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Epilepsy is a neurological disease characterised by recurrent seizures with complex aetiology. Temporal lobe epilepsy, the most common form in adults, can be acquired following brain insults including trauma, stroke, infection or sustained status epilepticus. The mechanisms that give rise to the formation and maintenance of hyperexcitable networks following acquired insults remain unknown, yet an extensive body of literature points towards persistent gene and epigenomic dysregulation as a potential mediator of this dysfunction. While much is known about the function of specific classes of epigenetic regulators (writers and erasers) in epilepsy, much less is known about the enzymes, which read the epigenome and modulate gene expression accordingly. Here, we explore the potential role for the epigenetic reader bromodomain and extra-terminal domain (BET) proteins in epilepsy. Using the intra-amygdala kainic acid model of temporal lobe epilepsy, we initially identified widespread dysregulation of important epigenetic regulators including EZH2 and REST as well as altered BRD4 expression in chronically epileptic mice. BRD4 activity was also notably affected by epilepsy-provoking insults as seen by elevated binding to and transcriptional regulation of the immediate early gene Fos. Despite influencing early aspects of epileptogenesis, blocking BET protein activity with JQ1 had no overt effects on epilepsy development in mice but did alter glial reactivity and influence gene expression patterns, promoting various neurotransmitter signalling mechanisms and inflammatory pathways in the hippocampus. Together, these results confirm that epigenetic reader activity is affected by epilepsy-provoking brain insults and that BET activity may exert cell-specific actions on inflammation in epilepsy.
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OBJECTIVE: Posttranscriptional mechanisms are increasingly recognized as important contributors to the formation of hyperexcitable networks in epilepsy. Messenger RNA (mRNA) polyadenylation is a key regulatory mechanism governing protein expression by enhancing mRNA stability and translation. Previous studies have shown large-scale changes in mRNA polyadenylation in the hippocampus of mice during epilepsy development. The cytoplasmic polyadenylation element-binding protein CPEB4 was found to drive epilepsy-induced poly(A) tail changes, and mice lacking CPEB4 develop a more severe seizure and epilepsy phenotype. The mechanisms controlling CPEB4 function and the downstream pathways that influence the recurrence of spontaneous seizures in epilepsy remain poorly understood. METHODS: Status epilepticus was induced in wild-type and CPEB4-deficient male mice via an intra-amygdala microinjection of kainic acid. CLOCK binding to the CPEB4 promoter was analyzed via chromatin immunoprecipitation assay and melatonin levels via high-performance liquid chromatography in plasma. RESULTS: Here, we show increased binding of CLOCK to recognition sites in the CPEB4 promoter region during status epilepticus in mice and increased Cpeb4 mRNA levels in N2A cells overexpressing CLOCK. Bioinformatic analysis of CPEB4-dependent genes undergoing changes in their poly(A) tail during epilepsy found that genes involved in the regulation of circadian rhythms are particularly enriched. Clock transcripts displayed a longer poly(A) tail length in the hippocampus of mice post-status epilepticus and during epilepsy. Moreover, CLOCK expression was increased in the hippocampus in mice post-status epilepticus and during epilepsy, and in resected hippocampus and cortex of patients with drug-resistant temporal lobe epilepsy. Furthermore, CPEB4 is required for CLOCK expression after status epilepticus, with lower levels in CPEB4-deficient compared to wild-type mice. Last, CPEB4-deficient mice showed altered circadian function, including altered melatonin blood levels and altered clustering of spontaneous seizures during the day. SIGNIFICANCE: Our results reveal a new positive transcriptional-translational feedback loop involving CPEB4 and CLOCK, which may contribute to the regulation of the sleep-wake cycle during epilepsy.
