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Papatheodoropoulos C. Compensatory Regulation of Excitation/Inhibition Balance in the Ventral Hippocampus: Insights from Fragile X Syndrome. BIOLOGY 2025; 14:363. [PMID: 40282228 PMCID: PMC12025323 DOI: 10.3390/biology14040363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2025] [Revised: 03/20/2025] [Accepted: 03/27/2025] [Indexed: 04/29/2025]
Abstract
The excitation/inhibition (E/I) balance is a critical feature of neural circuits, which is crucial for maintaining optimal brain function by ensuring network stability and preventing neural hyperexcitability. The hippocampus exhibits the particularly interesting characteristics of having different functions and E/I profiles between its dorsal and ventral segments. Furthermore, the hippocampus is particularly vulnerable to epilepsy and implicated in Fragile X Syndrome (FXS), disorders associated with heightened E/I balance and possible deficits in GABA-mediated inhibition. In epilepsy, the ventral hippocampus shows heightened susceptibility to seizures, while in FXS, recent evidence suggests differential alterations in excitability and inhibition between dorsal and ventral regions. This article explores the mechanisms underlying E/I balance regulation, focusing on the hippocampus in epilepsy and FXS, and emphasizing the possible mechanisms that may confer homeostatic flexibility to the ventral hippocampus in maintaining E/I balance. Notably, the ventral hippocampus in adult FXS models shows enhanced GABAergic inhibition, resistance to epileptiform activity, and physiological network pattern (sharp wave-ripples, SWRs), potentially representing a homeostatic adaptation. In contrast, the dorsal hippocampus in these FXS models is more vulnerable to aberrant discharges and displays altered SWRs. These findings highlight the complex, region-specific nature of E/I balance disruptions in neurological disorders and suggest that the ventral hippocampus may possess unique compensatory mechanisms. Specifically, it is proposed that the ventral hippocampus, the brain region most prone to hyperexcitability, may have unique adaptive capabilities at the cellular and network levels that maintain the E/I balance within a normal range to prevent the transition to hyperexcitability and preserve normal function. Investigating the mechanisms underlying these compensatory responses in the ventral hippocampus and their developmental trajectories may offer novel insights into strategies for mitigating E/I imbalances in epilepsy, FXS, and potentially other neuropsychiatric and neurodevelopmental disorders.
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2
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Bricault S, Dawson M, Lee J, Desai M, Schwalm M, Chung KS, DeTienne E, Fagan E, Li N, Becker A, Muthupalani S, Fränken JP, Pinotsis DA, Jasanoff A. Peripheral contributions to resting state brain dynamics. Nat Commun 2024; 15:10820. [PMID: 39737991 PMCID: PMC11685439 DOI: 10.1038/s41467-024-55064-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 11/28/2024] [Indexed: 01/01/2025] Open
Abstract
The correlational structure of brain activity dynamics in the absence of stimuli or behavior is often taken to reveal intrinsic properties of neural function. To test the limits of this assumption, we analyzed peripheral contributions to resting state activity measured by fMRI in unanesthetized, chemically immobilized male rats that emulate human neuroimaging conditions. We find that perturbation of somatosensory input channels modifies correlation strengths that relate somatosensory areas both to one another and to higher-order brain regions, despite the absence of ostensible stimuli or movements. Resting state effects are mediated by the same peripheral and thalamic structures that relay responses to overt sensory stimuli. The impact of basal peripheral input is reduced in a rat model of autism, which displays both lower somatosensory functional connectivity and insensitivity to vibrissa inactivation. These results demonstrate the influence of extrinsic influences on resting state brain phenotypes in health and disease.
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Affiliation(s)
- Sarah Bricault
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
- Department of Biology, Massachusetts Institute of Technology, Cambridge, US
| | - Miranda Dawson
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | - Jiyoung Lee
- Department of Neurobiology, Wellesley College, Wellesley, US
| | - Mitul Desai
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | - Miriam Schwalm
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | - Kevin Sunho Chung
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | - Elizabeth DeTienne
- Department of Electrical Engineering & Computer Science, Massachusetts Institute of Technology, Cambridge, US
| | - Erinn Fagan
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | - Nan Li
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | - Andrew Becker
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US
| | | | - Jan-Philipp Fränken
- Department of Psychology, University of Edinburgh, Edinburgh, United Kingdom
| | - Dimitris A Pinotsis
- Center for Mathematical Neuroscience and Psychology, Department of Psychology, City, University of London, London, United Kingdom
- Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, US
| | - Alan Jasanoff
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, US.
- Department of Brain & Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, US.
- Department of Nuclear Science & Engineering, Massachusetts Institute of Technology, Cambridge, US.
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3
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Reynolds KE, Huang E, Sabbineni M, Wiseman E, Murtaza N, Ahuja D, Napier M, Murphy KM, Singh KK, Scott AL. Purinergic Signalling Mediates Aberrant Excitability of Developing Neuronal Circuits in the Fmr1 Knockout Mouse Model. Mol Neurobiol 2024; 61:9507-9528. [PMID: 38652351 DOI: 10.1007/s12035-024-04181-w] [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: 12/06/2023] [Accepted: 04/15/2024] [Indexed: 04/25/2024]
Abstract
Neuronal hyperexcitability within developing cortical circuits is a common characteristic of several heritable neurodevelopmental disorders, including Fragile X Syndrome (FXS), intellectual disability and autism spectrum disorders (ASD). While this aberrant circuitry is typically studied from a neuron-centric perspective, glial cells secrete soluble factors that regulate both neurite extension and synaptogenesis during development. The nucleotide-mediated purinergic signalling system is particularly instrumental in facilitating these effects. We recently reported that within a FXS animal model, the Fmr1 KO mouse, the purinergic signalling system is upregulated in cortical astrocytes leading to altered secretion of synaptogenic and plasticity-related proteins. In this study, we examined whether elevated astrocyte purinergic signalling also impacts neuronal morphology and connectivity of Fmr1 KO cortical neurons. Here, we found that conditioned media from primary Fmr1 KO astrocytes was sufficient to enhance neurite extension and complexity of both wildtype and Fmr1 KO neurons to a similar degree as UTP-mediated outgrowth. Significantly enhanced firing was also observed in Fmr1 KO neuron-astrocyte co-cultures grown on microelectrode arrays but was associated with large deficits in firing synchrony. The selective P2Y2 purinergic receptor antagonist AR-C 118925XX effectively normalized much of the aberrant Fmr1 KO activity, designating P2Y2 as a potential therapeutic target in FXS. These results not only demonstrate the importance of astrocyte soluble factors in the development of neural circuitry, but also show that P2Y purinergic receptors play a distinct role in pathological FXS neuronal activity.
