MicroRNA-124 and -137 cooperativity controls caspase-3 activity through BCL2L13 in hippocampal neural stem cells

MiR-449b-5p Ameliorates Hypoxia-induced Cardiomyocyte Injury through Activating PI3K/AKT Pathway by Targeting BCL2L13

Recent reports show miR-449b-5p reduces liver and renal ischemia/reperfusion (I/R) injury, but its effects on hypoxia-induced cardiomyocyte injury in ischemic heart disease are still unknown. In this study, AC16 human cardiomyocytes underwent hypoxic conditions for durations of 24, 48, and 72 h. We observed that miR-449b-5p expression was significantly downregulated in hypoxic AC16 cardiomyocytes. Elevating the levels of miR-449b-5p in these cells resulted in enhanced cell survival, diminished release of LDH, and a reduction in cell apoptosis and oxidative stress using CCK-8, LDH assays, flow cytometry, TUNEL staining, and various commercial kits. Conversely, reducing miR-449b-5p levels resulted in the opposite effects. Through bioinformatics analysis and luciferase reporter assays, BCL2-like 13 (BCL2L13) was determined to be a direct target of miR-449b-5p. Inhibiting BCL2L13 greatly inhibited hypoxia-induced cell viability loss, LDH release, cell apoptosis, and excessive production of oxidative stress, whereas increasing BCL2L13 negated miR-449b-5p's protective impact in hypoxic AC16 cardiomyocytes. Additionally, miR-449b-5p elevated the levels of the proteins p-PI3K, p-AKT, and Bcl-2, while decreasing Bax expression in hypoxic AC16 cardiomyocytes by targeting BCL2L13. In summary, the research indicates that the protective effects of miR-449b-5p are facilitated through the activation of the PI3K/AKT pathway, which promotes cell survival, and by targeting BCL2L13, which inhibits apoptosis, offering a potential therapeutic strategy for ischemic heart disease by mitigating hypoxia-induced cardiomyocyte injury.

MicroRNA-335-5p suppresses voltage-gated sodium channel expression and may be a target for seizure control

There remains an urgent need for new therapies for treatment-resistant epilepsy. Sodium channel blockers are effective for seizure control in common forms of epilepsy, but loss of sodium channel function underlies some genetic forms of epilepsy. Approaches that provide bidirectional control of sodium channel expression are needed. MicroRNAs (miRNA) are small noncoding RNAs which negatively regulate gene expression. Here we show that genome-wide miRNA screening of hippocampal tissue from a rat epilepsy model, mice treated with the antiseizure medicine cannabidiol, and plasma from patients with treatment-resistant epilepsy, converge on a single target-miR-335-5p. Pathway analysis on predicted and validated miR-335-5p targets identified multiple voltage-gated sodium channels (VGSCs). Intracerebroventricular injection of antisense oligonucleotides against miR-335-5p resulted in upregulation of Scn1a, Scn2a, and Scn3a in the mouse brain and an increased action potential rising phase and greater excitability of hippocampal pyramidal neurons in brain slice recordings, consistent with VGSCs as functional targets of miR-335-5p. Blocking miR-335-5p also increased voltage-gated sodium currents and SCN1A, SCN2A, and SCN3A expression in human induced pluripotent stem cell-derived neurons. Inhibition of miR-335-5p increased susceptibility to tonic-clonic seizures in the pentylenetetrazol seizure model, whereas adeno-associated virus 9-mediated overexpression of miR-335-5p reduced seizure severity and improved survival. These studies suggest modulation of miR-335-5p may be a means to regulate VGSCs and affect neuronal excitability and seizures. Changes to miR-335-5p may reflect compensatory mechanisms to control excitability and could provide biomarker or therapeutic strategies for different types of treatment-resistant epilepsy.

MicroRNA‑124: an emerging therapeutic target in central nervous system disorders

The central nervous system (CNS) consists of neuron and non-neuron cells including neural stem/precursor cells (NSPCs), neuroblasts, glia cells (mainly astrocyte, oligodendroglia and microglia), which thereby form a precise and complicated network and exert diverse functions through interactions of numerous bioactive ingredients. MicroRNAs (miRNAs), with small size approximately  ~ 21nt and as well-documented post-transcriptional key regulators of gene expression, are a cluster of evolutionarily conserved endogenous non-coding RNAs. More than 2000 different miRNAs has been discovered till now. MicroRNA-124(miR-124), the most brain-rich microRNA, has been validated to possess important functions in the central nervous system, including neural stem cell proliferation and differentiation, cell fate determination, neuron migration, synapse plasticity and cognition, cell apoptosis etc. According to recent studies, herein, we provide a review of this conversant miR-124 to further understand the potential functions and therapeutic and clinical value in brain diseases.

Biological properties of the BCL-2 family protein BCL-RAMBO, which regulates apoptosis, mitochondrial fragmentation, and mitophagy

Mitochondria play an essential role in the regulation of cellular stress responses, including cell death. Damaged mitochondria are removed by fission and fusion cycles and mitophagy, which counteract cell death. BCL-2 family proteins possess one to four BCL-2 homology domains and regulate apoptosis signaling at mitochondria. BCL-RAMBO, also known as BCL2-like 13 (BCL2L13), was initially identified as one of the BCL-2 family proteins inducing apoptosis. Mitophagy receptors recruit the ATG8 family proteins MAP1LC3/GABARAP via the MAP1LC3-interacting region (LIR) motif to initiate mitophagy. In addition to apoptosis, BCL-RAMBO has recently been identified as a mitophagy receptor that possesses the LIR motif and regulates mitochondrial fragmentation and mitophagy. In the 20 years since its discovery, many important findings on BCL-RAMBO have been increasingly reported. The biological properties of BCL-RAMBO are reviewed herein.

PGAM5 interacts with Bcl-rambo and regulates apoptosis and mitophagy

Bcl-rambo, also known as BCL2L13, has been reported to regulate apoptosis, mitochondrial fragmentation, and mitophagy. However, the molecular mechanisms by which Bcl-rambo regulates these processes currently remain unclear. In the present study, we identified phosphoglycerate mutase member 5 (PGAM5) as an emerging partner interacting with Bcl-rambo through phenotypic Drosophila screening. The rough eye phenotype induced by human Bcl-rambo was partly rescued by the knockdown of pgam5-2, a mammalian ortholog of PGAM5. Bcl-rambo bound to PGAM5, and their interaction required the Bcl-rambo transmembrane domain. The co-expression of Bcl-rambo and PGAM5 promoted effector caspase activity in human embryonic kidney 293T cells. The transient overexpression of Bcl-rambo increased LC3B-II levels, which had been decreased by the co-expression of PGAM5. These results suggest that PGAM5 promotes Bcl-rambo-dependent apoptosis, but conversely interferes with Bcl-rambo-dependent mitophagy.

