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Davidson AM, Mejía-Gómez H, Wooten BM, Marqués S, Jacobowitz M, Ugidos IF, Mostany R. Differences in motor learning-related structural plasticity of layer 2/3 parvalbumin-positive interneurons of the young and aged motor cortex. GeroScience 2024:10.1007/s11357-024-01350-6. [PMID: 39343864 DOI: 10.1007/s11357-024-01350-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Accepted: 09/09/2024] [Indexed: 10/01/2024] Open
Abstract
Changes to neuronal connectivity are believed to be a key factor in cognitive impairments associated with normal aging. Because of its effect on activities of daily living, deficient motor control is a critical type of cognitive decline to understand. Diminished inhibitory networks in the cortex are implicated in such motor control deficits, pointing to the connectivity of inhibitory cortical interneurons as an important area for study. Here, we used chronic two-photon microscopy to track the structural plasticity of en passant boutons (EPBs) of parvalbumin-positive interneurons in the mouse motor cortex in the first longitudinal, in vivo study of inhibitory interneuron synapses in the context of aging. Young (3-5 months) and aged (23-28 months) mice underwent training on the accelerating rotarod to evoke motor learning-induced structural plasticity. Our analysis reveals that, in comparison with axons from young mice, those from aged mice have fewer EPBs at baseline that also tend to be larger in size. Aged axons also express learning-related structural plasticity-like new bouton stabilization and bouton enlargement-that is less persistent than that of young axons. This study reveals striking baseline differences in young and aged axon morphology as well as differences in the deployment of learning-related structural plasticity across axons.
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Affiliation(s)
- Andrew M Davidson
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, USA
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Hernán Mejía-Gómez
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
- Neuroscience Program, Brain Institute, Tulane University, New Orleans, LA, USA
| | - Bryn M Wooten
- Neuroscience Program, Brain Institute, Tulane University, New Orleans, LA, USA
| | - Sharai Marqués
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Michael Jacobowitz
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Irene F Ugidos
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA
- Brain Institute, Tulane University, New Orleans, LA, USA
| | - Ricardo Mostany
- Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA.
- Neuroscience Program, Brain Institute, Tulane University, New Orleans, LA, USA.
- Brain Institute, Tulane University, New Orleans, LA, USA.
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2
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Single-dose ethanol intoxication causes acute and lasting neuronal changes in the brain. Proc Natl Acad Sci U S A 2022; 119:e2122477119. [PMID: 35700362 DOI: 10.1073/pnas.2122477119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Alcohol intoxication at early ages is a risk factor for the development of addictive behavior. To uncover neuronal molecular correlates of acute ethanol intoxication, we used stable-isotope-labeled mice combined with quantitative mass spectrometry to screen more than 2,000 hippocampal proteins, of which 72 changed synaptic abundance up to twofold after ethanol exposure. Among those were mitochondrial proteins and proteins important for neuronal morphology, including MAP6 and ankyrin-G. Based on these candidate proteins, we found acute and lasting molecular, cellular, and behavioral changes following a single intoxication in alcohol-naïve mice. Immunofluorescence analysis revealed a shortening of axon initial segments. Longitudinal two-photon in vivo imaging showed increased synaptic dynamics and mitochondrial trafficking in axons. Knockdown of mitochondrial trafficking in dopaminergic neurons abolished conditioned alcohol preference in Drosophila flies. This study introduces mitochondrial trafficking as a process implicated in reward learning and highlights the potential of high-resolution proteomics to identify cellular mechanisms relevant for addictive behavior.
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3
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Kuijpers M. Keeping synapses in shape: degradation pathways in the healthy and aging brain. Neuronal Signal 2022; 6:NS20210063. [PMID: 35813265 PMCID: PMC9208270 DOI: 10.1042/ns20210063] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 11/17/2022] Open
Abstract
Synapses maintain their molecular composition, plasticity and function through the concerted action of protein synthesis and removal. The complex and polarized neuronal architecture poses specific challenges to the logistics of protein and organelle turnover since protein synthesis and degradation mainly happen in the cell soma. In addition, post-mitotic neurons accumulate damage over a lifetime, challenging neuronal degradative pathways and making them particularly susceptible to the effects of aging. This review will summarize the current knowledge on neuronal protein turnover mechanisms with a particular focus on the presynapse, including the proteasome, autophagy and the endolysosomal route and their roles in regulating presynaptic proteostasis and function. In addition, the author will discuss how physiological brain aging, which entails a progressive decline in cognitive functions, affects synapses and the degradative machinery.
