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Repressed memories

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https://www.readbyqxmd.com/read/28346453/activity-induced-histone-modifications-govern-neurexin-1-mrna-splicing-and-memory-preservation
#1
Xinlu Ding, Sanxiong Liu, Miaomiao Tian, Wenhao Zhang, Tao Zhu, Dongdong Li, Jiawei Wu, HaiTeng Deng, Yichang Jia, Wei Xie, Hong Xie, Ji-Song Guan
Epigenetic mechanisms regulate the formation, consolidation and reconsolidation of memories. However, the signaling path from neuronal activation to epigenetic modifications within the memory-related brain circuit remains unknown. We report that learning induces long-lasting histone modifications in hippocampal memory-activated neurons to regulate memory stability. Neuronal activity triggers a late-onset shift in Nrxn1 splice isoform choice at splicing site 4 by accumulating a repressive histone marker, H3K9me3, to modulate the splicing process...
March 27, 2017: Nature Neuroscience
https://www.readbyqxmd.com/read/28346433/a-cytosolic-ezh1-isoform-modulates-a-prc2-ezh1-epigenetic-adaptive-response-in-postmitotic-cells
#2
Beatrice Bodega, Federica Marasca, Valeria Ranzani, Alessandro Cherubini, Francesco Della Valle, Maria Victoria Neguembor, Michel Wassef, Alessio Zippo, Chiara Lanzuolo, Massimiliano Pagani, Valerio Orlando
The evolution of chromatin-based epigenetic cell memory may be driven not only by the necessity for cells to stably maintain transcription programs, but also by the need to recognize signals and allow plastic responses to environmental stimuli. The mechanistic role of the epigenome in adult postmitotic tissues, however, remains largely unknown. In vertebrates, two variants of the Polycomb repressive complex (PRC2-Ezh2 and PRC2-Ezh1) control gene silencing via methylation of histone H3 on Lys27 (H3K27me). Here we describe a reversible mechanism that involves a novel isoform of Ezh1 (Ezh1β)...
March 27, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/28342717/slow-chromatin-dynamics-allow-polycomb-target-genes-to-filter-fluctuations-in-transcription-factor-activity
#3
Scott Berry, Caroline Dean, Martin Howard
Genes targeted by Polycomb repressive complex 2 (PRC2) are regulated in cis by chromatin modifications and also in trans by diffusible regulators such as transcription factors. Here, we introduce a mathematical model in which transcription directly antagonizes Polycomb silencing, thereby linking these cis- and trans-regulatory inputs to gene expression. The model is parameterized by recent experimental data showing that PRC2-mediated repressive chromatin modifications accumulate extremely slowly. The model generates self-perpetuating, bistable active and repressed chromatin states that persist through DNA replication, thereby ensuring high-fidelity transmission of the current chromatin state...
March 21, 2017: Cell Systems
https://www.readbyqxmd.com/read/28304152/reprogramming-of-histone-methylation-controls-the-differentiation-of-monocytes-into-macrophages
#4
Qi-Fan Zheng, Hui-Min Wang, Zhan-Feng Wang, Jin-Yang Liu, Qi Zhang, Li Zhang, Yuan-Hua Lu, Han You, Guang-Hui Jin
Subset heterogeneity of the mononuclear phagocyte system (MPS) is controlled by defined transcriptional networks and programs; however, the dynamic establishment of programs that control broad, orchestrated expression of transcription factors (TFs) during the progression of monocyte-into-phagocyte (MP) differentiation remains largely unexplored. By using chromatin immunoprecipitation assays, we show the extensive trimethylation of histone H3 lysine 4 (H3K4me3) as well as histone H3 lysine 27 (H3K27me3) occupancy with broad footprints at the promoters of MP differentiation-related TFs, such as HOXA and FOXO genes, KLF4, IRF8 and others...
March 17, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28302795/causal-role-for-inheritance-of-h3k27me3-in-maintaining-the-off-state-of-a-drosophila-hox-gene
#5
Rory T Coleman, Gary Struhl
Many eukaryotic cells can respond to transient environmental or developmental stimuli with heritable changes in gene expression that are associated with nucleosome modifications. However, it remains uncertain whether modified nucleosomes play a causal role in transmitting such epigenetic memories, as opposed to controlling or merely reflecting transcriptional states inherited by other means. Here, we provide in vivo evidence that H3K27 trimethylated nucleosomes, once established at a repressed Drosophila HOX gene, remain heritably associated with that gene and can carry the memory of the silenced state through multiple rounds of replication, even when the capacity to copy the H3K27me3 mark to newly incorporated nucleosomes is diminished or abolished...