Impact of Gestational Haloperidol Exposure on miR-137-3p and Nr3c1 mRNA Expression in Hippocampus of Offspring Mice

BACKGROUND

Schizophrenia is a mental disorder caused by both environmental and genetic factors. Prenatal exposure to antipsychotics, an environmental factor for the fetal brain, induces apoptotic neurodegeneration and cognitive impairment of offspring similar to schizophrenia. The aim was to investigate molecular biological changes in the fetal hippocampus exposed to haloperidol (HAL) by RNA expression as a model of the disorder.

METHODS

HAL (1 mg/kg/d) was administered to pregnant mice. Upregulated and downregulated gene expressions in the hippocampus of offspring were studied with RNA-sequencing and validated with the qPCR method, and micro-RNA (miR) regulating mRNA expressional changes was predicted by in silico analysis. An in vitro experiment was used to identify the miRNA using a dual-luciferase assay.

RESULTS

There were significant gene expressional changes (1370 upregulated and 1260 downregulated genes) in the HAL group compared with the control group on RNA-sequencing analysis (P < .05 and q < 0.05). Of them, the increase of Nr3c1 mRNA expression was successfully validated, and in silico analysis predicted that microRNA-137-3p (miR-137-3p) possibly regulates that gene's expression. The expression of miR-137-3p in the hippocampus of offspring was significantly decreased in the first generation, but it increased in the second generation. In vitro experiments with Neuro2a cells showed that miR-137-3p inversely regulated Nr3c1 mRNA expression, which was upregulated in the HAL group.

CONCLUSIONS

These findings will be key for understanding the impact of the molecular biological effects of antipsychotics on the fetal brain.

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.

Early Induction of Neurotrophin Receptor and miRNA Genes in Mouse Brain after Pentilenetetrazole-Induced Neuronal Activity

Neurotrophin receptors regulate neuronal survival and network formation, as well as synaptic plasticity in the brain via interaction with their ligands. Here, we examined early changes in the expression of neurotrophin receptor genes Ntk1 (TrkA), Ntrk2 (TrkB), Ntrk3 (TrkC), Ngfr (p75NTR) and miRNAs that target theses gens in the mouse brain after induction of seizure activity by pentylenetetrazol. We found that expression of Ntrk3 and Ngfr was upregulated in the cortex and the hippocampus 1-3 hours after the seizures, while Ntrk2 expression increased after 3-6 hours in the anterior cortex and after 1 and 6 hours in the hippocampus. At the same time, the ratio of Bcl-2/Bax signaling proteins increased in the anterior and posterior cortex, but not in the hippocampus, suggesting the activation of anti-apoptotic signaling. Expression of miRNA-9 and miRNA-29a, which were predicted to target Ntrk3, was upregulated in the hippocampus 3 hours after pentylenetetrazol injection. Therefore, early cellular response to seizures in the brain includes induction of the Ntrk2, Ntrk3, Ngfr, miRNA-9, and miRNA-29a expression, as well as activation of Bcl-2 and Bax signaling pathways, which may characterize them as important mediators of neuronal adaptation and survival upon induction of the generalized brain activity.

The functions of repressor element 1-silencing transcription factor in models of epileptogenesis and post-ischemia

Epilepsy is a debilitating neurological disorder characterised by recurrent seizures for which 30% of patients are refractory to current treatments. The genetic and molecular aetiologies behind epilepsy are under investigation with the goal of developing new epilepsy medications. The transcriptional repressor REST (Repressor Element 1-Silencing Transcription factor) is a focus of interest as it is consistently upregulated in epilepsy patients and following brain insult in animal models of epilepsy and ischemia. This review analyses data from different epilepsy models and discusses the contribution of REST to epileptogenesis. We propose that in healthy brains REST acts in a protective manner to homeostatically downregulate increases in excitability, to protect against seizure through downregulation of BDNF (Brain-Derived Neurotrophic Factor) and its receptor, TrkB (Tropomyosin receptor kinase B). However, in epilepsy patients and post-seizure, REST may increase to a larger degree, which allows downregulation of the glutamate receptor subunit GluR2. This leads to AMPA glutamate receptors lacking GluR2 subunits, which have increased permeability to Ca²⁺, causing excitotoxicity, cell death and seizure. This concept highlights therapeutic potential of REST modulation through gene therapy in epilepsy patients.

Down-regulation of BCL2L13 renders poor prognosis in clear cell and papillary renal cell carcinoma

Background

BCL2L13 belongs to the BCL2 super family, with its protein product exhibits capacity of apoptosis-mediating in diversified cell lines. Previous studies have shown that BCL2L13 has functional consequence in several tumor types, including ALL and GBM, however, its function in kidney cancer remains as yet unclearly.

Methods

Multiple web-based portals were employed to analyze the effect of BCL2L13 in kidney cancer using the data from TCGA database. Functional enrichment analysis and hubs of BCL2L13 co-expressed genes in clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) were carried out on Cytoscape. Evaluation of BCL2L13 protein level was accomplished through immunohistochemistry on paraffin embedded renal cancer tissue sections. Western blotting and flow cytometry were implemented to further analyze the pro-apoptotic function of BCL2L13 in ccRCC cell line 786-0.

Results

BCL2L13 expression is significantly decreased in ccRCC and pRCC patients, however, mutations and copy number alterations are rarely observed. The poor prognosis of ccRCC that derived from down-regulated BCL2L13 is independent of patients’ gender or tumor grade. Furthermore, BCL2L13 only weakly correlates with the genes that mutated in kidney cancer or the genes that associated with inherited kidney cancer predisposing syndrome, while actively correlates with SLC25A4. As a downstream effector of BCL2L13 in its pro-apoptotic pathway, SLC25A4 is found as one of the hub genes that involved in the physiological function of BCL2L13 in kidney cancer tissues.

Conclusions

Down-regulation of BCL2L13 renders poor prognosis in ccRCC and pRCC. This disadvantageous factor is independent of any well-known kidney cancer related genes, so BCL2L13 can be used as an effective indicator for prognostic evaluation of renal cell carcinoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02039-y.

MicroRNA-210 Regulates Dendritic Morphology and Behavioural Flexibility in Mice

MicroRNAs are known to be critical regulators of neuronal plasticity. The highly conserved, hypoxia-regulated microRNA-210 (miR-210) has been shown to be associated with long-term memory in invertebrates and dysregulated in neurodevelopmental and neurodegenerative disease models. However, the role of miR-210 in mammalian neuronal function and cognitive behaviour remains unexplored. Here we generated Nestin-cre-driven miR-210 neuronal knockout mice to characterise miR-210 regulation and function using in vitro and in vivo methods. We identified miR-210 localisation throughout neuronal somas and dendritic processes and increased levels of mature miR-210 in response to neural activity in vitro. Loss of miR-210 in neurons resulted in higher oxidative phosphorylation and ROS production following hypoxia and increased dendritic arbour density in hippocampal cultures. Additionally, miR-210 knockout mice displayed altered behavioural flexibility in rodent touchscreen tests, particularly during early reversal learning suggesting processes underlying updating of information and feedback were impacted. Our findings support a conserved, activity-dependent role for miR-210 in neuroplasticity and cognitive function.

