An epigenetic feedback regulatory loop involving microRNA-195 and MBD1 governs neural stem cell differentiation

Putative Epigenetic Regulator microRNAs (epi-miRNAs) and Their Predicted Targets in High-Fat Diet-Induced Cardiac Dysfunction: An In Silico Analysis in Obese Rats

Obesity-related cardiac dysfunction is a significant global health challenge. High-fat diets (HFDs) are well-established models of obesity. HFD has been reported to induce cardiac dysfunction and alter cardiac miRNA expression, DNA methylation and histone modifications. Nevertheless, it remains unclear whether cardiac miRNAs altered due to HFD target epigenetic regulator enzymes and function as epigenetic regulator miRNAs (epi-miRNAs), thereby contributing to HFD-induced epigenetic changes and cardiac dysfunction. To address this gap in our knowledge, this study aimed to identify putative cardiac epi-miRNAs and their potential epigenetic targets through an in silico analysis of a previously published miRNA dataset from Sprague Dawley rats subjected to HFD. Using two independent databases, miRDB and miRWalk, predicted miRNA-mRNA interactions were analyzed. A total of 71 miRNAs were identified in our present study as putative epi-miRNAs. A total of 34 epi-miRNAs were upregulated (e.g., miR-92b-3p, let-7c-5p, miR-132-3p), and 37 were downregulated (e.g., miR-21-3p, miR-29c-3p, miR-199a-3p) in response to HFD. Epi-miRNAs targeted 81 individual epigenetic regulators (e.g., Dnmt3a, Ezh2, Hdac4, Kdm3a) with 202 possible miRNA-target interactions. Most of the targeted epigenetic regulators were involved in histone modification. An epi-miRNA-target analysis indicated increased DNA methylation and histone acetylation and decreased histone methylation in the hearts of HFD-fed rats. These findings suggest the importance of epi-miRNA-induced epigenetic changes in HFD-related cardiac dysfunction.

microRNA and the Post-Transcriptional Response to Oxidative Stress during Neuronal Differentiation: Implications for Neurodevelopmental and Psychiatric Disorders

Oxidative stress is one of the most important environmental exposures associated with psychiatric disorders, but the underlying molecular mechanisms remain to be elucidated. In a previous study, we observed a substantial alteration of the gene expression landscape in neuron-like cells that were differentiated from SH-SY5Y cells after or during exposure to oxidative stress, with a subset of dysregulated genes being enriched for neurodevelopmental processes. To further explore the regulatory mechanisms that might account for such profound perturbations, we have now applied small RNA-sequencing to investigate changes in the expression of miRNAs. These molecules are known to play crucial roles in brain development and response to stress through their capacity to suppress gene expression and influence complex biological networks. Through these analyses, we observed more than a hundred differentially expressed miRNAs, including 80 previously reported to be dysregulated in psychiatric disorders. The seven most influential miRNAs associated with pre-treatment exposure, including miR-138-5p, miR-96-5p, miR-34c-5p, miR-1287-5p, miR-497-5p, miR-195-5p, and miR-16-5p, supported by at least 10 negatively correlated mRNA connections, formed hubs in the interaction network with 134 genes enriched with neurobiological function, whereas in the co-treatment condition, miRNA-mRNA interaction pairs were enriched in cardiovascular and immunity-related disease ontologies. Interestingly, 12 differentially expressed miRNAs originated from the DLK1-DIO3 location, which encodes a schizophrenia-associated miRNA signature. Collectively, our findings suggest that early exposure to oxidative stress, before and during prenatal neuronal differentiation, might increase the risk of mental illnesses in adulthood by disturbing the expression of miRNAs that regulate neurodevelopmentally significant genes and networks.

MiR-181a-5p promotes neural stem cell proliferation and enhances the learning and memory of aged mice

Hippocampal neural stem cell (NSC) proliferation is known to decline with age, which is closely linked to learning and memory impairments. In the current study, we found that the expression level of miR-181a-5p was decreased in the hippocampal NSCs of aged mice and that exogenous overexpression of miR-181a-5p promoted NSC proliferation without affecting NSC differentiation into neurons and astrocytes. The mechanistic study revealed that phosphatase and tensin homolog (PTEN), a negative regulator of the AKT signaling pathway, was the target of miR-181a-5p and knockdown of PTEN could rescue the impairment of NSC proliferation caused by low miR-181a-5p levels. Moreover, overexpression of miR-181a-5p in the dentate gyrus enhanced the proliferation of NSCs and ameliorated learning and memory impairments in aged mice. Taken together, our findings indicated that miR-181a-5p played a functional role in NSC proliferation and aging-related, hippocampus-dependent learning and memory impairments.

Non-Coding RNAs in the Regulation of Hippocampal Neurogenesis and Potential Treatment Targets for Related Disorders

Non-coding RNAs (ncRNAs), including miRNAs, lncRNAs, circRNAs, and piRNAs, do not encode proteins. Nonetheless, they have critical roles in a variety of cellular activities-such as development, neurogenesis, degeneration, and the response to injury to the nervous system-via protein translation, RNA splicing, gene activation, silencing, modifications, and editing; thus, they may serve as potential targets for disease treatment. The activity of adult neural stem cells (NSCs) in the subgranular zone of the hippocampal dentate gyrus critically influences hippocampal function, including learning, memory, and emotion. ncRNAs have been shown to be involved in the regulation of hippocampal neurogenesis, including proliferation, differentiation, and migration of NSCs and synapse formation. The interaction among ncRNAs is complex and diverse and has become a major topic within the life science. This review outlines advances in research on the roles of ncRNAs in modulating NSC bioactivity in the hippocampus and discusses their potential applications in the treatment of illnesses affecting the hippocampus.

Adult Neural Stem Cell Regulation by Small Non-coding RNAs: Physiological Significance and Pathological Implications

The adult neurogenic niches are complex multicellular systems, receiving regulatory input from a multitude of intracellular, juxtacrine, and paracrine signals and biological pathways. Within the niches, adult neural stem cells (aNSCs) generate astrocytic and neuronal progeny, with the latter predominating in physiological conditions. The new neurons generated from this neurogenic process are functionally linked to memory, cognition, and mood regulation, while much less is known about the functional contribution of aNSC-derived newborn astrocytes and adult-born oligodendrocytes. Accumulating evidence suggests that the deregulation of aNSCs and their progeny can impact, or can be impacted by, aging and several brain pathologies, including neurodevelopmental and mood disorders, neurodegenerative diseases, and also by insults, such as epileptic seizures, stroke, or traumatic brain injury. Hence, understanding the regulatory underpinnings of aNSC activation, differentiation, and fate commitment could help identify novel therapeutic avenues for a series of pathological conditions. Over the last two decades, small non-coding RNAs (sncRNAs) have emerged as key regulators of NSC fate determination in the adult neurogenic niches. In this review, we synthesize prior knowledge on how sncRNAs, such as microRNAs (miRNAs) and piwi-interacting RNAs (piRNAs), may impact NSC fate determination in the adult brain and we critically assess the functional significance of these events. We discuss the concepts that emerge from these examples and how they could be used to provide a framework for considering aNSC (de)regulation in the pathogenesis and treatment of neurological diseases.

