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Lakhani A, Huang W, Rodgers CC, Wenner P. Whisker deprivation triggers a distinct form of cortical homeostatic plasticity that is impaired in the Fmr1 KO. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.23.614487. [PMID: 39386532 PMCID: PMC11463509 DOI: 10.1101/2024.09.23.614487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/12/2024]
Abstract
Mouse models of Fragile X Syndrome (FXS) have demonstrated impairments in excitatory and inhibitory sensory-evoked neuronal firing. Homeostatic plasticity, which encompasses a set of mechanisms to stabilize baseline activity levels, does not compensate for these changes in activity. Previous work has shown that impairments in homeostatic plasticity are observed in FXS, including deficits in synaptic scaling and intrinsic excitability. Here, we aimed to examine how homeostatic plasticity is altered in vivo in an Fmr1 KO mouse model following unilateral whisker deprivation (WD). We show that WD in the wild type leads to an increase in the proportion of L5/6 somatosensory neurons that are recruited, but this does not occur in the KO. In addition, we observed a change in the threshold of excitatory neurons at a later developmental stage in the KO. Compromised homeostatic plasticity in development could influence sensory processing and long-term cortical organization.
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2
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Zhao R, Ren B, Xiao Y, Tian J, Zou Y, Wei J, Qi Y, Hu A, Xie X, Huang ZJ, Shu Y, He M, Lu J, Tai Y. Axo-axonic synaptic input drives homeostatic plasticity by tuning the axon initial segment structurally and functionally. SCIENCE ADVANCES 2024; 10:eadk4331. [PMID: 39093969 PMCID: PMC11296346 DOI: 10.1126/sciadv.adk4331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 06/27/2024] [Indexed: 08/04/2024]
Abstract
Homeostatic plasticity maintains the stability of functional brain networks. The axon initial segment (AIS), where action potentials start, undergoes dynamic adjustment to exert powerful control over neuronal firing properties in response to network activity changes. However, it is poorly understood whether this plasticity involves direct synaptic input to the AIS. Here, we show that changes of GABAergic synaptic input from chandelier cells (ChCs) drive homeostatic tuning of the AIS of principal neurons (PNs) in the prelimbic (PL) region, while those from parvalbumin-positive basket cells do not. This tuning is evident in AIS morphology, voltage-gated sodium channel expression, and PN excitability. Moreover, the impact of this homeostatic plasticity can be reflected in animal behavior. Social behavior, inversely linked to PL PN activity, shows time-dependent alterations tightly coupled to changes in AIS plasticity and PN excitability. Thus, AIS-originated homeostatic plasticity in PNs may counteract deficits elicited by imbalanced ChC presynaptic input at cellular and behavioral levels.
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Affiliation(s)
- Rui Zhao
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Baihui Ren
- Center for Brain Science of Shanghai Children’s Medical Center, Department of Anatomy and Physiology, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
| | - Yujie Xiao
- Department of Neurology, Huashan Hospital, Institute for Translational Brain Research, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, MOE Innovative Center for New Drug Development of Immune Inflammatory Diseases, Fudan University, Shanghai 200032, China
| | - Jifeng Tian
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Yi Zou
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Jiafan Wei
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Yanqing Qi
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Ankang Hu
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Xiaoying Xie
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Z. Josh Huang
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Biomedical Engineering, Duke University Pratt School of Engineering, Durham, NC 27708, USA
| | - Yousheng Shu
- Department of Neurology, Huashan Hospital, Institute for Translational Brain Research, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, MOE Innovative Center for New Drug Development of Immune Inflammatory Diseases, Fudan University, Shanghai 200032, China
| | - Miao He
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
| | - Jiangteng Lu
- Center for Brain Science of Shanghai Children’s Medical Center, Department of Anatomy and Physiology, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
- Songjiang Research Institute, Shanghai Songjiang District Central Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai 200025, China
| | - Yilin Tai
- Institutes of Brain Science, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Neurobiology, Zhongshan Hospital, Fudan University, Shanghai 200032, China
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3
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Zhao R, Ren B, Xiao Y, Tian J, Zou Y, Wei J, Qi Y, Hu A, Xie X, Huang ZJ, Shu Y, He M, Lu J, Tai Y. Axo-axonic synaptic input drives homeostatic plasticity by tuning the axon initial segment structurally and functionally. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.11.589005. [PMID: 38659885 PMCID: PMC11042219 DOI: 10.1101/2024.04.11.589005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The stability of functional brain network is maintained by homeostatic plasticity, which restores equilibrium following perturbation. As the initiation site of action potentials, the axon initial segment (AIS) of glutamatergic projection neurons (PyNs) undergoes dynamic adjustment that exerts powerful control over neuronal firing properties in response to changes in network states. Although AIS plasticity has been reported to be coupled with the changes of network activity, it is poorly understood whether it involves direct synaptic input to the AIS. Here we show that changes of GABAergic synaptic input to the AIS of cortical PyNs, specifically from chandelier cells (ChCs), are sufficient to drive homeostatic tuning of the AIS within 1-2 weeks, while those from parvalbumin-positive basket cells do not. This tuning is reflected in the morphology of the AIS, the expression level of voltage-gated sodium channels, and the intrinsic neuronal excitability of PyNs. Interestingly, the timing of AIS tuning in PyNs of the prefrontal cortex corresponds to the recovery of changes in social behavior caused by alterations of ChC synaptic transmission. Thus, homeostatic plasticity of the AIS at postsynaptic PyNs may counteract deficits elicited by imbalanced ChC presynaptic input. Teaser Axon initial segment dynamically responds to changes in local input from chandelier cells to prevent abnormal neuronal functions.
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4
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Abbasi DA, Berry-Kravis E, Zhao X, Cologna SM. Proteomics insights into fragile X syndrome: Unraveling molecular mechanisms and therapeutic avenues. Neurobiol Dis 2024; 194:106486. [PMID: 38548140 DOI: 10.1016/j.nbd.2024.106486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 03/08/2024] [Accepted: 03/25/2024] [Indexed: 04/02/2024] Open
Abstract
Fragile X Syndrome (FXS) is a neurodevelopment disorder characterized by cognitive impairment, behavioral challenges, and synaptic abnormalities, with a genetic basis linked to a mutation in the FMR1 (Fragile X Messenger Ribonucleoprotein 1) gene that results in a deficiency or absence of its protein product, Fragile X Messenger Ribonucleoprotein (FMRP). In recent years, mass spectrometry (MS) - based proteomics has emerged as a powerful tool to uncover the complex molecular landscape underlying FXS. This review provides a comprehensive overview of the proteomics studies focused on FXS, summarizing key findings with an emphasis on dysregulated proteins associated with FXS. These proteins span a wide range of cellular functions including, but not limited to, synaptic plasticity, RNA translation, and mitochondrial function. The work conducted in these proteomic studies provides a more holistic understanding to the molecular pathways involved in FXS and considerably enhances our knowledge into the synaptic dysfunction seen in FXS.
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Affiliation(s)
- Diana A Abbasi
- Departments of Pediatrics and Neurological Sciences, Rush University Medical Center, Chicago, IL 60612, United States of America
| | - Elizabeth Berry-Kravis
- Departments of Pediatrics and Neurological Sciences, Rush University Medical Center, Chicago, IL 60612, United States of America
| | - Xinyu Zhao
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705, United States of America
| | - Stephanie M Cologna
- Department of Chemistry, University of Illinois Chicago, Chicago, IL 60607, United States of America.
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5
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Yuan X, Puvogel S, van Rhijn JR, Ciptasari U, Esteve-Codina A, Meijer M, Rouschop S, van Hugte EJH, Oudakker A, Schoenmaker C, Frega M, Schubert D, Franke B, Nadif Kasri N. A human in vitro neuronal model for studying homeostatic plasticity at the network level. Stem Cell Reports 2023; 18:2222-2239. [PMID: 37863044 PMCID: PMC10679660 DOI: 10.1016/j.stemcr.2023.09.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 09/18/2023] [Accepted: 09/19/2023] [Indexed: 10/22/2023] Open
Abstract
Mechanisms that underlie homeostatic plasticity have been extensively investigated at single-cell levels in animal models, but are less well understood at the network level. Here, we used microelectrode arrays to characterize neuronal networks following induction of homeostatic plasticity in human induced pluripotent stem cell (hiPSC)-derived glutamatergic neurons co-cultured with rat astrocytes. Chronic suppression of neuronal activity through tetrodotoxin (TTX) elicited a time-dependent network re-arrangement. Increased expression of AMPA receptors and the elongation of axon initial segments were associated with increased network excitability following TTX treatment. Transcriptomic profiling of TTX-treated neurons revealed up-regulated genes related to extracellular matrix organization, while down-regulated genes related to cell communication; also astrocytic gene expression was found altered. Overall, our study shows that hiPSC-derived neuronal networks provide a reliable in vitro platform to measure and characterize homeostatic plasticity at network and single-cell levels; this platform can be extended to investigate altered homeostatic plasticity in brain disorders.