By targeting apoptosis facilitator BCL2L13, microRNA miR-484 alleviates cerebral ischemia/reperfusion injury-induced neuronal apoptosis in mice

Neuronal apoptosis was considered as one of the main factors of cerebral ischemia/reperfusion injury. Understanding the molecular regulatory mechanism of neuronal apoptosis under the cerebral ischemia/reperfusion injury may provide the novel therapeutic targets for cerebral ischemia/reperfusion injury. However, the molecular regulatory mechanism of neurons fate determination under the cerebral ischemia/reperfusion injury remains poorly understood. This study was aimed to delve into the related molecular mechanism of miR-484 on the regulation of cerebral ischemia/reperfusion injury-induced neuronal apoptosis in mice. In this study, quantitative real-time polymerase chain reaction assays revealed that the expression level of miR-484 was down-regulated in neurons following OGD. Then, CCK8 assay western blot assay, and flow cytometry assay verified that upregulation of miR-484 increased viability and inhibited apoptosis of neurons following OGD. Further bioinformatics methods and dual-luciferase reporter assay were applied together to anticipate and certify the interaction between miR-484 and BCL2L13. Finally, cerebral infarct size assessment and TUNEL staining confirmed that overexpression of miR-484 alleviated cerebral ischemia/reperfusion injury in mice, and overexpression of BCL2L13 could abolish the effect of miR-484-suppressed cell apoptosis. All these results suggested that miR-484 alleviates cerebral ischemia/reperfusion injury-induced neuronal apoptosis in mice by targeting apoptosis facilitator BCL2L13.

BCL2L13: physiological and pathological meanings

BCL2L13 is a BCL2-like protein. It has been discovered for two decades, now on the way to be a hotspot of research with its physiological and pathological meanings found in recent years. Start with the pro-apoptotic activity, there have been reported consecutively that BCL2L13 could also induce mitochondrial fragmentation, inhibit cell death and promote mitophagy. Similar to BNIP3, BCL2L13 cannot be indiscriminately categorized into pro- or anti-apoptotic proteins. It anchors in the mitochondrial outer membrane, and expresses in various cells and tissues. This article reviews for the first time that BCL2L13 functions in physiological processes, such as growth and development and energy metabolism, and its dysregulation participating in pathological processes, including cancer, bacterial infection, cardiovascular diseases and degenerative diseases, suggesting its important roles in these events.

Prospects and Limitations Related to the Use of MicroRNA as a Biomarker of Epilepsy in Children: A Systematic Review

Epilepsy is one of the most common neurological diseases in children. There is an unmet need for new objective methods that would facilitate and accelerate the diagnostic process, thus improving the prognosis. In many studies, the participation of microRNA in epileptogenesis has been confirmed. Therefore, it seems to be a promising candidate for this role. Scientists show the possibility of using microRNAs as diagnostic and predictive biomarkers as well as novel therapeutic targets. Children with epilepsy would benefit particularly from the use of this innovative method. However, the number of studies related to this age group is very limited. This review is based on 10 studies in children and summarizes the information collected from studies on animal models and the adult population. A total of 136 manuscripts were included in the analysis. The aim of the review was to facilitate the design of studies in children and to draw attention to the challenges and traps related to the analysis of the results. Our review suggests a high potential for the use of microRNAs and the need for further research.

p53 upregulated mediator of apoptosis (Puma) deficiency increases survival of adult neural stem cells generated physiologically in the hippocampus, but does not protect stem cells generated in surplus after an excitotoxic lesion

OBJECTIVES

Neurogenesis occurs in the mammalian brain throughout adulthood and increases in response to metabolic, toxic or traumatic insults. To remove potentially superfluous or unwanted neural stem cells/neuronal progenitors, their rate of proliferation and differentiation is fine-tuned against their rate of apoptosis. Apoptosis requires the transcriptional and posttranslational activation of Bcl-2-homolgy domain 3 (BH3)-only proteins. Previously, we demonstrated that the BH3-only protein p53-upregulated mediator of apoptosis (Puma) controls the physiological rate of apoptosis of neural precursor cells in the adult mouse hippocampus. Puma's role in controlling a lesion-induced increase in neural stem cells is currently not known.

METHODS

We employed a model of local, N-methyl-D-asparte (NMDA)-induced excitotoxic injury to the CA1 hippocampal subfield and immunofluorescence labelling to produce increased neural stem cell proliferation/ neurogenesis in the dentate gyrus at two survival times following the excitotoxic lesion.

RESULTS

Deletion of puma failed to rescue any NMDA-induced increase in adult born cells as assessed by BrdU or Doublecortin labelling in the long-term. No difference in the proportion of BrdU/NeuN-positive cells comparing the different genotypes and treatments suggested that the phenotypic fate of the cells was preserved regardless of the genotype and the treatment.

CONCLUSIONS

While neurogenesis is up-regulated in puma-deficient animals following NMDA-induced excitotoxicity to the hippocampal CA1 subfield, puma deficiency could not protect this surplus of newly generated cells from apoptotic cell death.

Circadian glucocorticoid oscillations preserve a population of adult hippocampal neural stem cells in the aging brain

A decrease in adult hippocampal neurogenesis has been linked to age-related cognitive impairment. However, the mechanisms involved in this age-related reduction remain elusive. Glucocorticoid hormones (GC) are important regulators of neural stem/precursor cells (NSPC) proliferation. GC are released from the adrenal glands in ultradian secretory pulses that generate characteristic circadian oscillations. Here, we investigated the hypothesis that GC oscillations prevent NSPC activation and preserve a quiescent NSPC pool in the aging hippocampus. We found that hippocampal NSPC populations lacking expression of the glucocorticoid receptor (GR) decayed exponentially with age, while GR-positive populations decayed linearly and predominated in the hippocampus from middle age onwards. Importantly, GC oscillations controlled NSPC activation and GR knockdown reactivated NSPC proliferation in aged mice. When modeled in primary hippocampal NSPC cultures, GC oscillations control cell cycle progression and induce specific genome-wide DNA methylation profiles. GC oscillations induced lasting changes in the methylation state of a group of gene promoters associated with cell cycle regulation and the canonical Wnt signaling pathway. Finally, in a mouse model of accelerated aging, we show that disruption of GC oscillations induces lasting changes in dendritic complexity, spine numbers and morphology of newborn granule neurons. Together, these results indicate that GC oscillations preserve a population of GR-expressing NSPC during aging, preventing their activation possibly by epigenetic programming through methylation of specific gene promoters. Our observations suggest a novel mechanism mediated by GC that controls NSPC proliferation and preserves a dormant NSPC pool, possibly contributing to a neuroplasticity reserve in the aging brain.

miR-137: A Novel Therapeutic Target for Human Glioma

MicroRNA (miR)-137 is highly expressed in the brain and plays a crucial role in the development and prognosis of glioma. In this review, we aim to summarize the latest findings regarding miR-137 in glioma cell apoptosis, proliferation, migration, invasion, angiogenesis, drug resistance, and cancer treatment. In addition, we focus on the identified miR-137 targets and pathways in the occurrence and development of glioma. Finally, future implications for the diagnostic and therapeutic potential of miR-137 in glioma were discussed.