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Affiliation(s)
- Kathryn E Reynolds
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Eileen Huang
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Monica Sabbineni
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Eliza Wiseman
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Nadeem Murtaza
- McMaster Stem Cell and Cancer Research Institute, McMaster University, Hamilton, ON, Canada
| | - Desmond Ahuja
- Department of Psychology, Neuroscience, and Behaviour, McMaster University, Hamilton, ON, Canada
| | - Matt Napier
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada
- Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon St, Guelph, ON, Canada
| | - Kathryn M Murphy
- Department of Psychology, Neuroscience, and Behaviour, McMaster University, Hamilton, ON, Canada
| | | | - Angela L Scott
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
- Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon St, Guelph, ON, Canada.
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4
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Meneghetti N, Vannini E, Mazzoni A. Rodents' visual gamma as a biomarker of pathological neural conditions. J Physiol 2024; 602:1017-1048. [PMID: 38372352 DOI: 10.1113/jp283858] [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: 12/13/2022] [Accepted: 01/23/2024] [Indexed: 02/20/2024] Open
Abstract
Neural gamma oscillations (indicatively 30-100 Hz) are ubiquitous: they are associated with a broad range of functions in multiple cortical areas and across many animal species. Experimental and computational works established gamma rhythms as a global emergent property of neuronal networks generated by the balanced and coordinated interaction of excitation and inhibition. Coherently, gamma activity is strongly influenced by the alterations of synaptic dynamics which are often associated with pathological neural dysfunctions. We argue therefore that these oscillations are an optimal biomarker for probing the mechanism of cortical dysfunctions. Gamma oscillations are also highly sensitive to external stimuli in sensory cortices, especially the primary visual cortex (V1), where the stimulus dependence of gamma oscillations has been thoroughly investigated. Gamma manipulation by visual stimuli tuning is particularly easy in rodents, which have become a standard animal model for investigating the effects of network alterations on gamma oscillations. Overall, gamma in the rodents' visual cortex offers an accessible probe on dysfunctional information processing in pathological conditions. Beyond vision-related dysfunctions, alterations of gamma oscillations in rodents were indeed also reported in neural deficits such as migraine, epilepsy and neurodegenerative or neuropsychiatric conditions such as Alzheimer's, schizophrenia and autism spectrum disorders. Altogether, the connections between visual cortical gamma activity and physio-pathological conditions in rodent models underscore the potential of gamma oscillations as markers of neuronal (dys)functioning.
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Affiliation(s)
- Nicolò Meneghetti
- The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
- Department of Excellence for Robotics and AI, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Eleonora Vannini
- Neuroscience Institute, National Research Council (CNR), Pisa, Italy
| | - Alberto Mazzoni
- The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
- Department of Excellence for Robotics and AI, Scuola Superiore Sant'Anna, Pisa, Italy
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5
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He JL, Williams ZJ, Harris A, Powell H, Schaaf R, Tavassoli T, Puts NAJ. A working taxonomy for describing the sensory differences of autism. Mol Autism 2023; 14:15. [PMID: 37041612 PMCID: PMC10091684 DOI: 10.1186/s13229-022-00534-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 12/14/2022] [Indexed: 04/13/2023] Open
Abstract
BACKGROUND Individuals on the autism spectrum have been long described to process sensory information differently than neurotypical individuals. While much effort has been leveraged towards characterizing and investigating the neurobiology underlying the sensory differences of autism, there has been a notable lack of consistency in the terms being used to describe the nature of those differences. MAIN BODY We argue that inconsistent and interchangeable terminology-use when describing the sensory differences of autism has become problematic beyond mere pedantry and inconvenience. We begin by highlighting popular terms that are currently being used to describe the sensory differences of autism (e.g. "sensitivity", "reactivity" and "responsivity") and discuss why poor nomenclature may hamper efforts towards understanding the aetiology of sensory differences in autism. We then provide a solution to poor terminology-use by proposing a hierarchical taxonomy for describing and referring to various sensory features. CONCLUSION Inconsistent terminology-use when describing the sensory features of autism has stifled discussion and scientific understanding of the sensory differences of autism. The hierarchical taxonomy proposed was developed to help resolve lack of clarity when discussing the sensory differences of autism and to place future research targets at appropriate levels of analysis.