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Affiliation(s)
- Xiuming Yuan
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Sofía Puvogel
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Jon-Ruben van Rhijn
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Ummi Ciptasari
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Anna Esteve-Codina
- CNAG-CRG, Centre for Genomic Regulation, Barcelona Institute of Science and Technology, 08028 Barcelona, Spain; Universitat Pompeu Fabra (UPF), 08002 Barcelona, Spain
| | - Mandy Meijer
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Simon Rouschop
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Eline J H van Hugte
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Astrid Oudakker
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Chantal Schoenmaker
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Monica Frega
- Department of Clinical Neurophysiology, University of Twente, 7522 NB Enschede, the Netherlands
| | - Dirk Schubert
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Barbara Franke
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands; Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands
| | - Nael Nadif Kasri
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands; Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, 6500 HB Nijmegen, the Netherlands.
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6
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Marom S, Marder E. A biophysical perspective on the resilience of neuronal excitability across timescales. Nat Rev Neurosci 2023; 24:640-652. [PMID: 37620600 DOI: 10.1038/s41583-023-00730-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2023] [Indexed: 08/26/2023]
Abstract
Neuronal membrane excitability must be resilient to perturbations that can take place over timescales from milliseconds to months (or even years in long-lived animals). A great deal of attention has been paid to classes of homeostatic mechanisms that contribute to long-term maintenance of neuronal excitability through processes that alter a key structural parameter: the number of ion channel proteins present at the neuronal membrane. However, less attention has been paid to the self-regulating 'automatic' mechanisms that contribute to neuronal resilience by virtue of the kinetic properties of ion channels themselves. Here, we propose that these two sets of mechanisms are complementary instantiations of feedback control, together enabling resilience on a wide range of temporal scales. We further point to several methodological and conceptual challenges entailed in studying these processes - both of which involve enmeshed feedback control loops - and consider the consequences of these mechanisms of resilience.
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Affiliation(s)
- Shimon Marom
- Faculty of Medicine, Technion - Institute of Technology, Haifa, Israel.
| | - Eve Marder
- Biology Department, Brandeis University, Waltham, MA, USA.
- Volen National Center for Complex Systems, Brandeis University, Waltham, MA, USA.
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7
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Monday HR, Wang HC, Feldman DE. Circuit-level theories for sensory dysfunction in autism: convergence across mouse models. Front Neurol 2023; 14:1254297. [PMID: 37745660 PMCID: PMC10513044 DOI: 10.3389/fneur.2023.1254297] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Accepted: 08/14/2023] [Indexed: 09/26/2023] Open
Abstract
Individuals with autism spectrum disorder (ASD) exhibit a diverse range of behavioral features and genetic backgrounds, but whether different genetic forms of autism involve convergent pathophysiology of brain function is unknown. Here, we analyze evidence for convergent deficits in neural circuit function across multiple transgenic mouse models of ASD. We focus on sensory areas of neocortex, where circuit differences may underlie atypical sensory processing, a central feature of autism. Many distinct circuit-level theories for ASD have been proposed, including increased excitation-inhibition (E-I) ratio and hyperexcitability, hypofunction of parvalbumin (PV) interneuron circuits, impaired homeostatic plasticity, degraded sensory coding, and others. We review these theories and assess the degree of convergence across ASD mouse models for each. Behaviorally, our analysis reveals that innate sensory detection behavior is heightened and sensory discrimination behavior is impaired across many ASD models. Neurophysiologically, PV hypofunction and increased E-I ratio are prevalent but only rarely generate hyperexcitability and excess spiking. Instead, sensory tuning and other aspects of neural coding are commonly degraded and may explain impaired discrimination behavior. Two distinct phenotypic clusters with opposing neural circuit signatures are evident across mouse models. Such clustering could suggest physiological subtypes of autism, which may facilitate the development of tailored therapeutic approaches.
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Affiliation(s)
- Hannah R. Monday
- Department of Molecular and Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
| | | | - Daniel E. Feldman
- Department of Molecular and Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States
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8
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Valenti D, Vacca RA. Brain Mitochondrial Bioenergetics in Genetic Neurodevelopmental Disorders: Focus on Down, Rett and Fragile X Syndromes. Int J Mol Sci 2023; 24:12488. [PMID: 37569863 PMCID: PMC10419900 DOI: 10.3390/ijms241512488] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 07/31/2023] [Accepted: 08/04/2023] [Indexed: 08/13/2023] Open
Abstract
Mitochondria, far beyond their prominent role as cellular powerhouses, are complex cellular organelles active as central metabolic hubs that are capable of integrating and controlling several signaling pathways essential for neurological processes, including neurogenesis and neuroplasticity. On the other hand, mitochondria are themselves regulated from a series of signaling proteins to achieve the best efficiency in producing energy, in establishing a network and in performing their own de novo synthesis or clearance. Dysfunctions in signaling processes that control mitochondrial biogenesis, dynamics and bioenergetics are increasingly associated with impairment in brain development and involved in a wide variety of neurodevelopmental disorders. Here, we review recent evidence proving the emerging role of mitochondria as master regulators of brain bioenergetics, highlighting their control skills in brain neurodevelopment and cognition. We analyze, from a mechanistic point of view, mitochondrial bioenergetic dysfunction as causally interrelated to the origins of typical genetic intellectual disability-related neurodevelopmental disorders, such as Down, Rett and Fragile X syndromes. Finally, we discuss whether mitochondria can become therapeutic targets to improve brain development and function from a holistic perspective.
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Affiliation(s)
- Daniela Valenti
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), National Research Council (CNR), Via G. Amendola 122/O, 70126 Bari, Italy
| | - Rosa Anna Vacca
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), National Research Council (CNR), Via G. Amendola 122/O, 70126 Bari, Italy
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9
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Pellizzari S, Hu M, Amaral-Silva L, Saunders SE, Santin JM. Neuron populations use variable combinations of short-term feedback mechanisms to stabilize firing rate. PLoS Biol 2023; 21:e3001971. [PMID: 36689462 PMCID: PMC9894548 DOI: 10.1371/journal.pbio.3001971] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 02/02/2023] [Accepted: 12/19/2022] [Indexed: 01/24/2023] Open
Abstract
Neurons tightly regulate firing rate and a failure to do so leads to multiple neurological disorders. Therefore, a fundamental question in neuroscience is how neurons produce reliable activity patterns for decades to generate behavior. Neurons have built-in feedback mechanisms that allow them to monitor their output and rapidly stabilize firing rate. Most work emphasizes the role of a dominant feedback system within a neuronal population for the control of moment-to-moment firing. In contrast, we find that respiratory motoneurons use 2 activity-dependent controllers in unique combinations across cells, dynamic activation of an Na+ pump subtype, and rapid potentiation of Kv7 channels. Both systems constrain firing rate by reducing excitability for up to a minute after a burst of action potentials but are recruited by different cellular signals associated with activity, increased intracellular Na+ (the Na+ pump), and membrane depolarization (Kv7 channels). Individual neurons do not simply contain equal amounts of each system. Rather, neurons under strong control of the Na+ pump are weakly regulated by Kv7 enhancement and vice versa along a continuum. Thus, each motoneuron maintains its characteristic firing rate through a unique combination of the Na+ pump and Kv7 channels, which are dynamically regulated by distinct feedback signals. These results reveal a new organizing strategy for stable circuit output involving multiple fast activity sensors scaled inversely across a neuronal population.
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Affiliation(s)
- Sarah Pellizzari
- University of North Carolina at Greensboro, Greensboro, North Carolina, United States of America
| | - Min Hu
- University of North Carolina at Greensboro, Greensboro, North Carolina, United States of America
| | - Lara Amaral-Silva
- University of Missouri, Columbia, Missouri, United States of America
| | - Sandy E. Saunders
- University of Missouri, Columbia, Missouri, United States of America
| | - Joseph M. Santin
- University of Missouri, Columbia, Missouri, United States of America
- * E-mail:
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10
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Coordinated Regulation of CB1 Cannabinoid Receptors and Anandamide Metabolism Stabilizes Network Activity during Homeostatic Downscaling. eNeuro 2022; 9:ENEURO.0276-22.2022. [PMID: 36316118 PMCID: PMC9663203 DOI: 10.1523/eneuro.0276-22.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/20/2022] [Accepted: 09/28/2022] [Indexed: 12/24/2022] Open
Abstract
Neurons express overlapping homeostatic mechanisms to regulate synaptic function and network properties in response to perturbations of neuronal activity. Endocannabinoids (eCBs) are bioactive lipids synthesized in the postsynaptic compartments to regulate synaptic transmission, plasticity, and neuronal excitability primarily through retrograde activation of presynaptic cannabinoid receptor type 1 (CB1). The eCB system is well situated to regulate neuronal network properties and coordinate presynaptic and postsynaptic activity. However, the role of the eCB system in homeostatic adaptations to neuronal hyperactivity is unknown. To address this issue, we used Western blotting and targeted lipidomics to measure adaptations in eCB system to bicuculline (BCC)-induced chronic hyperexcitation in mature cultured rat cortical neurons, and used multielectrode array (MEA) recording and live-cell imaging of glutamate dynamics to test the effects of pharmacological manipulations of eCB on network activities. We show that BCC-induced chronic hyperexcitation triggers homeostatic downscaling and a coordinated adaptation to enhance tonic eCB signaling. Hyperexcitation triggers first the downregulation of fatty acid amide hydrolase (FAAH), the lipase that degrades the eCB anandamide, then an accumulation of anandamide and related metabolites, and finally a delayed upregulation of surface and total CB1. Additionally, we show that BCC-induced downregulation of surface AMPA-type glutamate receptors (AMPARs) and upregulation of CB1 occur through independent mechanisms. Finally, we show that endocannabinoids support baseline network activities before and after downscaling and is engaged to suppress network activity during adaptation to hyperexcitation. We discuss the implications of our findings in the context of downscaling and homeostatic regulation of in vitro oscillatory network activities.
