Mapping the epigenomic and transcriptomic interplay during memory formation and recall in the hippocampal engram ensemble
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ABSTRACT: Purpose: we utilized a mouse model that permanently labels neurons activated throughout a specific experience to decipher the interplay between chromatin accessibility, 3D-chromatin architecture and transcriptional changes across different memory phases. Non activated (basal) and activated neurons during memory encoding (early), consolidation (late) and recall (reactivated) were sorted and subjected to nuclear RNA sequencing (nRNA-seq) to determine gene expression, ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) to assess chromatin accessibility, chromosome conformation capture (Hi-C) to identify global 3D -genome architecture and promoter capture Hi-C to identify the long range promoter-enhancer interactions. Results: our data demonstrates that the initial phase of memory formation alters the chromatin accessibility landscape of activated neurons, with long lasting stable changes occurring predominantly within enhancer regions. Moreover, many of these enhancers did not return to their baseline state after stimulation ceased, but remain accessible and stable throughout all memory phases.
Project description:Purpose: we utilized a mouse model that permanently labels neurons activated throughout a specific experience to decipher the interplay between chromatin accessibility, 3D-chromatin architecture and transcriptional changes across different memory phases. Non activated (basal) and activated neurons during memory encoding (early), consolidation (late) and recall (reactivated) were sorted and subjected to nuclear RNA sequencing (nRNA-seq) to determine gene expression, ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) to assess chromatin accessibility, chromosome conformation capture (Hi-C) to identify global 3D -genome architecture and promoter capture Hi-C to identify the long range promoter-enhancer interactions. Results: We have found that during each memory phase, the same promoters interact more frequently with a distinct subset of enhancers (i.e. unique). We also identified a smaller subset of interactions in which the promoters were interacting with the same enhancers across different memory phases (i.e. common). Furthermore, Reactivated neurons presented significantly stronger interaction scores (as calculated by CHiCAGO). Hence, although the number of unique interactions was similar across early, late and reactivated states, stronger interaction scores indicate that specific promoter- enhancer interactions occur more frequently during memory recall.
Project description:Purpose: we utilized a mouse model that permanently labels neurons activated throughout a specific experience to decipher the interplay between chromatin accessibility, 3D-chromatin architecture and transcriptional changes across different memory phases. Non activated (basal) and activated neurons during memory encoding (early), consolidation (late) and recall (reactivated) were sorted and subjected to nuclear RNA sequencing (nRNA-seq) to determine gene expression, ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) to assess chromatin accessibility, chromosome conformation capture (Hi-C) to identify global 3D -genome architecture and promoter capture Hi-C to identify the long range promoter-enhancer interactions. Results: Our differentially expressed gene (DEG) analysis revealed relatively low amount of changes in the early phase, when compared to basal-state neurons (Basal vs. Early). In contrast, neurons from late phase presented higher numbers of DEGs despite there being more similarity in chromatin accessibility at these time points (Early vs. Late; Late vs. Reactivated). Our studies illuminate for the first time the unique transcriptional landscape of reactivated engram cells where we observed up-regulation of genes involved in mRNA transport and local protein translation in synaptic compartments. These changes corresponded to morphological and functional changes in those neurons.
Project description:Purpose: we utilized a mouse model that permanently labels neurons activated throughout a specific experience to decipher the interplay between chromatin accessibility, 3D-chromatin architecture and transcriptional changes across different memory phases. Non activated (basal) and activated neurons during memory encoding (early), consolidation (late) and recall (reactivated) were sorted and subjected to nuclear RNA sequencing (nRNA-seq) to determine gene expression, ATAC-seq (Assay for Transposase-Accessible Chromatin using sequencing) to assess chromatin accessibility, chromosome conformation capture (Hi-C) to identify global 3D -genome architecture and promoter capture Hi-C to identify the long range promoter-enhancer interactions. Results: Our analysis revealed dynamic changes in compartments organization, where we observed re-localization of large chromatin segments from inactive to permissive environment (and vice versa) during the initial and late phase of memory formation. Interestingly, 52% of the regions in the early phase that switched from B to A maintained that state in the late phase (i.e. remained in state A. Moreover, nearly all these regions significantly overlapped with gained DARs identified in our ATAC-seq analysis, confirming the transition of sub-compartment from inactive to permissive environment. This data indicates that while some loci undergo sub-compartment switching across different memory phases, the majority are stable, correlate with chromatin accessibility and therefore might contribute to long-term changes in neuronal properties and function after initial activation.
