scholarly journals Hyperactive mTOR signals in the proopiomelanocortin-expressing hippocampal neurons cause age-dependent epilepsy and premature death in mice

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Yuki Matsushita ◽  
Yasunari Sakai ◽  
Mitsunori Shimmura ◽  
Hiroshi Shigeto ◽  
Miki Nishio ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Focal Cortical Dysplasia ◽  
Mossy Fibers ◽  
Premature Death ◽  
Mtor Pathway ◽  
Conditional Knockout ◽  
Inhibitory Neurons ◽  
Sequencing Data ◽  
Functional Roles ◽  
Synaptic Markers

Abstract Epilepsy is a frequent comorbidity in patients with focal cortical dysplasia (FCD). Recent studies utilizing massive sequencing data identified subsets of genes that are associated with epilepsy and FCD. AKT and mTOR-related signals have been recently implicated in the pathogenic processes of epilepsy and FCD. To clarify the functional roles of the AKT-mTOR pathway in the hippocampal neurons, we generated conditional knockout mice harboring the deletion of Pten (Pten-cKO) in Proopiomelanocortin-expressing neurons. The Pten-cKO mice developed normally until 8 weeks of age, then presented generalized seizures at 8–10 weeks of age. Video-monitored electroencephalograms detected paroxysmal discharges emerging from the cerebral cortex and hippocampus. These mice showed progressive hypertrophy of the dentate gyrus (DG) with increased expressions of excitatory synaptic markers (Psd95, Shank3 and Homer). In contrast, the expression of inhibitory neurons (Gad67) was decreased at 6–8 weeks of age. Immunofluorescence studies revealed the abnormal sprouting of mossy fibers in the DG of the Pten-cKO mice prior to the onset of seizures. The treatment of these mice with an mTOR inhibitor rapamycin successfully prevented the development of seizures and reversed these molecular phenotypes. These data indicate that the mTOR pathway regulates hippocampal excitability in the postnatal brain.

scholarly journals STAG2 promotes the myelination transcriptional program in oligodendrocytes

2021 ◽  
Author(s):  
Ningyan Cheng ◽  
Mohammed Kanchwala ◽  
Bret M. Evers ◽  
Chao Xing ◽  
Hongtao Yu
Keyword(s):  
Nervous System ◽  
Growth Retardation ◽  
Premature Death ◽  
Nerve Fibers ◽  
Conditional Knockout ◽  
Cell Type ◽  
Transcriptional Program ◽  
Dna Loop ◽  
Delayed Maturation ◽  
Relevant Cell Type

SUMMARYCohesin folds chromosomes via DNA loop extrusion. Cohesin-mediated chromosome loops regulate transcription by shaping long-range enhancer-promoter interactions, among other mechanisms. Mutations of cohesin subunits and regulators cause human developmental diseases termed cohesinopathy. Vertebrate cohesin consists of SMC1, SMC3, RAD21, and either STAG1 or STAG2. To probe the physiological functions of cohesin, we created conditional knockout (cKO) mice with Stag2 deleted in the nervous system. Stag2 cKO mice exhibit growth retardation, neurological defects, and premature death, in part due to insufficient myelination of nerve fibers. Stag2 cKO oligodendrocytes exhibit delayed maturation and downregulation of myelination-related genes. Stag2 loss reduces promoter-anchored loops at downregulated genes in oligodendrocytes. Thus, STAG2-cohesin generates promoter-anchored loops at myelination-promoting genes to facilitate their transcription. Our study implicates defective myelination as a contributing factor to cohesinopathy and establishes oligodendrocytes as a relevant cell type to explore the mechanisms by which cohesin regulates transcription.

scholarly journals RTP801/REDD1 contributes to neuroinflammation severity and memory impairments in Alzheimer’s disease

2021 ◽  
Vol 12 (6) ◽  
Author(s):  
Leticia Pérez-Sisqués ◽  
Anna Sancho-Balsells ◽  
Júlia Solana-Balaguer ◽  
Genís Campoy-Campos ◽  
Marcel Vives-Isern ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Hippocampal Neurons ◽  
Mrna Levels ◽  
Spine Density ◽  
Memory Impairments ◽  
Protein Levels ◽  
Synaptic Markers ◽  
5Xfad Mice