Cell-free microRNAs in Parkinson's disease: potential biomarkers that provide new insights into disease pathogenesis

MicroRNAs (miRNAs) are master post-transcriptional regulators of gene expression and their specific footprints reflect disease conditions. Over the last few years, several primary reports have described the deregulation of cell-free miRNAs in Parkinson's disease (PD), however, results have been rather inconsistent due to preanalytical and analytical challenges. This study integrated the data across twenty-four reports to identify steadily deregulated miRNAs that may assist in the path towards biomarker development and molecular characterization of the underlying pathology. Stringent KEGG pathway analysis of the miRNA targets revealed FoxO, Prolactin, TNF, and ErbB signaling pathways as the most significantly enriched categories while Gene Ontology analysis revealed that the protein targets are mostly associated with transcription. Chromosomal location of the consistently deregulated miRNAs revealed that over a third of them were clustered at the same location at Chr14q32 suggesting that they are co-regulated by specific transcription factors. This genomic region is inherently unstable due to expanded TGG repeats and responsible for human abnormalities. Stringent analysis of transcription factor sites surrounding the deregulated miRNAs revealed that CREB1, CEBPB and MAZ sites existed in approximately half of the miRNAs, including all of the miRNAs located at Chr14q32. Additional studies are now needed to determine the biomarker potential of the consistently deregulated miRNAs in PD and the therapeutic implications of these bioinformatics insights.

Emerging molecular functions of microRNA-124: Cancer pathology and therapeutic implications

MicroRNAs are characterized as small, single-stranded, non-coding RNA molecules that bind to their target mRNA to prevent protein synthesis. MicroRNAs regulate various normal processes; however, they are aberrantly regulated in many cancers. They control the expression of various genes, including cancer-related genes. This causes microRNAs to be considered as a good target for further investigations for designing novel therapeutic strategies. Since miR124 is known for some time already, it has a tumor-suppressing role in various cancers. Numerous studies indicate its definite roles in malignant processes such as epithelial-to-mesenchymal transition, cell cycle arrest, metastasis, cancer stem cell formation and induction of apoptosis. However, some studies have indicated a dual role for miR-124 in oncogenic processes like autophagy and multi-drug resistance. In this article, we will review recent researches on the biological functions and clinical implications of miR-124. Subsequently, we will discuss future perspectives in terms of the roles of this miRNA in cancers.

The Potential Role of MicroRNA-124 in Cerebral Ischemia Injury

Cerebral ischemia injury, the leading cause of morbidity and mortality worldwide, initiates sequential molecular and cellular pathologies that underlie ischemic encephalopathy (IE), such as ischemic stroke, Alzheimer disease (AD), Parkinson's disease (PD), epilepsy, etc. Targeted therapeutic treatments are urgently needed to tackle the pathological processes implicated in these neurological diseases. Recently, accumulating studies demonstrate that microRNA-124 (miR-124), the most abundant miRNA in brain tissue, is aberrant in peripheral blood and brain vascular endothelial cells following cerebral ischemia. Importantly, miR-124 regulates a variety of pathophysiological processes that are involved in the pathogenesis of age-related IE. However, the role of miR-124 has not been systematically illustrated. Paradoxically, miR-124 exerts beneficial effects in the age-related IE via regulating autophagy, neuroinflammation, oxidative stress, neuronal excitability, neurodifferentiation, Aβ deposition, and hyperphosphorylation of tau protein, while it may play a dual role via regulating apoptosis and exerts detrimental effects on synaptic plasticity and axonal growth. In the present review, we thus focus on the paradoxical roles of miR-124 in age-related IE, as well as the underlying mechanisms. A great understanding of the effects of miR-124 on the hypoxic-ischemic brain will open new avenues for therapeutic approaches to protect against cerebral ischemia injury.

Extracellular Vesicles in the Forebrain Display Reduced miR-346 and miR-331-3p in a Rat Model of Chronic Temporal Lobe Epilepsy

An initial precipitating injury in the brain, such as after status epilepticus (SE), evolves into chronic temporal lobe epilepsy (TLE). We investigated changes in the miRNA composition of extracellular vesicles (EVs) in the forebrain after the establishment of SE-induced chronic TLE. We induced SE in young Fischer 344 rats through graded intraperitoneal injections of kainic acid, which resulted in consistent spontaneous recurrent seizures at ~ 3 months post-SE. We isolated EVs from the entire forebrain of chronically epileptic rats and age-matched naïve control animals through an ultracentrifugation method and performed miRNA-sequencing studies to discern changes in the miRNA composition of forebrain-derived EVs in chronic epilepsy. EVs from both naïve and epileptic forebrains displayed spherical or cup-shaped morphology, a comparable size range, and CD63 expression but lacked the expression of a deep cellular marker GM130. However, miRNA-sequencing studies suggested downregulation of 3 miRNAs (miR-187-5p, miR-346, and miR-331-3p) and upregulation of 4 miRNAs (miR-490-5p, miR-376b-3p, miR-493-5p, and miR-124-5p) in EVs from epileptic forebrains with fold changes ranging from 1.5 to 2.4 (p < 0.0006; FDR < 0.05). By using geNorm and Normfinder software, we identified miR-487 and miR-221 as the best combination of reference genes for measurement of altered miRNAs found in the epileptic forebrain through qRT-PCR studies. The validation revealed that only miR-346 and miR-331-3p were significantly downregulated in EVs from the epileptic forebrain. The enrichment pathway analysis of these miRNAs showed an overrepresentation of signaling pathways that are linked to molecular mechanisms underlying chronic epilepsy, including GABA-ergic (miR-346 targets) and mTOR (miR-331-3p targets) systems. Thus, the packaging of two miRNAs into EVs in neural cells is considerably altered in chronic epilepsy. Functional studies on these two miRNAs may uncover their role in the pathophysiology and treatment of TLE.

The orphan nuclear receptor TLX: an emerging master regulator of cross-talk between microglia and neural precursor cells

Neuroinflammation and neurogenesis have both been the subject of intensive investigation over the past 20 years. The sheer complexity of their regulation and their ubiquity in various states of health and disease have sometimes obscured the progress that has been made in unraveling their mechanisms and regulation. A recent study by Kozareva et al. (Neuronal Signaling (2019) 3), provides evidence that the orphan nuclear receptor TLX is central to communication between microglia and neural precursor cells and could help us understand how inflammation, mediated by microglia, influences the development of new neurons in the adult hippocampus. Here, we put recent studies on TLX into the context of what is known about adult neurogenesis and microglial activation in the brain, along with the many hints that these processes must be inter-related.