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11
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Abstract
The human brain consumes five orders of magnitude more energy than the sun by unit of mass and time. This staggering bioenergetic cost serves mostly synaptic transmission and actin cytoskeleton dynamics. The peak of both brain bioenergetic demands and the age of onset for neurodevelopmental disorders is approximately 5 years of age. This correlation suggests that defects in the machinery that provides cellular energy would be causative and/or consequence of neurodevelopmental disorders. We explore this hypothesis from the perspective of the machinery required for the synthesis of the electron transport chain, an ATP-producing and NADH-consuming enzymatic cascade. The electron transport chain is constituted by nuclear- and mitochondrial-genome-encoded subunits. These subunits are synthesized by the 80S and the 55S ribosomes, which are segregated to the cytoplasm and the mitochondrial matrix, correspondingly. Mitochondrial protein synthesis by the 55S ribosome is the rate-limiting step in the synthesis of electron transport chain components, suggesting that mitochondrial protein synthesis is a bottleneck for tissues with high bionergetic demands. We discuss genetic defects in the human nuclear and mitochondrial genomes that affect these protein synthesis machineries and cause a phenotypic spectrum spanning autism spectrum disorders to neurodegeneration during neurodevelopment. We propose that dysregulated mitochondrial protein synthesis is a chief, yet understudied, causative mechanism of neurodevelopmental and behavioral disorders.
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12
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Flanagan K, Baradaran-Heravi A, Yin Q, Dao Duc K, Spradling AC, Greenblatt EJ. FMRP-dependent production of large dosage-sensitive proteins is highly conserved. Genetics 2022; 221:6613139. [PMID: 35731217 PMCID: PMC9339308 DOI: 10.1093/genetics/iyac094] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 06/07/2022] [Indexed: 12/01/2022] Open
Abstract
Mutations in FMR1 are the most common heritable cause of autism spectrum disorder. FMR1 encodes an RNA-binding protein, FMRP, which binds to long, autism-relevant transcripts and is essential for normal neuronal and ovarian development. In contrast to the prevailing model that FMRP acts to block translation elongation, we previously found that FMRP activates the translation initiation of large proteins in Drosophila oocytes. We now provide evidence that FMRP-dependent translation is conserved and occurs in the mammalian brain. Our comparisons of the mammalian cortex and Drosophila oocyte ribosome profiling data show that translation of FMRP-bound mRNAs decreases to a similar magnitude in FMRP-deficient tissues from both species. The steady-state levels of several FMRP targets were reduced in the Fmr1 KO mouse cortex, including a ∼50% reduction of Auts2, a gene implicated in an autosomal dominant autism spectrum disorder. To distinguish between effects on elongation and initiation, we used a novel metric to detect the rate-limiting ribosome stalling. We found no evidence that FMRP target protein production is governed by translation elongation rates. FMRP translational activation of large proteins may be critical for normal human development, as more than 20 FMRP targets including Auts2 are dosage sensitive and are associated with neurodevelopmental disorders caused by haploinsufficiency.
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Affiliation(s)
- Keegan Flanagan
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3 Canada.,Department of Mathematics, University of British Columbia, 1984 Mathematics Road, Vancouver, British Columbia, BC V6T 1Z2
| | - Alireza Baradaran-Heravi
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3 Canada
| | - Qi Yin
- Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution for Science, 3520 San Martin Dr., Baltimore, Maryland 21218 USA
| | - Khanh Dao Duc
- Department of Mathematics, University of British Columbia, 1984 Mathematics Road, Vancouver, British Columbia, BC V6T 1Z2
| | - Allan C Spradling
- Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution for Science, 3520 San Martin Dr., Baltimore, Maryland 21218 USA
| | - Ethan J Greenblatt
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia, V6T 1Z3 Canada.,Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution for Science, 3520 San Martin Dr., Baltimore, Maryland 21218 USA
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13
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Bülow P, Segal M, Bassell GJ. Mechanisms Driving the Emergence of Neuronal Hyperexcitability in Fragile X Syndrome. Int J Mol Sci 2022; 23:ijms23116315. [PMID: 35682993 PMCID: PMC9181819 DOI: 10.3390/ijms23116315] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 05/24/2022] [Accepted: 05/27/2022] [Indexed: 02/04/2023] Open
Abstract
Hyperexcitability is a shared neurophysiological phenotype across various genetic neurodevelopmental disorders, including Fragile X syndrome (FXS). Several patient symptoms are associated with hyperexcitability, but a puzzling feature is that their onset is often delayed until their second and third year of life. It remains unclear how and why hyperexcitability emerges in neurodevelopmental disorders. FXS is caused by the loss of FMRP, an RNA-binding protein which has many critical roles including protein synthesis-dependent and independent regulation of ion channels and receptors, as well as global regulation of protein synthesis. Here, we discussed recent literature uncovering novel mechanisms that may drive the progressive onset of hyperexcitability in the FXS brain. We discussed in detail how recent publications have highlighted defects in homeostatic plasticity, providing new insight on the FXS brain and suggest pharmacotherapeutic strategies in FXS and other neurodevelopmental disorders.
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Affiliation(s)
- Pernille Bülow
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Correspondence: (P.B.); (G.J.B.)
| | - Menahem Segal
- Department of Brain Science, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Gary J. Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Correspondence: (P.B.); (G.J.B.)
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14
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Liu X, Kumar V, Tsai NP, Auerbach BD. Hyperexcitability and Homeostasis in Fragile X Syndrome. Front Mol Neurosci 2022; 14:805929. [PMID: 35069112 PMCID: PMC8770333 DOI: 10.3389/fnmol.2021.805929] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/14/2021] [Indexed: 01/13/2023] Open
Abstract
Fragile X Syndrome (FXS) is a leading inherited cause of autism and intellectual disability, resulting from a mutation in the FMR1 gene and subsequent loss of its protein product FMRP. Despite this simple genetic origin, FXS is a phenotypically complex disorder with a range of physical and neurocognitive disruptions. While numerous molecular and cellular pathways are affected by FMRP loss, there is growing evidence that circuit hyperexcitability may be a common convergence point that can account for many of the wide-ranging phenotypes seen in FXS. The mechanisms for hyperexcitability in FXS include alterations to excitatory synaptic function and connectivity, reduced inhibitory neuron activity, as well as changes to ion channel expression and conductance. However, understanding the impact of FMR1 mutation on circuit function is complicated by the inherent plasticity in neural circuits, which display an array of homeostatic mechanisms to maintain activity near set levels. FMRP is also an important regulator of activity-dependent plasticity in the brain, meaning that dysregulated plasticity can be both a cause and consequence of hyperexcitable networks in FXS. This makes it difficult to separate the direct effects of FMR1 mutation from the myriad and pleiotropic compensatory changes associated with it, both of which are likely to contribute to FXS pathophysiology. Here we will: (1) review evidence for hyperexcitability and homeostatic plasticity phenotypes in FXS models, focusing on similarities/differences across brain regions, cell-types, and developmental time points; (2) examine how excitability and plasticity disruptions interact with each other to ultimately contribute to circuit dysfunction in FXS; and (3) discuss how these synaptic and circuit deficits contribute to disease-relevant behavioral phenotypes like epilepsy and sensory hypersensitivity. Through this discussion of where the current field stands, we aim to introduce perspectives moving forward in FXS research.