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Affiliation(s)
- Marijn Kuijpers
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Straße 10, 13125 Berlin, Germany
- Department of Molecular Neurobiology, Donders Institute for Brain, Cognition and Behaviour and Faculty of Science, Radboud University, Nijmegen, The Netherlands
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4
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Deep-learning two-photon fiberscopy for video-rate brain imaging in freely-behaving mice. Nat Commun 2022; 13:1534. [PMID: 35318318 PMCID: PMC8940941 DOI: 10.1038/s41467-022-29236-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 03/01/2022] [Indexed: 01/04/2023] Open
Abstract
Scanning two-photon (2P) fiberscopes (also termed endomicroscopes) have the potential to transform our understanding of how discrete neural activity patterns result in distinct behaviors, as they are capable of high resolution, sub cellular imaging yet small and light enough to allow free movement of mice. However, their acquisition speed is currently suboptimal, due to opto-mechanical size and weight constraints. Here we demonstrate significant advances in 2P fiberscopy that allow high resolution imaging at high speeds (26 fps) in freely-behaving mice. A high-speed scanner and a down-sampling scheme are developed to boost imaging speed, and a deep learning (DL) algorithm is introduced to recover image quality. For the DL algorithm, a two-stage learning transfer strategy is established to generate proper training datasets for enhancing the quality of in vivo images. Implementation enables video-rate imaging at ~26 fps, representing 10-fold improvement in imaging speed over the previous 2P fiberscopy technology while maintaining a high signal-to-noise ratio and imaging resolution. This DL-assisted 2P fiberscope is capable of imaging the arousal-induced activity changes in populations of layer2/3 pyramidal neurons in the primary motor cortex of freely-behaving mice, providing opportunities to define the neural basis of behavior. The acquisition speed of two-photon fiberscopes is currently suboptimal. Here the authors report advances, including a high-speed scanner and down-sampling scheme as well as a two-stage deep learning (DL) algorithm, to allow high-speed, high-resolution imaging in freely moving mice.
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5
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Terashima H, Minatohara K, Maruoka H, Okabe S. Imaging neural circuit pathology of autism spectrum disorders: autism-associated genes, animal models and the application of in vivo two-photon imaging. Microscopy (Oxf) 2022; 71:i81-i99. [DOI: 10.1093/jmicro/dfab039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 09/11/2021] [Accepted: 11/08/2021] [Indexed: 11/12/2022] Open
Abstract
Abstract
Recent advances in human genetics identified genetic variants involved in causing autism spectrum disorders (ASDs). Mouse models that mimic mutations found in patients with ASD exhibit behavioral phenotypes consistent with ASD symptoms. These mouse models suggest critical biological factors of ASD etiology. Another important implication of ASD genetics is the enrichment of ASD risk genes in molecules involved in developing synapses and regulating neural circuit function. Sophisticated in vivo imaging technologies applied to ASD mouse models identify common synaptic impairments in the neocortex, with genetic-mutation-specific defects in local neural circuits. In this article, we review synapse- and circuit-level phenotypes identified by in vivo two-photon imaging in multiple mouse models of ASD and discuss the contributions of altered synapse properties and neural circuit activity to ASD pathogenesis.
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Affiliation(s)
- Hiroshi Terashima
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Keiichiro Minatohara
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hisato Maruoka
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shigeo Okabe
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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6
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Collins BE, Neul JL. Rett Syndrome and MECP2 Duplication Syndrome: Disorders of MeCP2 Dosage. Neuropsychiatr Dis Treat 2022; 18:2813-2835. [PMID: 36471747 PMCID: PMC9719276 DOI: 10.2147/ndt.s371483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 11/14/2022] [Indexed: 11/30/2022] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused predominantly by loss-of-function mutations in the gene Methyl-CpG-binding protein 2 (MECP2), which encodes the MeCP2 protein. RTT is a MECP2-related disorder, along with MECP2 duplication syndrome (MDS), caused by gain-of-function duplications of MECP2. Nearly two decades of research have advanced our knowledge of MeCP2 function in health and disease. The following review will discuss MeCP2 protein function and its dysregulation in the MECP2-related disorders RTT and MDS. This will include a discussion of the genetic underpinnings of these disorders, specifically how sporadic X-chromosome mutations arise and manifest in specific populations. We will then review current diagnostic guidelines and clinical manifestations of RTT and MDS. Next, we will delve into MeCP2 biology, describing the dual landscapes of methylated DNA and its reader MeCP2 across the neuronal genome as well as the function of MeCP2 as a transcriptional modulator. Following this, we will outline common MECP2 mutations and genotype-phenotype correlations in both diseases, with particular focus on mutations associated with relatively mild disease in RTT. We will also summarize decades of disease modeling and resulting molecular, synaptic, and behavioral phenotypes associated with RTT and MDS. Finally, we list several therapeutics in the development pipeline for RTT and MDS and available evidence of their safety and efficacy.