AbstractRTP801/REDD1 is a stress-regulated protein whose upregulation is necessary and sufficient to trigger neuronal death. Its downregulation in Parkinson’s and Huntington’s disease models ameliorates the pathological phenotypes. In the context of Alzheimer’s disease (AD), the coding gene for RTP801, DDIT4, is responsive to Aβ and modulates its cytotoxicity in vitro. Also, RTP801 mRNA levels are increased in AD patients’ lymphocytes. However, the involvement of RTP801 in the pathophysiology of AD has not been yet tested. Here, we demonstrate that RTP801 levels are increased in postmortem hippocampal samples from AD patients. Interestingly, RTP801 protein levels correlated with both Braak and Thal stages of the disease and with GFAP expression. RTP801 levels are also upregulated in hippocampal synaptosomal fractions obtained from murine 5xFAD and rTg4510 mice models of the disease. A local RTP801 knockdown in the 5xFAD hippocampal neurons with shRNA-containing AAV particles ameliorates cognitive deficits in 7-month-old animals. Upon RTP801 silencing in the 5xFAD mice, no major changes were detected in hippocampal synaptic markers or spine density. Importantly, we found an unanticipated recovery of several gliosis hallmarks and inflammasome key proteins upon neuronal RTP801 downregulation in the 5xFAD mice. Altogether our results suggest that RTP801 could be a potential future target for theranostic studies since it could be a biomarker of neuroinflammation and neurotoxicity severity of the disease and, at the same time, a promising therapeutic target in the treatment of AD.

Rapid Translocation of Zn2+ From Presynaptic Terminals Into Postsynaptic Hippocampal Neurons After Physiological Stimulation

2001 ◽  
Vol 86 (5) ◽  
pp. 2597-2604 ◽  
Author(s):  
Yang Li ◽  
Christopher J. Hough ◽  
Sang Won Suh ◽  
John M. Sarvey ◽  
Christopher J. Frederickson
Keyword(s):  
Hippocampal Neurons ◽  
Hippocampal Slices ◽  
Mossy Fibers ◽  
Synaptic Cleft ◽  
Immediate Release ◽  
Long Term Potentiation ◽  
Anatomical Location ◽  
Term Potentiation ◽  
Presynaptic Boutons

Zn2+ is found in glutamatergic nerve terminals throughout the mammalian forebrain and has diverse extracellular and intracellular actions. The anatomical location and possible synaptic signaling role for this cation have led to the hypothesis that Zn2+ is released from presynaptic boutons, traverses the synaptic cleft, and enters postsynaptic neurons. However, these events have not been directly observed or characterized. Here we show, using microfluorescence imaging in rat hippocampal slices, that brief trains of electrical stimulation of mossy fibers caused immediate release of Zn2+ from synaptic terminals into the extracellular microenvironment. Release was induced across a broad range of stimulus intensities and frequencies, including those likely to induce long-term potentiation. The amount of Zn2+ release was dependent on stimulation frequency (1–200 Hz) and intensity. Release of Zn2+ required sodium-dependent action potentials and was dependent on extracellular Ca2+. Once released, Zn2+ crosses the synaptic cleft and enters postsynaptic neurons, producing increases in intracellular Zn2+ concentration. These results indicate that, like a neurotransmitter, Zn2+ is stored in synaptic vesicles and is released into the synaptic cleft. However, unlike conventional transmitters, it also enters postsynaptic neurons, where it may have manifold physiological functions as an intracellular second messenger.

scholarly journals Network hubs in root-associated fungal metacommunities

2018 ◽  
Author(s):  
Hirokazu Toju ◽  
Akifumi S. Tanabe ◽  
Hirotoshi Sato
Keyword(s):  
Plant Species ◽  
Mycorrhizal Fungi ◽  
Arbuscular Mycorrhizal ◽  
Pathogenic Fungi ◽  
Pathogen Resistance ◽  
Climatic Region ◽  
Sequencing Data ◽  
Functional Roles ◽  
Scale Network ◽  
The Japanese Archipelago