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Affiliation(s)
- Xiaopeng Liu
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science & Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Vipendra Kumar
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Nien-Pei Tsai
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Benjamin D. Auerbach
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science & Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- *Correspondence: Benjamin D. Auerbach
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15
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Razak KA, Binder DK, Ethell IM. Neural Correlates of Auditory Hypersensitivity in Fragile X Syndrome. Front Psychiatry 2021; 12:720752. [PMID: 34690832 PMCID: PMC8529206 DOI: 10.3389/fpsyt.2021.720752] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/16/2021] [Indexed: 01/20/2023] Open
Abstract
The mechanisms underlying the common association between autism spectrum disorders (ASD) and sensory processing disorders (SPD) are unclear, and treatment options to reduce atypical sensory processing are limited. Fragile X Syndrome (FXS) is a leading genetic cause of intellectual disability and ASD behaviors. As in most children with ASD, atypical sensory processing is a common symptom in FXS, frequently manifesting as sensory hypersensitivity. Auditory hypersensitivity is a highly debilitating condition in FXS that may lead to language delays, social anxiety and ritualized repetitive behaviors. Animal models of FXS, including Fmr1 knock out (KO) mouse, also show auditory hypersensitivity, providing a translation relevant platform to study underlying pathophysiological mechanisms. The focus of this review is to summarize recent studies in the Fmr1 KO mouse that identified neural correlates of auditory hypersensitivity. We review results of electroencephalography (EEG) recordings in the Fmr1 KO mice and highlight EEG phenotypes that are remarkably similar to EEG findings in humans with FXS. The EEG phenotypes associated with the loss of FMRP include enhanced resting EEG gamma band power, reduced cross frequency coupling, reduced sound-evoked synchrony of neural responses at gamma band frequencies, increased event-related potential amplitudes, reduced habituation of neural responses and increased non-phase locked power. In addition, we highlight the postnatal period when the EEG phenotypes develop and show a strong association of the phenotypes with enhanced matrix-metalloproteinase-9 (MMP-9) activity, abnormal development of parvalbumin (PV)-expressing inhibitory interneurons and reduced formation of specialized extracellular matrix structures called perineuronal nets (PNNs). Finally, we discuss how dysfunctions of inhibitory PV interneurons may contribute to cortical hyperexcitability and EEG abnormalities observed in FXS. Taken together, the studies reviewed here indicate that EEG recordings can be utilized in both pre-clinical studies and clinical trials, while at the same time, used to identify cellular and circuit mechanisms of dysfunction in FXS. New therapeutic approaches that reduce MMP-9 activity and restore functions of PV interneurons may succeed in reducing FXS sensory symptoms. Future studies should examine long-lasting benefits of developmental vs. adult interventions on sensory phenotypes.
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Affiliation(s)
- Khaleel A. Razak
- Department of Psychology, University of California, Riverside, Riverside, CA, United States
- Graduate Neuroscience Program, University of California, Riverside, Riverside, CA, United States
| | - Devin K. Binder
- Graduate Neuroscience Program, University of California, Riverside, Riverside, CA, United States
- Division of Biomedical Sciences and Graduate Biomedical Sciences Program, School of Medicine, University of California, Riverside, Riverside, CA, United States
| | - Iryna M. Ethell
- Graduate Neuroscience Program, University of California, Riverside, Riverside, CA, United States
- Division of Biomedical Sciences and Graduate Biomedical Sciences Program, School of Medicine, University of California, Riverside, Riverside, CA, United States
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16
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Mizusaki BEP, O'Donnell C. Neural circuit function redundancy in brain disorders. Curr Opin Neurobiol 2021; 70:74-80. [PMID: 34416675 PMCID: PMC8694099 DOI: 10.1016/j.conb.2021.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 06/17/2021] [Accepted: 07/14/2021] [Indexed: 02/07/2023]
Abstract
Redundancy is a ubiquitous property of the nervous system. This means that vastly different configurations of cellular and synaptic components can enable the same neural circuit functions. However, until recently, very little brain disorder research has considered the implications of this characteristic when designing experiments or interpreting data. Here, we first summarise the evidence for redundancy in healthy brains, explaining redundancy and three related sub-concepts: sloppiness, dependencies and multiple solutions. We then lay out key implications for brain disorder research, covering recent examples of redundancy effects in experimental studies on psychiatric disorders. Finally, we give predictions for future experiments based on these concepts.
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Affiliation(s)
- Beatriz E P Mizusaki
- Computational Neuroscience Unit, School of Computer Science, Electrical and Electronic Engineering, and Engineering Mathematics, University of Bristol, BS8 1UB, United Kingdom
| | - Cian O'Donnell
- Computational Neuroscience Unit, School of Computer Science, Electrical and Electronic Engineering, and Engineering Mathematics, University of Bristol, BS8 1UB, United Kingdom.
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17
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Zhou Z, He G, Zhang X, Lv X, Zhang X, Liu A, Xia S, Xie H, Dang R, Han L, Qi J, Meng Y, Yu S, Xie W, Jia Z. NGPF2 triggers synaptic scaling up through ALK-LIMK-cofilin-mediated mechanisms. Cell Rep 2021; 36:109515. [PMID: 34407403 DOI: 10.1016/j.celrep.2021.109515] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 03/26/2021] [Accepted: 07/21/2021] [Indexed: 02/07/2023] Open
Abstract
Synaptic scaling is an extensively studied form of homeostatic plasticity critically involved in various brain functions. Although it is accepted that synaptic scaling is expressed through the postsynaptic accumulation of AMPA receptors (AMPARs), the induction mechanism remains elusive. In this study, we show that TTX treatment induces rapid but transient release of the neurite growth-promoting factor 2 (NGPF2), and this release is necessary and sufficient for TTX-induced scaling up. In addition, we show that inhibition of the anaplastic lymphoma kinase (ALK)-LIMK-cofilin signaling pathway blocks TTX- and NGPF2-induced synaptic scaling up. Furthermore, we show that TTX-induced release of NGPF2 is protein synthesis dependent and requires fragile X mental retardation protein 1 (FMRP1). These results indicate that activity blockade induces NGPF2 synthesis and release to trigger synaptic scaling up through LIMK-cofilin-dependent actin reorganization, spine enlargement, and stabilization of AMPARs at the synapse.
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Affiliation(s)
- Zikai Zhou
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China; School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; Zhongshan Institute for Drug Discovery, the Institutes of Drug Discovery and Development, Chinese Academy of Sciences, Zhongshan, China; Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China.
| | - Guiqin He
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China; School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Xiaoyun Zhang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; Zhongshan Institute for Drug Discovery, the Institutes of Drug Discovery and Development, Chinese Academy of Sciences, Zhongshan, China
| | - Xin Lv
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiaolin Zhang
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - An Liu
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Shuting Xia
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China; Neurosciences & Mental Health, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
| | - Hao Xie
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Rui Dang
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Lifang Han
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Junxia Qi
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Yanghong Meng
- Neurosciences & Mental Health, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
| | - Shunying Yu
- Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei Xie
- School of Life Science and Technology, Southeast University, 2 Sipailou Road, Nanjing 210096, China
| | - Zhengping Jia
- Neurosciences & Mental Health, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada; Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
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18
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Subrahmanyam R, Dwivedi D, Rashid Z, Bonnycastle K, Cousin MA, Chattarji S. Reciprocal regulation of spontaneous synaptic vesicle fusion by Fragile X mental retardation protein and group I metabotropic glutamate receptors. J Neurochem 2021; 158:1094-1109. [PMID: 34327719 DOI: 10.1111/jnc.15484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 06/21/2021] [Accepted: 07/22/2021] [Indexed: 11/29/2022]
Abstract
Fragile X mental retardation protein (FMRP) is a neuronal protein mediating multiple functions, with its absence resulting in one of the most common monogenic causes of autism, Fragile X syndrome (FXS). Analyses of FXS pathophysiology have identified a range of aberrations in synaptic signaling pathways and plasticity associated with group I metabotropic glutamate (mGlu) receptors. These studies, however, have mostly focused on the post-synaptic functions of FMRP and mGlu receptor activation, and relatively little is known about their presynaptic effects. Neurotransmitter release is mediated via multiple forms of synaptic vesicle (SV) fusion, each of which contributes to specific neuronal functions. The impacts of mGlu receptor activation and loss of FMRP on these SV fusion events remain unexplored. Here we combined electrophysiological and fluorescence imaging analyses on primary hippocampal cultures prepared from an Fmr1 knockout (KO) rat model. Compared to wild-type (WT) hippocampal neurons, KO neurons displayed an increase in the frequency of spontaneous excitatory post-synaptic currents (sEPSCs), as well as spontaneous SV fusion events. Pharmacological activation of mGlu receptors in WT neurons caused a similar increase in spontaneous SV fusion and sEPSC frequency. Notably, this increase in SV fusion was not observed when spontaneous activity was blocked using the sodium channel antagonist tetrodotoxin. Importantly, the effect of mGlu receptor activation on spontaneous SV fusion was occluded in Fmr1 KO neurons. Together, our results reveal that FMRP represses spontaneous presynaptic SV fusion, whereas mGlu receptor activation increases this event. This reciprocal control appears to be mediated via their regulation of intrinsic neuronal excitability.
