RESUMEN
In recent years, the classification of adult-type diffuse gliomas has undergone a revolution, wherein specific molecular features now represent defining diagnostic criteria of IDH-wild-type glioblastomas, IDH-mutant astrocytomas, and IDH-mutant 1p/19q-codeleted oligodendrogliomas. With the introduction of the 2021 WHO CNS classification, additional molecular alterations are now integrated into the grading of these tumors, given equal weight to traditional histologic features. However, there remains a great deal of heterogeneity in patient outcome even within these established tumor subclassifications that is unexplained by currently codified molecular alterations, particularly in the IDH-mutant astrocytoma category. There is also significant intercellular genetic and epigenetic heterogeneity and plasticity with resulting phenotypic heterogeneity, making these tumors remarkably adaptable and robust, and presenting a significant barrier to the design of effective therapeutics. Herein, we review the mechanisms and consequences of genetic and epigenetic instability, including chromosomal instability (CIN), microsatellite instability (MSI)/mismatch repair (MMR) deficits, and epigenetic instability, in the underlying biology, tumorigenesis, and progression of IDH-mutant astrocytomas. We also discuss the contribution of recent high-resolution transcriptomics studies toward defining tumor heterogeneity with single-cell resolution. While intratumoral heterogeneity is a well-known feature of diffuse gliomas, the contribution of these various processes has only recently been considered as a potential driver of tumor aggressiveness. CIN has an independent, adverse effect on patient survival, similar to the effect of histologic grade and homozygous CDKN2A deletion, while MMR mutation is only associated with poor overall survival in univariate analysis but is highly correlated with higher histologic/molecular grade and other aggressive features. These forms of genomic instability, which may significantly affect the natural progression of these tumors, response to therapy, and ultimately clinical outcome for patients, are potentially measurable features which could aid in diagnosis, grading, prognosis, and development of personalized therapeutics.
Asunto(s)
Astrocitoma , Neoplasias Encefálicas , Progresión de la Enfermedad , Epigénesis Genética , Isocitrato Deshidrogenasa , Mutación , Humanos , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/patología , Astrocitoma/genética , Astrocitoma/patología , Isocitrato Deshidrogenasa/genética , Mutación/genética , Epigénesis Genética/genéticaRESUMEN
Maintaining cellular homeostasis necessitates precise control of gene expression, a process that molds both the transcriptome and proteome to adapt to internal and external changes effectively. MicroRNAs (miRNAs) are small RNAs (~ 22nucleotides) belonging to a broad family of non-coding RNAs and are important regulators of gene expression. While numerous studies have advanced our understanding of the common processes underlying miRNA biogenesis and function, individual cell types in diverse organisms have evolved distinct mechanisms for regulating them. In this current issue, Satoshi Oikawa and colleagues delve into the molecular dynamics of miRNAs in adult skeletal muscles. Their research introduces intriguing new inquiries for further investigations to uncover alternative mechanisms of miRNA biogenesis in skeletal muscle.
Asunto(s)
MicroARNs , MicroARNs/genética , MicroARNs/metabolismo , HomeostasisRESUMEN
Late prenatal development of the human neocortex encompasses a critical period of gliogenesis and cortical expansion. However, systematic single-cell analyses to resolve cellular diversity and gliogenic lineages of the third trimester are lacking. Here, we present a comprehensive single-nucleus RNA sequencing atlas of over 200,000 nuclei derived from the proliferative germinal matrix and laminating cortical plate of 15 prenatal, non-pathological postmortem samples from 17 to 41 gestational weeks, and 3 adult controls. This dataset captures prenatal gliogenesis with high temporal resolution and is provided as a resource for further interrogation. Our computational analysis resolves greater complexity of glial progenitors, including transient glial intermediate progenitor cell (gIPC) and nascent astrocyte populations in the third trimester of human gestation. We use lineage trajectory and RNA velocity inference to further characterize specific gIPC subpopulations preceding both oligodendrocyte (gIPC-O) and astrocyte (gIPC-A) lineage differentiation. We infer unique transcriptional drivers and biological pathways associated with each developmental state, validate gIPC-A and gIPC-O presence within the human germinal matrix and cortical plate in situ, and demonstrate gIPC states being recapitulated across adult and pediatric glioblastoma tumors.