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Proteínas CLOCK , Epilepsia Refractaria , Epilepsia del Lóbulo Temporal , Melatonina , Proteínas de Unión al ARN , Estado Epiléptico , Animales , Humanos , Masculino , Ratones , Epilepsia del Lóbulo Temporal/metabolismo , Hipocampo , Melatonina/sangre , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Convulsiones , Estado Epiléptico/inducido químicamente , Estado Epiléptico/genética , Factores de Transcripción/metabolismo , Proteínas CLOCK/genéticaRESUMEN
Temporal lobe epilepsy is the most common drug-resistant form of epilepsy in adults. The reorganization of neural networks and the gene expression landscape underlying pathophysiologic network behavior in brain structures such as the hippocampus has been suggested to be controlled, in part, by microRNAs. To systematically assess their significance, we sequenced Argonaute-loaded microRNAs to define functionally engaged microRNAs in the hippocampus of three different animal models in two species and at six time points between the initial precipitating insult through to the establishment of chronic epilepsy. We then selected commonly up-regulated microRNAs for a functional in vivo therapeutic screen using oligonucleotide inhibitors. Argonaute sequencing generated 1.44 billion small RNA reads of which up to 82% were microRNAs, with over 400 unique microRNAs detected per model. Approximately half of the detected microRNAs were dysregulated in each epilepsy model. We prioritized commonly up-regulated microRNAs that were fully conserved in humans and designed custom antisense oligonucleotides for these candidate targets. Antiseizure phenotypes were observed upon knockdown of miR-10a-5p, miR-21a-5p, and miR-142a-5p and electrophysiological analyses indicated broad safety of this approach. Combined inhibition of these three microRNAs reduced spontaneous seizures in epileptic mice. Proteomic data, RNA sequencing, and pathway analysis on predicted and validated targets of these microRNAs implicated derepressed TGF-ß signaling as a shared seizure-modifying mechanism. Correspondingly, inhibition of TGF-ß signaling occluded the antiseizure effects of the antagomirs. Together, these results identify shared, dysregulated, and functionally active microRNAs during the pathogenesis of epilepsy which represent therapeutic antiseizure targets.
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Epilepsia del Lóbulo Temporal/tratamiento farmacológico , Epilepsia del Lóbulo Temporal/metabolismo , MicroARNs/efectos de los fármacos , MicroARNs/metabolismo , Oligonucleótidos Antisentido/farmacología , Convulsiones/tratamiento farmacológico , Convulsiones/metabolismo , Animales , Antagomirs/farmacología , Proteínas Argonautas/genética , Proteínas Argonautas/metabolismo , Biomarcadores , Modelos Animales de Enfermedad , Epilepsia , Femenino , Hipocampo/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , MicroARNs/genética , Proteómica , Ratas , Ratas Sprague-Dawley , Convulsiones/genética , Análisis de Sistemas , Regulación hacia Arriba/efectos de los fármacosRESUMEN
Oligonucleotide therapies offer precision treatments for a variety of neurological diseases, including epilepsy, but their deployment is hampered by the blood-brain barrier (BBB). Previous studies showed that intracerebroventricular injection of an antisense oligonucleotide (antagomir) targeting microRNA-134 (Ant-134) reduced evoked and spontaneous seizures in animal models of epilepsy. In this study, we used assays of serum protein and tracer extravasation to determine that BBB disruption occurring after status epilepticus in mice was sufficient to permit passage of systemically injected Ant-134 into the brain parenchyma. Intraperitoneal and intravenous injection of Ant-134 reached the hippocampus and blocked seizure-induced upregulation of miR-134. A single intraperitoneal injection of Ant-134 at 2 h after status epilepticus in mice resulted in potent suppression of spontaneous recurrent seizures, reaching a 99.5% reduction during recordings at 3 months. The duration of spontaneous seizures, when they occurred, was also reduced in Ant-134-treated mice. In vivo knockdown of LIM kinase-1 (Limk-1) increased seizure frequency in Ant-134-treated mice, implicating de-repression of Limk-1 in the antagomir mechanism. These studies indicate that systemic delivery of Ant-134 reaches the brain and produces long-lasting seizure-suppressive effects after systemic injection in mice when timed with BBB disruption and may be a clinically viable approach for this and other disease-modifying microRNA therapies.