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Affiliation(s)
- Rohini Subrahmanyam
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India
| | - Deepanjali Dwivedi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India
| | - Zubin Rashid
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India
| | - Katherine Bonnycastle
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK.,The Patrick Wild Centre, University of Edinburgh, Edinburgh, UK.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK.,The Patrick Wild Centre, University of Edinburgh, Edinburgh, UK.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Sumantra Chattarji
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, India.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK.,The Patrick Wild Centre, University of Edinburgh, Edinburgh, UK.,Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bengaluru, India
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19
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Bülow P, Wenner PA, Faundez V, Bassell GJ. Mitochondrial Structure and Polarity in Dendrites and the Axon Initial Segment Are Regulated by Homeostatic Plasticity and Dysregulated in Fragile X Syndrome. Front Cell Dev Biol 2021; 9:702020. [PMID: 34350185 PMCID: PMC8327182 DOI: 10.3389/fcell.2021.702020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/14/2021] [Indexed: 12/21/2022] Open
Abstract
Mitochondrial dysfunction has long been overlooked in neurodevelopmental disorders, but recent studies have provided new links to genetic forms of autism, including Rett syndrome and fragile X syndrome (FXS). Mitochondria show plasticity in morphology and function in response to neuronal activity, and previous research has reported impairments in mitochondrial morphology and function in disease. We and others have previously reported abnormalities in distinct types of homeostatic plasticity in FXS. It remains unknown if or how activity deprivation triggering homeostatic plasticity affects mitochondria in axons and/or dendrites and whether impairments occur in neurodevelopmental disorders. Here, we test the hypothesis that mitochondria are structurally and functionally modified in a compartment-specific manner during homeostatic plasticity using a model of activity deprivation in cortical neurons from wild-type mice and that this plasticity-induced regulation is altered in Fmr1-knockout (KO) neurons. We uncovered dendrite-specific regulation of the mitochondrial surface area, whereas axon initial segment (AIS) mitochondria show changes in polarity; both responses are lost in the Fmr1 KO. Taken together, our results demonstrate impairments in mitochondrial plasticity in FXS, which has not previously been reported. These results suggest that mitochondrial dysregulation in FXS could contribute to abnormal neuronal plasticity, with broader implications to other neurodevelopmental disorders and therapeutic strategies.
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Affiliation(s)
- Pernille Bülow
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Peter A Wenner
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Victor Faundez
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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20
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Booker SA, Kind PC. Mechanisms regulating input-output function and plasticity of neurons in the absence of FMRP. Brain Res Bull 2021; 175:69-80. [PMID: 34245842 DOI: 10.1016/j.brainresbull.2021.06.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 06/13/2021] [Accepted: 06/29/2021] [Indexed: 12/12/2022]
Abstract
The function of brain circuits relies on high-fidelity information transfer within neurons. Synaptic inputs arrive primarily at dendrites, where they undergo integration and summation throughout the somatodendritic domain, ultimately leading to the generation of precise patterns of action potentials. Emerging evidence suggests that the ability of neurons to transfer synaptic information and modulate their output is impaired in a number of neurodevelopmental disorders including Fragile X Syndrome. In this review we summarise recent findings that have revealed the pathophysiological and plasticity mechanisms that alter the ability of neurons in sensory and limbic circuits to reliably code information in the absence of FMRP. We examine which aspects of this transform may result directly from the loss of FMRP and those that a result from compensatory or homeostatic alterations to neuronal function. Dissection of the mechanisms leading to altered input-output function of neurons in the absence of FMRP and their effects on regulating neuronal plasticity throughout development could have important implications for potential therapies for Fragile X Syndrome, including directing the timing and duration of different treatment options.
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Affiliation(s)
- Sam A Booker
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK; Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.
| | - Peter C Kind
- Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK; Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK; Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK; National Centre for Biological Sciences (NCBS), Bangalore, India.
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21
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Ellingford RA, Panasiuk MJ, de Meritens ER, Shaunak R, Naybour L, Browne L, Basson MA, Andreae LC. Cell-type-specific synaptic imbalance and disrupted homeostatic plasticity in cortical circuits of ASD-associated Chd8 haploinsufficient mice. Mol Psychiatry 2021; 26:3614-3624. [PMID: 33837267 PMCID: PMC8505247 DOI: 10.1038/s41380-021-01070-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 02/28/2021] [Accepted: 03/19/2021] [Indexed: 12/11/2022]
Abstract
Heterozygous mutation of chromodomain helicase DNA binding protein 8 (CHD8) is strongly associated with autism spectrum disorder (ASD) and results in dysregulated expression of neurodevelopmental and synaptic genes during brain development. To reveal how these changes affect ASD-associated cortical circuits, we studied synaptic transmission in the prefrontal cortex of a haploinsufficient Chd8 mouse model. We report profound alterations to both excitatory and inhibitory synaptic transmission onto deep layer projection neurons, resulting in a reduced excitatory:inhibitory balance, which were found to vary dynamically across neurodevelopment and result from distinct effects of reduced Chd8 expression within individual neuronal subtypes. These changes were associated with disrupted regulation of homeostatic plasticity mechanisms operating via spontaneous neurotransmission. These findings therefore directly implicate CHD8 mutation in the disruption of ASD-relevant circuits in the cortex.
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Affiliation(s)
- Robert A Ellingford
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
- Centre for Craniofacial & Regenerative Biology, King's College London, London, UK
| | - Martyna J Panasiuk
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
- MRC Centre for Neurodevelopmental Disorders, King's College London, London, UK
| | - Emilie Rabesahala de Meritens
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Raghav Shaunak
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Liam Naybour
- Centre for Craniofacial & Regenerative Biology, King's College London, London, UK
| | - Lorcan Browne
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - M Albert Basson
- Centre for Craniofacial & Regenerative Biology, King's College London, London, UK.
- MRC Centre for Neurodevelopmental Disorders, King's College London, London, UK.
| | - Laura C Andreae
- Centre for Developmental Neurobiology, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK.
- MRC Centre for Neurodevelopmental Disorders, King's College London, London, UK.
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22
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Brighi C, Salaris F, Soloperto A, Cordella F, Ghirga S, de Turris V, Rosito M, Porceddu PF, D’Antoni C, Reggiani A, Rosa A, Di Angelantonio S. Novel fragile X syndrome 2D and 3D brain models based on human isogenic FMRP-KO iPSCs. Cell Death Dis 2021; 12:498. [PMID: 33993189 PMCID: PMC8124071 DOI: 10.1038/s41419-021-03776-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 04/26/2021] [Accepted: 04/28/2021] [Indexed: 02/04/2023]
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder, characterized by intellectual disability and sensory deficits, caused by epigenetic silencing of the FMR1 gene and subsequent loss of its protein product, fragile X mental retardation protein (FMRP). Delays in synaptic and neuronal development in the cortex have been reported in FXS mouse models; however, the main goal of translating lab research into pharmacological treatments in clinical trials has been so far largely unsuccessful, leaving FXS a still incurable disease. Here, we generated 2D and 3D in vitro human FXS model systems based on isogenic FMR1 knock-out mutant and wild-type human induced pluripotent stem cell (hiPSC) lines. Phenotypical and functional characterization of cortical neurons derived from FMRP-deficient hiPSCs display altered gene expression and impaired differentiation when compared with the healthy counterpart. FXS cortical cultures show an increased number of GFAP positive cells, likely astrocytes, increased spontaneous network activity, and depolarizing GABAergic transmission. Cortical brain organoid models show an increased number of glial cells, and bigger organoid size. Our findings demonstrate that FMRP is required to correctly support neuronal and glial cell proliferation, and to set the correct excitation/inhibition ratio in human brain development.
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Affiliation(s)
- Carlo Brighi
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Physiology and Pharmacology, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Federico Salaris
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Biology and Biotechnologies “Charles Darwin”, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Alessandro Soloperto
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy
| | - Federica Cordella
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Physiology and Pharmacology, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Silvia Ghirga
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Physics, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Valeria de Turris
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy
| | - Maria Rosito
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy
| | - Pier Francesca Porceddu
- grid.25786.3e0000 0004 1764 2907D3 Validation Research Line, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Chiara D’Antoni
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Physiology and Pharmacology, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Angelo Reggiani
- grid.25786.3e0000 0004 1764 2907D3 Validation Research Line, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Alessandro Rosa
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Biology and Biotechnologies “Charles Darwin”, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
| | - Silvia Di Angelantonio
- grid.25786.3e0000 0004 1764 2907Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161 Rome, Italy ,grid.7841.aDepartment of Physiology and Pharmacology, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy
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23
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Heavner WE, Lautz JD, Speed HE, Gniffke EP, Immendorf KB, Welsh JP, Baertsch NA, Smith SEP. Remodeling of the Homer-Shank interactome mediates homeostatic plasticity. Sci Signal 2021; 14:14/681/eabd7325. [PMID: 33947797 DOI: 10.1126/scisignal.abd7325] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Neurons maintain stable levels of excitability using homeostatic synaptic scaling, which adjusts the strength of a neuron's postsynaptic inputs to compensate for extended changes in overall activity. Here, we investigated whether prolonged changes in activity affect network-level protein interactions at the synapse. We assessed a glutamatergic synapse protein interaction network (PIN) composed of 380 binary associations among 21 protein members in mouse neurons. Manipulating the activation of cultured mouse cortical neurons induced widespread bidirectional PIN alterations that reflected rapid rearrangements of glutamate receptor associations involving synaptic scaffold remodeling. Sensory deprivation of the barrel cortex in live mice (by whisker trimming) caused specific PIN rearrangements, including changes in the association between the glutamate receptor mGluR5 and the kinase Fyn. These observations are consistent with emerging models of experience-dependent plasticity involving multiple types of homeostatic responses. However, mice lacking Homer1 or Shank3B did not undergo normal PIN rearrangements, suggesting that the proteins encoded by these autism spectrum disorder-linked genes serve as structural hubs for synaptic homeostasis. Our approach demonstrates how changes in the protein content of synapses during homeostatic plasticity translate into functional PIN alterations that mediate changes in neuron excitability.