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Affiliation(s)
- Jason L He
- Department of Forensic and Neurodevelopmental Sciences, Sackler Institute for Translational Neurodevelopment, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, UK.
| | - Zachary J Williams
- Medical Scientist Training Program, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA
- Frist Center for Autism and Innovation, Vanderbilt University, Nashville, TN, USA
- Vanderbilt Kennedy Center, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Ashley Harris
- Department of Radiology, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada
| | - Helen Powell
- Department of Forensic and Neurodevelopmental Sciences, Sackler Institute for Translational Neurodevelopment, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, UK
| | - Roseann Schaaf
- Department of Occupational Therapy, Thomas Jefferson University, Philadelphia, PA, USA
| | - Teresa Tavassoli
- School of Psychology and Clinical Language Sciences, University of Reading, Reading, RG6 6AL, UK
| | - Nicolaas A J Puts
- Department of Forensic and Neurodevelopmental Sciences, Sackler Institute for Translational Neurodevelopment, Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, UK
- MRC Centre for Neurodevelopmental Disorders, King's College London, London, UK
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6
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Abstract
The fragile X-related disorders are an important group of hereditary disorders that are caused by expanded CGG repeats in the 5' untranslated region of the FMR1 gene or by mutations in the coding sequence of this gene. Two categories of pathological CGG repeats are associated with these disorders, full mutation alleles and shorter premutation alleles. Individuals with full mutation alleles develop fragile X syndrome, which causes autism and intellectual disability, whereas those with premutation alleles, which have shorter CGG expansions, can develop fragile X-associated tremor/ataxia syndrome, a progressive neurodegenerative disease. Thus, fragile X-related disorders can manifest as neurodegenerative or neurodevelopmental disorders, depending on the size of the repeat expansion. Here, we review mouse models of fragile X-related disorders and discuss how they have informed our understanding of neurodegenerative and neurodevelopmental disorders. We also assess the translational value of these models for developing rational targeted therapies for intellectual disability and autism disorders.
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Affiliation(s)
- Rob Willemsen
- Department of Clinical Genetics, Erasmus University Medical Center, 3015 CN Rotterdam, the Netherlands. Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium
| | - R. Frank Kooy
- Department of Clinical Genetics, Erasmus University Medical Center, 3015 CN Rotterdam, the Netherlands. Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium
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7
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Kat R, Kas MJH. Largely unaffected auditory and visual sensory processing phenotypes in the evoked potentials of Fmr1 KO2 mice. Eur J Neurosci 2022; 56:5260-5273. [PMID: 36017614 PMCID: PMC9826194 DOI: 10.1111/ejn.15808] [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: 11/16/2021] [Revised: 07/05/2022] [Accepted: 07/06/2022] [Indexed: 01/11/2023]
Abstract
Sensory sensitivity symptoms are common in autism spectrum disorders and fragile X syndrome. Mainly in the auditory modality, disturbed processing has been found in both fragile X patients and the corresponding genetic mouse model, the Fmr1 knockout mouse. Here, we tried to replicate the auditory deficits and assess whether also visual processing is affected, using electroencephalography readouts under freely behaving conditions in the second-generation Fmr1 knockout mice. No differences between wild-type and knockout animals were found in single auditory and visual evoked potentials in response to pure sine tones and full-field light flashes. Visual sensory gating was enhanced in the early but not the late components of the evoked potentials, but no changes were found in auditory sensory gating. The higher harmonics of the synchronisation response to flickering visual stimuli seemed to be reduced with 10, but not 20 or 40 Hz, stimulation. However, this effect was not reproduced in an independent second cohort of animals. No synchronisation differences were found in response to a chirp stimulus, of which the frequency steadily increased. Taken together, this study could not reproduce earlier reported increased amplitudes in auditory responses, nor could it convincingly show that synchronisation deficits found to be present in the auditory modality also existed in the visual modality. The discrepancies within this study as well as between various studies assessing sensory processing in the Fmr1 KO raise questions about the external validity of these phenotypes and warrant careful interpretation of these phenotypes.
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Affiliation(s)
- Renate Kat
- Groningen Institute for Evolutionary Life Sciences (GELIFES)University of GroningenGroningenThe Netherlands
| | - Martien J. H. Kas
- Groningen Institute for Evolutionary Life Sciences (GELIFES)University of GroningenGroningenThe Netherlands
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8
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Shing N, Walker MC, Chang P. The Role of Aberrant Neural Oscillations in the Hippocampal-Medial Prefrontal Cortex Circuit in Neurodevelopmental and Neurological Disorders. Neurobiol Learn Mem 2022; 195:107683. [PMID: 36174886 DOI: 10.1016/j.nlm.2022.107683] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 09/09/2022] [Accepted: 09/20/2022] [Indexed: 11/30/2022]
Abstract
The hippocampus (HPC) and medial prefrontal cortex (mPFC) have well-established roles in cognition, emotion, and sensory processing. In recent years, interests have shifted towards developing a deeper understanding of the mechanisms underlying interactions between the HPC and mPFC in achieving these functions. Considerable research supports the idea that synchronized activity between the HPC and the mPFC is a general mechanism by which brain functions are regulated. In this review, we summarize current knowledge on the hippocampal-medial prefrontal cortex (HPC-mPFC) circuit in normal brain function with a focus on oscillations and highlight several neurodevelopmental and neurological disorders associated with aberrant HPC-mPFC circuitry. We further discuss oscillatory dynamics across the HPC-mPFC circuit as potentially useful biomarkers to assess interventions for neurodevelopmental and neurological disorders. Finally, advancements in brain stimulation, gene therapy and pharmacotherapy are explored as promising therapies for disorders with aberrant HPC-mPFC circuit dynamics.
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Affiliation(s)
- Nathanael Shing
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, WC1N 3BG, UK; Department of Medicine, University of Central Lancashire, Preston, PR17BH, UK
| | - Matthew C Walker
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Pishan Chang
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT.
