comparing against existing algorithms and against tools that process standard electron microscopy images. We also used a semi-supervised algorithm that leverages unlabeled data to overcome sample heterogeneity and improve performance. Our algorithms are highly efficient and scalable and are freely available for others to use.

Availability: Code is available at http://www.cs.cmu.edu/∼saketn/detect_synapses/

Contact:zivbj@cs.cmu.edu

Chromatin regulators of neural development

During all stages of neural development-from the fate switches of neural precursor/progenitor cells to activity-dependent synapse maturation-chromatin-level modifications are important regulators of the gene expression that control developmental programs. Such modifications, including both alterations of histone tails and cytosine residues in the DNA, as well as changes in the chromatin structure, act dynamically throughout development and work together to determine the chromatin state at each time point. While many studies have shown localized action of chromatin modifiers at relevant gene loci, recent reports have also indicated that some chromatin modifications work on a more global scale, altering many loci throughout the genome. Here we review recent papers that describe the roles of chromatin-level regulation, at both the local and global scale, in the development of the mouse brain.

Bioinformatics and Gene Network Analyses of the Swine Mammary Gland Transcriptome during Late Gestation

We used the newly-developed Dynamic Impact Approach (DIA) and gene network analysis to study the sow mammary transcriptome at 80, 100, and 110 days of pregnancy. A swine oligoarray with 13,290 inserts was used for transcriptome profiling. An ANOVA with false discovery rate (FDR < 0.15) correction resulted in 1,409 genes with a significant time effect across time comparisons. The DIA uncovered that Fatty acid biosynthesis, Interleukin-4 receptor binding, Galactose metabolism, and mTOR signaling were among the most-impacted pathways. IL-4 receptor binding, ABC transporters, cytokine-cytokine receptor interaction, and Jak-STAT signaling were markedly activated at 110 days compared with 80 and 100 days. Epigenetic and transcription factor regulatory mechanisms appear important in coordinating the final stages of mammary development during pregnancy. Network analysis revealed a crucial role for TP53, ARNT2, E2F4, and PPARG. The bioinformatics analyses revealed a number of pathways and functions that perform an irreplaceable role during late gestation to farrowing.

Comparative DNA methylation among females with neurodevelopmental disorders and seizures identifies TAC1 as a MeCP2 target gene

Background

Several proteins involved in epigenetic regulation cause syndromic neurodevelopmental disorders when human genes are mutated. More general involvement of epigenetic mechanisms in neurodevelopmental phenotypes is unclear.

Methods

In an attempt to determine whether DNA methylation differentiates clinical subgroups, profiling was performed on bisulfite converted DNA from lymphoblastoid cell lines (LCLs) in discovery (n = 20) and replication (n = 40) cohorts of females with Rett syndrome (RTT; n = 18), autism (AUT; n = 17), seizure disorder (SEZ; n = 6), and controls (CTL; n = 19) using Illumina HumanMethylation27 arrays. TAC1 CpGs were validated using a Sequenom EpiTYPER assay and expression was measured in LCLs and postmortem brain. Chromatin immunoprecipitation was performed in HEK cells. Cells were treated with valproic acid and MeCP2 binding was assessed.

Results

Two female-only cohorts were analyzed. DNA methylation profiling in a discovery cohort identified 40 CpGs that exhibited statistically significant differential methylation (≥15%) between clinical groups (P <0.01). Hierarchical clustering and principal components analysis suggested neurodevelopmental groups were distinct from CTL, but not from each other. In a larger and more heterogeneous replication cohort, these 40 CpG sites suggested no clear difference between clinical groups. Pooled analysis of DNA methylation across all 60 samples suggested only four differentially methylated CpG sites (P <0.0005), including TAC1. TAC1 promoter CpG hypermethylation was validated in AUT and SEZ (P <0.005). Analyzed for the first time in postmortem brain, TAC1 expression was reduced in cingulate cortex in RTT and AUT+SEZ (P = 0.003). However, no significant difference in TAC1 promoter CpG methylation was detected in RTT and AUT+SEZ brains. Additional molecular analyses revealed that MeCP2 binds directly to the TAC1 promoter and is sensitive to antiepileptic drug treatment.

Conclusion

These data suggest that DNA methylation is not widely altered in RTT, consistent with subtle changes in gene expression previously observed. However, TAC1 may be an important target for further functional analyses in RTT. Studies of larger sample cohorts using primary cells that also consider shared clinical features and drug treatments may be required to address apparent subtle disruptions of DNA methylation in neurodevelopmental disorders.