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Affiliation(s)
- Whitney E Heavner
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Jonathan D Lautz
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Haley E Speed
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Edward P Gniffke
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Karen B Immendorf
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - John P Welsh
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA.,Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98195, USA.,University of Washington Autism Center, Seattle, WA 98195, USA.,Graduate Program in Neuroscience, University of Washington, Seattle, WA 98195, USA
| | - Nathan A Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA.,Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Stephen E P Smith
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA. .,Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98195, USA.,Graduate Program in Neuroscience, University of Washington, Seattle, WA 98195, USA
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24
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Bülow P, Zlatic SA, Wenner PA, Bassell GJ, Faundez V. FMRP attenuates activity dependent modifications in the mitochondrial proteome. Mol Brain 2021; 14:75. [PMID: 33931071 PMCID: PMC8086361 DOI: 10.1186/s13041-021-00783-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 04/21/2021] [Indexed: 12/21/2022] Open
Abstract
Homeostatic plasticity is necessary for the construction and maintenance of functional neuronal networks, but principal molecular mechanisms required for or modified by homeostatic plasticity are not well understood. We recently reported that homeostatic plasticity induced by activity deprivation is dysregulated in cortical neurons from Fragile X Mental Retardation protein (FMRP) knockout mice (Bulow et al. in Cell Rep 26: 1378-1388 e1373, 2019). These findings led us to hypothesize that identifying proteins sensitive to activity deprivation and/or FMRP expression could reveal pathways required for or modified by homeostatic plasticity. Here, we report an unbiased quantitative mass spectrometry used to quantify steady-state proteome changes following chronic activity deprivation in wild type and Fmr1-/y cortical neurons. Proteome hits responsive to both activity deprivation and the Fmr1-/y genotype were significantly annotated to mitochondria. We found an increased number of mitochondria annotated proteins whose expression was sensitive to activity deprivation in Fmr1-/y cortical neurons as compared to wild type neurons. These findings support a novel role of FMRP in attenuating mitochondrial proteome modifications induced by activity deprivation.
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Affiliation(s)
- Pernille Bülow
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Stephanie A Zlatic
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Peter A Wenner
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
| | - Victor Faundez
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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25
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Vandenberg GG, Dawson NJ, Head A, Scott GR, Scott AL. Astrocyte-mediated disruption of ROS homeostasis in Fragile X mouse model. Neurochem Int 2021; 146:105036. [PMID: 33785420 DOI: 10.1016/j.neuint.2021.105036] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 03/03/2021] [Accepted: 03/22/2021] [Indexed: 12/19/2022]
Abstract
Astrocytes, glial cells within the brain, work to protect neurons during high levels of activity by maintaining oxidative homeostasis via regulation of energy supply and antioxidant systems. In recent years, mitochondrial dysfunction has been highlighted as an underlying factor of pathology in many neurological disorders. In animal studies of Fragile X Syndrome (FXS), the leading genetic cause of autism, higher levels of reactive oxygen species, lipid peroxidation, and protein oxidation within the brain indicates that mitochondria function is also altered in FXS. Despite their integral contribution to redox homeostasis within the CNS, the role of astrocytes on the occurrence or progression of neurodevelopmental disorders in this way is rarely considered. This study specifically examines changes to astrocyte mitochondrial function and antioxidant expression that may occur in FXS. Using the Fmr1 knockout (KO) mouse model, mitochondrial respiration and reactive oxygen species (ROS) emission were analyzed in primary cortical astrocytes. While mitochondrial respiration was similar between genotypes, ROS emission was significantly elevated in Fmr1 KO astrocytes. Notably, NADPH-oxidase 2 expression in Fmr1 KO astrocytes was also enhanced but only changes in catalase antioxidant enzyme expression were noted. Characterization of astrocyte factors involved in redox imbalance is invaluable to uncovering potential sources of oxidative stress in neurodevelopmental disorders and more specifically, the intercellular mechanisms that contribute to dysfunction in FXS.
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Affiliation(s)
- Gregory G Vandenberg
- Department of Pathology and Molecular Medicine, McMaster University, 1200 Main St. West, Hamilton, Ontario, L8N 3Z5, Canada
| | - Neal J Dawson
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, L8S 4K1, Canada
| | - Alison Head
- Department of Pathology and Molecular Medicine, McMaster University, 1200 Main St. West, Hamilton, Ontario, L8N 3Z5, Canada
| | - Graham R Scott
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, L8S 4K1, Canada
| | - Angela L Scott
- Department of Pathology and Molecular Medicine, McMaster University, 1200 Main St. West, Hamilton, Ontario, L8N 3Z5, Canada.
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26
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Jiménez JA, Ptacek TS, Tuttle AH, Schmid RS, Moy SS, Simon JM, Zylka MJ. Chd8 haploinsufficiency impairs early brain development and protein homeostasis later in life. Mol Autism 2020; 11:74. [PMID: 33023670 PMCID: PMC7537101 DOI: 10.1186/s13229-020-00369-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 08/07/2020] [Indexed: 12/26/2022] Open
Abstract
Background Chromodomain helicase DNA-binding protein 8 (Chd8) is a high-confidence risk gene for autism spectrum disorder (ASD). However, how Chd8 haploinsufficiency impairs gene expression in the brain and impacts behavior at different stages of life is unknown. Methods We generated a mutant mouse line with an ASD-linked loss-of-function mutation in Chd8 (V986*; stop codon mutation). We examined the behavior of Chd8 mutant mice along with transcriptional changes in the cerebral cortex as a function of age, with a focus on one embryonic (E14.5) and three postnatal ages (1, 6, and 12 months). Results Chd8V986*/+ mutant mice displayed macrocephaly, reduced rearing responses and reduced center time in the open field, and enhanced social novelty preference. Behavioral phenotypes were more evident in Chd8V986*/+ mutant mice at 1 year of age. Pup survival was reduced in wild-type x Chd8V986*/+ crosses when the mutant parent was female. Transcriptomic analyses indicated that pathways associated with synaptic and neuronal projections and sodium channel activity were reduced in the cortex of embryonic Chd8V986*/+ mice and then equalized relative to wild-type mice in the postnatal period. At 12 months of age, expression of genes associated with endoplasmic reticulum (ER) stress, chaperone-mediated protein folding, and the unfolded protein response (UPR) were reduced in Chd8V986*/+ mice, whereas genes associated with the c-MET signaling pathway were increased in expression. Limitations It is unclear whether the transcriptional changes observed with age in Chd8V986*/+ mice reflect a direct effect of CHD8-regulated gene expression, or if CHD8 indirectly affects the expression of UPR/ER stress genes in adult mice as a consequence of neurodevelopmental abnormalities. Conclusions Collectively, these data suggest that UPR/ER stress pathways are reduced in the cerebral cortex of aged Chd8V986*/+ mice. Our study uncovers neurodevelopmental and age-related phenotypes in Chd8V986*/+ mice and highlights the importance of controlling for age when studying Chd8 haploinsufficient mice.
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Affiliation(s)
- Jessica A Jiménez
- Curriculum in Toxicology & Environmental Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Travis S Ptacek
- UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Carolina Institute for Developmental Disabilities, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Alex H Tuttle
- UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Carolina Institute for Developmental Disabilities, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Ralf S Schmid
- UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Sheryl S Moy
- Carolina Institute for Developmental Disabilities, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Department of Psychiatry, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Jeremy M Simon
- UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Carolina Institute for Developmental Disabilities, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Department of Genetics, The University of North Carolina at Chapel Hill, Campus Box #7264, Chapel Hill, NC, 27599, USA
| | - Mark J Zylka
- UNC Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA. .,Carolina Institute for Developmental Disabilities, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA. .,Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
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27
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Booker SA, Simões de Oliveira L, Anstey NJ, Kozic Z, Dando OR, Jackson AD, Baxter PS, Isom LL, Sherman DL, Hardingham GE, Brophy PJ, Wyllie DJ, Kind PC. Input-Output Relationship of CA1 Pyramidal Neurons Reveals Intact Homeostatic Mechanisms in a Mouse Model of Fragile X Syndrome. Cell Rep 2020; 32:107988. [PMID: 32783927 PMCID: PMC7435362 DOI: 10.1016/j.celrep.2020.107988] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 04/01/2020] [Accepted: 07/14/2020] [Indexed: 12/13/2022] Open
Abstract
Cellular hyperexcitability is a salient feature of fragile X syndrome animal models. The cellular basis of hyperexcitability and how it responds to changing activity states is not fully understood. Here, we show increased axon initial segment length in CA1 of the Fmr1-/y mouse hippocampus, with increased cellular excitability. This change in length does not result from reduced AIS plasticity, as prolonged depolarization induces changes in AIS length independent of genotype. However, depolarization does reduce cellular excitability, the magnitude of which is greater in Fmr1-/y neurons. Finally, we observe reduced functional inputs from the entorhinal cortex, with no genotypic difference in the firing rates of CA1 pyramidal neurons. This suggests that AIS-dependent hyperexcitability in Fmr1-/y mice may result from adaptive or homeostatic regulation induced by reduced functional synaptic connectivity. Thus, while AIS length and intrinsic excitability contribute to cellular hyperexcitability, they may reflect a homeostatic mechanism for reduced synaptic input onto CA1 neurons.