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Affiliation(s)
- Bridget E Collins
- Medical Scientist Training Program, Vanderbilt University, Nashville, TN, USA
| | - Jeffrey L Neul
- Vanderbilt Kennedy Center, Departments of Pediatrics, Pharmacology, and Special Education, Vanderbilt University Medical Center and Vanderbilt University, Nashville, TN, USA
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Yue Y, Xu P, Liu Z, Sun X, Su J, Du H, Chen L, Ash RT, Smirnakis S, Simha R, Kusner L, Zeng C, Lu H. Motor training improves coordination and anxiety in symptomatic Mecp2-null mice despite impaired functional connectivity within the motor circuit. SCIENCE ADVANCES 2021; 7:eabf7467. [PMID: 34678068 PMCID: PMC8535852 DOI: 10.1126/sciadv.abf7467] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 09/01/2021] [Indexed: 05/03/2023]
Abstract
Rett syndrome (RTT) is a severe neurodevelopmental disorder caused by loss of function of the X-linked methyl-CpG–binding protein 2 (MECP2). Several case studies report that gross motor function can be improved in children with RTT through treadmill walking, but whether the MeCP2-deficient motor circuit can support actual motor learning remains unclear. We used two-photon calcium imaging to simultaneously observe layer (L) 2/3 and L5a excitatory neuronal activity in the motor cortex (M1) while mice adapted to changing speeds on a computerized running wheel. Despite circuit hypoactivity and weakened functional connectivity across L2/3 and L5a, the Mecp2-null circuit’s firing pattern evolved with improved performance over 2 weeks. Moreover, trained mice became less anxious and lived 20% longer than untrained mice. Because motor deficits and anxiety are core symptoms of RTT, which is not diagnosed until well after symptom onset, these results underscore the benefit of motor learning.
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Affiliation(s)
- Yuanlei Yue
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Pan Xu
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Zhichao Liu
- Department of Physics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Xiaoqian Sun
- Department of Computer Science, School of Engineering and Applied Science, The George Washington University, Washington, DC 20037, USA
| | - Juntao Su
- Department of Statistics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Hongfei Du
- Department of Statistics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Lingling Chen
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Ryan T. Ash
- Department of Psychiatry, Stanford University, Palo Alto, CA 94305, USA
| | - Stelios Smirnakis
- Department of Neurology, Brigham and Women’s Hospital, Jamaica Plain VA Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Rahul Simha
- Department of Computer Science, School of Engineering and Applied Science, The George Washington University, Washington, DC 20037, USA
| | - Linda Kusner
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
| | - Chen Zeng
- Department of Physics, Columbian College of Arts and Sciences, The George Washington University, Washington, DC 20037, USA
| | - Hui Lu
- Department of Pharmacology and Physiology, School of Medicine and Health Sciences, The George Washington University, Washington, DC 20037, USA
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8
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Ash RT, Buffington SA, Park J, Suter B, Costa-Mattioli M, Zoghbi HY, Smirnakis SM. Inhibition of Elevated Ras-MAPK Signaling Normalizes Enhanced Motor Learning and Excessive Clustered Dendritic Spine Stabilization in the MECP2-Duplication Syndrome Mouse Model of Autism. eNeuro 2021; 8:ENEURO.0056-21.2021. [PMID: 34021030 PMCID: PMC8260274 DOI: 10.1523/eneuro.0056-21.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 04/06/2021] [Accepted: 04/07/2021] [Indexed: 12/26/2022] Open
Abstract
The inflexible repetitive behaviors and "insistence on sameness" seen in autism imply a defect in neural processes controlling the balance between stability and plasticity of synaptic connections in the brain. It has been proposed that abnormalities in the Ras-ERK/MAPK pathway, a key plasticity-related cell signaling pathway known to drive consolidation of clustered synaptic connections, underlie altered learning phenotypes in autism. However, a link between altered Ras-ERK signaling and clustered dendritic spine plasticity has yet to be explored in an autism animal model in vivo The formation and stabilization of dendritic spine clusters is abnormally increased in the MECP2-duplication syndrome mouse model of syndromic autism, suggesting that ERK signaling may be increased. Here, we show that the Ras-ERK pathway is indeed hyperactive following motor training in MECP2-duplication mouse motor cortex. Pharmacological inhibition of ERK signaling normalizes the excessive clustered spine stabilization and enhanced motor learning behavior in MECP2-duplication mice. We conclude that hyperactive ERK signaling may contribute to abnormal clustered dendritic spine consolidation and motor learning in this model of syndromic autism.