MiR-135a-5p Is Critical for Exercise-Induced Adult Neurogenesis

Physical exercise stimulates adult hippocampal neurogenesis and is considered a relevant strategy for preventing age-related cognitive decline in humans. The underlying mechanisms remains controversial. Here, we show that exercise increases proliferation of neural precursor cells (NPCs) of the mouse dentate gyrus (DG) via downregulation of microRNA 135a-5p (miR-135a). MiR-135a inhibition stimulates NPC proliferation leading to increased neurogenesis, but not astrogliogenesis, in DG of resting mice, and intriguingly it re-activates NPC proliferation in aged mice. We identify 17 proteins (11 putative targets) modulated by miR-135 in NPCs. Of note, inositol 1,4,5-trisphosphate (IP3) receptor 1 and inositol polyphosphate-4-phosphatase type I are among the modulated proteins, suggesting that IP3 signaling may act downstream miR-135. miR-135 is the first noncoding RNA essential modulator of the brain's response to physical exercise. Prospectively, the miR-135-IP3 axis might represent a novel target of therapeutic intervention to prevent pathological brain aging.

The human Bcl-2 family member Bcl-rambo and voltage-dependent anion channels manifest a genetic interaction in Drosophila and cooperatively promote the activation of effector caspases in human cultured cells

We previously reported that the Bcl-2 family member human Bcl-rambo, also known as BCL2L13, induces apoptosis in human embryonic kidney 293T cells. Mouse Bcl-rambo has recently been reported to mediate mitochondrial fragmentation and mitophagy. In the present study, we showed that the transfection of human Bcl-rambo and its microtubule-associated protein light chain 3-interacting region motif mutant (W276A/I279A) caused mitochondrial fragmentation and the perinuclear accumulation of fragmented mitochondria in human lung adenocarcinoma A549 cells. In comprehensive screening using the Drosophila model in which human Bcl-rambo was ectopically expressed in eye imaginal discs, voltage-dependent anion channels (VDAC), also known as mitochondrial porin, were found to manifest a genetic interaction with human Bcl-rambo. In addition to human adenine nucleotide translocase (ANT) 1 and ANT2, the human Bcl-rambo protein bound to human VDAC1, albeit to a lesser extent than ANT2. Moreover, human VDAC1 and human VDAC2 in particular promoted the activation of effector caspases only when they were co-expressed with human Bcl-rambo in 293T cells. Bcl-rambo induced the perinuclear accumulation of fragmented mitochondria by the knockdown of VDAC1, VDAC2, and VDAC3 in A549 cells. Thus, the present study revealed that human Bcl-rambo and VDAC cooperatively promote the activation of effector caspases in human cultured cells.

Dgcr8 knockout approaches to understand microRNA functions in vitro and in vivo

Biologic function of the majority of microRNAs (miRNAs) is still unknown. Uncovering the function of miRNAs is hurdled by redundancy among different miRNAs. The deletion of Dgcr8 leads to the deficiency in producing all canonical miRNAs, therefore, overcoming the redundancy issue. Dgcr8 knockout strategy has been instrumental in understanding the function of miRNAs in a variety of cells in vitro and in vivo. In this review, we will first give a brief introduction about miRNAs, miRNA biogenesis pathway and the role of Dgcr8 in miRNA biogenesis. We will then summarize studies performed with Dgcr8 knockout cell models with a focus on embryonic stem cells. After that, we will summarize results from various in vivo Dgcr8 knockout models. Given significant phenotypic differences in various tissues between Dgcr8 and Dicer knockout, we will also briefly review current progresses on understanding miRNA-independent functions of miRNA biogenesis factors. Finally, we will discuss the potential use of a new strategy to stably express miRNAs in Dgcr8 knockout cells. In future, Dgcr8 knockout approaches coupled with innovations in miRNA rescue strategy may provide further insights into miRNA functions in vitro and in vivo.

Co-administration of Anti microRNA-124 and -137 Oligonucleotides Prevents Hippocampal Neural Stem Cell Loss Upon Non-convulsive Seizures

Convulsive seizures promote adult hippocampal neurogenesis (AHN) through a transient activation of neural stem/progenitor cells (NSPCs) in the subgranular zone (SGZ) of the dentate gyrus (DG). However, in a significant population of epilepsy patients, non-convulsive seizures (ncSZ) are observed. The response of NSPCs to non-convulsive seizure induction has not been characterized before. We here studied first the short-term effects of controlled seizure induction on NSPCs fate and identity. We induced seizures of controlled intensity by intrahippocampally injecting increasing doses of the chemoconvulsant kainic acid (KA) and analyzed their effect on subdural EEG recordings, hippocampal structure, NSPC proliferation and the number and location of immature neurons shortly after seizure onset. After establishing a KA dose that elicits ncSZ, we then analyzed the effects of ncSZ on NSPC proliferation and NSC identity in the hippocampus. ncSZ specifically triggered neuroblast proliferation, but did not induce proliferation of NSPCs in the SGZ, 3 days post seizure onset. However, ncSZ induced significant changes in NSPC composition in the hippocampus, including the generation of reactive NSCs. Interestingly, intrahippocampal injection of a combination of two anti microRNA oligonucleotides targeting microRNA-124 and -137 normalized neuroblast proliferation and prevented NSC loss in the DG upon ncSZ. Our results show for the first time that ncSZ induce significant changes in neuroblast proliferation and NSC composition. Simultaneous antagonism of both microRNA-124 and -137 rescued seizure-induced alterations in NSPC, supporting their coordinated action in the regulation of NSC fate and proliferation and their potential for future seizure therapies.

Ciphers and Executioners: How 3'-Untranslated Regions Determine the Fate of Messenger RNAs

The sequences and structures of 3'-untranslated regions (3'UTRs) of messenger RNAs govern their stability, localization, and expression. 3'UTR regulatory elements are recognized by a wide variety of trans-acting factors that include microRNAs (miRNAs), their associated machinery, and RNA-binding proteins (RBPs). In turn, these factors instigate common mechanistic strategies to execute the regulatory programs encoded by 3'UTRs. Here, we review classes of factors that recognize 3'UTR regulatory elements and the effector machineries they guide toward mRNAs to dictate their expression and fate. We outline illustrative examples of competitive, cooperative, and coordinated interplay such as mRNA localization and localized translation. We further review the recent advances in the study of mRNP granules and phase transition, and their possible significance for the functions of 3'UTRs. Finally, we highlight some of the most recent strategies aimed at deciphering the complexity of the regulatory codes of 3'UTRs, and identify some of the important remaining challenges.

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.