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Affiliation(s)
- Sam A. Booker
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Corresponding author
| | - Laura Simões de Oliveira
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK
| | - Natasha J. Anstey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Zrinko Kozic
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Owen R. Dando
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Dementia Research Institute, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Adam D. Jackson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Paul S. Baxter
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Dementia Research Institute, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Lori L. Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109-5632, USA
| | - Diane L. Sherman
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Giles E. Hardingham
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Dementia Research Institute, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Peter J. Brophy
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - David J.A. Wyllie
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Peter C. Kind
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India,Corresponding author
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28
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Homeostatic Recovery of Embryonic Spinal Activity Initiated by Compensatory Changes in Resting Membrane Potential. eNeuro 2020; 7:ENEURO.0526-19.2020. [PMID: 32540879 PMCID: PMC7340840 DOI: 10.1523/eneuro.0526-19.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 05/08/2020] [Accepted: 05/22/2020] [Indexed: 01/20/2023] Open
Abstract
When baseline activity in a neuronal network is modified by external challenges, a set of mechanisms is prompted to homeostatically restore activity levels. These homeostatic mechanisms are thought to be profoundly important in the maturation of the network. It has been shown that blockade of either excitatory GABAergic or glutamatergic transmission in the living chick embryo transiently blocks the movements generated by spontaneous network activity (SNA) in the spinal cord. However, the embryonic movements then begin to recover by 2 h and are completely restored by 12 h of persistent receptor blockade. It remains unclear what mechanisms mediate this early recovery (first hours) after neurotransmitter blockade, or even if the same mechanisms are triggered following GABAergic and glutamatergic antagonists. Here we find two distinct mechanisms that could underlie this homeostatic recovery. First, we see a highly robust compensatory mechanism observed shortly after neurotransmitter receptor blockade. In the first 2 h of GABAergic or glutamatergic blockade in vitro, there was a clear depolarization of resting membrane potential (RMP) in both motoneurons and interneurons. These changes reduced threshold current and were observed in the continued presence of the antagonist. Therefore, it appears that fast changes in RMP represent a key fast homeostatic mechanism for the maintenance of network activity. Second, we see a less consistent compensatory change in the absolute threshold voltage in the first several hours of in vitro and in vivo neurotransmitter blockade. These mechanisms likely contribute to the homeostatic recovery of embryonic movements following neurotransmitter blockade.
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29
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Das Sharma S, Pal R, Reddy BK, Selvaraj BT, Raj N, Samaga KK, Srinivasan DJ, Ornelas L, Sareen D, Livesey MR, Bassell GJ, Svendsen CN, Kind PC, Chandran S, Chattarji S, Wyllie DJA. Cortical neurons derived from human pluripotent stem cells lacking FMRP display altered spontaneous firing patterns. Mol Autism 2020; 11:52. [PMID: 32560741 PMCID: PMC7304215 DOI: 10.1186/s13229-020-00351-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 05/11/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Fragile X syndrome (FXS), a neurodevelopmental disorder, is a leading monogenetic cause of intellectual disability and autism spectrum disorder. Notwithstanding the extensive studies using rodent and other pre-clinical models of FXS, which have provided detailed mechanistic insights into the pathophysiology of this disorder, it is only relatively recently that human stem cell-derived neurons have been employed as a model system to further our understanding of the pathophysiological events that may underlie FXS. Our study assesses the physiological properties of human pluripotent stem cell-derived cortical neurons lacking fragile X mental retardation protein (FMRP). METHODS Electrophysiological whole-cell voltage- and current-clamp recordings were performed on two control and three FXS patient lines of human cortical neurons derived from induced pluripotent stem cells. In addition, we also describe the properties of an isogenic pair of lines in one of which FMR1 gene expression has been silenced. RESULTS Neurons lacking FMRP displayed bursts of spontaneous action potential firing that were more frequent but shorter in duration compared to those recorded from neurons expressing FMRP. Inhibition of large conductance Ca2+-activated K+ currents and the persistent Na+ current in control neurons phenocopies action potential bursting observed in neurons lacking FMRP, while in neurons lacking FMRP pharmacological potentiation of voltage-dependent Na+ channels phenocopies action potential bursting observed in control neurons. Notwithstanding the changes in spontaneous action potential firing, we did not observe any differences in the intrinsic properties of neurons in any of the lines examined. Moreover, we did not detect any differences in the properties of miniature excitatory postsynaptic currents in any of the lines. CONCLUSIONS Pharmacological manipulations can alter the action potential burst profiles in both control and FMRP-null human cortical neurons, making them appear like their genetic counterpart. Our studies indicate that FMRP targets that have been found in rodent models of FXS are also potential targets in a human-based model system, and we suggest potential mechanisms by which activity is altered.
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Affiliation(s)
- Shreya Das Sharma
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India.,The University of Trans-Displinary Health Sciences and Technology, Bangalore, 560064, India
| | - Rakhi Pal
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India
| | - Bharath Kumar Reddy
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India
| | - Bhuvaneish T Selvaraj
- Centre for Clinical Brain Sciences, University of Edinburgh, Chancellor's Building, Edinburgh, EH16 4SB, UK.,UK Dementia Research Institute at the University of Edinburgh, Edinburgh Medical School, Chancellor's Building, Edinburgh, EH16 4SB, UK
| | - Nisha Raj
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Krishna Kumar Samaga
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India
| | - Durga J Srinivasan
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India.,The University of Trans-Displinary Health Sciences and Technology, Bangalore, 560064, India
| | - Loren Ornelas
- The Board of Governors Regenerative Medicine Institute and Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA.,iPSC Core, The David Janet Polak Foundation Stem Cell Core Laboratory, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA.,Cedars-Sinai Biomanufacturing Center, West Hollywood, CA, 90069, USA
| | - Dhruv Sareen
- The Board of Governors Regenerative Medicine Institute and Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA.,iPSC Core, The David Janet Polak Foundation Stem Cell Core Laboratory, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA.,Cedars-Sinai Biomanufacturing Center, West Hollywood, CA, 90069, USA.,Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA
| | - Matthew R Livesey
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Clive N Svendsen
- The Board of Governors Regenerative Medicine Institute and Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA.,Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA
| | - Peter C Kind
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India.,Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK.,Patrick Wild Centre, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK
| | - Siddharthan Chandran
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India.,Centre for Clinical Brain Sciences, University of Edinburgh, Chancellor's Building, Edinburgh, EH16 4SB, UK.,UK Dementia Research Institute at the University of Edinburgh, Edinburgh Medical School, Chancellor's Building, Edinburgh, EH16 4SB, UK.,Patrick Wild Centre, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK
| | - Sumantra Chattarji
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India. .,Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK. .,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK. .,National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, 560065, India.
| | - David J A Wyllie
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, Bangalore, 560065, India. .,Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK. .,Patrick Wild Centre, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK. .,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, Edinburgh, EH8 9XD, UK.
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30
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Nguyen AO, Binder DK, Ethell IM, Razak KA. Abnormal development of auditory responses in the inferior colliculus of a mouse model of Fragile X Syndrome. J Neurophysiol 2020; 123:2101-2121. [PMID: 32319849 DOI: 10.1152/jn.00706.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sensory processing abnormalities are frequently associated with autism spectrum disorders, but the underlying mechanisms are unclear. Here we studied auditory processing in a mouse model of Fragile X Syndrome (FXS), a leading known genetic cause of autism and intellectual disability. Both humans with FXS and the Fragile X mental retardation gene (Fmr1) knockout (KO) mouse model show auditory hypersensitivity, with the latter showing a strong propensity for audiogenic seizures (AGS) early in development. Because midbrain abnormalities cause AGS, we investigated whether the inferior colliculus (IC) of the Fmr1 KO mice shows abnormal auditory processing compared with wild-type (WT) controls at specific developmental time points. Using antibodies against neural activity marker c-Fos, we found increased density of c-Fos+ neurons in the IC, but not auditory cortex, of Fmr1 KO mice at P21 and P34 following sound presentation. In vivo single-unit recordings showed that IC neurons of Fmr1 KO mice are hyperresponsive to tone bursts and amplitude-modulated tones during development and show broader frequency tuning curves. There were no differences in rate-level responses or phase locking to amplitude-modulated tones in IC neurons between genotypes. Taken together, these data provide evidence for the development of auditory hyperresponsiveness in the IC of Fmr1 KO mice. Although most human and mouse work in autism and sensory processing has centered on the forebrain, our new findings, along with recent work on the lower brainstem, suggest that abnormal subcortical responses may underlie auditory hypersensitivity in autism spectrum disorders.NEW & NOTEWORTHY Autism spectrum disorders (ASD) are commonly associated with sensory sensitivity issues, but the underlying mechanisms are unclear. This study presents novel evidence for neural correlates of auditory hypersensitivity in the developing inferior colliculus (IC) in Fmr1 knockout (KO) mouse, a mouse model of Fragile X Syndrome (FXS), a leading genetic cause of ASD. Responses begin to show genotype differences between postnatal days 14 and 21, suggesting an early developmental treatment window.