AbstractBackgroundAlthough a number of recent studies have uncovered remarkable diversity of microbes associated with plants, understanding and managing dynamics of plant microbiomes remain major scientific challenges. In this respect, network analytical methods have provided a basis for exploring “hub” microbial species, which potentially organize community-scale processes of plant-microbe interactions.MethodsBy compiling Illumina sequencing data of root-associated fungi in eight forest ecosystems across the Japanese Archipelago, we explored hubs within “metacommunity-scale” networks of plant-fungus associations. In total, the metadata included 8,080 fungal operational taxonomic units (OTUs) detected from 227 local populations of 150 plant species/taxa.ResultsFew fungal OTUs were common across all the eight forests. However, in each metacommunity-scale network representing northern four localities or southern four localities, diverse mycorrhizal, endophytic, and pathogenic fungi were classified as “metacommunity hubs”, which were detected from diverse host plant taxa throughout a climatic region. Specifically, Mortierella (Mortierellales), Cladophialophora (Chaetothyriales), Ilyonectria (Hypocreales), Pezicula (Helotiales), and Cadophora (incertae sedis) had broad geographic and host ranges across the northern (cool-temperate) region, while Saitozyma/Cryptococcus (Tremellales/Trichosporonales) and Mortierella as well as some arbuscular mycorrhizal fungi were placed at the central positions of the metacommunity-scale network representing warm-temperate and subtropical forests in southern Japan.ConclusionsThe network theoretical framework presented in this study will help us explore prospective fungi and bacteria, which have high potentials for agricultural application to diverse plant species within each climatic region. As some of those fungal taxa with broad geographic and host ranges have been known to increase the growth and pathogen resistance of host plants, further studies elucidating their functional roles are awaited.

scholarly journals Preferential Pharmacological Inhibition of Nav1.6, but not Nav1.1, Abolishes Epileptiform Activity Induced by 4-AP in Mouse Cortical Slices

2020 ◽  
Author(s):  
Reesha R. Patel ◽  
Xingjie Ping ◽  
Shaun R. Patel ◽  
Jeff S. McDermott ◽  
Jeffrey L. Krajewski ◽  
...  
Keyword(s):  
Expression Patterns ◽  
Epileptiform Activity ◽  
Inhibitory Neurons ◽  
Hek293 Cells ◽  
Functional Roles ◽  
Voltage Gated Sodium Channels ◽  
Whole Cell Patch Clamp ◽  
Epileptic Syndromes ◽  
The Brain ◽  
Cortical Slices

ABSTRACTBrain isoforms of voltage-gated sodium channels (VGSCs) have distinct cellular and subcellular expression patterns as well as functional roles that are critical for normal physiology as aberrations in their expression or activity lead to pathophysiological conditions. In this study, we asked how inhibition of select isoforms of VGSCs alters epileptiform activity to further parse out the roles of VGSCs in the brain. We first determined the relative selectivity of recently discovered small molecule, aryl sulfonamide, inhibitors (ICA-121431 and Compound 801) against Nav1.1, Nav1.2, and Nav1.6 activity using whole-cell patch clamp recordings obtained from HEK293 cells. To test the effects of these inhibitors on epileptiform activity, we obtained multielectrode array (MEA) recordings from mouse cortical slices in the presence of 4-aminopyridine (4-AP) to induce epileptiform activity. We found that the ICA-121431 and Compound 801 compounds are relatively selective for Nav1.1 and Nav1.6, respectively. From the MEA recordings, we found that inhibition of Nav1.6 and Nav1.2 with 500nM of the Compound 801 compound completely abolishes ictal local field potentials induced by 4-AP, whereas inhibition of Nav1.1 with 500nM of the ICA-121431 compound had minimal effect on epileptiform activity induced by 4-AP. Due to the prominent expression of Nav1.1 in inhibitory neurons, we asked whether inhibition of Nav1.1 alone alters activity. We found that, indeed, inhibition of Nav1.1 with the ICA-121431 compound increased basal activity in the absence of 4-AP. These findings expand our current understanding of the roles of VGSC isoforms in the brain and suggest that selective targeting of Nav1.6 may be a more efficacious treatment strategy for epileptic syndromes.

scholarly journals Dense Functional and Molecular Readout of a Circuit Hub in Sensory Cortex

2021 ◽  
Author(s):  
Cameron Condylis ◽  
Abed Ghanbari ◽  
Nikita Manjrekar ◽  
Karina Bistrong ◽  
Shenqin Yao ◽  
...  
Keyword(s):  
Memory Task ◽  
Molecular Classification ◽  
Cell Types ◽  
Inhibitory Neurons ◽  
Functional Roles ◽  
Tactile Stimuli ◽  
Layer 2 ◽  
Functional And Anatomical Connectivity ◽  
Tactile Working Memory ◽  
Different Cell Types

