Mapping Gene Expression in Excitatory Neurons During Hippocampal Late-Phase Long-term Potentiation
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ABSTRACT: The long-lasting changes in synaptic connectivity that underlie long-term memory require new RNA and protein synthesis for their persistence. To elucidate the temporal pattern of gene expression that gives rise to long-lasting, learning-related neuronal plasticity, we profiled RNAs in mouse hippocampal CA3-CA1 slices following induction of late phase long-term potentiation (LTP), analyzing differential expression (DE) specifically within pyramidal excitatory neurons by Translating Ribosome Affinity Purification RNA sequencing (TRAP-seq). We detected time-dependent changes in up- and down-regulated ribosome-associated mRNAs over the two hours following LTP induction, with minimal overlap of DE transcripts between time points. TRAP-seq revealed greater numbers and amplitudes of LTP-induced changes than RNA-seq of all cell types in the hippocampus. Transcripts that were DE by TRAP-seq but not RNA-seq were enriched in mRNAs encoding cytoskeletal and cell adhesion proteins, while RNA-seq identified DE in many non-neuronal mRNAs. Together our results highlight the importance of considering both the time course and the cell-type specificity of activity-dependent gene expression during memory formation.
Project description:Dysregulated protein synthesis is a core pathogenic mechanism in Fragile X Syndrome (FX). The mGluR Theory of FX predicts that pathological synaptic changes arise from the excessive translation of mRNAs downstream of mGlu1/5 activation. Here, we use a combination of CA1 pyramidal neuron-specific Translating Ribosome Affinity Purification and RNA-seq (TRAP-seq) and proteomics to identify the overtranslating mRNAs supporting exaggerated mGlu1/5 -induced long-term synaptic depression (mGluR-LTD) in the FX mouse model (Fmr1-/y). Our results identify a robust translation of ribosomal proteins (RPs) upon mGlu1/5 stimulation that coincides with a reduced translation of long mRNAs encoding synaptic proteins. These changes are mimicked and occluded in Fmr1-/y neurons. In addition, proteomics analyses identify increased degradation of multiple proteins at hippocampal synapses, many of which are underexpressed at steady-state.
Project description:Neuromodulatory cells transduce environmental information into long lasting behavioral responses. However, the mechanisms governing how defined neuronal cell types influence behavioral plasticity are difficult to characterize. Here we adapted the Translating Ribosome Affinity Purification (TRAP) approach in C. elegans to profile ribosome-associated mRNAs from three major tissues and the neuromodulatory dopaminergic and serotonergic cells. We identified elc-2, an Elongin C ortholog, specifically expressed in stress-sensing ADF serotonergic sensory neurons, and found that it plays a role in mediating long-lasting change in serotonin-dependent feeding behavior induced by heat stress. We demonstrate that ELC-2 and the von Hippel-Lindau protein VHL-1, components of an Elongin-Cullin-SOCS-box (ECS) E3 ubiquitin ligase, modulate this behavior after experiencing stress. Also, heat stress induces a transient redistribution of ELC-2, becoming more nuclearly enriched. Together, our results demonstrate dynamic regulation of an E3 ligase, and a role for an ECS complex in neuromodulation and control of lasting behavioral states.
Project description:mRNAs are generally assumed to be loaded instantly with ribosomes upon entry into the cytoplasm. To measure ribosome density on nascent mRNA, we developed nascent Ribo-Seq (nRibo-Seq) by combining Ribo-Seq with progressive 4-thiouridine labelling. In mouse macrophages, we experimentally determined, for the first time, the lag between the appearance of nascent RNA and its association with ribosomes, which was calculated to be 20 - 22 min for bulk mRNA, and approximated the time it takes for mRNAs to be fully loaded with ribosomes to be 41 - 44 min. Notably, ribosomal loading time is adapted to gene function as rapid loading was observed with highly regulated genes. The lag and ribosomal loading time correlate positively with ORF size and mRNA half-life, and negatively with tRNA adaptation index. Similar results were obtained in mouse embryonic stem cells, where the lag in ribosome loading was even more pronounced with 35 - 38 min. We validated our measurements after stimulation of macrophages with lipopolysaccharide, where the lag between cytoplasmic and translated mRNA leads to uncoupling between input and ribosome-protected fragments. Uncoupling is stronger for mRNAs with long ORFs or half-lives, a finding we also confirmed at the level of protein production by nascent chain proteomics. As a consequence of the lag in ribosome loading, ribosome density measurements are distorted when performed under conditions where mRNA levels are far from steady state expression, and transcriptional changes affect ribosome density in a passive way. This study uncovers an unexpected and considerable lag in ribosome loading, and provides guidelines for the interpretation of Ribo-Seq data taking passive effects on ribosome density into account.
Project description:we compared changes in the transcriptome and the translatome of M. truncatula roots upon rhizobial infection using direct RNA-seq and Translating Ribosome Affinity Purification (TRAP) combined with RNA-seq (TRAP-seq), respectively. TRAP is a ribosome immunopurification approach that has been extensively used in plants and mammals to assess translational changes
Project description:General anesthesia is a common clinical procedure yet can result in long term CNS-adverse effects, particularly in the elderly, or dementia patients. Suppression of cortical activity is a key feature of the anesthetic-induced unconscious state, with activity being a well-described regulator of pathways important for brain health. However the extent to which the effects of anesthesia go beyond simple suppression of neuronal activity is incompletely understood, as are its effects on non-neuronal cell types such as astrocytes, which are important integrators of both neuronal activity and inflammatory signalling. In order to address these questions, we performed a combination of RNA-seq and TRAP-seq (Translating Ribosome Affinity Purification, where astrocyte-specific translating mRNAs are sequenced) on mouse cortical tissue and primary cortical neurons.