The Protective Effect of Picroside II on Isoflurane-Induced Neuronal Injury in Rats via Downregulating miR-195

INTRODUCTION

Numerous pieces of evidence demonstrated that isoflurane induces hippocampal cell injury and cognitive impairments. Picroside II has been investigated for its anti-apoptosis and antioxidant neuroprotective effects. We aimed to explore the protective effects of picroside II and the role of microRNA-195 (miR-195) on isoflurane-induced neuronal injury in rats.

METHODS

The Morris water maze test was used to evaluate the effects of isoflurane on rats regarding escape latency and time in quadrant parameters. Real-time quantitative PCR was used to detect the expression levels of miR-195 and pro-inflammatory cytokines, including inter-leukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) mRNA, in the hippocampal tissues and neuronal cells.

RESULTS

The picroside II significantly improves isoflurane-induced higher escape latency and lower time spent in the quadrant compared with the control rats. Picroside II also promotes cell viability and suppresses cell apoptosis of isoflurane-induced neuronal cells. Besides, picroside II suppresses the expression of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and miR-195 in vivo and in vitro. Furthermore, overexpression of miR-195 abrogates the effects of picroside II on the expression of pro-inflammatory cytokines. The appropriate dose of picroside II is 20 mg/kg.

CONCLUSION

Picroside II could protect the nervous system possibly through inhibiting the inflammatory response in the isoflurane-induced neuronal injury of rats. The protective effect of picroside II may be achieved by downregulating the expression of miR-195 and then inhibiting the inflammatory response.

Arid1a regulates neural stem/progenitor cell proliferation and differentiation during cortical development

Objective

Neurodevelopmental diseases are common disorders caused by the disruption of essential neurodevelopmental processes. Recent human exome sequencing and genome‐wide association studies have shown that mutations in the subunits of the SWI/SNF (BAF) complex are risk factors for neurodevelopmental diseases. Clinical studies have found that ARID1A (BAF250a) is the most frequently mutated SWI/SNF gene and its mutations lead to mental retardation and microcephaly. However, the function of ARID1A in brain development and its underlying mechanisms still remain elusive.

Methods

The present study used Cre/loxP system to generate an Arid1a conditional knockout mouse line. Cell proliferation, cell apoptosis and cell differentiation of NSPCs were studied by immunofluorescence staining. In addition, RNA‐seq and RT‐PCR were performed to dissect the molecular mechanisms of Arid1a underlying cortical neurogenesis. Finally, rescue experiments were conducted to evaluate the effects of Neurod1 or Fezf2 overexpression on the differentiation of NSPCs in vitro.

Results

Conditional knockout of Arid1a reduces cortical thickness in the developing cortex. Arid1a loss of function inhibits the proliferation of radial glial cells, and increases cell death during late cortical development, and leads to dysregulated expression of genes associated with proliferation and differentiation. Overexpression of Neurod1 or Fezf2 in Arid1a cKO NSPCs rescues their neural differentiation defect in vitro.

Conclusions

This study demonstrates for the first time that Arid1a plays an important role in regulating the proliferation and differentiation of NSPCs during cortical development, and proposes several gene candidates that are worth to understand the pathological mechanisms and to develop novel interventions of neurodevelopment disorders caused by Arid1a mutations.

Overview of host miRNA properties and their association with epigenetics, long non-coding RNAs, and Xeno-infectious factors

MicroRNA-derived structures play impressive roles in various biological processes. So dysregulation of miRNAs can lead to different human diseases. Recent studies have extended our comprehension of the control of miRNA function and features. Here, we overview some remarkable miRNA properties that have potential implications for the miRNA functions, including different variants of a miRNA called isomiRs, miRNA arm selection/arm switching, and the effect of these factors on miRNA target selection. Besides, we review some aspects of miRNA interactions such as the interaction between epigenetics and miRNA (different miRNAs and their related processing enzymes are epigenetically regulated by multiple DNA methylation enzymes. moreover, DNA methylation could be controlled by diverse mechanisms related to miRNAs), direct and indirect crosstalk between miRNA and lnc (Long Non-Coding) RNAs as a further approach to conduct intercellular regulation called "competing endogenous RNA" (ceRNA) that is involved in the pathogenesis of different diseases, and the interaction of miRNA activities and some Xeno-infectious (virus/bacteria/parasite) factors, which result in modulation of the pathogenesis of infections. This review provides some related studies to a better understanding of miRNA involvement mechanisms and overcoming the complexity of related diseases that may be applicable and useful to prognostic, diagnostic, therapeutic purposes and personalized medicine in the future.

ADNCR modulates neural stem cell differentiation and proliferation through the regulation of TCF3 expression

Background

Neural stem cells (NSCs) are undifferentiated precursor cells that have the ability to self-renew and proliferate and have the capacity to become either glia (oligodendrocytes and astrocytes) or neurons. NSCs can act as beneficial adjuncts for many neurological disorders, such as cerebral infarction, spinal cord injuries, Alzheimer's disease, and Parkinson's disease. Long noncoding RNAs (lncRNAs) play essential roles during cell differentiation, proliferation, and metabolism. This study aimed to explore the role played by adipocyte differentiation-associated long noncoding RNA (ADNCR) in the self-renewal and multipotency of NSCs.

Methods

In this study, we identified NSCs and verified that these cells were able to regenerate and differentiate into both astrocytes and neurons. Then we studied the relation between expression of ADNCR and transcription factor 3 (TCF3) and proliferation of NSCs.

Results

ADNCR and TCF3 expression have been shown to decrease during the differentiation of NSCs into both neurons and astrocyte induction cells. However, the expression of the microRNA miR-204-5p increased over time during the differentiation of NSCs into both neurons and astrocyte induction cells. ADNCR acts as a competing endogenous RNA (ceRNA) for miR-204-5p, and the overexpression of ADNCR suppressed miR-204-5p expression and enhanced TCF3 expression in NSCs, which resulted in enhanced proliferation and suppressed neural differentiation.

