ABSTRACT: Remote memory and cortical synaptic plasticity require neuronal CCCTC-binding factor (CTCF), a central organizer of 3D chromatin architecture
Project description:Molecular mechanism of long-term memory has been extensively studied in the context of hippocampus-dependent recent memory examined within several days; however, months-old remote memory maintained in the cortex for long-term has not much been investigated at molecular levels yet. Various epigenetic mechanisms are known to be important for long-term memory, but how 3D chromatin architecture and its regulator molecules contribute to neuronal plasticity and memory consolidation are still largely unknown. To assess memory upon perturbation of 3D chromatin structure, we chose CCCTC-binding factor (CTCF), a seven-zinc finger protein well known for its role as a transcription factor and a chromatin regulator, and created the conditional knockout (cKO) mice, in which CTCF is lost in neurons during adulthood. Our CTCF cKO mice showed normal recent memory in contextual fear conditioning and spatial water maze task. However, they showed remarkable impairments in remote memory in both tasks. Underlying the remote memory-specific phenotypes, we found that loss of CTCF disrupts cortical long-term potentiation (LTP) but not hippocampal LTP. Through RNA-sequencing, we found that CTCF KD cultured cortical neurons have altered the expression of hundreds of genes, some of which we uncovered to be regulated by neuronal activity. These results suggest that remote memory storage in the cortex requires CTCF-mediated chromatin regulation in neurons while recent memory formation in the hippocampus does not.
Project description:Epigenetic aberrations are suggested to play an important role in transcriptional alterations in Alzheimer's disease (AD). One of the key mechanisms of epigenetic regulation of gene expression is through the dynamic organization of chromatin structure via the master genome architecture protein, CCCTC-binding factor (CTCF). By forming chromatin loops, CTCF can influence gene transcription in a complex manner. To find out whether genome-wide DNA binding sites for CTCF are altered in AD, we compared CTCF chromatin immunoprecipitation sequencing (ChIP-Seq) data from frontal cortex of human AD patients and normal controls (n=9 pairs, all females). We have revealed that CTCF-binding affinity on many genes is significantly reduced in AD patients, and these genes are enriched in synaptic organization, cell adhesion, and actin cytoskeleton, including synaptic scaffolding molecules and receptors, such as SHANK2, HOMER1, NRXN1, CNTNAP2 and GRIN2A, and protocadherin (PCDH) and cadherin (CDH) family members. By comparing transcriptomic data from AD patients, we have discovered that many of the synaptic and adhesion genes with reduced CTCF binding in AD are significantly reduced in their mRNA expression. Moreover, a significant overlap of genes with the diminished CTCF binding and the reduced H3K27ac is identified in AD, with the common genes enriched in synaptic organization. These data suggest that the CTCF-controlled 3D chromatin organization is perturbed in AD, which may be linked to the diminished expression of target genes, probably through changes in histone modification.
Project description:Remembrances of traumata range among the most enduring forms of memories. Despite the elevated lifetime prevalence of anxiety disorders, effective strategies to attenuate long-term traumatic memories are scarce. The most efficacious treatments to diminish recent (i.e., day-old) traumata capitalize on memory updating mechanisms during reconsolidation that are initiated upon memory recall. Here, we show that in mice successful reconsolidation-updating paradigms for recent memories fail to attenuate remote (i.e., month-old) ones. We find that whereas recent memory recall induces a limited period of hippocampal neuroplasticity mediated, in part, by S-nitrosylation of HDAC2 and histone acetylation, such plasticity is absent for remote memories. However, by using an HDAC2-targeting inhibitor (HDACi) during reconsolidation, even remote memories can be persistently attenuated. This intervention epigenetically primes the expression of neuroplasticity-related genes as revealed by whole genome RNA sequencing, which is accompanied by higher metabolic, synaptic and structural plasticity. Thus, applying HDACis during memory reconsolidation might constitute a treatment option for remote traumata. 3 biological replicates per group were analyzed. The material analyzed was whole hippocampi from one brain hemisphere, from which total RNA was extracted.
Project description:CCCTC-binding factor (CTCF) is a conserved protein able to block communication between regulatory elements and gene promoters in flies and mammals. Here, we studied CTCF function in the Drosophila central nervous system (CNS) in which we find CTCF plays a vital role. Hi-C experiments on dissected larval CNSs of wildtype controls and CTCF[0] mutants that completely lack CTCF revealed that CTCF forms hundreds of physical boundaries in fly chromosomes.