Epigenetic layers and players underlying neurodevelopment

Epigenetic mechanisms convey information above and beyond the sequence of DNA, so it is predicted that they are critical in the complex regulation of brain development and explain the long-lived effects of environmental cues on pre- and early post-natal brain development. Neurons have a complex epigenetic landscape that changes dynamically with transcriptional activity in early life. Here, we summarize progress in our understanding of the discrete layers of the dynamic methylome, chromatin proteome, noncoding RNAs, chromatin loops, and long-range interactions in neuronal development and maturation. Many neurodevelopmental disorders have genetic alterations in these epigenetic modifications or regulators, and these human genetics lessons have demonstrated the importance of these epigenetic players and the epigenetic layers that transcriptional events lay down in the early brain.

The impact of MeCP2 loss- or gain-of-function on synaptic plasticity

Methyl-CpG-binding protein 2 (MeCP2) is a transcriptional regulator of gene expression that is an important epigenetic factor in the maintenance and development of the central nervous system. The neurodevelopmental disorders Rett syndrome and MECP2 duplication syndrome arise from loss-of-function and gain-of-function alterations in MeCP2 expression, respectively. Several animal models have been developed to recapitulate the symptoms of Rett syndrome and MECP2 duplication syndrome. Cell morphology, neurotransmission, and cellular processes that support learning and memory are compromised as a result of MeCP2 loss- or gain-of-function. Interestingly, loss-of-MeCP2 function and MeCP2 overexpression trigger diametrically opposite changes in synaptic transmission. These findings indicate that the precise regulation of MeCP2 expression is a key requirement for the maintenance of synaptic and neuronal homeostasis and underscore its importance in central nervous system function. This review highlights the functional role of MeCP2 in the brain as a regulator of synaptic and neuronal plasticity as well as its etiological role in the development of Rett syndrome and MECP2 duplication syndrome.

Neonatal MeCP2 is important for the organization of sex differences in vasopressin expression

Several neurodevelopmental disorders are marked by atypical Methyl-CpG-binding protein 2 (MeCP2) expression or function; however, the role of MeCP2 is complex and not entirely clear. Interestingly, there are sex differences in some of these disorders, and it appears that MeCP2 has sex-specific roles during development. Specifically, recent data indicate that a transient reduction in MeCP2 within developing amygdala reduces juvenile social play behavior in males to female-typical levels. These data suggest that MeCP2 within the amygdala is involved in programming lasting sex differences in social behavior. In the present study, we infused MeCP2 or control siRNA into the amygdala of male and female rats during the first three days of postnatal life in order to assess the impact of a transient reduction in MeCP2 on arginine vasopressin (AVP), a neural marker that is expressed differentially between males and females and is linked to a number of social behaviors. The expression of AVP, as well as several other genes, was measured in two-week old and adult animals. Two-week old males expressed more AVP and galanin mRNA in the amygdala than females, and a transient reduction in MeCP2 eliminated this sex difference by reducing the expression of both gene products in males. A transient reduction in MeCP2 also decreased androgen receptor (AR) mRNA in two-week old males. In adulthood, control males had more AVP-immunoreactive (AVP-ir) cells than females in the centromedial amygdala (CMA), bed nucleus of the stria terminalis (BST) and in the fibers that project from these cells to the lateral septum (LS). A transient reduction in MeCP2 eliminated this sex difference. Interestingly, there were no lasting differences in galanin or AR levels in adulthood. Reducing MeCP2 levels during development did not alter estrogen receptorα, neurofilament or Foxg1. We conclude that a transient reduction in MeCP2 expression in the developing male amygdala has a transient impact on galanin and AR expression but a lasting impact on AVP expression, highlighting the importance of MeCP2 in organizing sex differences in the amygdala.

Up-regulated methyl CpG binding protein-2 in intractable temporal lobe epilepsy patients and a rat model