Construction of an miRNA‑gene regulatory network in colorectal cancer through integrated analysis of mRNA and miRNA microarrays

The aim of the present study was to identify potential biomarkers associated with colorectal cancer (CRC). The GSE32323 and GSE53592 mRNA and microRNA (miRNA) expression profiles were selected from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) in CRC tissue samples compared with surrounding control tissue samples (DEGs‑CC), and DEGs in cells treated with 5‑aza‑2'‑deoxycitidine compared with untreated cells (DEGs‑TC) were identified with the Limma package. The Database for Annotation, Visualization and Integrated Discovery was used to conduct the functional and pathways enrichment analysis. Differential co‑regulation networks were constructed using the DCGL package of R. The targets of DEMs were identified using TargetScan. The overlaps between DEGs and the targets were selected. The miRNA‑gene regulatory network of the overlaps was established. There were 145 DEMs, and 1,284 DEGs in DEGs‑CC, and 101 DEGs in DEGs‑TC. DEGs‑CC were enriched in 196 Gene Ontology (GO) terms and 23 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. DEGs‑TC were enriched in 46 GO terms and two KEGG pathways. A differential co‑regulation network of the DEGs and a miRNA‑gene regulatory network between DEMs and overlapped DEGs were respectively constructed. miR‑124‑3p, miR‑145‑5p and miR‑320a may be critical in CRC, and serum/glucocorticoid regulated kinase 1 and SRY‑box 9 may be potential biomarkers for CRC tumor progression.

Potential Role of miRNAs as Theranostic Biomarkers of Epilepsy

Epilepsy includes a group of disorders of the brain characterized by an enduring predisposition to generate epileptic seizures. Although familial epilepsy has a genetic component and heritability, the etiology of the majority of non-familial epilepsies has no known associated genetic mutations. In epilepsy, recent epigenetic profiles have highlighted a possible role of microRNAs in its pathophysiology. In particular, molecular profiling identifies a significant number of microRNAs (miRNAs) altered in epileptic hippocampus of both animal models and human tissues. In this review, analyzing molecular profiles of different animal models of epilepsy, we identified a group of 20 miRNAs commonly altered in different epilepsy-animal models. As emerging evidences highlighted the poor overlap between signatures of animal model tissues and human samples, we focused our analysis on miRNAs, circulating in human biofluids, with a principal role in epilepsy hallmarks, and we identified a group of 8 diagnostic circulating miRNAs. We discussed the functional role of these 8 miRNAs in the epilepsy hallmarks. A few of them have also been proposed as therapeutic molecules for epilepsy treatment, revealing a great potential for miRNAs as theranostic molecules in epilepsy.

MicroRNA-96 is responsible for sevoflurane-induced cognitive dysfunction in neonatal rats via inhibiting IGF1R

Sevoflurane is an experimental potent yet volatile anesthesia agent characterized by a low blood/gas partition coefficient. However, exposure to sevoflurane in neonatal mice has been speculated to result in learning deficits and abnormal social behavior. The aim of the present study was to investigate the relationship between sevoflurane and miR-96, in an attempt to identify the means by which it mediates IGF1R to influence the cognitive dysfunction (CD) in neonatal rats. Relationship between differentially expressed miRNAs and sevoflurane concentration was identified. The potential underlying regulatory mechanisms involved with sevoflurane were investigated through the administration of varying concentrations of the agent (1%, 2% and 4%), combined with miR-96 mimic or an inhibitor. A target prediction program was utilized, while the luciferase activity was determined in order to verify whether miR-96 targets IGF1R. The mRNA and protein levels of IGF1R, Bcl-2, Bax, and caspase-3 were measured followed by the determination of hippocampal neuron apoptosis. Learning and memory performance was assessed using the Morris water maze (MWM) test and step-down test. The obtained results highlighted a positive correlation between miR-96 and the concentration of sevoflurane, while miR-96 was confirmed to negatively target IGF1R. Our analyses indicated that 4% sevoflurane had a significantly stronger effect on reducing the levels of IGF1R and Bcl-2, while elevating the levels of miR-96, Bax and caspase-3 more so than that of 1% or 2% sevoflurane, which resulted in increased hippocampal neuron apoptosis but diminished the learning and memory performance of the rats. The addition of miR-96 mimic was demonstrated to exacerbate the influence of sevoflurane on hippocampal neurons as well as the cognitive function of the rats. The key findings of our study highlighted the role of miR-96 in the potential mechanism of sevoflurane anesthesia-induced CD in neonatal rats through the downregulation of IGF1R.

Glucocorticoid-mediated modulation of morphological changes associated with aging in microglia

Microglia dynamically adapt their morphology and function during increasing age. However, the mechanisms behind these changes are to date poorly understood. Glucocorticoids (GCs) are long known and utilized for their immunomodulatory actions and endogenous GC levels are described to alter with advancing age. We here tested the hypothesis that age‐associated elevations in GC levels implicate microglia function and morphology. Our data indicate a decrease in microglial complexity and a concomitant increase in GC levels during aging. Interestingly, enhancing GC levels in young mice enhanced microglial ramifications, while the knockdown of the glucocorticoid receptor expression in old mice aggravated age‐associated microglial amoebification. These data suggest that GCs increase ramification of hippocampal microglia and may modulate age‐associated changes in microglial morphology.

Regulation of Ion Channels by MicroRNAs and the Implication for Epilepsy

PURPOSE OF REVIEW

The goal of this focused review is to describe recent studies supporting a critical role of microRNAs in the regulation of ion channels and discuss the resulting implications for the modulation of neuronal excitability in epilepsy.

RECENT FINDINGS

MicroRNA-induced silencing of ion channels has been shown in several different studies in recent years, and some of these reports suggest a prominent role in epilepsy. The ion channels regulated by microRNAs include ligand- and voltage-gated channels and are not only limited to the central nervous system but have also been found in the peripheral nervous system. Ion channel-targeting microRNAs can regulate the intrinsic excitability of neurons, and thus influence entire networks in the brain. Their dysregulation in epilepsy may contribute to the disease phenotype. More research is needed to better understand the molecular mechanisms of how microRNAs regulate ion channels to control neuronal excitability, and how these processes are altered in epilepsy.

Validation and bioinformatic analysis of propofol-induced differentially expressed microRNAs in primary cultured neural stem cells

Propofol, a widely used intravenous anesthetic, was previously considered as a neuroprotective agent. Recently, however, accumulating evidence suggests that it may cause neurotoxicity, especially in the development of neural stem cells (NSCs). The potential mechanisms contributing to propofol-induced neurotoxicity during neurogenesis, such as those involving microRNAs (miRNAs), are still unknown. In this study, a total of 27 differentially expressed miRNAs were identified in our initial screen and 6 miRNAs were validated by qRT-PCR. Three miRNAs were up-regulated (miR-377-5p, miR-194-3p and miR-143-5p), and three were down-regulated (miR-3583-3p, miR-466b-5p and miR-410-5p). Following gene ontology and KEGG pathway enrichment analysis, Gabbr1, Canca1b and Gabbr2, which are enriched in the GABAergic synapse pathway, were selected as genes potentially playing a role in propofol-induced neurotoxicity. Gabbr1 and Cacna1b, which are targeted by miRNAs that are up-regulated following propofol exposure, showed decreased expression at the mRNA and protein levels. Gabbr2, targeted by miRNAs that were down-regulated following treatment with propofol, was up-regulated at both the levels of mRNA and protein expression. The two clusters of miRNAs that show differential expression following propofol exposure may act in a synergistic manner to regulate several genes simultaneously during the development of NSCs. Our results may contribute to clarify the molecular mechanism and provide potential therapeutic targets for propofol induced neurotoxicity.