March 16, 2017: Science
https://www.readbyqxmd.com/read/28302792/propagation-of-polycomb-repressed-chromatin-requires-sequence-specific-recruitment-to-dna
#6
Friederike Laprell, Katja Finkl, Jürg Müller
Epigenetic inheritance models posit that during Polycomb repression, Polycomb Repressive Complex 2 (PRC2) propagates histone H3K27 tri-methylation (H3K27me3) independently of DNA sequence. We show that insertion of Polycomb Response Element (PRE) DNA into the Drosophila genome creates extended domains of H3K27me3-modified nucleosomes in the flanking chromatin and causes repression of a linked reporter gene. After excision of PRE DNA, H3K27me3 nucleosomes become diluted with each round of DNA replication and reporter gene repression is lost, whereas in replication-stalled cells, H3K27me3 levels stay high and repression persists...
March 16, 2017: Science
https://www.readbyqxmd.com/read/28279665/multiple-sevoflurane-anesthesia-in-pregnant-mice-inhibits-neurogenesis-of-fetal-hippocampus-via-repressing-transcription-factor-pax6
#7
Fang Fang, Ruixue Song, Xiaomim Ling, Mengyuan Peng, Zhanggang Xue, Jing Cang
Sevoflurane is widely used in non-obstetric surgeries of pregnant women, but its influences on fetal brain are still not fully known. We set out to assess the effects of multiple maternal sevoflurane exposure on neurogenesis and cognitive dysfunction in fetus and offspring. Pregnant mice (gestational day 15.5) and cultured mouse neural stem cells (NSCs) received daily sevoflurane exposure (2.5%×2h and 4.1%×2h respectively) for three consecutive days. Cognitive function of the offspring was determined with the Morris water maze...
March 6, 2017: Life Sciences
https://www.readbyqxmd.com/read/28246360/multiple-histone-lysine-methyltransferases-are-required-for-the-establishment-and-maintenance-of-hiv-1-latency
#8
Kien Nguyen, Biswajit Das, Curtis Dobrowolski, Jonathan Karn
We showed previously that the histone lysine methyltransferase (HKMT) H3K27me3 (EZH2) is the catalytic subunit of Polycomb repressive complex 2 (PRC2) and is required for the maintenance of HIV-1 latency in Jurkat T cells. Here we show, by using chromatin immunoprecipitation experiments, that both PRC2 and euchromatic histone-lysine N-methyltransferase 2 (EHMT2), the G9a H3K9me2-3 methyltransferase, are highly enriched at the proviral 5' long terminal repeat (LTR) and rapidly displaced upon proviral reactivation...
February 28, 2017: MBio
https://www.readbyqxmd.com/read/28219680/the-regulation-of-transcriptional-repression-in-hypoxia
#9
Miguel A S Cavadas, Alex Cheong, Cormac T Taylor
A sufficient supply molecular oxygen is essential for the maintenance of physiologic metabolism and bioenergetic homeostasis for most metazoans. For this reason, mechanisms have evolved for eukaryotic cells to adapt to conditions where oxygen demand exceeds supply (hypoxia). These mechanisms rely on the modification of pre-existing proteins, translational arrest and transcriptional changes. The hypoxia inducible factor (HIF; a master regulator of gene induction in response to hypoxia) is responsible for the majority of induced gene expression in hypoxia...
February 20, 2017: Experimental Cell Research
https://www.readbyqxmd.com/read/28208656/primetime-for-learning-genes
#10
REVIEW
Joyce Keifer
Learning genes in mature neurons are uniquely suited to respond rapidly to specific environmental stimuli. Expression of individual learning genes, therefore, requires regulatory mechanisms that have the flexibility to respond with transcriptional activation or repression to select appropriate physiological and behavioral responses. Among the mechanisms that equip genes to respond adaptively are bivalent domains. These are specific histone modifications localized to gene promoters that are characteristic of both gene activation and repression, and have been studied primarily for developmental genes in embryonic stem cells...