Methyl CpG binding protein-2 (MeCP2) is a multifunctional nuclear protein, and regulates dendritic morphology, synaptic transmission, spontaneous neurotransmission, and short-term synaptic plasticity in the central nervous system. This study was designed to investigate the expression of MeCP2 mRNA and protein in intractable temporal lobe epilepsy (TLE) patients and an experimental animal model. MeCP2 expression was detected in 35 temporal neocortex tissue samples from patients with intractable TLE and 14 histologically normal temporal lobe tissue samples from trauma patients without epilepsy by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry and double-label immunofluorescence. In addition, the timing of MeCP2 expression was evaluated in the hippocampus and adjacent cortex of lithium chloride/pilocarpine-induced TLE rats and uninduced controls. MeCP2 was found to be expressed mainly in the nuclei of neurons, and not expressed in astrocytes. MeCP2 expression was significantly higher in the TLE patients and rats than in the control groups. Following seizures in the rat model, MeCP2 expression gradually increased in the hippocampus and adjacent cortex during the acute period (days 1 and 2) and the latent period (days 7 and 14), but decreased during the chronic period (days 30 and 60). Up-regulated expression of MeCP2 in intractable TLE patients and experimental animals suggested that MeCP2 may be involved in the pathogenesis of TLE.

Crosstalk among Epigenetic Pathways Regulates Neurogenesis

The process of neurogenesis includes neural stem cell proliferation, fate specification, young neuron migration, neuronal maturation, and functional integration into existing circuits. Although neurogenesis occurs largely during embryonic development, low levels but functionally important neurogenesis persists in restricted regions of the postnatal brain, including the subgranular zone of the dentate gyrus in the hippocampus and the subventricular zone of the lateral ventricles. This review will cover both embryonic and adult neurogenesis with an emphasis on the latter. Of the many endogenous mediators of postnatal neurogenesis, epigenetic pathways, such as mediators of DNA methylation, chromatin remodeling systems, and non-coding RNA modulators, appear to play an integral role. Mounting evidence shows that such epigenetic factors form regulatory networks, which govern each step of postnatal neurogenesis. In this review, we explore the emerging roles of epigenetic mechanisms particularly microRNAs, element-1 silencing transcription factor/neuron-restrictive silencing factor (REST/NRSF), polycomb proteins, and methyl-CpG bindings proteins, in regulating the entire process of postnatal and adult neurogenesis. We further summarize recent data regarding how the crosstalk among these different epigenetic proteins forms the critical regulatory network that regulates neuronal development. We finally discuss how crosstalk between these pathways may serve to translate environmental cues into control of the neurogenic process.

MeCP2: phosphorylated locally, acting globally

In this issue of Neuron, Greenberg and colleagues revise our understanding of how activity-dependent MeCP2 phosphorylation regulates distinct aspects of brain development and circuit function. The study also suggests a prominent role for MeCP2 in the regulation of global chromatin state in vivo.

MicroRNA212/132 family: molecular transducer of neuronal function and plasticity

MicroRNAs (miRNAs) are small non-coding RNAs that mediate post-transcriptional gene silencing. It is increasingly clear that miRNAs are key regulatory factors for a tight gene expression control. MiRNAs are involved in many aspects of organism development and function, in physiological and pathological conditions. MiRNA expression varies with cell type, tissue and developmental stages. The microRNA212/132 family is one of the most studied miRNA family due to the involvement of miR132 and miR212 in important cellular processes, especially in the brain. MiR132 and miR212 have been implicated in tissue development and in the formation and plasticity of neuronal connections. The main aim of this review is to highlight recent discoveries about miR212/132 family functions and its possible involvement in pathological processes.

Drosophila modeling of heritable neurodevelopmental disorders

Heritable neurodevelopmental disorders are multifaceted disease conditions encompassing a wide range of symptoms including intellectual disability, cognitive dysfunction, autism and myriad other behavioral impairments. In cases where single, causative genetic defects have been identified, such as Angelman syndrome, Rett syndrome, Neurofibromatosis Type 1 and Fragile X syndrome, the classical Drosophila genetic system has provided fruitful disease models. Recent Drosophila studies have advanced our understanding of UBE3A, MECP2, NF1 and FMR1 function, respectively, in genetic, biochemical, anatomical, physiological and behavioral contexts. Investigations in Drosophila continue to provide the essential mechanistic understanding required to facilitate the conception of rational therapeutic treatments.

Emerging roles of epigenetic mechanisms in the enduring effects of early-life stress and experience on learning and memory

Epigenetic mechanisms are involved in programming gene expression throughout development. In addition, they are key contributors to the processes by which early-life experience fine-tunes the expression levels of key neuronal genes, governing learning and memory throughout life. Here we describe the long-lasting, bi-directional effects of early-life experience on learning and memory. We discuss how enriched postnatal experience enduringly augments spatial learning, and how chronic early-life stress results in persistent and progressive deficits in the structure and function of hippocampal neurons. The existing and emerging roles of epigenetic mechanisms in these fundamental neuroplasticity phenomena are illustrated.