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9
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Yamazaki M, Arai T, Yarimizu J, Matsumoto M. 5-HT5A Receptor Antagonist ASP5736 Ameliorates Several Abnormal Behaviors in an Fmr1-Targeted Transgenic Male Rat Model of Fragile X Syndrome. Int J Neuropsychopharmacol 2022; 25:786-793. [PMID: 35882205 PMCID: PMC9515134 DOI: 10.1093/ijnp/pyac041] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 06/24/2022] [Accepted: 07/23/2022] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Fragile X syndrome (FXS) is a genetic condition that causes a range of developmental problems, including intellectual disability, aggressive behavior, anxiety, abnormal sensory processing, and cognitive impairment. Despite intensive preclinical research in Fmr1-targeted transgenic mice, an effective treatment for FXS has yet to be developed. We previously demonstrated that ASP5736, a 5-Hydroxytryptamine (serotonin) receptor 5A receptor antagonist, ameliorated scopolamine-induced working memory deficits in mice, reference memory impairment in aged rats, and methamphetamine-induced positive symptoms and phencyclidine-induced cognitive impairment in animal models of schizophrenia. We hypothesized that ASP5736 may be effective for ameliorating similar behavior deficits in male Fmr1-targeted transgenic rats as a preclinical model of FXS. METHODS We evaluated the effect of acute oral administration of ASP5736 on the abnormal behavior of hyperactivity (0.01, 0.1 mg/kg), prepulse inhibition (0.01, 0.03, 0.1 mg/kg), and the novel object recognition task (0.1 mg/kg) in Frmr1-knockout (KO) rats. RESULTS Fmr1-KO rats showed body weight gain, hyperactivity, abnormal sensory motor gating, and cognitive impairment. ASP5736 (0.1 mg/kg) reversed the hyperactivity and ameliorated the sensory motor gating deficits (0.03-0.1 mg/kg). ASP5736 (0.01 mg/kg) also improved cognitive impairment. CONCLUSIONS ASP5736 is a potential drug candidate for FXS. Further studies are needed to confirm its clinical efficacy.
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Affiliation(s)
- Mayako Yamazaki
- Correspondence: Mayako Yamazaki, PhD, Research Fellow, Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba-shi, Ibaraki, 305-8585, Japan ()
| | - Takatomo Arai
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., Tsukuba-shi, Ibaraki, Japan
| | - Junko Yarimizu
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., Tsukuba-shi, Ibaraki, Japan
| | - Mitsuyuki Matsumoto
- Department of Neuroscience, Drug Discovery Research, Astellas Pharma Inc., Tsukuba-shi, Ibaraki, Japan,Neuroscience, La Jolla Laboratory, Astellas Research Institute of America LLC, San Diego, CA, USA
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10
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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: 1.7] [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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11
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Contractor A, Ethell IM, Portera-Cailliau C. Cortical interneurons in autism. Nat Neurosci 2021; 24:1648-1659. [PMID: 34848882 PMCID: PMC9798607 DOI: 10.1038/s41593-021-00967-6] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 09/21/2021] [Indexed: 01/01/2023]
Abstract
The mechanistic underpinnings of autism remain a subject of debate and controversy. Why do individuals with autism share an overlapping set of atypical behaviors and symptoms, despite having different genetic and environmental risk factors? A major challenge in developing new therapies for autism has been the inability to identify convergent neural phenotypes that could explain the common set of symptoms that result in the diagnosis. Although no striking macroscopic neuropathological changes have been identified in autism, there is growing evidence that inhibitory interneurons (INs) play an important role in its neural basis. In this Review, we evaluate and interpret this evidence, focusing on recent findings showing reduced density and activity of the parvalbumin class of INs. We discuss the need for additional studies that investigate how genes and the environment interact to change the developmental trajectory of INs, permanently altering their numbers, connectivity and circuit engagement.
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Affiliation(s)
- Anis Contractor
- Department of Neuroscience Feinberg School of Medicine, Weinberg College of Arts and Sciences, Northwestern University, Chicago, IL, USA
- Department of Neurobiology, Weinberg College of Arts and Sciences, Northwestern University, Chicago, IL, USA
| | - Iryna M Ethell
- Division of Biomedical Sciences, UC Riverside School of Medicine, Riverside, CA, USA
| | - Carlos Portera-Cailliau
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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12
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Restoration of FMRP expression in adult V1 neurons rescues visual deficits in a mouse model of fragile X syndrome. Protein Cell 2021; 13:203-219. [PMID: 34714519 PMCID: PMC8901859 DOI: 10.1007/s13238-021-00878-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 07/26/2021] [Indexed: 11/22/2022] Open
Abstract
Many people affected by fragile X syndrome (FXS) and autism spectrum disorders have sensory processing deficits, such as hypersensitivity to auditory, tactile, and visual stimuli. Like FXS in humans, loss of Fmr1 in rodents also cause sensory, behavioral, and cognitive deficits. However, the neural mechanisms underlying sensory impairment, especially vision impairment, remain unclear. It remains elusive whether the visual processing deficits originate from corrupted inputs, impaired perception in the primary sensory cortex, or altered integration in the higher cortex, and there is no effective treatment. In this study, we used a genetic knockout mouse model (Fmr1KO), in vivo imaging, and behavioral measurements to show that the loss of Fmr1 impaired signal processing in the primary visual cortex (V1). Specifically, Fmr1KO mice showed enhanced responses to low-intensity stimuli but normal responses to high-intensity stimuli. This abnormality was accompanied by enhancements in local network connectivity in V1 microcircuits and increased dendritic complexity of V1 neurons. These effects were ameliorated by the acute application of GABAA receptor activators, which enhanced the activity of inhibitory neurons, or by reintroducing Fmr1 gene expression in knockout V1 neurons in both juvenile and young-adult mice. Overall, V1 plays an important role in the visual abnormalities of Fmr1KO mice and it could be possible to rescue the sensory disturbances in developed FXS and autism patients.