February 11, 2017: Genes
https://www.readbyqxmd.com/read/28027601/hysteresis-in-myo-inositol-utilization-by-salmonella-typhimurium
#11
Jessica Hellinckx, Thilo M Fuchs
Growth of Salmonella enterica serovar Typhimurium strain 14028 with myo-inositol (MI) as the sole carbon and energy source is characterized by a bistable phenotype that manifests in a growth phenotype with an extraordinarily long and length-variable lag phase. However, in the presence of hydrogen carbonate, in the absence of IolR that represses the MI degradation pathway, or if cells are already adapted to minimal medium (MM) with MI, the lag phase is drastically shortened, and the bistable phenotype is abolished...
December 27, 2016: MicrobiologyOpen
https://www.readbyqxmd.com/read/28018990/the-tcf1-bcl6-axis-counteracts-type-i-interferon-to-repress-exhaustion-and-maintain-t-cell-stemness
#12
Tuoqi Wu, Yun Ji, E Ashley Moseman, Haifeng C Xu, Monica Manglani, Martha Kirby, Stacie M Anderson, Robin Handon, Elizabeth Kenyon, Abdel Elkahloun, Weiwei Wu, Philipp A Lang, Luca Gattinoni, Dorian B McGavern, Pamela L Schwartzberg
During chronic viral infections and in cancer, T cells become dysfunctional, a state known as T cell exhaustion. Although it is well recognized that memory CD8 T cells account for the persistence of CD8 T cell immunity after acute infection, how exhausted T cells persist remains less clear. Using chronic infection with lymphocytic choriomeningitis virus clone 13 and tumor samples, we demonstrate that CD8 T cells differentiate into a less exhausted TCF1(high) and a more exhausted TCF1(low) population. Virus-specific TCF1(high) CD8 T cells, which resemble T follicular helper (TFH) cells, persist and recall better than do TCF1(low) cells and act as progenitor cells to replenish TCF1(low) cells...
December 23, 2016: Science Immunology
https://www.readbyqxmd.com/read/28011866/the-aryl-hydrocarbon-receptor-controls-cell-fate-decisions-in-b-cells
#13
Bharat Vaidyanathan, Ashutosh Chaudhry, William T Yewdell, Davide Angeletti, Wei-Feng Yen, Adam K Wheatley, Christopher A Bradfield, Adrian B McDermott, Jonathan W Yewdell, Alexander Y Rudensky, Jayanta Chaudhuri
Generation of cellular heterogeneity is an essential feature of the adaptive immune system. This is best exemplified during humoral immune response when an expanding B cell clone assumes multiple cell fates, including class-switched B cells, antibody-secreting plasma cells, and memory B cells. Although each cell type is essential for immunity, their generation must be exquisitely controlled because a class-switched B cell cannot revert back to the parent isotype, and a terminally differentiated plasma cell cannot contribute to the memory pool...
January 2017: Journal of Experimental Medicine
https://www.readbyqxmd.com/read/27992519/site-dependent-differences-in-dna-methylation-and-their-impact-on-plant-establishment-and-phosphorus-nutrition-in-populus-trichocarpa
#14
Brigitte Schönberger, Xiaochao Chen, Svenja Mager, Uwe Ludewig
The propagation via clonal stem cuttings is a frequent practice in tree plantations. Despite their clonal origin, the trees establish differently according to weather, temperature and nutrient availability, as well as the presence of various stresses. Here, clonal Populus trichocarpa (cv. Muhle Larson) cuttings from different sites were transferred into a common, fully nutrient supplied environment. Despite identical underlying genetics, stem cuttings derived from sites with lower phosphorus availability established worse, independent of phosphorus (P) level after transplantation...
2016: PloS One
https://www.readbyqxmd.com/read/27984208/oral-administration-of-grape-seed-polyphenol-extract-restores-memory-deficits-in-chronic-cerebral-hypoperfusion-rats
#15
Chen Chen, Yake Zheng, Tianwen Wu, Chuanjie Wu, Xuan Cheng
Chronic cerebral hypoperfusion (CCH) has been recognized as an important cause of both vascular dementia and Alzheimer's disease (AD), the two most prominent neurodegenerative diseases causing memory impairment in the elderly. However, an effective therapy for CCH-induced memory impairment has not yet been established. Grape seed polyphenol extract (GSPE) has powerful antioxidant properties and protects neurons and glia during ischemic injury, but its potential use in the prevention of CCH-induced memory impairment has not yet been investigated...