Conclusions

These data suggested that the use of ADNCR may represent a new strategy for expanding the interventions used to treat neurological disorders.

miR-762 regulates the proliferation and differentiation of retinal progenitor cells by targeting NPDC1

Retinal degenerations, which lead to irreversible decline in visual function, are still no effective recovery treatments. Currently, retinal progenitor cell (RPC) transplantation therapy is expected to provide a new approach to treat these diseases; however, the limited proliferation capacity and differentiation potential toward specific retinal neurons of RPCs hinder their potential clinical applications. microRNAs have been reported to serve as important regulators in the cell fate determination of stem/progenitor cells. In this study, our data demonstrated that miR-762 inhibited NPDC1 expression to positively regulate RPC proliferation and suppress RPC neuronal differentiation. Furthermore, the knockdown of miR-762 upregulated NPDC1 expression in RPCs, leading to the inhibition of RPC proliferation and the increase in neuronal differentiation. Moreover, NPDC1 could rescue anti-miR-762-induced RPC proliferation deficiency and the inhibitory effect of miR-762 on RPC differentiation. In conclusion, our study demonstrated that miR-762 plays a crucial role in regulating RPC proliferation and differentiation by directly targeting NPDC1, which is firstly reported that microRNAs positively regulate RPC proliferation and negatively regulate RPC differentiation, which provides a comprehensive understanding of the molecular mechanisms that dominate RPC proliferation and differentiation in vitro.

The molecular mechanism underlying GABAergic dysfunction in nucleus accumbens of depression-like behaviours in mice

Depression is the most frequent psychiatric disorder in the world. Recent evidence has shown that stress-induced GABAergic dysfunction in the nucleus accumbens (NAc) contributed to the pathophysiology of depression. However, the molecular mechanisms underlying these pathological changes remain unclear. In this study, mice were constantly treated with the chronic unpredictable mild stress (CUMS) till showing depression-like behaviours expression. GABA synthesis, release and uptake in the NAc tissue were assessed by analysing the expression level of genes and proteins of Gad-1, VGAT and GAT-3 by qRT-PCR and Western blotting. The miRNA/mRNA network regulating GABA was constructed based on the bioinformatics prediction software and further validated by dual-luciferase reporter assay in vitro and qRT-PCR in vivo, respectively. Our results showed that the expression level of GAT-3, Gad-1 and VGAT mRNA and protein significantly decreased in the NAc tissue from CUMS-induced depression-like mice than that of control mice. However, miRNA-144-3p, miRNA-879-5p, miR-15b-5p and miRNA-582-5p that directly down-regulated the expression of Gad-1, VGAT and GAT-3 were increased. In the mRNA/miRNA regulatory GABA network, Gad-1 and VGAT were directly regulated by binding seed sequence of miR-144-3p, and miR-15b-5p, miR-879-5p could be served negative post-regulators by binding to the different sites of VGAT 3'-UTR. Chronic stress causes the impaired GABA synthesis, release and uptake by up-regulating miRNAs and down-regulating mRNAs and proteins, which may reveal the molecular mechanisms for the decreased GABA concentrations in the NAc tissue of CUMS-induced depression.

Inhibition of MicroRNA-195 Alleviates Neuropathic Pain by Targeting Patched1 and Inhibiting SHH Signaling Pathway Activation

Trigeminal neuralgia (TN) is a type of chronic neuropathic pain that is caused by peripheral nerve lesions that result from various conditions, including the compression of vessels, tumors and viral infections. MicroRNAs (miRs) are increasingly recognized as potential regulators of neuropathic pain. Previous evidence has demonstrated that miR-195 is involved in neuropathic pain, but the mechanism remains unclear. To investigate the pathophysiological role of miR-195 and Shh signaling in TN, persistent facial pain was induced by infraorbital nerve chronic constriction injury (CCI-IoN), and facial pain responses were evaluated by Von Frey hairs. qPCR and Western blotting were used to determine the relative expression of miR-195 and Patched1, the major receptor of the Sonic Hedgehog (Shh) signaling pathway, in the caudal brain stem at distinct time points after CCI-IoN. Here, we found that the expression of miR-195 was increased in a rat model of CCI-IoN. In contrast, the expression of Patched1 decreased significantly. Luciferase assays confirmed the binding of miR-195 to Patched1. In addition, the overexpression of miR-195 by an intracerebroventricular (i.c.v) administration of LV-miR-195 aggravated facial pain development, and this was reversed by upregulating the expression of Patched1. These results suggest that miR-195 is involved in the development of TN by targeting Patched1 in the Shh signaling pathway, thus regulating extracellular glutamate.

The role of adult hippocampal neurogenesis in brain health and disease

Adult neurogenesis in the dentate gyrus of the hippocampus is highly regulated by a number of environmental and cell-intrinsic factors to adapt to environmental changes. Accumulating evidence suggests that adult-born neurons may play distinct physiological roles in hippocampus-dependent functions, such as memory encoding and mood regulation. In addition, several brain diseases, such as neurological diseases and mood disorders, have deleterious effects on adult hippocampal neurogenesis, and some symptoms of those diseases can be partially explained by the dysregulation of adult hippocampal neurogenesis. Here we review a possible link between the physiological functions of adult-born neurons and their roles in pathological conditions.

Cell Cycle Regulation of Stem Cells by MicroRNAs

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules involved in the regulation of gene expression. They are involved in the fine-tuning of fundamental biological processes such as proliferation, differentiation, survival and apoptosis in many cell types. Emerging evidence suggests that miRNAs regulate critical pathways involved in stem cell function. Several miRNAs have been suggested to target transcripts that directly or indirectly coordinate the cell cycle progression of stem cells. Moreover, previous studies have shown that altered expression levels of miRNAs can contribute to pathological conditions, such as cancer, due to the loss of cell cycle regulation. However, the precise mechanism underlying miRNA-mediated regulation of cell cycle in stem cells is still incompletely understood. In this review, we discuss current knowledge of miRNAs regulatory role in cell cycle progression of stem cells. We describe how specific miRNAs may control cell cycle associated molecules and checkpoints in embryonic, somatic and cancer stem cells. We further outline how these miRNAs could be regulated to influence cell cycle progression in stem cells as a potential clinical application.

Regulation of Adult Neurogenesis by Non-coding RNAs: Implications for Substance Use Disorders

The discovery of non-coding RNAs (ncRNAs)has been one of the central findings from early genomic sequencing studies. Not only was the presence of these genes unknown previously, it was the staggering disproportionate share of the genome that was predicted to be encoded by ncRNAs that was truly significant in genomic research. Over the years the function of various classes of these ncRNAs has been revealed. One of the first and enduring regulatory programs associated with these factors was development. In the neurosciences, the discovery of adult derived populations of dividing cells within the brain was equally substantial. The brain was hypothesized to be plastic only in its neuronal connectivity, but the discovery of the generation of new neurons was a novel mechanism of neuronal and behavioral plasticity. The process of adult neurogenesis resembles early neuronal development and has been found to share many parallels in the proper stages of specified genetic programs. Adult neurogenesis has also been found to play a role in learning and memory involved in particular hippocampal-dependent behaviors. Substance use disorders (SUDs) are an example of a behavioral condition that is associated with and possibly driven by hippocampal alterations. Our laboratory has determined that hippocampal adult neurogenesis is necessary for a rodent model of methamphetamine relapse. Due to the previous research on ncRNAs in development and in other brain regions involved in SUDs, we posit that ncRNAs may play a role in adult neurogenesis associated with this disorder. This review will cover the regulatory mechanisms of various classes of ncRNAs on the coordinated genetic program associated with adult neurogenesis with a special focus on how these programs could be dysregulated in SUDs.