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Antagomirs/genética , Barrera Hematoencefálica/metabolismo , Epilepsia/genética , Epilepsia/terapia , Animales , Antagomirs/administración & dosificación , Barrera Hematoencefálica/patología , Manejo de la Enfermedad , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Regulación de la Expresión Génica , Silenciador del Gen , Técnicas de Transferencia de Gen , Predisposición Genética a la Enfermedad , Terapia Genética , Ratones , MicroARNs/genética , Interferencia de ARN , Resultado del TratamientoRESUMEN
Epilepsy is a network disorder driven by fundamental changes in the function of the cells which compose these networks. Driving this aberrant cellular function are large scale changes in gene expression and gene expression regulation. Recent studies have revealed rapid and persistent changes in epigenetic control of gene expression as a critical regulator of the epileptic transcriptome. Epigenetic-mediated gene output regulates many aspects of cellular physiology including neuronal structure, neurotransmitter assembly and abundance, protein abundance of ion channels and other critical neuronal processes. Thus, understanding the contribution of epigenetic-mediated gene regulation could illuminate novel regulatory mechanisms which may form the basis of novel therapeutic approaches to treat epilepsy. In this review we discuss the effects of epileptogenic brain insults on epigenetic regulation of gene expression, recent efforts to target epigenetic processes to block epileptogenesis and the prospects of an epigenetic-based therapy for epilepsy, and finally we discuss technological advancements which have facilitated the interrogation of the epigenome.
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Epigénesis Genética , Síndromes Epilépticos/genética , Regulación de la Expresión Génica , HumanosRESUMEN
Synaptic downscaling is a homeostatic mechanism that allows neurons to reduce firing rates during chronically elevated network activity. Although synaptic downscaling is important in neural circuit development and epilepsy, the underlying mechanisms are poorly described. We performed small RNA profiling in picrotoxin (PTX)-treated hippocampal neurons, a model of synaptic downscaling. Thereby, we identified eight microRNAs (miRNAs) that were increased in response to PTX, including miR-129-5p, whose inhibition blocked synaptic downscaling in vitro and reduced epileptic seizure severity in vivo Using transcriptome, proteome, and bioinformatic analysis, we identified the calcium pump Atp2b4 and doublecortin (Dcx) as miR-129-5p targets. Restoring Atp2b4 and Dcx expression was sufficient to prevent synaptic downscaling in PTX-treated neurons. Furthermore, we characterized a functional crosstalk between miR-129-5p and the RNA-binding protein (RBP) Rbfox1. In the absence of PTX, Rbfox1 promoted the expression of Atp2b4 and Dcx. Upon PTX treatment, Rbfox1 expression was downregulated by miR-129-5p, thereby allowing the repression of Atp2b4 and Dcx. We therefore identified a novel activity-dependent miRNA/RBP crosstalk during synaptic scaling, with potential implications for neural network homeostasis and epileptogenesis.
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Regulación de la Expresión Génica , MicroARNs/metabolismo , Factores de Empalme de ARN/metabolismo , Sinapsis/fisiología , Animales , Biología Computacional , Proteínas de Dominio Doblecortina , Proteína Doblecortina , Perfilación de la Expresión Génica , Hipocampo/efectos de los fármacos , Hipocampo/fisiología , Ratones , Proteínas Asociadas a Microtúbulos/metabolismo , Neuropéptidos/metabolismo , Picrotoxina/metabolismo , ATPasas Transportadoras de Calcio de la Membrana Plasmática/metabolismo , Proteoma/análisisRESUMEN
Epileptic encephalopathies (EE) are severe epilepsy syndromes characterized by multiple seizure types, developmental delay and even regression. This class of disorders are increasingly being identified as resulting from de novo genetic mutations including many identified mutations in the family of chromodomain helicase DNA binding (CHD) proteins. In particular, several de novo pathogenic mutations have been identified in the gene encoding chromodomain helicase DNA binding protein 2 (CHD2), a member of the sucrose nonfermenting (SNF-2) protein family of epigenetic regulators. These mutations in the CHD2 gene are causative of early onset epileptic encephalopathy, abnormal brain function, and intellectual disability. Our understanding of the mechanisms by which modification or loss of CHD2 cause this condition remains poorly understood. Here, we review what is known and still to be elucidated as regards the structure and function of CHD2 and how its dysregulation leads to a highly variable range of phenotypic presentations.