April 2017: Behavioural Pharmacology
https://www.readbyqxmd.com/read/27983596/estrogenic-endocrine-disrupting-chemicals-influencing-nrf1-regulated-gene-networks-in-the-development-of-complex-human-brain-diseases
#16
REVIEW
Mark Preciados, Changwon Yoo, Deodutta Roy
During the development of an individual from a single cell to prenatal stages to adolescence to adulthood and through the complete life span, humans are exposed to countless environmental and stochastic factors, including estrogenic endocrine disrupting chemicals. Brain cells and neural circuits are likely to be influenced by estrogenic endocrine disruptors (EEDs) because they strongly dependent on estrogens. In this review, we discuss both environmental, epidemiological, and experimental evidence on brain health with exposure to oral contraceptives, hormonal therapy, and EEDs such as bisphenol-A (BPA), polychlorinated biphenyls (PCBs), phthalates, and metalloestrogens, such as, arsenic, cadmium, and manganese...
December 13, 2016: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/27939580/microrna-101-regulates-multiple-developmental-programs-to-constrain-excitation-in-adult-neural-networks
#17
Giordano Lippi, Catarina C Fernandes, Laura A Ewell, Danielle John, Benedetto Romoli, Giulia Curia, Seth R Taylor, E Paxon Frady, Anne B Jensen, Jerry C Liu, Melanie M Chaabane, Cherine Belal, Jason L Nathanson, Michele Zoli, Jill K Leutgeb, Giuseppe Biagini, Gene W Yeo, Darwin K Berg
A critical feature of neural networks is that they balance excitation and inhibition to prevent pathological dysfunction. How this is achieved is largely unknown, although deficits in the balance contribute to many neurological disorders. We show here that a microRNA (miR-101) is a key orchestrator of this essential feature, shaping the developing network to constrain excitation in the adult. Transient early blockade of miR-101 induces long-lasting hyper-excitability and persistent memory deficits. Using target site blockers in vivo, we identify multiple developmental programs regulated in parallel by miR-101 to achieve balanced networks...
December 21, 2016: Neuron
https://www.readbyqxmd.com/read/27939357/%C3%AE-isocubebenol-alleviates-scopolamine-induced-cognitive-impairment-by-repressing-acetylcholinesterase-activity
#18
Sung Hwa Song, Seong Mi Choi, Ji Eun Kim, Ji Eun Sung, Hyun Ah Lee, Yung Hyun Choi, Chang Joon Bae, Young Whan Choi, Dae Youn Hwang
α-Isocubebenol (ICO) isolated from Schisandra chinensis fruit was recently shown to exert neuroprotective properties with significant anti-neuroinflammatory effects. Here, we present evidence of the novel effects of ICO on alleviation of cognitive impairment. To confirm these effects, ICR mice were pretreated with two different doses of ICO for 3 weeks and scopolamine (SP) to induce memory impairment for the last 7days of the period. A passive avoidance test showed that ICO pretreatment recovered memory impairment in SP treated mice, although there was no difference between the two doses...
December 7, 2016: Neuroscience Letters
https://www.readbyqxmd.com/read/27933319/a-metabolic-widget-adjusts-the-phosphoenolpyruvate-dependent-fructose-influx-in-pseudomonas-putida
#19
Max Chavarría, Ángel Goñi-Moreno, Víctor de Lorenzo, Pablo I Nikel
Fructose uptake in the soil bacterium Pseudomonas putida occurs through a canonical phosphoenolpyruvate (PEP)-dependent sugar transport system (PTS(Fru)). The logic of the genetic circuit that rules its functioning is puzzling: the transcription of the fruBKA operon, encoding all the components of PTS(Fru), can escape the repression exerted by the catabolite repressor/activator protein Cra solely in the presence of intracellular fructose-1-P, an agonist formed only when fructose has been already transported...
November 2016: MSystems
https://www.readbyqxmd.com/read/27932388/from-embryo-to-adult-pirna-mediated-silencing-throughout-germline-development-in-drosophila
#20
Pauline P Marie, Stéphane Ronsseray, Antoine Boivin
In metazoan germ cells, transposable element activity is repressed by small noncoding PIWI-associated RNAs (piRNAs). Numerous studies in Drosophila have elucidated the mechanism of this repression in the adult germline. However, when and how transposable element repression is established during germline development, has not been addressed. Here, we show that homology-dependent trans silencing is active in female primordial germ cells from late embryogenesis through pupal stages, and that genes related to the adult piRNA pathway are required for silencing during development...
December 14, 2016: G3: Genes—Genomes—Genetics
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