Asunto(s)
Neuroglía , Oligodendroglía , Niño , Humanos , Neuroglía/metabolismo , Células Madre/metabolismo , Diferenciación Celular/genética , Neurogénesis/genéticaRESUMEN
The pathophysiology of epilepsy underlies a complex network dysfunction between neurons and glia, the molecular cell type-specific contributions of which remain poorly defined in the human disease. In this study, we validated a method that simultaneously isolates neuronal (NEUN +), astrocyte (PAX6 + NEUN-), and oligodendroglial progenitor (OPC) (OLIG2 + NEUN-) enriched nuclei populations from non-diseased, fresh-frozen human neocortex and then applied it to characterize the distinct transcriptomes of such populations isolated from electrode-mapped temporal lobe epilepsy (TLE) surgical samples. Nuclear RNA-seq confirmed cell type specificity and informed both common and distinct pathways associated with TLE in astrocytes, OPCs, and neurons. Compared to postmortem control, the transcriptome of epilepsy astrocytes showed downregulation of mature astrocyte functions and upregulation of development-related genes. To gain further insight into glial heterogeneity in TLE, we performed single cell transcriptomics (scRNA-seq) on four additional human TLE samples. Analysis of the integrated TLE dataset uncovered a prominent subpopulation of glia that express a hybrid signature of both reactive astrocyte and OPC markers, including many cells with a mixed GFAP + OLIG2 + phenotype. A further integrated analysis of this TLE scRNA-seq dataset and a previously published normal human temporal lobe scRNA-seq dataset confirmed the unique presence of hybrid glia only in TLE. Pseudotime analysis revealed cell transition trajectories stemming from this hybrid population towards both OPCs and reactive astrocytes. Immunofluorescence studies in human TLE samples confirmed the rare presence of GFAP + OLIG2 + glia, including some cells with proliferative activity, and functional analysis of cells isolated directly from these samples disclosed abnormal neurosphere formation in vitro. Overall, cell type-specific isolation of glia from surgical epilepsy samples combined with transcriptomic analyses uncovered abnormal glial subpopulations with de-differentiated phenotype, motivating further studies into the dysfunctional role of reactive glia in temporal lobe epilepsy.
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Epilepsia del Lóbulo Temporal , Humanos , Epilepsia del Lóbulo Temporal/genética , Epilepsia del Lóbulo Temporal/patología , Transcriptoma , Neuroglía/patología , Astrocitos/patología , ARN Nuclear/metabolismoRESUMEN
Social anxiety disorder is characterized by a persistent fear and avoidance of social situations, but available treatment options are rather unspecific. Using an established mouse social fear conditioning (SFC) paradigm, we profiled gene expression and chromatin alterations after the acquisition and extinction of social fear within the septum, a brain region important for social fear and social behaviors. Here, we particularly focused on the successful versus unsuccessful outcome of social fear extinction training, which corresponds to treatment responsive versus resistant patients in the clinics. Validation of coding and non-coding RNAs revealed specific isoforms of the long non-coding RNA (lncRNA) Meg3 regulated, depending on the success of social fear extinction. Moreover, PI3K/AKT was differentially activated with extinction success in SFC-mice. In vivo knockdown of specific Meg3 isoforms increased baseline activity of PI3K/AKT signaling, and mildly delayed social fear extinction. Using ATAC-Seq and CUT&RUN, we found alterations in the chromatin structure of specific genes, which might be direct targets of lncRNA Meg3.