ABSTRACTInformation processing in the neocortex is carried out by neuronal circuits composed of different cell types. Recent census of the neocortex using single cell transcriptomic profiling has uncovered more than 100 putative cell types which subdivide major classes of excitatory and inhibitory neurons into distinct subclasses. The extent to which this molecular classification predicts distinct functional roles during behavior is unclear. Here, we combined population recordings using two-photon calcium imaging with spatial transcriptomics using multiplexed fluorescent in situ hybridization to achieve dense functional and molecular readout of cortical circuits during behavior. We characterized task-related responses across major transcriptomic neuronal subclasses and types in layer 2/3 of primary somatosensory cortex as mice performed a tactile working memory task. We find that as neurons are segregated into increasingly discrete molecular types, their task-related properties continue to differentiate. We identify an excitatory cell type, Baz1a, that is highly driven by tactile stimuli. Baz1a neurons homeostatically maintain stimulus responsiveness during altered sensory experience and show persistent enrichment of subsets of immediately early genes including Fos. Measurements of functional and anatomical connectivity reveal that upper layer 2/3 Baz1a neurons preferentially innervate somatostatin-expressing inhibitory neurons. We propose that this connection motif reflects a sensory-driven circuit hub that orchestrates local sensory processing in superficial layers of the neocortex.

Long noncoding RNA Nespas inhibits apoptosis of epileptiform hippocampal neurons by inhibiting the PI3K/Akt/mTOR pathway

2021 ◽  
Vol 398 (1) ◽  
pp. 112384
Author(s):  
Hongxuan Feng ◽  
Qian Gui ◽  
Guanhui Wu ◽  
Wei Zhu ◽  
Xiaofeng Dong ◽  
...  
Keyword(s):  
Long Noncoding Rna ◽  
Hippocampal Neurons ◽  
Noncoding Rna ◽  
Mtor Pathway

Abstract P111: Rheb-mTOR Signaling Pathway Regulates Cardiomyocyte Mass During Post-Neonatal Period

2011 ◽  
Vol 109 (suppl_1) ◽  
Author(s):  
Takahito Tamai ◽  
Shungo Hikoso ◽  
Tomokazu Murakawa ◽  
Jota Oyabu ◽  
Takafumi Oka ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Neonatal Period ◽  
Contractile Function ◽  
Microscopic Analysis ◽  
Mrna Translation ◽  
Premature Death ◽  
Mtor Pathway ◽  
Heart Weight ◽  
Electron Microscopic ◽  
Cross Sectional

Rheb (Ras homologue enriched in brain) is a major activator of mTOR. Rheb-mTOR pathway is a critical mechanism for maintenance of homeostasis, cell growth and stress response by regulating both protein synthesis and degradation. In this study, we attempted to clarify the role of Rheb-mTOR pathway in the heart using cardiac-specific Rheb-deficient mice (Rheb −/− ). We generated floxed Rheb mice and crossed them with transgenic mice expressing Cre recombinase in cardiac-specific mannner to generate Rheb −/− . Rheb −/− were born in Mendelian ratio, but they started to die 8 days after birth and all of them had died until 10 days after birth. Echocardiographic analysis revealed that chamber dimension and contractile function of Rheb −/− were indistinguishable from those of control mice (Rheb +/+ ) 5 days after birth. However, Rheb −/− exhibited cardiac dilatation and reduced contractility 8 days after birth (LV end diastolic dimension, Rheb −/− : 2.5±0.2 mm vs. Rheb +/+ : 2.1±0.2 mm, p<0.01, fractional shortening, Rheb −/− : 19.7 ± 9.7 % vs. Rheb +/+ : 48.6 ± 8.8 %, p<0.01). These suggest that Rheb −/− died of cardiac dysfunction and heart failure. Heart weight and cross-sectional area of cardiomyocytes were significantly lower in Rheb −/− 8 days after birth. Electron microscopic analysis revealed that the area of sarcomere was significantly lower in Rheb −/− cardiomyocytes. Expressions of sarcomeric proteins, such as myosin heavy chain, actin or desmin, were decreased in Rheb −/− , while the mRNA expression of desmin was significantly increased in Rheb −/− . Thus impairment of cardiomyocyte growth observed in Rheb −/− could be due to either increased degradation or decreased translation. Although autophagic activity was enhanced in Rheb −/− heart, ablation of Atg5, an essential molecule for autophagy, could not prevent premature death of Rheb −/− . On the other hand, polysome analysis revealed that the mRNA translation activity had decreased in Rheb −/− heart compared with Rheb +/+ . Thus, we concluded that Rheb-mTOR pathway in the heart is essential to regulate mRNA translation activity and protein synthesis, thereby to cardiomyocyte growth in neonatal period.

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