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13
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Nomura T. Interneuron Dysfunction and Inhibitory Deficits in Autism and Fragile X Syndrome. Cells 2021; 10:2610. [PMID: 34685590 PMCID: PMC8534049 DOI: 10.3390/cells10102610] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 09/27/2021] [Accepted: 09/28/2021] [Indexed: 01/18/2023] Open
Abstract
The alteration of excitatory-inhibitory (E-I) balance has been implicated in various neurological and psychiatric diseases, including autism spectrum disorder (ASD). Fragile X syndrome (FXS) is a single-gene disorder that is the most common known cause of ASD. Understanding the molecular and physiological features of FXS is thought to enhance our knowledge of the pathophysiology of ASD. Accumulated evidence implicates deficits in the inhibitory circuits in FXS that tips E-I balance toward excitation. Deficits in interneurons, the main source of an inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), have been reported in FXS, including a reduced number of cells, reduction in intrinsic cellular excitability, or weaker synaptic connectivity. Manipulating the interneuron activity ameliorated the symptoms in the FXS mouse model, which makes it reasonable to conceptualize FXS as an interneuronopathy. While it is still poorly understood how the developmental profiles of the inhibitory circuit go awry in FXS, recent works have uncovered several developmental alterations in the functional properties of interneurons. Correcting disrupted E-I balance by potentiating the inhibitory circuit by targeting interneurons may have a therapeutic potential in FXS. I will review the recent evidence about the inhibitory alterations and interneuron dysfunction in ASD and FXS and will discuss the future directions of this field.
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Affiliation(s)
- Toshihiro Nomura
- Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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14
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Moskalyuk A, Van De Vijver S, Verstraelen P, De Vos WH, Kooy RF, Giugliano M. Single-Cell and Neuronal Network Alterations in an In Vitro Model of Fragile X Syndrome. Cereb Cortex 2021; 30:31-46. [PMID: 30958540 DOI: 10.1093/cercor/bhz068] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Fragile X mental retardation protein (FMRP) is involved in many cellular processes and it regulates synaptic and network development in neurons. Its absence is known to lead to intellectual disability, with a wide range of comorbidities including autism. Over the past decades, FMRP research focused on abnormalities both in glutamatergic and GABAergic signaling, and an altered balance between excitation and inhibition has been hypothesized to underlie the clinical consequences of absence of the protein. Using Fmrp knockout mice, we studied an in vitro model of cortical microcircuitry and observed that the loss of FMRP largely affected the electrophysiological correlates of network development and maturation but caused less alterations in single-cell phenotypes. The loss of FMRP also caused a structural increase in the number of excitatory synaptic terminals. Using a mathematical model, we demonstrated that the combination of an increased excitation and reduced inhibition describes best our experimental observations during the ex vivo formation of the network connections.
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Affiliation(s)
- Anastasiya Moskalyuk
- Molecular, Cellular, and Network Excitability Lab, University of Antwerp, Wilrijk, Flanders, Belgium
| | - Sebastiaan Van De Vijver
- Molecular, Cellular, and Network Excitability Lab, University of Antwerp, Wilrijk, Flanders, Belgium
| | - Peter Verstraelen
- Laboratory of Cell Biology and Histology, University of Antwerp, Wilrijk, Flanders, Belgium
| | - Winnok H De Vos
- Laboratory of Cell Biology and Histology, University of Antwerp, Wilrijk, Flanders, Belgium
| | - R Frank Kooy
- Department of Medical Genetics, University of Antwerp, Edegem, Flanders, Belgium
| | - Michele Giugliano
- Molecular, Cellular, and Network Excitability Lab, University of Antwerp, Wilrijk, Flanders, Belgium.,International School for Advanced Studies (SISSA), Trieste, Italy
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15
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Gamma power abnormalities in a Fmr1-targeted transgenic rat model of fragile X syndrome. Sci Rep 2020; 10:18799. [PMID: 33139785 PMCID: PMC7608556 DOI: 10.1038/s41598-020-75893-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 10/21/2020] [Indexed: 12/11/2022] Open
Abstract
Fragile X syndrome (FXS) is characteristically displayed intellectual disability, hyperactivity, anxiety, and abnormal sensory processing. Electroencephalography (EEG) abnormalities are also observed in subjects with FXS, with many researchers paying attention to these as biomarkers. Despite intensive preclinical research using Fmr1 knock out (KO) mice, an effective treatment for FXS has yet to be developed. Here, we examined Fmr1-targeted transgenic rats (Fmr1-KO rats) as an alternative preclinical model of FXS. We characterized the EEG phenotypes of Fmr1-KO rats by measuring basal EEG power and auditory steady state response (ASSR) to click trains of stimuli at a frequency of 10–80 Hz. Fmr1-KO rats exhibited reduced basal alpha power and enhanced gamma power, and these rats showed enhanced locomotor activity in novel environment. While ASSR clearly peaked at around 40 Hz, both inter-trial coherence (ITC) and event-related spectral perturbation (ERSP) were significantly reduced at the gamma frequency band in Fmr1-KO rats. Fmr1-KO rats showed gamma power abnormalities and behavioral hyperactivity that were consistent with observations reported in mouse models and subjects with FXS. These results suggest that gamma power abnormalities are a translatable biomarker among species and demonstrate the utility of Fmr1-KO rats for investigating drugs for the treatment of FXS.