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Extinción Psicológica , Miedo , ARN Largo no Codificante , Animales , Ratones , Cromatina , Fosfatidilinositol 3-Quinasas , Proteínas Proto-Oncogénicas c-akt , ARN Largo no Codificante/genética , TranscriptomaRESUMEN
MicroRNAs (miRNAs) are a large class of small noncoding RNAs that regulate the expression of distinct target mRNAs. miRNAs are incorporated into Argonaute (AGO) proteins and guide them to their target mRNAs. Subsequently, AGO proteins recruit a member of the glycine-tryptophan-rich (GW) protein family by direct protein-protein interaction. GW proteins coordinate all downstream processes leading to robust and efficient gene silencing. A short peptide of GW proteins comprising the AGO interaction motif can be used to biochemically isolate endogenous AGO protein complexes. Furthermore, within a cell such a peptide competes with endogenous GW proteins for AGO binding and thus can be used as potent inhibitor of the miRNA pathway. Here, we describe a method that utilizes a GW-based polypeptide (T6B-assay) to validate miRNA-mRNA interactions in tissue culture systems.
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Proteínas Argonautas/metabolismo , Inmunoprecipitación/métodos , MicroARNs/antagonistas & inhibidores , Péptidos/uso terapéutico , Silenciador del Gen/efectos de los fármacos , MicroARNs/genética , MicroARNs/metabolismo , Péptidos/metabolismo , Unión Proteica , Mapas de Interacción de Proteínas/genética , ARN Mensajero/antagonistas & inhibidoresRESUMEN
microRNAs (miRNAs) are major regulators of protein synthesis in the brain. A major goal is to identify changes in miRNA expression underlying protein synthesis-dependent forms of synaptic plasticity such as long-term potentiation (LTP). Previous analyses focused on changes in miRNA levels in total lysate samples. Here, we asked whether changes in total miRNA accurately reflect changes in the amount of miRNA bound to Argonaute protein within the miRNA-induced silencing complex (miRISC). Ago2 immunoprecipitation was used to isolate RISC-associated miRNAs following high-frequency stimulation (HFS)-induced LTP in the dentate gyrus of anesthetized rats. Using locked-nucleic acid-based PCR cards for high-throughput screening and independent validation by quantitative TaqMan RT-PCR, we identified differential regulation of Ago2-associated and total miRNA expression. The ratio of Ago2/total miRNA expression was regulated bidirectionally in a miRNA-specific manner and was largely dependent on N-methyl-D-aspartate receptor (NMDA) activation during LTP induction. The present results identify miRNA association with Ago2 as a potential control point in activity-dependent synaptic plasticity in the adult brain. Finally, novel computational analysis for targets of the Ago2-associated miRNAs identifies 21 pathways that are enriched and differentially targeted by the miRNAs including axon guidance, mTOR, MAPK, Ras, and LTP.
RESUMEN
mRNA translation, or protein synthesis, is a major component of the transformation of the genetic code into any cellular activity. This complicated, multistep process is divided into three phases: initiation, elongation, and termination. Initiation is the step at which the ribosome is recruited to the mRNA, and is regarded as the major rate-limiting step in translation, while elongation consists of the elongation of the polypeptide chain; both steps are frequent targets for regulation, which is defined as a change in the rate of translation of an mRNA per unit time. In the normal brain, control of translation is a key mechanism for regulation of memory and synaptic plasticity consolidation, i.e., the off-line processing of acquired information. These regulation processes may differ between different brain structures or neuronal populations. Moreover, dysregulation of translation leads to pathological brain function such as memory impairment. Both normal and abnormal function of the translation machinery is believed to lead to translational up-regulation or down-regulation of a subset of mRNAs. However, the identification of these newly synthesized proteins and determination of the rates of protein synthesis or degradation taking place in different neuronal types and compartments at different time points in the brain demand new proteomic methods and system biology approaches. Here, we discuss in detail the relationship between translation regulation and memory or synaptic plasticity consolidation while focusing on a model of cortical-dependent taste learning task and hippocampal-dependent plasticity. In addition, we describe a novel systems biology perspective to better describe consolidation.