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Proteínas de Unión al ADN/genética , Epilepsia Generalizada/genética , Predisposición Genética a la Enfermedad/genética , Discapacidad Intelectual/genética , Mutación , Animales , Modelos Animales de Enfermedad , Electroencefalografía , Epilepsia Generalizada/patología , Epilepsia Generalizada/fisiopatología , Regulación de la Expresión Génica , Humanos , Discapacidad Intelectual/fisiopatologíaRESUMEN
Mesial temporal lobe epilepsy (mTLE) is a chronic neurological disease characterized by recurrent seizures. The antiepileptic drugs currently available to treat mTLE are ineffective in one-third of patients and lack disease-modifying effects. miRNAs, a class of small noncoding RNAs which control gene expression at the post-transcriptional level, play a key role in the pathogenesis of mTLE and other epilepsies. Although manipulation of miRNAs at acute stages has been reported to reduce subsequent spontaneous seizures, it is uncertain whether targeting miRNAs at chronic stages of mTLE can also reduce seizures. Furthermore, the functional role and downstream targets of most epilepsy-associated miRNAs remain poorly understood. Here, we show that miR-135a is selectively upregulated within neurons in epileptic brain and report that targeting miR-135a in vivo using antagomirs after onset of spontaneous recurrent seizures can reduce seizure activity at the chronic stage of experimental mTLE in male mice. Further, by using an unbiased approach combining immunoprecipitation and RNA sequencing, we identify several novel neuronal targets of miR-135a, including Mef2a Mef2 proteins are key regulators of excitatory synapse density. Mef2a and miR-135a show reciprocal expression regulation in human (of both sexes) and experimental TLE, and miR-135a regulates dendritic spine number and type through Mef2. Together, our data show that miR-135a is target for reducing seizure activity in chronic epilepsy, and that deregulation of miR-135a in epilepsy may alter Mef2a expression and thereby affect synaptic function and plasticity.SIGNIFICANCE STATEMENT miRNAs are post-transcriptional regulators of gene expression with roles in the pathogenesis of epilepsy. However, the precise mechanism of action and therapeutic potential of most epilepsy-associated miRNAs remain poorly understood. Our study reveals dramatic upregulation of the key neuronal miRNA miR-135a in both experimental and human mesial temporal lobe epilepsy. Silencing miR-135a in experimental temporal lobe epilepsy reduces seizure activity at the spontaneous recurrent seizure stage. These data support the exciting possibility that miRNAs can be targeted to combat seizures after spontaneous seizure activity has been established. Further, by using unbiased approaches novel neuronal targets of miR-135a, including members of the Mef2 protein family, are identified that begin to explain how deregulation of miR-135a may contribute to epilepsy.
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Antagomirs/uso terapéutico , Epilepsia del Lóbulo Temporal/tratamiento farmacológico , Hipocampo/efectos de los fármacos , MicroARNs/antagonistas & inhibidores , Convulsiones/tratamiento farmacológico , Animales , Antagomirs/farmacología , Modelos Animales de Enfermedad , Epilepsia del Lóbulo Temporal/genética , Epilepsia del Lóbulo Temporal/metabolismo , Hipocampo/metabolismo , Factores de Transcripción MEF2/genética , Factores de Transcripción MEF2/metabolismo , Masculino , Ratones , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Convulsiones/genética , Convulsiones/metabolismo , Resultado del TratamientoRESUMEN
Epilepsy diagnosis is complex, requires a team of specialists and relies on in-depth patient and family history, MRI-imaging and EEG monitoring. There is therefore an unmet clinical need for a non-invasive, molecular-based, biomarker to either predict the development of epilepsy or diagnose a patient with epilepsy who may not have had a witnessed seizure. Recent studies have demonstrated a role for microRNAs in the pathogenesis of epilepsy. MicroRNAs are short non-coding RNA molecules which negatively regulate gene expression, exerting profound influence on target pathways and cellular processes. The presence of microRNAs in biofluids, ease of detection, resistance to degradation and functional role in epilepsy render them excellent candidate biomarkers. Here we performed the first multi-model, genome-wide profiling of plasma microRNAs during epileptogenesis and in chronic temporal lobe epilepsy animals. From video-EEG monitored rats and mice we serially sampled blood samples and identified a set of dysregulated microRNAs comprising increased miR-93-5p, miR-142-5p, miR-182-5p, miR-199a-3p and decreased miR-574-3p during one or both phases. Validation studies found miR-93-5p, miR-199a-3p and miR-574-3p were also dysregulated in plasma from patients with intractable temporal lobe epilepsy. Treatment of mice with common anti-epileptic drugs did not alter the expression levels of any of the five miRNAs identified, however administration of an anti-epileptogenic microRNA treatment prevented dysregulation of several of these miRNAs. The miRNAs were detected within the Argonuate2-RISC complex from both neurons and microglia indicating these miRNA biomarker candidates can likely be traced back to specific brain cell types. The current studies identify additional circulating microRNA biomarkers of experimental and human epilepsy which may support diagnosis of temporal lobe epilepsy via a quick, cost-effective rapid molecular-based test.