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Affiliation(s)
- Anna O Nguyen
- Bioengineering Program, University of California, Riverside, California
| | - Devin K Binder
- Graduate Neuroscience Program, University of California, Riverside, California.,Division of Biomedical Sciences, University of California, Riverside, California
| | - Iryna M Ethell
- Graduate Neuroscience Program, University of California, Riverside, California.,Division of Biomedical Sciences, University of California, Riverside, California
| | - Khaleel A Razak
- Graduate Neuroscience Program, University of California, Riverside, California.,Psychology Department, University of California, Riverside, California
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31
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Markicevic M, Fulcher BD, Lewis C, Helmchen F, Rudin M, Zerbi V, Wenderoth N. Cortical Excitation:Inhibition Imbalance Causes Abnormal Brain Network Dynamics as Observed in Neurodevelopmental Disorders. Cereb Cortex 2020; 30:4922-4937. [PMID: 32313923 PMCID: PMC7391279 DOI: 10.1093/cercor/bhaa084] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Abnormal brain development manifests itself at different spatial scales. However, whether abnormalities at the cellular level can be diagnosed from network activity measured with functional magnetic resonance imaging (fMRI) is largely unknown, yet of high clinical relevance. Here a putative mechanism reported in neurodevelopmental disorders, that is, excitation-to-inhibition ratio (E:I), was chemogenetically increased within cortical microcircuits of the mouse brain and measured via fMRI. Increased E:I caused a significant "reduction" of long-range connectivity, irrespective of whether excitatory neurons were facilitated or inhibitory Parvalbumin (PV) interneurons were suppressed. Training a classifier on fMRI signals, we were able to accurately classify cortical areas exhibiting increased E:I. This classifier was validated in an independent cohort of Fmr1y/- knockout mice, a model for autism with well-documented loss of parvalbumin neurons and chronic alterations of E:I. Our findings demonstrate a promising novel approach towards inferring microcircuit abnormalities from macroscopic fMRI measurements.
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Affiliation(s)
- Marija Markicevic
- Neural Control of Movement Lab, HEST, ETH Zürich, 8093 Zurich, Switzerland.,Neuroscience Center Zurich, University and ETH Zurich, 8057 Zurich, Switzerland
| | - Ben D Fulcher
- School of Physics, The University of Sydney, NSW 2006, Australia
| | - Christopher Lewis
- Brain Research Institute, University of Zurich, 8057 Zurich, Switzerland
| | - Fritjof Helmchen
- Neuroscience Center Zurich, University and ETH Zurich, 8057 Zurich, Switzerland.,Brain Research Institute, University of Zurich, 8057 Zurich, Switzerland
| | - Markus Rudin
- Neuroscience Center Zurich, University and ETH Zurich, 8057 Zurich, Switzerland.,Institute of Pharmacology and Toxicology, University of Zurich, 8057 Zurich, Switzerland.,Institute for Biomedical Engineering, University and ETH Zurich, 8093 Zurich, Switzerland
| | - Valerio Zerbi
- Neural Control of Movement Lab, HEST, ETH Zürich, 8093 Zurich, Switzerland.,Neuroscience Center Zurich, University and ETH Zurich, 8057 Zurich, Switzerland
| | - Nicole Wenderoth
- Neural Control of Movement Lab, HEST, ETH Zürich, 8093 Zurich, Switzerland.,Neuroscience Center Zurich, University and ETH Zurich, 8057 Zurich, Switzerland
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32
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M-Current Inhibition in Hippocampal Excitatory Neurons Triggers Intrinsic and Synaptic Homeostatic Responses at Different Temporal Scales. J Neurosci 2020; 40:3694-3706. [PMID: 32277041 DOI: 10.1523/jneurosci.1914-19.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 03/10/2020] [Accepted: 03/11/2020] [Indexed: 11/21/2022] Open
Abstract
Persistent alterations in neuronal activity elicit homeostatic plastic changes in synaptic transmission and/or intrinsic excitability. However, it is unknown whether these homeostatic processes operate in concert or at different temporal scales to maintain network activity around a set-point value. Here we show that chronic neuronal hyperactivity, induced by M-channel inhibition, triggered intrinsic and synaptic homeostatic plasticity at different timescales in cultured hippocampal pyramidal neurons from mice of either sex. Homeostatic changes of intrinsic excitability occurred at a fast timescale (1-4 h) and depended on ongoing spiking activity. This fast intrinsic adaptation included plastic changes in the threshold current and a distal relocation of FGF14, a protein physically bridging Nav1.6 and Kv7.2 channels along the axon initial segment. In contrast, synaptic adaptations occurred at a slower timescale (∼2 d) and involved decreases in miniature EPSC amplitude. To examine how these temporally distinct homeostatic responses influenced hippocampal network activity, we quantified the rate of spontaneous spiking measured by multielectrode arrays at extended timescales. M-Channel blockade triggered slow homeostatic renormalization of the mean firing rate (MFR), concomitantly accompanied by a slow synaptic adaptation. Thus, the fast intrinsic adaptation of excitatory neurons is not sufficient to account for the homeostatic normalization of the MFR. In striking contrast, homeostatic adaptations of intrinsic excitability and spontaneous MFR failed in hippocampal GABAergic inhibitory neurons, which remained hyperexcitable following chronic M-channel blockage. Our results indicate that a single perturbation such as M-channel inhibition triggers multiple homeostatic mechanisms that operate at different timescales to maintain network mean firing rate.SIGNIFICANCE STATEMENT Persistent alterations in synaptic input elicit homeostatic plastic changes in neuronal activity. Here we show that chronic neuronal hyperexcitability, induced by M-type potassium channel inhibition, triggered intrinsic and synaptic homeostatic plasticity at different timescales in hippocampal excitatory neurons. The data indicate that the fast adaptation of intrinsic excitability depends on ongoing spiking activity but is not sufficient to provide homeostasis of the mean firing rate. Our results show that a single perturbation such as M-channel inhibition can trigger multiple homeostatic processes that operate at different timescales to maintain network mean firing rate.
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Tatavarty V, Torrado Pacheco A, Groves Kuhnle C, Lin H, Koundinya P, Miska NJ, Hengen KB, Wagner FF, Van Hooser SD, Turrigiano GG. Autism-Associated Shank3 Is Essential for Homeostatic Compensation in Rodent V1. Neuron 2020; 106:769-777.e4. [PMID: 32199104 DOI: 10.1016/j.neuron.2020.02.033] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 02/04/2020] [Accepted: 02/26/2020] [Indexed: 12/20/2022]
Abstract
Mutations in Shank3 are strongly associated with autism spectrum disorders and neural circuit changes in several brain areas, but the cellular mechanisms that underlie these defects are not understood. Homeostatic forms of plasticity allow central circuits to maintain stable function during experience-dependent development, leading us to ask whether loss of Shank3 might impair homeostatic plasticity and circuit-level compensation to perturbations. We found that Shank3 loss in vitro abolished synaptic scaling and intrinsic homeostatic plasticity, deficits that could be rescued by treatment with lithium. Further, Shank3 knockout severely compromised the in vivo ability of visual cortical circuits to recover from perturbations to sensory drive. Finally, lithium treatment ameliorated a repetitive self-grooming phenotype in Shank3 knockout mice. These findings demonstrate that Shank3 loss severely impairs the ability of central circuits to harness homeostatic mechanisms to compensate for perturbations in drive, which, in turn, may render them more vulnerable to such perturbations.
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Affiliation(s)
| | | | | | - Heather Lin
- Department of Biology, Brandeis University, Waltham, MA 02493, USA
| | - Priya Koundinya
- Department of Biology, Brandeis University, Waltham, MA 02493, USA
| | | | - Keith B Hengen
- Department of Biology, Brandeis University, Waltham, MA 02493, USA
| | - Florence F Wagner
- Stanley Center for Psychiatric Research, Broad Institute of Massachusetts Institute of Technology and Harvard University, Cambridge, MA, USA
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