Project description:We have examined the roles of yeast mRNA decapping-activators Pat1 and Dhh1 in repressing the translation and abundance of specific mRNAs in nutrient-replete cells using a combination of ribosome profiling, RNA-Seq, CAGE analysis of capped mRNAs, RNA Polymerase II ChIP-Seq, and TMT-mass spectrometry of mutants lacking one or both factors.
Project description:Long-term potentiation (LTP) of synaptic transmission is recognized as a cellular mechanism for learning and memory storage. Although de novo gene transcription is known to be required in the formation of stable LTP, the molecular mechanisms underlying synaptic plasticity remain elusive.This study investigates the DNA-methylation levels of promoters and CpG-islands of LTP-associated genes identified from Maag et al. 2015 (DOI: 10.3389/fnins.2015.00351) (See E-MTAB-3375).
Project description:Expression of VP16-CREB, a constitutively active form of CREB, in hippocampal neurons of the CA1 region lowers the threshold for eliciting the late, persistent phase of long-term potentiation (L-LTP) in the Schaffer collateral pathway. This VP16-CREB-mediated L-LTP differs from the conventional late phase of LTP in not being dependent on new transcription. This finding suggests that in the transgenic mice the mRNA transcript(s) encoding the protein(s) necessary for this form of L-LTP might already be present in CA1 neurons in the basal condition. We used high-density oligonucleotide arrays to identify the mRNAs differentially expressed in the hippocampus of transgenic and wild-type mice. Keywords: Genetic modification, time course
Project description:Many thousand long non-coding (lnc) RNAs are mapped in the human genome. Time consuming studies using reverse genetic approaches by post-transcriptional knock-down or genetic modification of the locus demonstrated diverse biological functions for a few of these transcripts. The Human Gene Trap Mutant Collection in haploid KBM7 cells is a ready-to-use tool for studying protein-coding gene function. As lncRNAs show remarkable differences in RNA biology compared to protein-coding genes, it is unclear if this gene trap collection is useful for functional analysis of lncRNAs. Here we use the uncharacterized LOC100288798 lncRNA as a model to answer this question. Using public RNA-seq data we show that LOC100288798 is ubiquitously expressed, but inefficiently spliced. The minor spliced LOC100288798 isoforms are exported to the cytoplasm, whereas the major unspliced isoform is nuclear localized. This shows that LOC100288798 RNA biology differs markedly from typical mRNAs. De novo assembly from RNA-seq data suggests that LOC100288798 extends 289kb beyond its annotated 3' end and overlaps the downstream SLC38A4 gene. Three cell lines with independent gene trap insertions in LOC100288798 were available from the KBM7 gene trap collection. RT-qPCR and RNA-seq confirmed successful lncRNA truncation and its extended length. Expression analysis from RNA-seq data shows significant deregulation of 41 protein-coding genes upon LOC100288798 truncation. Our data shows that gene trap collections in human haploid cell lines are useful tools to study lncRNAs, and identifies the previously uncharacterized LOC100288798 as a potential gene regulator.
Project description:Many thousand long non-coding (lnc) RNAs are mapped in the human genome. Time consuming studies using reverse genetic approaches by post-transcriptional knock-down or genetic modification of the locus demonstrated diverse biological functions for a few of these transcripts. The Human Gene Trap Mutant Collection in haploid KBM7 cells is a ready-to-use tool for studying protein-coding gene function. As lncRNAs show remarkable differences in RNA biology compared to protein-coding genes, it is unclear if this gene trap collection is useful for functional analysis of lncRNAs. Here we use the uncharacterized LOC100288798 lncRNA as a model to answer this question. Using public RNA-seq data we show that LOC100288798 is ubiquitously expressed, but inefficiently spliced. The minor spliced LOC100288798 isoforms are exported to the cytoplasm, whereas the major unspliced isoform is nuclear localized. This shows that LOC100288798 RNA biology differs markedly from typical mRNAs. De novo assembly from RNA-seq data suggests that LOC100288798 extends 289kb beyond its annotated 3' end and overlaps the downstream SLC38A4 gene. Three cell lines with independent gene trap insertions in LOC100288798 were available from the KBM7 gene trap collection. RT-qPCR and RNA-seq confirmed successful lncRNA truncation and its extended length. Expression analysis from RNA-seq data shows significant deregulation of 41 protein-coding genes upon LOC100288798 truncation. Our data shows that gene trap collections in human haploid cell lines are useful tools to study lncRNAs, and identifies the previously uncharacterized LOC100288798 as a potential gene regulator. We cultured and processed 8 KBM7 cell lines in one batch. These cell lines were: two wild type KBM7 cells (WT2 and WT3), two monoclonal KBM7 cell lines with gene trap cassette insertions outside of the body of LOC100288798 (C1 and C2), two independently obtained KBM7 clones with gene trap cassette insertion 3kb downstream LOC100288798 transcriptional start site (TSS) (3kb1 and 3kb2), one independently obtained KBM7 clone with gene trap cassette insertion 100kb downstream LOC100288798 TSS replicated twice at the thawing step (100kb1 and 100kb2). We isolated total RNA from all th 8 cell lines, applied DNAseI treatment and ribosomal RNA depletion, and thhen prepared strand-specific RNA-seq libraries, which were pooled in equal molarities and sequenced using Illumina HiSeq 2000 (8 pooled samples were sequence on 2 lanes). We performed 50bp single-end RNA-seq. We used these 8 samples (4 untreated: WT2, WT3, C1, C2 and 4 treated:3kb1, 3kb2, 100kbk1, 100kb2) to analyze genome-wide gene deregulation associated with LOC100288798 lncRNA truncation