A direct regulatory link between microRNA-137 and SHANK2: implications for neuropsychiatric disorders

BACKGROUND

Mutations in the SHANK genes, which encode postsynaptic scaffolding proteins, have been linked to a spectrum of neurodevelopmental disorders. The SHANK genes and the schizophrenia-associated microRNA-137 show convergence on several levels, as they are both expressed at the synapse, influence neuronal development, and have a strong link to neurodevelopmental and neuropsychiatric disorders like intellectual disability, autism, and schizophrenia. This compiled evidence raised the question if the SHANKs might be targets of miR-137.

METHODS

In silico analysis revealed a putative binding site for microRNA-137 (miR-137) in the SHANK2 3'UTR, while this was not the case for SHANK1 and SHANK3. Luciferase reporter assays were performed by overexpressing wild type and mutated SHANK2-3'UTR and miR-137 in human neuroblastoma cells and mouse primary hippocampal neurons. miR-137 was also overexpressed or inhibited in hippocampal neurons, and Shank2 expression was analyzed by quantitative real-time PCR and Western blot. Additionally, expression levels of experimentally validated miR-137 target genes were analyzed in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia and control individuals using the RNA-Seq data from the CommonMind Consortium.

RESULTS

miR-137 directly targets the 3'UTR of SHANK2 in a site-specific manner. Overexpression of miR-137 in mouse primary hippocampal neurons significantly lowered endogenous Shank2 protein levels without detectable influence on mRNA levels. Conversely, miR-137 inhibition increased Shank2 protein expression, indicating that miR-137 regulates SHANK2 expression by repressing protein translation rather than inducing mRNA degradation. To find out if the miR-137 signaling network is altered in schizophrenia, we compared miR-137 precursor and miR-137 target gene expression in the DLPFC of schizophrenia and control individuals using the CommonMind Consortium RNA sequencing data. Differential expression of 23% (16/69) of known miR-137 target genes was detected in the DLPFC of schizophrenia individuals compared with controls. We propose that in further targets (e.g., SHANK2, as described in this paper) which are not regulated on RNA level, effects may only be detectable on protein level.

CONCLUSION

Our study provides evidence that a direct regulatory link exists between miR-137 and SHANK2 and supports the finding that miR-137 signaling might be altered in schizophrenia.

Hypoxia-Induced MicroRNA-210 Targets Neurodegenerative Pathways

Hypoxia-regulated microRNA-210 (miR-210) is a highly conserved microRNA, known to regulate various processes under hypoxic conditions. Previously we found that miR-210 is also involved in honeybee learning and memory, raising the questions of how neural activity may induce hypoxia-regulated genes and how miR-210 may regulate plasticity in more complex mammalian systems. Using a pull-down approach, we identified 620 unique target genes of miR-210 in humans, among which there was a significant enrichment of age-related neurodegenerative pathways, including Huntington's, Alzheimer's, and Parkinson's diseases. We have also validated that miR-210 directly regulates various identified target genes of interest involved with neuronal plasticity, neurodegenerative diseases, and miR-210-associated cancers. This data suggests a potentially novel mechanism for how metabolic changes may couple plasticity to neuronal activity through hypoxia-regulated genes such as miR-210.

A comprehensive review of the genetic and biological evidence supports a role for MicroRNA-137 in the etiology of schizophrenia

Since it was first associated with schizophrenia (SCZ) in a 2011 genome-wide association study (GWAS), there have been over 100 publications focused on MIR137, the gene encoding microRNA-137. These studies have examined everything from its fundamental role in the development of mice, flies, and fish to the intriguing enrichment of its target gene network in SCZ. Indeed, much of the excitement surrounding MIR137 is due to the distinct possibility that it could regulate a gene network involved in SCZ etiology, a disease which we now recognize is highly polygenic. Here we comprehensively review, to the best of our ability, all published genetic and biological evidence that could support or refute a role for MIR137 in the etiology of SCZ. Through a careful consideration of the literature, we conclude that the data gathered to date continues to strongly support the involvement of MIR137 and its target gene network in neuropsychiatric traits, including SCZ risk. There remain, however, more unanswered than answered questions regarding the mechanisms linking MIR137 genetic variation with behavior. These questions need answers before we can determine whether there are opportunities for diagnostic or therapeutic interventions based on MIR137. We conclude with a number of suggestions for future research on MIR137 that could help to provide answers and hope for a greater understanding of this devastating disorder.

The Challenge of microRNA as a Biomarker of Epilepsy

BACKGROUND

Epilepsy is one of chronic severe neurological disorders possess to recurring seizures. And now anti-epileptic drugs are only effective in less than one third of epilepsy patients, and biomarkers predicting are not available when the specific antiepileptic drugs treated. Advanced studies have showed that miRNA may be a key in the pathogenesis of epilepsy beginning in the early 2000 years. Several target genes and pathways of miRNA which related to the therapeutic methods to epilepsy.

METHOD

We searched PubMed from Jan 1,2000 to Jan 1, 2017, using the terms "epilepsy AND microRNA AND biomarker" and "seizure AND microRNA AND biomarker". We selected articles that featured novel miRNAs in vivo epilepsy models and patients. We then selected the most relevant articles based on a subjective appraisal of their quality and mechanistic insight that could be relevant to epilepsy.

RESULTS

Decrease the expression of has-miR134 could be a potential non-invasive biomarker to use in diagnosis for the epilepsy patients for using hsa-miR-134 also be identified to distinguish patients with and without epilepsy. miR-181a show significant downregulation in the acute stage, but up regulation in the chronic stage and in the latent stage there is no changing and how about this phenomenon appearance in different stage still should be discussed in the future. Besides that, miR- 146a can down-regulated in the patients using genome-wide for serum in circulating miRNAs.miR- 124, miR-199a, and miR-128 etc. could be a candidate for the biomarker in future. miR-15a-5p and -194-5p down-regulated in epilepsy patients, in the future, it may be used as a novel biomarker for improve diagnosis.

CONCLUSION

These observations give a chance that new development for diagnosis and treatment of epilepsy patients. Advanced technique and miRNA combination may product more effective roles in epilepsy and other disease. These reports will be available to solve the application of miRNAs as biomarkers and novel therapy approaches for epilepsy. In summary, researcher who focus on miRNAs should be understanding of the causes, treatment, and diagnosis of epilepsy. exploration of any of these effects on the efficacy of these drugs is worthwhile.