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MicroARN Circulante/genética , Epilepsia del Lóbulo Temporal/genética , Animales , Anticonvulsivantes/farmacología , Barrera Hematoencefálica/metabolismo , MicroARN Circulante/efectos de los fármacos , Modelos Animales de Enfermedad , Estimulación Eléctrica , Epilepsia del Lóbulo Temporal/sangre , Epilepsia del Lóbulo Temporal/inducido químicamente , Agonistas de Aminoácidos Excitadores/toxicidad , Ácido Kaínico/toxicidad , Masculino , Ratones , Agonistas Muscarínicos/toxicidad , Vía Perforante , Pilocarpina/toxicidad , RatasRESUMEN
Cells have developed complex transcriptional regulatory mechanisms to maintain intracellular homeostasis and withstand pathophysiological stressors. Feed-forward loops comprising transcription factors that drive expression of both target gene and a microRNA as negative regulator, are gaining increasing recognition as key regulatory elements of cellular homeostasis. The ATP-gated purinergic P2X7 receptor (P2X7R) is an important driver of inflammation and has been implicated in the pathogenesis of numerous brain diseases including epilepsy. Changes in P2X7R expression have been reported in both experimental models and in epilepsy patients but the mechanism(s) controlling P2X7R levels remain incompletely understood. The specificity protein 1 (Sp1) has been shown to induce P2X7R transcription in vitro and recent data has identified microRNA-22 as a post-transcriptional repressor of P2X7R expression after seizures. In the present study we show that Sp1 can induce the transcription of both microRNA-22 and P2X7R in vitro during increased neuronal activity and in vivo in a mouse model of status epilepticus. We further show that Sp1-driven microRNA-22 transcription is calcium-sensitive and Sp1 occupancy of the microRNA-22 promoter region is blocked under conditions of seizure activity sufficient to elicit neuronal death. Taken together, our results suggest a neuronal activity-dependent P2X7R expression which is induced by the transcription factor Sp1 and repressed in a calcium-dependent manner by microRNA-22.
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Adenosina Trifosfato/metabolismo , Calcio/metabolismo , MicroARNs/metabolismo , Receptores Purinérgicos P2X7/fisiología , Factor de Transcripción Sp1/fisiología , Animales , Masculino , Ratones , Ratones Endogámicos C57BL , MicroARNs/genética , Regiones Promotoras Genéticas , Receptores Purinérgicos P2X7/genética , Transcripción Genética/fisiologíaRESUMEN
OBJECTIVE: Inhibition of microRNA-134 by an oligonucleotide antagomir (ant-134) has been shown to produce powerful antiseizure effects in multiple models of epilepsy. However, to successfully translate the treatment to the clinic, it is important to assess what potential adverse effects it may have on naive brain tissue. METHODS: To investigate this, adult male Sprague-Dawley rats were treated with either ant-134 or a scrambled control sequence. Animals were later assessed for spatial navigation, before ex vivo slices were taken to assess the effects of microRNA-134 knockdown on well-defined measures of intrinsic and synaptic properties. RESULTS: Hippocampal field potential recordings determined that silencing of microRNA-134 by ant-134 injection was associated with a reduction in epileptiform activity following application of 9 mmol/L K+ . Nevertheless, rats performed normally in the novel object location test. Action potential waveforms and miniature excitatory synaptic currents recorded in CA1 pyramidal neurons were unaffected by ant-134. SIGNIFICANCE: These results demonstrate that ant-134 confers a seizure-protective effect without obvious interference with hippocampal neuronal properties or network function. These findings support further development of this novel approach to epilepsy treatment.