MicroRNAs Engage in Complex Circuits Regulating Adult Neurogenesis

The finding that the adult mammalian brain is still capable of producing neurons has ignited a new field of research aiming to identify the molecular mechanisms regulating adult neurogenesis. An improved understanding of these mechanisms could lead to the development of novel approaches to delay cognitive decline and facilitate neuroregeneration in the adult human brain. Accumulating evidence suggest microRNAs (miRNAs), which represent a class of post-transcriptional gene expression regulators, as crucial part of the gene regulatory networks governing adult neurogenesis. This review attempts to illustrate how miRNAs modulate key processes in the adult neurogenic niche by interacting with each other and with transcriptional regulators. We discuss the function of miRNAs in adult neurogenesis following the life-journey of an adult-born neuron from the adult neural stem cell (NSCs) compartment to its final target site. We first survey how miRNAs control the initial step of adult neurogenesis, that is the transition of quiescent to activated proliferative adult NSCs, and then go on to discuss the role of miRNAs to regulate neuronal differentiation, survival, and functional integration of the newborn neurons. In this context, we highlight miRNAs that converge on functionally related targets or act within cross talking gene regulatory networks. The cooperative manner of miRNA action and the broad target repertoire of each individual miRNA could make the miRNA system a promising tool to gain control on adult NSCs in the context of therapeutic approaches.

Polycomb protein family member CBX7 regulates intrinsic axon growth and regeneration

Neurons in the central nervous system (CNS) lose their intrinsic ability and fail to regenerate, but the underlying mechanisms are largely unknown. Polycomb group (PcG) proteins, which include PRC1 and PRC2 complexes function as gene repressors and are involved in many biological processes. Here we report that PRC1 components (polycomb chromobox (CBX) 2, 7, and 8) are novel regulators of axon growth and regeneration. Especially, knockdown of CBX7 in either embryonic cortical neurons or adult dorsal root ganglion (DRG) neurons enhances their axon growth ability. Two important transcription factors GATA4 and SOX11 are functional downstream targets of CBX7 in controlling axon regeneration. Moreover, knockdown of GATA4 or SOX11 in cultured DRG neurons inhibits axon regeneration response from CBX7 downregulation in DRG neurons. These findings suggest that targeting CBX signaling pathway may be a novel approach for promoting the intrinsic regenerative capacity of damaged CNS neurons.

Review: adult neurogenesis contributes to hippocampal plasticity

Adult hippocampal neurogenesis is the process by which new functional neurons are added to the adult dentate gyrus of the hippocampus. Animal studies have shown that the degree of adult hippocampal neurogenesis is regulated by local environmental cues as well as neural network activities. Furthermore, accumulating evidence has suggested that adult hippocampal neurogenesis plays prominent roles in hippocampus-dependent brain functions. In this review, we summarize the mechanisms underlying the regulation of adult hippocampal neurogenesis at various developmental stages and propose how adult-born neurons contribute to structural and functional hippocampal plasticity.

DNA Methylation and Adult Neurogenesis

The role of DNA methylation in brain development is an intense area of research because the brain has particularly high levels of CpG and mutations in many of the proteins involved in the establishment, maintenance, interpretation, and removal of DNA methylation impact brain development and/or function. These include DNA methyltransferase (DNMT), Ten-Eleven Translocation (TET), and Methyl-CpG binding proteins (MBPs). Recent advances in sequencing breadth and depth as well the detection of different forms of methylation have greatly expanded our understanding of the diversity of DNA methylation in the brain. The contributions of DNA methylation and associated proteins to embryonic and adult neurogenesis will be examined. Particular attention will be given to the impact on adult hippocampal neurogenesis (AHN), which is a key mechanism contributing to brain plasticity, learning, memory and mood regulation. DNA methylation influences multiple aspects of neurogenesis from stem cell maintenance and proliferation, fate specification, neuronal differentiation and maturation, and synaptogenesis. In addition, DNA methylation during neurogenesis has been shown to be responsive to many extrinsic signals, both under normal conditions and during disease and injury. Finally, crosstalk between DNA methylation, Methyl-DNA binding domain (MBD) proteins such as MeCP2 and MBD1 and histone modifying complexes is used as an example to illustrate the extensive interconnection between these epigenetic regulatory systems.

Methyl-CpG-Binding Protein MBD1 Regulates Neuronal Lineage Commitment through Maintaining Adult Neural Stem Cell Identity

Methyl-CpG-binding domain 1 (MBD1) belongs to a family of methyl-CpG-binding proteins that are epigenetic "readers" linking DNA methylation to transcriptional regulation. MBD1 is expressed in neural stem cells residing in the dentate gyrus of the adult hippocampus (aNSCs) and MBD1 deficiency leads to reduced neuronal differentiation, impaired neurogenesis, learning deficits, and autism-like behaviors in mice; however, the precise function of MBD1 in aNSCs remains unexplored. Here, we show that MBD1 is important for maintaining the integrity and stemness of NSCs, which is critical for their ability to generate neurons. MBD1 deficiency leads to the accumulation of undifferentiated NSCs and impaired transition into the neuronal lineage. Transcriptome analysis of neural stem and progenitor cells isolated directly from the dentate gyrus of MBD1 mutant (KO) and WT mice showed that gene sets related to cell differentiation, particularly astrocyte lineage genes, were upregulated in KO cells. We further demonstrated that, in NSCs, MBD1 binds and represses directly specific genes associated with differentiation. Our results suggest that MBD1 maintains the multipotency of NSCs by restraining the onset of differentiation genes and that untimely expression of these genes in MBD1-deficient stem cells may interfere with normal cell lineage commitment and cause the accumulation of undifferentiated cells. Our data reveal a novel role for MBD1 in stem cell maintenance and provide insight into how epigenetic regulation contributes to adult neurogenesis and the potential impact of its dysregulation.

SIGNIFICANCE STATEMENT

Adult neural stem cells (aNSCs) in the hippocampus self-renew and generate neurons throughout life. We show that methyl-CpG-binding domain 1 (MBD1), a DNA methylation "reader," is important for maintaining the integrity of NSCs, which is critical for their neurogenic potency. Our data reveal a novel role for MBD1 in stem cell maintenance and provide insight into how epigenetic regulation preserves the multipotency of stem cells for subsequent differentiation.