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Affiliation(s)
- Ryan Thomas Ash
- Department of Psychiatry and Behavioral Sciences, Stanford University, CA 94305
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Medical Scientist Training Program, Baylor College of Medicine, Houston, TX 77030
- Department of Neurology, Brigham and Women's Hospital and Jamaica Plain Veterans Administration Hospital, Harvard Medical School, Boston, MA 02115
| | - Shelly Alexandra Buffington
- Memory and Brain Research Center, Baylor College of Medicine, Houston, TX 77030
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX 77555
| | - Jiyoung Park
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Department of Neurology, Brigham and Women's Hospital and Jamaica Plain Veterans Administration Hospital, Harvard Medical School, Boston, MA 02115
| | - Bernhard Suter
- Department of Neurology, Brigham and Women's Hospital and Jamaica Plain Veterans Administration Hospital, Harvard Medical School, Boston, MA 02115
- Department of Pediatrics, Texas Children's Hospital and Baylor College of Medicine, Houston, TX 77030
| | - Mauro Costa-Mattioli
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Memory and Brain Research Center, Baylor College of Medicine, Houston, TX 77030
| | - Huda Yaya Zoghbi
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Department of Pediatrics, Texas Children's Hospital and Baylor College of Medicine, Houston, TX 77030
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
- Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX 77030
- Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030
| | - Stelios Manolis Smirnakis
- Department of Neurology, Brigham and Women's Hospital and Jamaica Plain Veterans Administration Hospital, Harvard Medical School, Boston, MA 02115
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9
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D'Mello SR. MECP2 and the Biology of MECP2 Duplication Syndrome. J Neurochem 2021; 159:29-60. [PMID: 33638179 DOI: 10.1111/jnc.15331] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/21/2021] [Accepted: 02/18/2021] [Indexed: 11/27/2022]
Abstract
MECP2 duplication syndrome (MDS), a rare X-linked genomic disorder affecting predominantly males, is caused by duplication of the chromosomal region containing the methyl CpG binding protein-2 (MECP2) gene, which encodes methyl-CpG-binding protein 2 (MECP2), a multi-functional protein required for proper brain development and maintenance of brain function during adulthood. Disease symptoms include severe motor and cognitive impairment, delayed or absent speech development, autistic features, seizures, ataxia, recurrent respiratory infections and shortened lifespan. The cellular and molecular mechanisms by which a relatively modest increase in MECP2 protein causes such severe disease symptoms are poorly understood and consequently there are no treatments available for this fatal disorder. This review summarizes what is known to date about the structure and complex regulation of MECP2 and its many functions in the developing and adult brain. Additionally, recent experimental findings on the cellular and molecular underpinnings of MDS based on cell culture and mouse models of the disorder are reviewed. The emerging picture from these studies is that MDS is a neurodegenerative disorder in which neurons die in specific parts of the central nervous system, including the cortex, hippocampus, cerebellum and spinal cord. Neuronal death likely results from astrocytic dysfunction, including a breakdown of glutamate homeostatic mechanisms. The role of elevations in the expression of glial acidic fibrillary protein (GFAP) in astrocytes and the microtubule-associated protein, Tau, in neurons to the pathogenesis of MDS is discussed. Lastly, potential therapeutic strategies to potentially treat MDS are discussed.