MicroRNA-induced silencing in epilepsy: Opportunities and challenges for clinical application

MicroRNAs are master regulators of gene expression. Single microRNAs influence multiple proteins within diverse molecular pathways and networks. Therefore, changes in levels or activity of microRNAs can have profound effects on cellular function. This makes dysregulated microRNA-induced silencing an attractive potential disease mechanism in complex disorders like epilepsy, where numerous cellular pathways and processes are affected simultaneously. Indeed, several years of research in rodent models have provided strong evidence that acute or recurrent seizures change microRNA expression and function. Moreover, altered microRNA expression has been observed in brain and blood from patients with various epilepsy disorders, such as tuberous sclerosis. MicroRNAs can be easily manipulated using sense or antisense oligonucleotides, opening up opportunities for therapeutic intervention. Here, we summarize studies using these techniques to identify microRNAs that modulate seizure susceptibility, describe protein targets mediating some of these effects, and discuss cellular pathways, for example neuroinflammation, that are controlled by epilepsy-associated microRNAs. We critically assess current gaps in knowledge regarding target- and cell-specificity of microRNAs that have to be addressed before clinical application as therapeutic targets or biomarkers. The recent progress in understanding microRNA function in epilepsy has generated strong momentum to encourage in-depth mechanistic studies to develop microRNA-targeted therapies. Developmental Dynamics 247:94-110, 2018. © 2017 Wiley Periodicals, Inc.

A distinct microRNA expression profile is associated with α[11C]-methyl-L-tryptophan (AMT) PET uptake in epileptogenic cortical tubers resected from patients with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is characterized by hamartomatous lesions in various organs and arises due to mutations in the TSC1 or TSC2 genes. TSC mutations lead to a range of neurological manifestations including epilepsy, cognitive impairment, autism spectrum disorders (ASD), and brain lesions that include cortical tubers. There is evidence that seizures arise at or near cortical tubers, but it is unknown why some tubers are epileptogenic while others are not. We have previously reported increased tryptophan metabolism measured with α[11C]-methyl-l-tryptophan (AMT) positron emission tomography (PET) in epileptogenic tubers in approximately two-thirds of patients with tuberous sclerosis and intractable epilepsy. However, the underlying mechanisms leading to seizure onset in TSC remain poorly characterized. MicroRNAs are enriched in the brain and play important roles in neurodevelopment and brain function. Recent reports have shown aberrant microRNA expression in epilepsy and TSC. In this study, we performed microRNA expression profiling in brain specimens obtained from TSC patients undergoing epilepsy surgery for intractable epilepsy. Typically, in these resections several non-seizure onset tubers are resected together with the seizure-onset tubers because of their proximity. We directly compared seizure onset tubers, with and without increased tryptophan metabolism measured with PET, and non-onset tubers to assess the role of microRNAs in epileptogenesis associated with these lesions. Whether a particular tuber was epileptogenic or non-epileptogenic was determined with intracranial electrocorticography, and tryptophan metabolism was measured with AMT PET. We identified a set of five microRNAs (miR-142-3p, 142-5p, 223-3p, 200b-3p and 32-5p) that collectively distinguish among the three primary groups of tubers: non-onset/AMT-cold (NC), onset/AMT-cold (OC), and onset/AMT-hot (OH). These microRNAs were significantly upregulated in OH tubers compared to the other two groups, and microRNA expression was most significantly associated with AMT-PET uptake. The microRNAs target a group of genes enriched for synaptic signaling and epilepsy risk, including SLC12A5, SYT1, GRIN2A, GRIN2B, KCNB1, SCN2A, TSC1, and MEF2C. We confirmed the interaction between miR-32-5p and SLC12A5 using a luciferase reporter assay. Our findings provide a new avenue for subsequent mechanistic studies of tuber epileptogenesis in TSC.

When dying is not the end: Apoptotic caspases as drivers of proliferation

Caspases are well known for their role as executioners of apoptosis. However, recent studies have revealed that these lethal enzymes also have important mitogenic functions. Caspases can promote proliferation through autonomous regulation of the cell cycle, as well as by induction of secreted signals, which have a profound impact in neighboring tissues. Here, I review the proliferative role of caspases during development and homeostasis, in addition to their key regenerative function during tissue repair upon injury. Furthermore, the emerging properties of apoptotic caspases as drivers of carcinogenesis are discussed, as well as their involvement in other diseases. Finally, I examine further effects of caspases regulating death and survival in a non-autonomous manner.

miRNA-Mediated Regulation of Adult Hippocampal Neurogenesis; Implications for Epilepsy

Hippocampal neural stem/progenitor cells (NSPCs) proliferate and differentiate to generate new neurons across the life span of most mammals, including humans. This process takes place within a characteristic local microenvironment where NSPCs interact with a variety of other cell types and encounter systemic regulatory factors. Within this microenvironment, cell intrinsic gene expression programs are modulated by cell extrinsic signals through complex interactions, in many cases involving short non-coding RNA molecules, such as miRNAs. Here we review the regulation of gene expression in NSPCs by miRNAs and its possible implications for epilepsy, which has been linked to alterations in adult hippocampal neurogenesis.

Gene regulation in adult neural stem cells. Current challenges and possible applications

Adult neural stem and progenitor cells (NSPCs) offer a unique opportunity for neural regeneration and niche modification in physiopathological conditions, harnessing the capability to modify from neuronal circuits to glial scar. Findings exposing the vast plasticity and potential of NSPCs have accumulated over the past years and we currently know that adult NSPCs can naturally give rise not only to neurons but also to astrocytes and reactive astrocytes, and eventually to oligodendrocytes through genetic manipulation. We can consider NSPCs as endogenous flexible tools to fight against neurodegenerative and neurological disorders and aging. In addition, NSPCs can be considered as active agents contributing to chronic brain alterations and as relevant cell populations to be preserved, so that their main function, neurogenesis, is not lost in damage or disease. Altogether we believe that learning to manipulate NSPC is essential to prevent, ameliorate or restore some of the cognitive deficits associated with brain disease and injury, and therefore should be considered as target for future therapeutic strategies. The first step to accomplish this goal is to target them specifically, by unveiling and understanding their unique markers and signaling pathways.

Systematic review and meta-analysis of differentially expressed miRNAs in experimental and human temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is a common chronic neurological disease in humans. A number of studies have demonstrated differential expression of miRNAs in the hippocampus of humans with TLE and in animal models of experimental epilepsy. However, the dissimilarities in experimental design have led to largely discordant results across these studies. Thus, a comprehensive comparison is required in order to better characterize miRNA profiles obtained in various post-status epilepticus (SE) models. We therefore created a database and performed a meta-analysis of differentially expressed miRNAs across 3 post-SE models of epileptogenesis (electrical stimulation, pilocarpine and kainic acid) and human TLE with hippocampal sclerosis (TLE-HS). The database includes data from 11 animal post-SE studies and 3 human TLE-HS studies. A total of 378 differentially expressed miRNAs were collected (274 up-regulated and 198 down-regulated) and analyzed with respect to the post-SE model, time point and animal species. We applied the novel robust rank aggregation method to identify consistently differentially expressed miRNAs across the profiles. It highlighted common and unique miRNAs at different stages of epileptogenesis. The pathway analysis revealed involvement of these miRNAs in key pathogenic pathways underlying epileptogenesis, including inflammation, gliosis and deregulation of the extracellular matrix.