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16
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Schiavi S, Carbone E, Melancia F, Buzzelli V, Manduca A, Campolongo P, Pallottini V, Trezza V. Perinatal supplementation with omega-3 fatty acids corrects the aberrant social and cognitive traits observed in a genetic model of autism based on FMR1 deletion in rats. Nutr Neurosci 2020; 25:898-911. [PMID: 32912100 DOI: 10.1080/1028415x.2020.1819107] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Background and objective: Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder for which no treatments exist. Fragile X syndrome (FXS) is the most common form of inherited mental retardation and the most frequent monogenic cause of ASD. Given the lack of pharmacological treatments for ASD, increasing interest is devoted to non-pharmacological approaches, including dietary interventions. Omega-3 polyunsaturated fatty acids (PUFAs) are critical for neurobehavioraldevelopment. This study had two aims: 1. To validatethe recently developed Fmr1-Δexon 8 rat model of FXS; 2. To assess the impact of omega-3 PUFAs dietary supplementation during pregnancy and lactation on the altered behavior displayed by Fmr1-Δexon 8 rats.Methods: Female Fmr1-Δexon 8 and wild-type Sprague-Dawley rats were fed with either an omega-3 PUFAs enriched diet or with an isocaloric control diet during pregnancy and lactation. Behavioral experiments were carried out on the infant (Postnatal days (PNDs) 9 and 13), juvenile (PND 35) and adult (PND 90) male offspring.Results: Fmr1-Δexon 8 pups showed hypolocomotion, reduced ultrasonic vocalizations (USVs) emission and impaired social discrimination compared to wild-type controls. Juvenile and adult Fmr1-Δexon 8 rats showed deficits in the social and cognitive domains, that were counteracted by perinatal omega-3 PUFAs supplementation.Conclusion: Our results support the validity of the Fmr1-Δexon 8 rat model to mimic key autistic-like features and support an important role of omega-3 PUFAs during of neurodevelopment. Although the mechanisms underlying the beneficial effects of omega-3 PUFAs supplementation in ASD needs to be clarified, this dietary intervention holds promise to mitigate core and comorbid autistic features.
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Affiliation(s)
- Sara Schiavi
- Department of Science, University 'Roma Tre', Rome Italy
| | - Emilia Carbone
- Department of Science, University 'Roma Tre', Rome Italy
| | | | | | | | - Patrizia Campolongo
- Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy.,Neurobiology of Behavior Laboratory, Santa Lucia Foundation, Rome, Italy
| | | | - Viviana Trezza
- Department of Science, University 'Roma Tre', Rome Italy
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17
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Motanis H, Buonomano D. Decreased reproducibility and abnormal experience-dependent plasticity of network dynamics in Fragile X circuits. Sci Rep 2020; 10:14535. [PMID: 32884028 PMCID: PMC7471942 DOI: 10.1038/s41598-020-71333-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 08/10/2020] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome is a neurodevelopmental disorder associated with a broad range of neural phenotypes. Interpreting these findings has proven challenging because some phenotypes may reflect compensatory mechanisms or normal forms of plasticity differentially engaged by experiential differences. To help minimize compensatory and experiential influences, we used an ex vivo approach to study network dynamics and plasticity of cortical microcircuits. In Fmr1-/y circuits, the spatiotemporal structure of Up-states was less reproducible, suggesting alterations in the plasticity mechanisms governing network activity. Chronic optical stimulation revealed normal homeostatic plasticity of Up-states, however, Fmr1-/y circuits exhibited abnormal experience-dependent plasticity as they did not adapt to chronically presented temporal patterns in an interval-specific manner. These results, suggest that while homeostatic plasticity is normal, Fmr1-/y circuits exhibit deficits in the ability to orchestrate multiple forms of synaptic plasticity and to adapt to sensory patterns in an experience-dependent manner-which is likely to contribute to learning deficits.
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Affiliation(s)
- Helen Motanis
- Departments of Neurobiology and Psychology, and Integrative Center for Learning and Memory, University of California, 630 Charles E Young Dr S, Center for Health Sciences Building, Los Angeles, CA, 90095, USA
| | - Dean Buonomano
- Departments of Neurobiology and Psychology, and Integrative Center for Learning and Memory, University of California, 630 Charles E Young Dr S, Center for Health Sciences Building, Los Angeles, CA, 90095, USA.
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18
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Szpirer C. Rat models of human diseases and related phenotypes: a systematic inventory of the causative genes. J Biomed Sci 2020; 27:84. [PMID: 32741357 PMCID: PMC7395987 DOI: 10.1186/s12929-020-00673-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/09/2020] [Indexed: 12/13/2022] Open
Abstract
The laboratory rat has been used for a long time as the model of choice in several biomedical disciplines. Numerous inbred strains have been isolated, displaying a wide range of phenotypes and providing many models of human traits and diseases. Rat genome mapping and genomics was considerably developed in the last decades. The availability of these resources has stimulated numerous studies aimed at discovering causal disease genes by positional identification. Numerous rat genes have now been identified that underlie monogenic or complex diseases and remarkably, these results have been translated to the human in a significant proportion of cases, leading to the identification of novel human disease susceptibility genes, helping in studying the mechanisms underlying the pathological abnormalities and also suggesting new therapeutic approaches. In addition, reverse genetic tools have been developed. Several genome-editing methods were introduced to generate targeted mutations in genes the function of which could be clarified in this manner [generally these are knockout mutations]. Furthermore, even when the human gene causing a disease had been identified without resorting to a rat model, mutated rat strains (in particular KO strains) were created to analyze the gene function and the disease pathogenesis. Today, over 350 rat genes have been identified as underlying diseases or playing a key role in critical biological processes that are altered in diseases, thereby providing a rich resource of disease models. This article is an update of the progress made in this research and provides the reader with an inventory of these disease genes, a significant number of which have similar effects in rat and humans.
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Affiliation(s)
- Claude Szpirer
- Université Libre de Bruxelles, B-6041, Gosselies, Belgium.
- , Waterloo, Belgium.