Project description:Remembrances of traumata range among the most enduring forms of memories. Despite the elevated lifetime prevalence of anxiety disorders, effective strategies to attenuate long-term traumatic memories are scarce. The most efficacious treatments to diminish recent (i.e., day-old) traumata capitalize on memory updating mechanisms during reconsolidation that are initiated upon memory recall. Here, we show that in mice successful reconsolidation-updating paradigms for recent memories fail to attenuate remote (i.e., month-old) ones. We find that whereas recent memory recall induces a limited period of hippocampal neuroplasticity mediated, in part, by S-nitrosylation of HDAC2 and histone acetylation, such plasticity is absent for remote memories. However, by using an HDAC2-targeting inhibitor (HDACi) during reconsolidation, even remote memories can be persistently attenuated. This intervention epigenetically primes the expression of neuroplasticity-related genes as revealed by whole genome RNA sequencing, which is accompanied by higher metabolic, synaptic and structural plasticity. Thus, applying HDACis during memory reconsolidation might constitute a treatment option for remote traumata.
Project description:We investigate the gene expression changes occurring during the transition of aversive episodic memories from recent to remote. Early mechanisms of memory formation (synaptic consolidation) have been extensively characterized. However, delayed mechanisms (systems consolidation), which maintain hippocampal activity as memories stabilize in cortical circuits, are not well understood. Transcriptomic analysis reveals that, contrary to the transient expression of early- and delayed-response genes, the expression of cytoskeleton- and extracellular matrix- associated genes remains dynamic even at remote time points. The most profound expression changes clustered around primary cilium-associated and collagen genes.
Project description:Neuronal activity induced by Brain-Derived Neurotrophic Factor (BDNF) is crucial for neuronal survival, differentiation, synaptic plasticity, memory formation, and neurocognitive health. Molecular mechanisms of BDNF promoting cellular survival and synaptic plasticity have been intensely studied, yet its role in genome regulation is obscure. Here, through temporal profiling of chromatin accessibility and transcription in mouse primary cortical neurons upon BDNF treatment or depolarization (KCl), we identified BDNF-specific chromatin-to-gene expression programs. Our analyses revealed that enhancer activation is an early event in the regulatory control of BDNF treated neurons, where bZIP pioneered chromatin opening and co-regulatory transcription factors (Homeobox, EGRs, and CTCF) cooperate to induce fine-grained transcription. Deleting such cis-regulatory sequences decreased the BDNF mediated expression of Arc, a key regulator of synaptic plasticity. Furthermore, BDNF-induced accessible regions are linked to preferential exon usage of neurodevelopmental disorder related genes and heritability of neuronal complex traits. In conclusion, this work provides a comprehensive view of BDNF-mediated genome regulatory features and emphasizes the usage of genomic approaches on dissecting mammalian neuronal activity.
Project description:The pleiotropic CCCTC-binding factor (CTCF) plays a role in homologous recombination (HR) repair of DNA double-strand breaks (DSBs). However, the precise mechanistic role of CTCF in HR remains largely unclear. Here, we show that CTCF engages in DNA end resection, which is the initial, crucial step in HR, through its interactions with MRE11 and CtIP. Depletion of CTCF profoundly impairs HR and attenuates CtIP recruitment at DSBs. CTCF physically interacts with MRE11 and CtIP and promotes CtIP recruitment to sites of DNA damage. Subsequently, CTCF facilitates DNA end resection to allow HR, in conjunction with MRE11-CtIP. Notably, the zinc finger domain of CTCF binds to both MRE11 and CtIP and enables proficient CtIP recruitment, DNA end resection, and HR. The N-terminus of CTCF is able to bind to only MRE11 and its C-terminus is incapable of binding to MRE11 and CtIP, thereby resulting in compromised CtIP recruitment, DSB resection, and HR. Overall, this suggests an important function of CTCF in DNA end resection through the recruitment of CtIP at DSBs. Collectively, our findings identify a critical role of CTCF at the first control point in selecting the HR repair pathway
Project description:Chromatin organization is critical for cell growth, differentiation, and disease development, however, its functions in peripheral myelination and myelin repair remain elusive. Here we observed a global diminution of chromatin accessibility during Schwann cell differentiation and demonstrated that the chromatin organizer CCCTC-binding factor (CTCF) is critical for Schwann cell myelination and myelin regeneration after nerve injury. Inhibition of Ctcf or its deletion blocked Schwann cell differentiation at the pre-myelinating stage, whereas overexpression of CTCF promoted the myelination program. CTCF establishes the chromatin interaction loop between promoters and regulatory elements to promote expression of key pro-myelinogenic factors such as EGR2. In addition, CTCF interacts with SUZ12, a component of polycomb-repressive-complex 2, to repress expression of immature Schwann cell-associated regulators including HES1, RSPO2, and CALCA. Together, our findings reveal the dual role of CTCF-dependent chromatin organization in promoting myelinogenic programs and recruiting chromatin-repressive complexes to block differentiation inhibitors to control peripheral myelination and myelin repair.