MiR-203 Interplays with Polycomb Repressive Complexes to Regulate the Proliferation of Neural Stem/Progenitor Cells

The polycomb repressive complexes 1 (PRC1) and 2 (PRC2) are two distinct polycomb group (PcG) proteins that maintain the stable silencing of specific sets of genes through chromatin modifications. Although the PRC2 component EZH2 has been known as an epigenetic regulator in promoting the proliferation of neural stem/progenitor cells (NSPCs), the regulatory network that controls this process remains largely unknown. Here we show that miR-203 is repressed by EZH2 in both embryonic and adult NSPCs. MiR-203 negatively regulates the proliferation of NSPCs. One of PRC1 components, Bmi1, is a downstream target of miR-203 in NSPCs. Conditional knockout of Ezh2 results in decreased proliferation ability of both embryonic and adult NSPCs. Meanwhile, ectopic overexpression of BMI1 rescues the proliferation defects exhibited by miR-203 overexpression or EZH2 deficiency in NSPCs. Therefore, this study provides evidence for coordinated function of the EZH2-miR-203-BMI1 regulatory axis that regulates the proliferation of NSPCs.

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MiR-203 is repressed by EZH2 in NSPCs

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MiR-203 negatively regulates the proliferation of NSPCs

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Bmi1 is a downstream target of miR-203 in NSPCs

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MiR-203 is a mediator between PRC2 and PRC1 that modulates the proliferation of NSPCs

The therapeutic contribution of nanomedicine to treat neurodegenerative diseases via neural stem cell differentiation

The discovery of adult neurogenesis drastically changed the therapeutic approaches of central nervous system regenerative medicine. The stimulation of this physiologic process can increase memory and motor performances in patients affected by neurodegenerative diseases. Neural stem cells contribute to the neurogenesis process through their differentiation into specialized neuronal cells. In this review, we describe the most important methods developed to restore neurological functions via neural stem cell differentiation. In particular, we focused on the role of nanomedicine. The application of nanostructured scaffolds, nanoparticulate drug delivery systems, and nanotechnology-based real-time imaging has significantly improved the safety and the efficacy of neural stem cell-based treatments. This review provides a comprehensive background on the contribution of nanomedicine to the modulation of neurogenesis via neural stem cell differentiation.

Regulatory Axis of miR-195/497 and HMGA1-Id3 Governs Muscle Cell Proliferation and Differentiation

Myocytes withdraw from the cell cycle to differentiate during muscle development. Given the capacity of microRNAs (miRNAs) to regulate gene expression during development, we screened for miRNAs that were associated with muscle development. S-Poly(T) Plus analysis of 273 miRNAs in porcine longissimus dorsi muscles revealed 14 miRNAs that were strongly upregulated with age of postnatal muscle development in vivo, including miR-195 and miR-497. These two miRNAs were also strongly upregulated at late differentiation stages of mouse skeletal myoblast C2C12 cells, and demethylation treatment induced significant upregulation of miR-195/497. Manipulation of miR-195/497 expression resulted in dramatic changes in the proliferation and differentiation of C2C12 cells. We identified high-mobility group AT-hook 1 (Hmga1) mRNA as a highly conserved target of miR-195/497 in C2C12 myoblasts. Overexpression of miR-195/497 or Hmga1 silencing in C2C12 cells promoted myogenic differentiation. Moreover, we showed that miR-195/497 repressed Hmga1, which in turn downregulated one of the HMGA1 downstream targets Id3, whose inhibitory effect on myogenic differentiation is well established. Our study revealed a subset of potential development-associated miRNAs and suggests a novel regulatory axis for myogenesis in which miR-195/497 promote myogenic differentiation by repressing the HMGA1-Id3 pathway.

Circulating miRNAs as intercellular messengers, potential biomarkers and therapeutic targets for Type 2 diabetes

miRNAs have emerged as key epigenetic regulators of metabolism. Their deregulation contributes to metabolic abnormalities, proposing their potential role as therapeutic targets for Type 2 diabetes. The exciting finding that miRNAs exist in the bloodstream suggests that circulating miRNAs may act in a hormone-like fashion. Despite the fact that significant progress has been made in understanding circulating miRNAs, this topic is full of complexities and many questions remain unanswered. The goal of this review is to bring together up-to-date knowledge about circulating miRNAs and their role as intercellular communicators as well as potential biomarkers and therapeutic targets in metabolic diseases, providing examples of possible clinical applications for circulating miRNAs in diabetes and cardiovascular complications.

Genetics and Epigenetics in Adult Neurogenesis

The cellular basis of adult neurogenesis is neural stem cells residing in restricted areas of the adult brain. These cells self-renew and are multipotent. The maintenance of "stemness" and commitment to differentiation are tightly controlled by intricate molecular networks. Epigenetic mechanisms, including chromatin remodeling, DNA methylation, and noncoding RNAs (ncRNAs), have profound regulatory roles in mammalian gene expression. Significant advances have been made regarding the dynamic roles of epigenetic modulation and function. It has become evident that epigenetic regulators are key players in neural-stem-cell self-renewal, fate specification, and final maturation of new neurons, therefore, adult neurogenesis. Altered epigenetic regulation can result in a number of neurological and neurodevelopmental disorders. Here, we review recent discoveries that advance our knowledge in epigenetic regulation of mammalian neural stem cells and neurogenesis. Insights from studies of epigenetic gene regulation in neurogenesis may lead to new therapies for the treatment of neurodevelopmental disorders.

Inhibition of miR-15a Promotes BDNF Expression and Rescues Dendritic Maturation Deficits in MeCP2-Deficient Neurons

In both the embryonic and adult brain, a critical step in neurogenesis is neuronal maturation. Deficiency of MeCP2 leads to Rett syndrome, a severe neurodevelopmental disorder. We have previously shown that MeCP2 plays critical roles in the maturation step of new neurons during neurogenesis. MeCP2 is known to regulate the expression of brain-derived neurotrophic factor (BDNF), a potent neurotrophic factor for neuronal maturation. Nevertheless, how MeCP2 regulates BDNF expression and how MeCP2 deficiency leads to reduced BDNF expression remain unclear. Here, we show that MeCP2 regulates the expression of a microRNA, miR-15a. We find that miR-15a plays a significant role in the regulation of neuronal maturation. Overexpression of miR-15a inhibits dendritic morphogenesis in immature neurons. Conversely, a reduction in miR-15a has the opposite effect. We further show that miR-15a regulates expression levels of BDNF, and exogenous BDNF could partially rescue the neuronal maturation deficits resulting from miR-15a overexpression. Finally, inhibition of miR-15a could rescue neuronal maturation deficits in MeCP2-deficient adult-born new neurons. These results demonstrate a novel role for miR-15a in neuronal development and provide a missing link in the regulation of BDNF by MeCP2.

Identification of a panel of five serum miRNAs as a biomarker for Parkinson's disease

BACKGROUND AND OBJECTIVE

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder after Alzheimer's disease. The aim of this work was to determine whether the differences of serum miRNAs profiling could distinguish PD patients from healthy individuals.

METHODS

We collected serum samples from 106 sporadic PD patients and 91 age/gender-matched healthy controls. Serum miRNAs were analysed by Solexa sequencing followed by a qRT-PCR examination. The qRT-PCR assay, which was divided into two phases, was used to validate the expression of miRNAs screened by Solexa sequencing. Receiver operating characteristic (ROC) curve analysis and clustering analysis were performed to determine the diagnostic usefulness of the selected miRNAs for PD.