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10
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Ash RT, Park J, Suter B, Zoghbi HY, Smirnakis SM. Excessive Formation and Stabilization of Dendritic Spine Clusters in the MECP2-Duplication Syndrome Mouse Model of Autism. eNeuro 2021; 8:ENEURO.0282-20.2020. [PMID: 33168618 PMCID: PMC7877475 DOI: 10.1523/eneuro.0282-20.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/11/2020] [Accepted: 09/14/2020] [Indexed: 11/21/2022] Open
Abstract
Autism-associated genetic mutations may perturb the balance between stability and plasticity of synaptic connections in the brain. Here, we report an increase in the formation and stabilization of dendritic spines in the cerebral cortex of the mouse model of MECP2-duplication syndrome, a high-penetrance form of syndromic autism. Increased stabilization is mediated entirely by spines that form cooperatively in 10-μm clusters and is observable across multiple cortical areas both spontaneously and following motor training. Excessive stability of dendritic spine clusters could contribute to behavioral rigidity and other phenotypes in syndromic autism.
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Affiliation(s)
- Ryan Thomas Ash
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Medical Scientist Training Program, Baylor College of Medicine, Houston, TX 77030
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115
| | - Jiyoung Park
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115
| | - Bernhard Suter
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115
- Department of Pediatrics, Texas Children's Hospital and Baylor College of Medicine, Houston, TX 77030
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
| | - Huda Yaya Zoghbi
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Department of Pediatrics, Texas Children's Hospital and Baylor College of Medicine, Houston, TX 77030
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
- Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, TX 77030
- Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030
| | - Stelios Manolis Smirnakis
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115
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Liang W, Park HC, Li K, Li A, Chen D, Guan H, Yue Y, Gau YTA, Bergles DE, Li MJ, Lu H, Li X. Throughput-Speed Product Augmentation for Scanning Fiber-Optic Two-Photon Endomicroscopy. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:3779-3787. [PMID: 32746124 PMCID: PMC7773217 DOI: 10.1109/tmi.2020.3005067] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Compactness, among several others, is one unique and very attractive feature of a scanning fiber-optic two-photon endomicroscope. To increase the scanning area and the total number of resolvable pixels (i.e., the imaging throughput), it typically requires a longer cantilever which, however, leads to a much undesired, reduced scanning speed (and thus imaging frame rate). Herein we introduce a new design strategy for a fiber-optic scanning endomicroscope, where the overall numerical aperture (NA) or beam focusing power is distributed over two stages: 1) a mode-field focuser engineered at the tip of a double-clad fiber (DCF) cantilever to pre-amplify the single-mode core NA, and 2) a micro objective of a lower magnification (i.e., ∼ 2× in this design) to achieve final tight beam focusing. This new design enables either an ~9-fold increase in imaging area (throughput) or an ~3-fold improvement in imaging frame rate when compared to traditional fiber-optic endomicroscope designs. The performance of an as-designed endomicroscope of an enhanced throughput-speed product was demonstrated by two representative applications: (1) high-resolution imaging of an internal organ (i.e., mouse kidney) in vivo over a large field of view without using any fluorescent contrast agents, and (2) real-time neural imaging by visualizing dendritic calcium dynamics in vivo with sub-second temporal resolution in GCaMP6m-expressing mouse brain. This cascaded NA amplification strategy is universal and can be readily adapted to other types of fiber-optic scanners in compact linear or nonlinear endomicroscopes.
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12
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Gyertyán I. How can preclinical cognitive research further neuropsychiatric drug discovery? Chances and challenges. Expert Opin Drug Discov 2020; 15:659-670. [DOI: 10.1080/17460441.2020.1739645] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- István Gyertyán
- Cognitive Translational Behavioural Pharmacology Group, Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary
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13
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Lees RM, Johnson JD, Ashby MC. Presynaptic Boutons That Contain Mitochondria Are More Stable. Front Synaptic Neurosci 2020; 11:37. [PMID: 31998110 PMCID: PMC6966497 DOI: 10.3389/fnsyn.2019.00037] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 12/18/2019] [Indexed: 01/04/2023] Open
Abstract
The addition and removal of presynaptic terminals reconfigures neuronal circuits of the mammalian neocortex, but little is known about how this presynaptic structural plasticity is controlled. Since mitochondria can regulate presynaptic function, we investigated whether the presence of axonal mitochondria relates to the structural plasticity of presynaptic boutons in mouse neocortex. We found that the overall density of axonal mitochondria did not appear to influence the loss and gain of boutons. However, positioning of mitochondria at individual presynaptic sites did relate to increased stability of those boutons. In line with this, synaptic localization of mitochondria increased as boutons aged and showed differing patterns of localization at en passant and terminaux boutons. These results suggest that mitochondria accumulate locally at boutons over time to increase bouton stability.