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Hipocampo/citología , MicroARNs/metabolismo , Neuronas/fisiología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Modelos Animales de Enfermedad , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Conducta Exploratoria/efectos de los fármacos , Hipocampo/efectos de los fármacos , Técnicas In Vitro , Masculino , MicroARNs/química , MicroARNs/genética , Neuronas/efectos de los fármacos , Oligodesoxirribonucleótidos Antisentido/farmacología , Potasio/farmacología , Ratas , Ratas Sprague-DawleyRESUMEN
MicroRNAs have emerged as important regulators of the gene expression landscape in temporal lobe epilepsy. The mechanisms that control microRNA levels and influence target choice remain, however, poorly understood. RNA editing is a post-transcriptional mechanism mediated by the adenosine acting on RNA (ADAR) family of proteins that introduces base modification that diversifies the gene expression landscape. RNA editing has been studied for the mRNA landscape but the extent to which microRNA editing occurs in human temporal lobe epilepsy is unknown. Here, we used small RNA-sequencing data to characterize the identity and extent of microRNA editing in human temporal lobe epilepsy brain samples. This detected low-to-high editing in over 40 of the identified microRNAs. Among microRNA exhibiting the highest editing was miR-376a-3p, which was edited in the seed region and this was predicted to significantly change the target pool. The edited form was expressed at lower levels in human temporal lobe epilepsy samples. We modelled the shift in editing levels of miR-376a-3p in human-induced pluripotent stem cell-derived neurons. Reducing levels of the edited form of miR-376a-3p using antisense oligonucleotides resulted in extensive gene expression changes, including upregulation of mitochondrial and metabolism-associated pathways. Together, these results show that differential editing of microRNAs may re-direct targeting and result in altered functions relevant to the pathophysiology of temporal lobe epilepsy and perhaps other disorders of neuronal hyperexcitability.
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MicroRNAs are key posttranscriptional regulators of protein levels in cells. The brain is particularly enriched in microRNAs, and important roles have been demonstrated for these noncoding RNAs in various neurological disorders. To this end, visualization of microRNAs in specific cell types and subcellular compartments within tissue sections provides researchers with essential insights that support understanding of the cell and molecular mechanisms of microRNAs in brain diseases. In this chapter we describe an in situ hybridization protocol for the detection of microRNAs in mouse brain sections, which provides cellular resolution of the expression of microRNAs in the brain.
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Encefalopatías , MicroARNs , Animales , Ratones , Humanos , MicroARNs/genética , Hibridación in Situ , Encéfalo , InvestigadoresRESUMEN
The diagnosis of epilepsy is complex and challenging and would benefit from the availability of molecular biomarkers, ideally measurable in a biofluid such as blood. Experimental and human epilepsy are associated with altered brain and blood levels of various microRNAs (miRNAs). Evidence is lacking, however, as to whether any of the circulating pool of miRNAs originates from the brain. To explore the link between circulating miRNAs and the pathophysiology of epilepsy, we first sequenced argonaute 2 (Ago2)-bound miRNAs in plasma samples collected from mice subject to status epilepticus induced by intraamygdala microinjection of kainic acid. This identified time-dependent changes in plasma levels of miRNAs with known neuronal and microglial-cell origins. To explore whether the circulating miRNAs had originated from the brain, we generated mice expressing FLAG-Ago2 in neurons or microglia using tamoxifen-inducible Thy1 or Cx3cr1 promoters, respectively. FLAG immunoprecipitates from the plasma of these mice after seizures contained miRNAs, including let-7i-5p and miR-19b-3p. Taken together, these studies confirm that a portion of the circulating pool of miRNAs in experimental epilepsy originates from the brain, increasing support for miRNAs as mechanistic biomarkers of epilepsy.