RESULTS

In this study, we generated a profile of 5 serum miRNAs: miR-195 was up-regulated, and miR-185, miR-15b, miR-221 and miR-181a were down-regulated.

CONCLUSION

This group of five miRNAs can precisely distinguish PD patients from health individuals and may be used as a potential serum-based biomarker for the diagnosis of PD.

RNA interference machinery-mediated gene regulation in mouse adult neural stem cells

Background

Neurogenesis in the brain of adult mammals occurs throughout life in two locations: the subventricular zone of the lateral ventricle and the subgranular zone of the dentate gyrus in the hippocampus. RNA interference mechanisms have emerged as critical regulators of neuronal differentiation. However, to date, little is known about its function in adult neurogenesis.

Results

Here we show that the RNA interference machinery regulates Doublecortin levels and is associated with chromatin in differentiating adult neural progenitors. Deletion of Dicer causes abnormal higher levels of Doublecortin. The microRNA pathway plays an important role in Doublecortin regulation. In particular miRNA-128 overexpression can reduce Doublecortin levels in differentiating adult neural progenitors.

Conclusions

We conclude that the RNA interference components play an important role, even through chromatin association, in regulating neuron-specific gene expression programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-015-0198-7) contains supplementary material, which is available to authorized users.

MicroRNA-378 regulates neural stem cell proliferation and differentiation in vitro by modulating Tailless expression

Previous studies have suggested that microRNAs (miRNAs) play an important role in regulating neural stem cell (NSC) proliferation and differentiation. However, the precise role of miRNAs in NSC remains largely unexplored. In this study, we showed that miR-378 can target Tailless (TLX), a critical regulator of NSC, to regulate NSC proliferation and differentiation. By bioinformatic algorithms, miR-378 was found to have a predicted target site in the 3'-untranslated region of TLX, which was verified by a dual-luciferase reporter assay. The expression of miR-378 was increased during NSC differentiation and inversely correlated with TLX expression. qPCR and Western blot analysis also showed that miR-378 negatively regulated TLX mRNA and protein expression in neural stem cells (NSCs). Intriguingly, overexpression of miR-378 increased NSC differentiation and reduced NSC proliferation, whereas suppression of miR-378 led to decreased NSC differentiation and increased NSC proliferation. Moreover, the downstream targets of TLX, including p21, PTEN and Wnt/β-catenin were also found to be regulated by miR-378. Additionally, overexpression of TLX rescued the NSC proliferation deficiency induced by miR-378 overexpression and abolished miR-378-promoted NSC differentiation. Taken together, our data suggest that miR-378 is a novel miRNA that regulates NSC proliferation and differentiation via targeting TLX. Therefore, manipulating miR-378 in NSCs could be a novel strategy to develop novel interventions for the treatment of relevant neurological disorders.

MicroRNA and Posttranscriptional Dysregulation in Psychiatry

Psychiatric syndromes, including schizophrenia, mood disorders, and autism spectrum disorders, are characterized by a complex range of symptoms, including psychosis, depression, mania, and cognitive deficits. Although the mechanisms driving pathophysiology are complex and remain largely unknown, advances in the understanding of gene association and gene networks are providing significant clues to their etiology. In recent years, small noncoding RNA molecules known as microRNA (miRNA) have emerged as potential players in the pathophysiology of mental illness. These small RNAs regulate hundreds of target transcripts by modifying their stability and translation on a broad scale, influencing entire gene networks in the process. There is evidence to suggest that numerous miRNAs are dysregulated in postmortem neuropathology of neuropsychiatric disorders, and there is strong genetic support for association of miRNA genes and their targets with these conditions. This review presents the accumulated evidence linking miRNA dysregulation and dysfunction with schizophrenia, bipolar disorder, major depressive disorder, and autism spectrum disorders and the potential of miRNAs as biomarkers or therapeutics for these disorders. We further assess the functional roles of some outstanding miRNAs associated with these conditions and how they may be influencing the development of psychiatric symptoms.

MicroRNAs and their potential therapeutic applications in neural tissue engineering

The inherent poor regeneration capacity of nerve tissues, especially in the central nervous system, poses a grand challenge for neural tissue engineering. After injuries, the local microenvironment often contains potent inhibitory molecules and glial scars, which do not actively support axonal regrowth. MicroRNAs can direct fate of neural cells and are tightly controlled during nerve development. Thus, RNA interference using microRNAs is a promising method to enhance nerve regeneration. Although the physiological roles of microRNA expression levels in various cellular activities or disease conditions have been extensively investigated, the translational use of these understanding for neural tissue engineering remains limited. This review aims to highlight essential microRNAs that participate in cellular behaviors within the adult nervous system and their potential therapeutic applications. In addition, possible delivery methods are also suggested for effective gene silencing in neural tissue engineering.

Non-coding RNAs as direct and indirect modulators of epigenetic regulation

Epigenetic regulation of gene expression is an increasingly well-understood concept that explains much of the contribution of an organism's environment and experience to its biology. However, discussion persists as to which mechanisms can be classified as epigenetic. Ongoing research continues to uncover novel pathways, including the important role of non-protein coding RNA transcripts in epigenetic gene regulation. We know that the majority of human and other mammalian transcripts are not translated but that many of these are nonetheless functional. These non-coding RNAs (ncRNAs) can be short (<200 nt) or long (<200 nt) and are further classified by genomic origin and mechanism of action. We discuss examples of ncRNAs that interact with histone modifying complexes or DNA methyltransferases to regulate gene expression, others that are targets of these epigenetic mechanisms, and propose a model in which such transcripts feed back into an epigenetic regulatory network.

Expression quantitative trait loci (eQTLs) in microRNA genes are enriched for schizophrenia and bipolar disorder association signals

BACKGROUND

Schizophrenia (SZ) and bipolar disorder (BD) have substantial negative impact on the quality of human life. Both, microRNA (miRNA) expression profiling in SZ and BD postmortem brains [and genome-wide association studies (GWAS)] have implicated miRNAs in disease etiology. Here, we aim to determine whether significant GWAS signals observed in the Psychiatric Genetic Consortium (PGC) are enriched for miRNAs.

METHOD

A two-stage approach was used to determine whether association signals from PGC affect miRNAs: (i) statistical assessment of enrichment using a Simes test and sum of squares test (SST) and (ii) biological evidence that quantitative trait loci (eQTL) mapping to known miRNA genes affect their expression in an independent sample of 78 postmortem brains from the Stanley Medical Research Institute.

RESULTS

A total of 2567 independent single nucleotide polymorphisms (SNPs) (R2 > 0.8) were mapped locally, within 1 Mb, to all known miRNAs (miRBase v. 21). We show robust enrichment for SZ- and BD-related SNPs with miRNAs using Simes (SZ: p ≤ 0.0023, BD: p ≤ 0.038), which remained significant after adjusting for background inflation in SZ (empirical p = 0.018) and approached significance in BD (empirical p = 0.07). At a false discovery rate of 10%, we identified a total of 32 eQTLs to influence miRNA expression; 11 of these overlapped with BD.