Project description:To identify distal chromatin contacts between promoters and their putative regulatory elements in SGBS preadipocytes and hypothalamic arcuate-like neurons derived from iPSC, we performed Hi-C with a capture step to enrich the library for contacts involving promoters. Hi-C with a capture step was performed according to PMID: 29988018
Project description:Sparse populations of neurons in the dentate gyrus (DG) of the hippocampus are causally implicated in the encoding of contextual fear memories. However, engram-specific molecular mechanisms underlying memory consolidation remain largely unknown. Here we perform unbiased RNA sequencing of DG engram neurons 24h after contextual fear conditioning to identify transcriptome changes specific to memory consolidation. DG engram neurons exhibit a highly distinct pattern of gene expression, in which CREB-dependent transcription features prominently (P=6.2x10-13), including Atf3 (P=2.4x10-41), Penk (P=1.3x10-15), and Kcnq3 (P=3.1x10-12). Moreover, we validate the functional relevance of the RNAseq findings by establishing the causal requirement of intact CREB function specifically within the DG engram during memory consolidation, and identify a novel group of CREB target genes involved in the encoding of long-term memory.
Project description:To investigate the mechanisms underlying the rearrangement patterns,we compared the rearrangement map with local chromatin structures and the three-dimensional genome architecture via assay for transposase-accessible chromatin using sequencing (ATAC-seq) and genome-wide chromosome conformation capture (Hi-C), respectively
Project description:we report a novel method, Hi-C on Accessible Regulatory DNA (HiCAR), which leverages principles of ATAC-seq and high-throughput 3C-assay for genome-wide profiling of chromatin accessibility and open chromatin anchored cRE interactions.
Project description:To investigate chromatin accessibility in peri-infarct neurons on day 4 after ischemic stroke, we performed assay for transposase-accessible chromatin with sequencing (ATAC-seq) in peri-infarct neurons from Padi4 non-dificient mice.
Project description:<p>Non-coding regions comprise most of the human genome and harbor a significant fraction of risk alleles for neuropsychiatric diseases, yet their functions remain poorly defined. We created a high-resolution map of non-coding elements involved in human cortical neurogenesis by contrasting chromatin accessibility and gene expression in the germinal zone and cortical plate of the developing cerebral cortex. To obtain a high resolution depiction of chromatin structure and gene expression in developing human fetal cortex, we dissected the post-conception week (PCW) 15-17 human neocortex into two major anatomical divisions to distinguish between proliferating neural progenitors and post mitotic neurons: (1) GZ: the neural progenitor-enriched region encompassing the ventricular zone (VZ), subventricular zone (SVZ), and intermediate zone (IZ) and (2) CP: the neuron-enriched region containing the subplate (SP), cortical plate (CP), and marginal zone (MZ). Tissues were obtained from three independent donors and three to four technical replicates from each tissue were processed for ATAC-seq to define the landscape of accessible chromatin and RNA-seq for genome-wide gene expression profiling.</p>
Project description:Mitosis entails global alterations to chromosome structure and nuclear architecture, concomitant with transient silencing of transcription. How cells transmit transcriptional states through mitosis remains incompletely understood. While many nuclear factors dissociate from mitotic chromosomes, the observation that certain nuclear factors and chromatin features remain associated with individual loci during mitosis originated the hypothesis that they could provide transcriptional memory through mitosis. To obtain the first genome-wide view of the dynamics of chromatin structure during mitosis, we compared the DNase sensitivity of interphase and mitotic chromatin at two stages of cellular maturation in a rapidly dividingmurine erythroblastmodel. Despite global chromosome condensation visible during mitosis at the microscopic level, the chromatin accessibility landscape is largely unaltered. However, mitotic chromatin accessibility is locally dynamic, with individual loci maintaining none, some, or all of their interphase accessibility. Mitotic reduction in accessibility occurs primarily within narrow, highly hypersensitive sites that frequently coincide with transcription factor binding sites, whereas broader domains of moderate accessibility tend to be more stable. In mitosis, proximal promoters generally maintain their accessibility, whereas distal regulatory elements preferentially lose accessibility. Promoters with the highest degree of accessibility preservation in mitosis tend to also be accessible across many murine tissues in interphase. Transcription factor GATA1 exerts site-specific changes in interphase accessibility that are most pronounced at distal regulatory elements, but does not visibly influence mitotic accessibility. We conclude that features of open chromatin are remarkably stable through mitosis and are modulated at the level of individual genes and regulatory elements. Dnase-Seq data is integrated with Chip-seq [GSE36589, GSE30142] and RNA-seq to examine epigentic changes in mitosis. We performed DNase-seq on two cell lines, G1E and G1E-ER4, both on an asynchronus population, and on a sample of cells in mitosis; each of the 4 experiments in triplicate.