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19
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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: 1.8] [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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20
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Bülow P, Murphy TJ, Bassell GJ, Wenner P. Homeostatic Intrinsic Plasticity Is Functionally Altered in Fmr1 KO Cortical Neurons. Cell Rep 2020; 26:1378-1388.e3. [PMID: 30726724 PMCID: PMC6443253 DOI: 10.1016/j.celrep.2019.01.035] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 11/20/2018] [Accepted: 01/09/2019] [Indexed: 12/12/2022] Open
Abstract
Cortical hyperexcitability is a hallmark of fragile X syndrome (FXS). In the Fmr1 knockout (KO) mouse model of FXS,
cortical hyperexcitability is linked to sensory hypersensitivity and seizure susceptibility. It remains unclear why homeostatic
mechanisms fail to prevent such activity. Homeostatic intrinsic plasticity (HIP) adjusts membrane excitability through regulation
of ion channels to maintain activity levels following activity perturbation. Despite the critical role of HIP in the maturation of
excitability, it has not been examined in FXS. Here, we demonstrate that HIP does not operate normally in a disease model, FXS.
HIP was either lost or exaggerated in two distinct neuronal populations from Fmr1 KO cortical cultures. In addition, we have
identified a mechanism for homeostatic intrinsic plasticity. Compromising HIP function during development could leave cortical
neurons in the FXS nervous system vulnerable to hyperexcitability. Fragile X syndrome (FXS) is characterized by cortical hyperexcitability, but the mechanisms driving hyperexcitability are
poorly understood. Homeostatic intrinsic plasticity (HIP) regulates ion channel function to maintain appropriate activity levels.
Bülow et al. show that HIP is functionally altered in FXS neurons, which may leave cortical neurons vulnerable to
hyperexcitability.
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Affiliation(s)
- Pernille Bülow
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA; Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - T J Murphy
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA.
| | - Peter Wenner
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA.
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21
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The Application of Adeno-Associated Viral Vector Gene Therapy to the Treatment of Fragile X Syndrome. Brain Sci 2019; 9:brainsci9020032. [PMID: 30717399 PMCID: PMC6406794 DOI: 10.3390/brainsci9020032] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/30/2019] [Accepted: 01/31/2019] [Indexed: 01/18/2023] Open
Abstract
Viral vector-mediated gene therapy has grown by leaps and bounds over the past several years. Although the reasons for this progress are varied, a deeper understanding of the basic biology of the viruses, the identification of new and improved versions of viral vectors, and simply the vast experience gained by extensive testing in both animal models of disease and in clinical trials, have been key factors. Several studies have investigated the efficacy of adeno-associated viral (AAV) vectors in the mouse model of fragile X syndrome where AAVs have been used to express fragile X mental retardation protein (FMRP), which is missing or highly reduced in the disorder. These studies have demonstrated a range of efficacies in different tests from full correction, to partial rescue, to no effect. Here we provide a backdrop of recent advances in AAV gene therapy as applied to central nervous system disorders, outline the salient features of the fragile X studies, and discuss several key issues for moving forward. Collectively, the findings to date from the mouse studies on fragile X syndrome, and data from clinical trials testing AAVs in other neurological conditions, indicate that AAV-mediated gene therapy could be a viable strategy for treating fragile X syndrome.
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22
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Antoine MW, Langberg T, Schnepel P, Feldman DE. Increased Excitation-Inhibition Ratio Stabilizes Synapse and Circuit Excitability in Four Autism Mouse Models. Neuron 2019; 101:648-661.e4. [PMID: 30679017 DOI: 10.1016/j.neuron.2018.12.026] [Citation(s) in RCA: 269] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 11/19/2018] [Accepted: 12/19/2018] [Indexed: 01/08/2023]
Abstract
Distinct genetic forms of autism are hypothesized to share a common increase in excitation-inhibition (E-I) ratio in cerebral cortex, causing hyperexcitability and excess spiking. We provide a systematic test of this hypothesis across 4 mouse models (Fmr1-/y, Cntnap2-/-, 16p11.2del/+, Tsc2+/-), focusing on somatosensory cortex. All autism mutants showed reduced feedforward inhibition in layer 2/3 coupled with more modest, variable reduction in feedforward excitation, driving a common increase in E-I conductance ratio. Despite this, feedforward spiking, synaptic depolarization, and spontaneous spiking were largely normal. Modeling revealed that E and I conductance changes in each mutant were quantitatively matched to yield stable, not increased, synaptic depolarization for cells near spike threshold. Correspondingly, whisker-evoked spiking was not increased in vivo despite detectably reduced inhibition. Thus, elevated E-I ratio is a common circuit phenotype but appears to reflect homeostatic stabilization of synaptic drive rather than driving network hyperexcitability in autism.
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Affiliation(s)
- Michelle W Antoine
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720, USA.
| | - Tomer Langberg
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720, USA
| | - Philipp Schnepel
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720, USA
| | - Daniel E Feldman
- Department of Molecular and Cellular Biology and Helen Wills Neuroscience Institute, UC Berkeley, Berkeley, CA 94720, USA.
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23
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Wen TH, Lovelace JW, Ethell IM, Binder DK, Razak KA. Developmental Changes in EEG Phenotypes in a Mouse Model of Fragile X Syndrome. Neuroscience 2018; 398:126-143. [PMID: 30528856 DOI: 10.1016/j.neuroscience.2018.11.047] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 11/27/2018] [Accepted: 11/29/2018] [Indexed: 01/29/2023]
Abstract
Fragile X Syndrome (FXS) is a leading genetic cause of autism and intellectual disabilities. Sensory-processing deficits are common in humans with FXS and an animal model, the Fmr1 knockout (KO) mouse, manifesting in the auditory system as debilitating hypersensitivity and abnormal electroencephalographic (EEG) and event-related potential (ERP) phenotypes. FXS is a neurodevelopmental disorder, but how EEG/ERP phenotypes change during development is unclear. Therefore, we characterized baseline and stimulus-evoked EEG in auditory and frontal cortex of developing (postnatal day (P) 21 and P30) and adult (P60) wildtype (WT) and Fmr1 KO mice with the FVB genetic background. We found that baseline gamma-band power and N1 amplitude of auditory ERP were increased in frontal cortex of Fmr1 KO mice during development and in adults. Baseline gamma power was increased in auditory cortex at P30. Genotype differences in stimulus-evoked gamma power were present in both cortical regions, but the direction and strength of the changes were age-dependent. These findings suggest that cortical deficits are present during early development and may contribute to sensory-processing deficits in FXS, which in turn may lead to anxiety and delayed language. Developmental changes in EEG measures indicate that observations at a single time-point during development are not reflective of FXS disease progression and highlight the need to identify developmental trajectories and optimal windows for treatment.