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Brain development occurs until adulthood, with time-sensitive processes happening during embryo development, childhood, and puberty. During early life and childhood, dynamic changes in the brain are critical for physiological brain maturation, and these changes are tightly regulated by the expression of specific regulatory genetic elements. Early life insults, such as hypoxia, can alter the course of brain maturation, resulting in lifelong neurodevelopmental conditions. MicroRNAs are small non-coding RNAs, which regulate and coordinate gene expression. It is estimated that one single microRNA can regulate the expression of hundreds of protein-coding genes.. Uncovering the miRNome and microRNA-regulated transcriptomes may help to understand the patterns of genes regulating brain maturation, and their contribution to neurodevelopmental pathologies following hypoxia at Postnatal day 7. Here, using a PCR-based platform, we analyzed the microRNA profile postnatally in the hippocampus of control mice at postnatal day 8, 14, and 42 and after hypoxia at postnatal day 7, to elucidate the set of microRNAs which may be key for postnatal hippocampus maturation. We observed that microRNAs can be divided in four groups based on their temporal expression. Further after an early life insult, hypoxia at P7, 15 microRNAs showed a misregulation over time, including Let7a. We speculated that the transcriptional regulator c-myc is a contributor to this process. In conclusion, here, we observed that microRNAs are regulated postnatally in the hippocampus and alteration of their expression after hypoxia at birth may be regulated by the transcriptional regulator c-myc.
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The International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force established the TASK3 working groups to create common data elements (CDEs) for various preclinical epilepsy research disciplines. This is the second in a two-part series of omics papers, with the other including genomics, transcriptomics, and epigenomics. The aim of the CDEs was to improve the standardization of experimental designs across a range of epilepsy research-related methods. We have generated CDE tables with key parameters and case report forms (CRFs) containing the essential contents of the study protocols for proteomics, lipidomics, and metabolomics of samples from rodent models and people with epilepsy. We discuss the important elements that need to be considered for the proteomics, lipidomics, and metabolomics methodologies, providing a rationale for the parameters that should be documented.
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The International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force established the TASK3 working groups to create common data elements (CDEs) for various preclinical epilepsy research disciplines. The aim of the CDEs is to improve the standardization of experimental designs across a range of epilepsy research-related methods. Here, we have generated CDE tables with key parameters and case report forms (CRFs) containing the essential contents of the study protocols for genomics, transcriptomics, and epigenomics in rodent models of epilepsy, with a specific focus on adult rats and mice. We discuss the important elements that need to be considered for genomics, transcriptomics, and epigenomics methodologies, providing a rationale for the parameters that should be collected. This is the first in a two-part series of omics papers with the second installment to cover proteomics, lipidomics, and metabolomics in adult rodents.
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RNA modifications have emerged as an additional layer of regulatory complexity governing the function of almost all species of RNA. N 6-methyladenosine (m6A), the addition of methyl groups to adenine residues, is the most abundant and well understood RNA modification. The current review discusses the regulatory mechanisms governing m6A, how this influences neuronal development and function and how aberrant m6A signaling may contribute to neurological disease. M6A is known to regulate the stability of mRNA, the processing of microRNAs and function/processing of tRNAs among other roles. The development of antibodies against m6A has facilitated the application of next generation sequencing to profile methylated RNAs in both health and disease contexts, revealing the extent of this transcriptomic modification. The mechanisms by which m6A is deposited, processed, and potentially removed are increasingly understood. Writer enzymes include METTL3 and METTL14 while YTHDC1 and YTHDF1 are key reader proteins, which recognize and bind the m6A mark. Finally, FTO and ALKBH5 have been identified as potential erasers of m6A, although there in vivo activity and the dynamic nature of this modification requires further study. M6A is enriched in the brain and has emerged as a key regulator of neuronal activity and function in processes including neurodevelopment, learning and memory, synaptic plasticity, and the stress response. Changes to m6A have recently been linked with Schizophrenia and Alzheimer disease. Elucidating the functional consequences of m6A changes in these and other brain diseases may lead to novel insight into disease pathomechanisms, molecular biomarkers and novel therapeutic targets.