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Regulación de la Expresión Génica/fisiología , Memoria/fisiología , Biosíntesis de Proteínas/fisiología , Animales , Corteza Cerebral/metabolismo , Hipocampo/metabolismo , Humanos , MicroARNs/metabolismo , Modelos Moleculares , Enfermedades del Sistema Nervioso/genética , Enfermedades del Sistema Nervioso/metabolismo , Neuronas/fisiología , Neurotransmisores/metabolismo , Gusto/fisiologíaRESUMEN
Expression of activity-regulated cytoskeleton associated protein (Arc) is crucial for diverse types of experience-dependent synaptic plasticity and long-term memory in mammals. However, the mechanisms governing Arc-specific translation are little understood. Here, we asked whether Arc translation is regulated by microRNAs. Bioinformatic analysis predicted numerous candidate miRNA binding sites within the Arc 3'-untranslated region (UTR). Transfection of the corresponding microRNAs in human embryonic kidney cells inhibited expression of an Arc 3'UTR luciferase reporter from between 10 to 70% across 16 microRNAs tested. Point mutation and deletion of the microRNA-binding seed-region for miR-34a, miR-326, and miR-19a partially or fully rescued reporter expression. In addition, expression of specific microRNA pairs synergistically modulated Arc reporter expression. In primary rat hippocampal neuronal cultures, ectopic expression of miR-34a, miR-193a, or miR-326, downregulated endogenous Arc protein expression in response to BDNF treatment. Conversely, treatment of neurons with cell-penetrating, peptide nucleic acid (PNA) inhibitors of miR-326 enhanced Arc mRNA expression. BDNF dramatically upregulated neuronal expression of Arc mRNA and miR-132, a known BDNF-induced miRNA, without affecting expression of Arc-targeting miRNAs. Developmentally, miR-132 was upregulated at day 10 in vitro whereas Arc-targeting miRNAs were downregulated. In the adult brain, LTP induction in the dentate gyrus triggered massive upregulation of Arc and upregulation of miR-132 without affecting levels of mature Arc-targeting miRNAs. Turning to examine miRNA localization, qPCR analysis of dentate gyrus synaptoneurosome and total lysates fractions demonstrated synaptic enrichment relative to small nucleolar RNA. In conclusion, we find that Arc is regulated by multiple miRNAs and modulated by specific miRNA pairs in vitro. Furthermore, we show that, in contrast to miR-132, steady state levels of Arc-targeting miRNAs do not change in response to activity-dependent expression of Arc in hippocampal neurons in vitro or during LTP in vivo.
Asunto(s)
Proteínas del Citoesqueleto/genética , MicroARNs/genética , MicroARNs/metabolismo , Proteínas del Tejido Nervioso/genética , Plasticidad Neuronal/genética , Sinapsis/metabolismo , Regiones no Traducidas 3'/genética , Animales , Secuencia de Bases , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Proteínas del Citoesqueleto/metabolismo , Dendritas/metabolismo , Células HEK293 , Hipocampo/citología , Hipocampo/fisiología , Humanos , Espacio Intracelular/metabolismo , Potenciación a Largo Plazo/genética , Masculino , Proteínas del Tejido Nervioso/metabolismo , Neuronas/citología , Neuronas/metabolismo , Oligonucleótidos Antisentido/genética , Mutación Puntual , Transporte de Proteínas , Ratas , Ratas Sprague-Dawley , Eliminación de Secuencia , Transcriptoma , Regulación hacia Arriba/genéticaRESUMEN
The immediate early gene Arc is emerging as a versatile, finely tuned system capable of coupling changes in neuronal activity patterns to synaptic plasticity, thereby optimizing information storage in the nervous system. Here, we attempt to overview the Arc system spanning from transcriptional regulation of the Arc gene, to dendritic transport, metabolism, and translation of Arc mRNA, to post-translational modification, localization, and degradation of Arc protein. Within this framework we discuss the function of Arc in regulation of actin cytoskeletal dynamics underlying consolidation of long-term potentiation (LTP) and regulation of AMPA-type glutamate receptor endocytosis underlying long-term depression (LTD) and homeostatic plasticity. Behaviorally, Arc has a key role in consolidation of explicit and implicit forms of memory, with recent work implicating Arc in adaptation to stress as well as maladaptive plasticity connected to drug addiction. Arc holds considerable promise as a "master regulator" of protein synthesis-dependent forms of synaptic plasticity, but the mechanisms that modulate and switch Arc function are only beginning to be elucidated.