CONCLUSIONS

Our approach of integrating PGC findings with eQTL results can be used to generate specific hypotheses regarding the role of miRNAs in SZ and BD.

An epigenetic regulator: methyl-CpG-binding domain protein 1 (MBD1)

DNA methylation is an important form of epigenetic regulation in both normal development and cancer. Methyl-CpG-binding domain protein 1 (MBD1) is highly related to DNA methylation. Its MBD domain recognizes and binds to methylated CpGs. This binding allows it to trigger methylation of H3K9 and results in transcriptional repression. The CXXC3 domain of MBD1 makes it a unique member of the MBD family due to its affinity to unmethylated DNA. MBD1 acts as an epigenetic regulator via different mechanisms, such as the formation of the MCAF1/MBD1/SETDB1 complex or the MBD1-HDAC3 complex. As methylation status always changes along with carcinogenesis or neurogenesis, MBD1 with its interacting partners, including proteins and non-coding RNAs, participates in normal or pathological processes and functions in different regulatory systems. Because of the important role of MBD1 in epigenetic regulation, it is a good candidate as a therapeutic target for diseases.

The NF-ҡB modulated miR-195/497 inhibit myoblast proliferation by targeting Igf1r/Insr and cyclin genes

MicroRNAs (miRNAs) play important roles in the development of skeletal muscle. In our previous study, expression of miR-195 and miR-497 were shown to be up-regulated during muscle development in pigs. In this study, we investigated the roles of these two miRNAs in myogenesis and analyzed their transcriptional regulation. Our results showed that miR-195 and miR-497 were up-regulated during muscle development and myoblast differentiation. Moreover, miR-195/497 inhibited proliferation but not differentiation in C2C12 cells. Further investigation revealed that Igf1r, Insr, Ccnd2, and Ccne1 were directly targeted by miR-195/497 in myoblasts. In addition, we confirmed that similarly expressed miR-195 and miR-497 were negatively regulated by nuclear factor-kappaB (NF-ҡB) in both myoblasts and skeletal muscle tissue. Our data illustrated that the NF-ҡB-miR-195/497-Igf1r/Insr-Ccnd2/Ccne1 signaling pathway played important roles in the myogenesis. Our study provides novel evidence for the roles of miR-195/497 in muscle development.

miR-326-histone deacetylase-3 feedback loop regulates the invasion and tumorigenic and angiogenic response to anti-cancer drugs

Histone modification is known to be associated with multidrug resistance phenotypes. Cancer cell lines that are resistant or have been made resistant to anti-cancer drugs showed lower expression levels of histone deacetylase-3 (HDAC3), among the histone deacetylase(s), than cancer cell lines that were sensitive to anti-cancer drugs. Celastrol and Taxol decreased the expression of HDAC3 in cancer cell lines sensitive to anti-cancer drugs. HDAC3 negatively regulated the invasion, migration, and anchorage-independent growth of cancer cells. HDAC3 conferred sensitivity to anti-cancer drugs in vitro and in vivo. TargetScan analysis predicted miR-326 as a negative regulator of HDAC3. ChIP assays and luciferase assays showed a negative feedback loop between HDAC3 and miR-326. miR-326 decreased the apoptotic effect of anti-cancer drugs, and the miR-326 inhibitor increased the apoptotic effect of anti-cancer drugs. miR-326 enhanced the invasion and migration potential of cancer cells. The miR-326 inhibitor negatively regulated the tumorigenic, metastatic, and angiogenic potential of anti-cancer drug-resistant cancer cells. HDAC3 showed a positive feedback loop with miRNAs such as miR-200b, miR-217, and miR-335. miR-200b, miR-217, and miR-335 negatively regulated the expression of miR-326 and the invasion and migration potential of cancer cells while enhancing the apoptotic effect of anti-cancer drugs. TargetScan analysis predicted miR-200b and miR-217 as negative regulators of cancer-associated gene, a cancer/testis antigen, which is known to regulate the response to anti-cancer drugs. HDAC3 and miR-326 acted upstream of the cancer-associated gene. Thus, we show that the miR-326-HDAC3 feedback loop can be employed as a target for the development of anti-cancer therapeutics.

MicroRNAs: Small molecules with big roles in neurodevelopment and diseases

MicroRNAs (miRNAs) are single-stranded, non-coding RNA molecules that play important roles in the development and functions of the brain. Extensive studies have revealed critical roles for miRNAs in brain development and function. Dysregulation or altered expression of miRNAs is associated with abnormal brain development and pathogenesis of neurodevelopmental diseases. This review serves to highlight the versatile roles of these small RNA molecules in normal brain development and their association with neurodevelopmental disorders, in particular, two closely related neuropsychiatric disorders of neurodevelopmental origin, schizophrenia and bipolar disorder.

Regulation of microRNA function in somatic stem cell proliferation and differentiation

microRNAs (miRNAs) are important modulators of development. Owing to their ability to simultaneously silence hundreds of target genes, they have key roles in large-scale transcriptomic changes that occur during cell fate transitions. In somatic stem and progenitor cells--such as those involved in myogenesis, haematopoiesis, skin and neural development--miRNA function is carefully regulated to promote and stabilize cell fate choice. miRNAs are integrated within networks that form both positive and negative feedback loops. Their function is regulated at multiple levels, including transcription, biogenesis, stability, availability and/or number of target sites, as well as their cooperation with other miRNAs and RNA-binding proteins. Together, these regulatory mechanisms result in a refined molecular response that enables proper cellular differentiation and function.

Identifying a polymorphic 'switch' that influences miRNAs' regulation of a myasthenia gravis risk pathway

The significant roles of genetic variants in myasthenia gravis (MG) pathogenesis have been demonstrated in many studies, and recently it has been revealed that aberrant level/regulation of microRNAs (miRNAs) might contribute to the initiation and progression of MG. However, the dysfunction of miRNA associated with single nucleotide polymorphisms (miRSNPs) has not been well investigated in MG. In this study, we created a contemporary catalog of 89 MG risk genes via manual literature-mining. Based on this risk gene catalog, we obtained 18 MG risk pathways. Furthermore, we identified 93 miRNAs that target MG risk pathways and revealed the miRSNPs ‘switches’ in miRNA regulation in the MG risk pathways by integrating the database information of miRSNPs. We also constructed a miRNA-mediated SNP switching pathway network (MSSPN) to intuitively analyze miRNA regulation of MG risk pathways and the relationship of the polymorphism ‘switch’ with these changes in regulation. Moreover, we carried out in-depth dissection on the correlation between hsa05200 (pathway in cancer) and MG development, and elaborated the significance of 4 high-risk genes. By network analysis and literature mining, we proposed a potential mechanism of miRSNPs→gene→pathway effects on MG pathogenesis, especially for rs28457673 (miR-15/16/195/424/497 family)→IGF1R→hsa05200 (pathway in cancer). Therefore, our studies have revealed a functional role for genetic modulators in MG pathogenesis at a systemic level, which could be informative for further miRNA and miRSNPs studies in MG.