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Affiliation(s)
| | | | - Michael C. Ashby
- School of Physiology, Pharmacology, and Neuroscience, Faculty of Biomedical Sciences, University of Bristol, Bristol, United Kingdom
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14
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Kastellakis G, Poirazi P. Synaptic Clustering and Memory Formation. Front Mol Neurosci 2019; 12:300. [PMID: 31866824 PMCID: PMC6908852 DOI: 10.3389/fnmol.2019.00300] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 11/25/2019] [Indexed: 01/12/2023] Open
Abstract
In the study of memory engrams, synaptic memory allocation is a newly emerged theme that focuses on how specific synapses are engaged in the storage of a given memory. Cumulating evidence from imaging and molecular experiments indicates that the recruitment of synapses that participate in the encoding and expression of memory is neither random nor uniform. A hallmark observation is the emergence of groups of synapses that share similar response properties and/or similar input properties and are located within a stretch of a dendritic branch. This grouping of synapses has been termed "synapse clustering" and has been shown to emerge in many different memory-related paradigms, as well as in in vitro studies. The clustering of synapses may emerge from synapses receiving similar input, or via many processes which allow for cross-talk between nearby synapses within a dendritic branch, leading to cooperative plasticity. Clustered synapses can act in concert to maximally exploit the nonlinear integration potential of the dendritic branches in which they reside. Their main contribution is to facilitate the induction of dendritic spikes and dendritic plateau potentials, which provide advanced computational and memory-related capabilities to dendrites and single neurons. This review focuses on recent evidence which investigates the role of synapse clustering in dendritic integration, sensory perception, learning, and memory as well as brain dysfunction. We also discuss recent theoretical work which explores the computational advantages provided by synapse clustering, leading to novel and revised theories of memory. As an eminent phenomenon during memory allocation, synapse clustering both shapes memory engrams and is also shaped by the parallel plasticity mechanisms upon which it relies.
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Affiliation(s)
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology Hellas (FORTH), Heraklion, Greece
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Banerjee A, Miller MT, Li K, Sur M, Kaufmann WE. Towards a better diagnosis and treatment of Rett syndrome: a model synaptic disorder. Brain 2019; 142:239-248. [PMID: 30649225 DOI: 10.1093/brain/awy323] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 10/31/2018] [Indexed: 12/21/2022] Open
Abstract
With the recent 50th anniversary of the first publication on Rett syndrome, and the almost 20 years since the first report on the link between Rett syndrome and MECP2 mutations, it is important to reflect on the tremendous advances in our understanding and their implications for the diagnosis and treatment of this neurodevelopmental disorder. Rett syndrome features an interesting challenge for biologists and clinicians, as the disorder lies at the intersection of molecular mechanisms of epigenetic regulation and neurophysiological alterations in synapses and circuits that together contribute to severe pathophysiological endophenotypes. Genetic, clinical, and neurobiological evidences support the notion that Rett syndrome is primarily a synaptic disorder, and a disease model for both intellectual disability and autism spectrum disorder. This review examines major developments in both recent neurobiological and preclinical findings of Rett syndrome, and to what extent they are beginning to impact our understanding and management of the disorder. It also discusses potential applications of knowledge on synaptic plasticity abnormalities in Rett syndrome to its diagnosis and treatment.
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Affiliation(s)
- Abhishek Banerjee
- Laboratory of Neural Circuit Dynamics, Brain Research Institute, University of Zürich, Zürich, Switzerland
| | - Meghan T Miller
- Roche Pharma Research and Early Development, Roche Innovation Center, F. Hoffman-La Roche, Basel, Switzerland
| | - Keji Li
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Mriganka Sur
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Walter E Kaufmann
- Department of Human Genetics, Emory University School of Medicine, Atlanta GA, USA
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