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Background and Rationale: Bi-directional neuronal-glial communication is a critical mediator of normal brain function and is disrupted in the epileptic brain. The potential role of aberrant microglia and astrocyte function during epileptogenesis is important because the mediators involved provide tangible targets for intervention and prevention of epilepsy. Glial activation is intrinsically involved in the generation of childhood febrile seizures (FS), and prolonged FS (febrile status epilepticus, FSE) antecede a proportion of adult temporal lobe epilepsy (TLE). Because TLE is often refractory to treatment and accompanied by significant memory and emotional difficulties, we probed the role of disruptions of glial-neuronal networks in the epileptogenesis that follows experimental FSE (eFSE). Methods: We performed a multi-pronged examination of neuronal-glia communication and the resulting activation of molecular signaling cascades in these cell types following eFSE in immature mice and rats. Specifically, we examined pathways involving cytokines, microRNAs, high mobility group B-1 (HMGB1) and the prostaglandin E2 signaling. We aimed to block epileptogenesis using network-specific interventions as well as via a global anti-inflammatory approach using dexamethasone. Results: (A) eFSE elicited a strong inflammatory response with rapid and sustained upregulation of pro-inflammatory cytokines. (B) Within minutes of the end of the eFSE, HMGB1 translocated from neuronal nuclei to dendrites, en route to the extracellular space and glial Toll-like receptors. Administration of an HMGB1 blocker to eFSE rat pups did not decrease expression of downstream inflammatory cascades and led to unacceptable side effects. (C) Prolonged seizure-like activity caused overall microRNA-124 (miR-124) levels to plunge in hippocampus and release of this microRNA from neurons via extra-cellular vesicles. (D) Within hours of eFSE, structural astrocyte and microglia activation was associated not only with cytokine production, but also with activation of the PGE2 cascade. However, administration of TG6-10-1, a blocker of the PGE2 receptor EP2 had little effect on spike-series provoked by eFSE. (E) In contrast to the failure of selective interventions, a 3-day treatment of eFSE-experiencing rat pups with the broad anti-inflammatory drug dexamethasone attenuated eFSE-provoked pro-epileptogenic EEG changes. Conclusions: eFSE, a provoker of TLE-like epilepsy in rodents leads to multiple and rapid disruptions of interconnected glial-neuronal networks, with a likely important role in epileptogenesis. The intricate, cell-specific and homeostatic interplays among these networks constitute a serious challenge to effective selective interventions that aim to prevent epilepsy. In contrast, a broad suppression of glial-neuronal dysfunction holds promise for mitigating FSE-induced hyperexcitability and epileptogenesis in experimental models and in humans.
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Seizures result from hypersynchronous, abnormal firing of neuronal populations and are the primary clinical symptom of the epilepsies. Brain tissue from animal models and patients with acquired forms of epilepsy commonly features selective neuronal loss, gliosis, inflammatory markers and microscopic and macroscopic reorganization of networks. The gene expression landscape is a critical driver of these changes, and gene expression is fine tuned by small, non-coding RNAs called microRNAs (miRNAs). miRNAs inhibit the function of protein-coding transcripts, resulting in changes in multiple aspects of cell structure and function, including axonal and dendritic structure and the repertoire of neurotransmitter receptors, ion channels and transporters that establish neurophysiological functions. Dysregulation of the miRNA system has emerged as a mechanism that underlies epileptogenesis. Given that miRNAs can act on multiple mRNA targets, their manipulation offers a novel, multi-targeting approach to correct disturbed gene expression patterns. Targeting of some miRNAs has also been used to selectively upregulate individual transcripts, offering the possibility of precision therapy approaches for disorders of haploinsufficiency. In this Review, we discuss how miRNAs determine and control neuronal and glial functions, how this process is altered in states associated with hyperexcitability, and the prospects for miRNA targeting for the treatment of epilepsy.