Regulation of pri-miRNA processing by a long noncoding RNA transcribed from an ultraconserved region

Noncoding RNAs (ncRNAs) control cellular programs by affecting protein-coding genes, but evidence increasingly points to their involvement in a network of ncRNA-ncRNA interactions. Here, we show that a long ncRNA, Uc.283+A, controls pri-miRNA processing. Regulation requires complementarity between the lower stem region of the pri-miR-195 transcript and an ultraconserved sequence in Uc.283+A, which prevents pri-miRNA cleavage by Drosha. Mutation of the site in either RNA molecule uncouples regulation in vivo and in vitro. We propose a model in which lower-stem strand invasion by Uc.283+A impairs microprocessor recognition and efficient pri-miRNA cropping. In addition to identifying a case of RNA-directed regulation of miRNA biogenesis, our study reveals regulatory networks involving different ncRNA classes of importance in cancer.

Neuroepigenetics of memory formation and impairment: the role of microRNAs

MicroRNAs (miRNAs) are a class of short non-coding RNAs that primarily regulate protein synthesis through reversible translational repression or mRNA degradation. MiRNAs can act by translational control of transcription factors or via direct action on the chromatin, and thereby contribute to the non-genetic control of gene-environment interactions. MiRNAs that regulate components of pathways required for learning and memory further modulate the influence of epigenetics on cognition in the normal and diseased brain. This review summarizes recent data exemplifying the known roles of miRNAs in memory formation in different model organisms, and describes how neuronal plasticity regulates miRNA biogenesis, activity and degradation. It also examines the relevance of miRNAs for memory impairment in human, using recent clinical observations related to neurodevelopmental and neurodegenerative diseases, and discusses the potential mechanisms by which these miRNAs may contribute to memory disorders.

MicroRNAs and epigenetics in adult neurogenesis

Neurogenesis occurs throughout adulthood in the mammalian brain. Neural stem cells (NSCs) exist in three distinct areas of the brain: the subventricular zone, the olfactory bulb, and the dentate gyrus of the hippocampus. MicroRNAs (miRNAs) are small noncoding RNA molecules that posttranscriptionally regulate gene expression. Epigenetic regulation of gene expression, which includes DNA methylation and histone modification, plays a significant role in modulating NSC proliferation and differentiation. However, the functions of miRNAs in neurogenesis are just beginning to be understood. Based on the recent literature, miRNAs are suggested to play an important role in the epigenetic regulation of NSCs and differentiation of lineage populations, which include neurons, astrocytes, and oligodendrocytes. Recent studies have elucidated the roles of miRNAs in embryonic and adult neurogenesis, specifically, their involvement in stem cell maintenance and differentiation, neuronal maturation and neurite outgrowth, dendritogenesis, and spine formation. The cross-talk between miRNAs and epigenetic regulators appears to modulate neurogenesis in the adult mammalian brain. Since the dysfunction in miRNA machinery contributes to many types of neurodegenerative disorders, a better understanding of how miRNAs influence the neurogenesis and differentiation may offer novel targets for therapeutic application.

miR-200b and cancer/testis antigen CAGE form a feedback loop to regulate the invasion and tumorigenic and angiogenic responses of a cancer cell line to microtubule-targeting drugs

Cancer/testis antigen cancer-associated gene (CAGE) is known to be involved in various cellular processes, such as proliferation, cell motility, and anti-cancer drug resistance. However, the mechanism of the expression regulation of CAGE remains unknown. Target scan analysis predicted the binding of microRNA-200b (miR-200b) to CAGE promoter sequences. The expression of CAGE showed an inverse relationship with miR-200b in various cancer cell lines. miR-200b was shown to bind to the 3'-UTR of CAGE and to regulate the expression of CAGE at the transcriptional level. miR-200b also enhanced the sensitivities to microtubule-targeting drugs in vitro. miR-200b and CAGE showed opposite regulations on invasion potential and responses to microtubule-targeting drugs. Xenograft experiments showed that miR-200b had negative effects on the tumorigenic and metastatic potential of cancer cells. The effect of miR-200b on metastatic potential involved the expression regulation of CAGE by miR-200b. miR-200b decreased the tumorigenic potential of a cancer cell line resistant to microtubule-targeting drugs in a manner associated with the down-regulation of CAGE. ChIP assays showed the direct regulation of miR-200b by CAGE. CAGE enhanced the invasion potential of a cancer cell line stably expressing miR-200b. miR-200b exerted a negative regulation on tumor-induced angiogenesis. The down-regulation of CAGE led to the decreased expression of plasminogen activator inhibitor-1, a TGFβ-responsive protein involved in angiogenesis, and VEGF. CAGE mediated tumor-induced angiogenesis and was necessary for VEGF-promoted angiogenesis. Human recombinant CAGE protein displayed angiogenic potential. Thus, miR-200b and CAGE form a feedback regulatory loop and regulate the response to microtubule-targeting drugs, as well as the invasion, tumorigenic potential, and angiogenic potential.

MicroRNAs in cerebral ischemia-induced neurogenesis

Cerebral ischemia induces neurogenesis, including proliferation and differentiation of neural progenitor cells and migration of newly generated neuroblasts. MicroRNAs (miRNAs) are small noncoding RNAs that decrease gene expression through mRNA destabilization and/or translational repression. Emerging data indicate that miRNAs have a role in mediating processes of proliferation and differentiation of adult neural progenitor cells. This article reviews recent findings on miRNA profile changes in neural progenitor cells after cerebral infarction and the contributions of miRNAs to their ischemia-induced proliferation and differentiation. We highlight interactions between the miR-124 and the miR17-92 cluster and the Notch and Sonic hedgehog signaling pathways in mediating stroke-induced neurogenesis.

Tuning the cell fate of neurons and glia by microRNAs

The proper function of the nervous system depends on precise production and connection of distinct neurons and glia. Cell fate determination of neurons and glia is tightly controlled by complex gene expression regulation in the developing and adult nervous system. Emerging evidence has demonstrated the importance of noncoding microRNAs (miRNAs) in neural development and function. This review highlights current discoveries of miRNA functions in specifying neuronal and glial cell fate. We summarize the roles of miRNAs in expansion and differentiation of neural stem cells, specification of neuronal subtypes and glial cells, reprogramming of functional neurons from embryonic stem cells and fibroblasts, and left-right asymmetric organization of neuronal subtypes. Investigating the network of interactions between miRNAs and target genes will reveal new gene regulation machinery involved in tuning the cell fate decisions of neurons and glia.