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Affiliation(s)
- Teresa H Wen
- Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA
| | - Jonathan W Lovelace
- Psychology Department and Psychology Graduate Program, University of California Riverside, Riverside, CA 92521, USA
| | - Iryna M Ethell
- Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA; Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA
| | - Devin K Binder
- Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA; Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, CA 92521, USA
| | - Khaleel A Razak
- Neuroscience Graduate Program, University of California Riverside, Riverside, CA 92521, USA; Psychology Department and Psychology Graduate Program, University of California Riverside, Riverside, CA 92521, USA.
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24
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Melancia F, Trezza V. Modelling fragile X syndrome in the laboratory setting: A behavioral perspective. Behav Brain Res 2018; 350:149-163. [DOI: 10.1016/j.bbr.2018.04.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/24/2018] [Accepted: 04/24/2018] [Indexed: 12/13/2022]
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25
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Sunamura N, Iwashita S, Enomoto K, Kadoshima T, Isono F. Loss of the fragile X mental retardation protein causes aberrant differentiation in human neural progenitor cells. Sci Rep 2018; 8:11585. [PMID: 30072797 PMCID: PMC6072755 DOI: 10.1038/s41598-018-30025-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 07/20/2018] [Indexed: 12/20/2022] Open
Abstract
Fragile X syndrome (FXS) is caused by transcriptional silencing of the FMR1 gene during embryonic development with the consequent loss of the encoded fragile X mental retardation protein (FMRP). The pathological mechanisms of FXS have been extensively studied using the Fmr1-knockout mouse, and the findings suggest important roles for FMRP in synaptic plasticity and proper functioning of neural networks. However, the function of FMRP during early development in the human nervous system remains to be confirmed. Here we describe human neural progenitor cells (NPCs) as a model for studying FMRP functions and FXS pathology. Transcriptome analysis of the NPCs derived from FMR1-knockout human induced pluripotent stem cells (iPSCs) showed altered expression of neural differentiation markers, particularly a marked induction of the astrocyte marker glial fibrillary acidic protein (GFAP). When induced to differentiate, FMRP-deficient neurons continued to express GFAP, and showed less spontaneous calcium bursts than the parental iPSC-derived neurons. Interestingly, the aberrant expression of GFAP and the impaired firing was corrected by treatment with the protein kinase inhibitor LX7101. These findings underscore the modulatory roles of FMRP in human neurogenesis, and further demonstrate that the defective phenotype of FXS could be reversed at least partly by small molecule kinase inhibitors.
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Affiliation(s)
- Naohiro Sunamura
- Asubio Pharma Co., Ltd., 6-4-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Shinzo Iwashita
- Asubio Pharma Co., Ltd., 6-4-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Kei Enomoto
- Asubio Pharma Co., Ltd., 6-4-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan
| | - Taisuke Kadoshima
- Asubio Pharma Co., Ltd., 6-4-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
| | - Fujio Isono
- Asubio Pharma Co., Ltd., 6-4-3 Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.
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26
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Colonnese MT, Phillips MA. Thalamocortical function in developing sensory circuits. Curr Opin Neurobiol 2018; 52:72-79. [PMID: 29715588 DOI: 10.1016/j.conb.2018.04.019] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Accepted: 04/13/2018] [Indexed: 12/12/2022]
Abstract
Thalamocortical activity patterns, both spontaneous and evoked, undergo a dramatic shift in preparation for the onset of rich sensory experience (e.g. birth in humans; eye-opening in rodents). This change is the result of a switch from thalamocortical circuits tuned for transmission of spontaneous bursting in sense organs, to circuits capable of high resolution, active sensory processing. Early 'pre-sensory' tuning uses amplification generated by corticothalamic excitatory feedback and early-born subplate neurons to ensure transmission of bursts, at the expense of stimulus discrimination. The switch to sensory circuits is due, at least in part, to the coordinated remodeling of inhibitory circuits in thalamus and cortex. Appreciation of the distinct rules that govern early circuit function can, and should, inform translational studies of genetic and acquired developmental dysfunction.
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Affiliation(s)
- Matthew T Colonnese
- Department of Pharmacology and Physiology, Institute for Neuroscience, The George Washington University, United States.
| | - Marnie A Phillips
- Department of Pharmacology and Physiology, Institute for Neuroscience, The George Washington University, United States
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27
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Drozd M, Bardoni B, Capovilla M. Modeling Fragile X Syndrome in Drosophila. Front Mol Neurosci 2018; 11:124. [PMID: 29713264 PMCID: PMC5911982 DOI: 10.3389/fnmol.2018.00124] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/29/2018] [Indexed: 01/18/2023] Open
Abstract
Intellectual disability (ID) and autism are hallmarks of Fragile X Syndrome (FXS), a hereditary neurodevelopmental disorder. The gene responsible for FXS is Fragile X Mental Retardation gene 1 (FMR1) encoding the Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein involved in RNA metabolism and modulating the expression level of many targets. Most cases of FXS are caused by silencing of FMR1 due to CGG expansions in the 5'-UTR of the gene. Humans also carry the FXR1 and FXR2 paralogs of FMR1 while flies have only one FMR1 gene, here called dFMR1, sharing the same level of sequence homology with all three human genes, but functionally most similar to FMR1. This enables a much easier approach for FMR1 genetic studies. Drosophila has been widely used to investigate FMR1 functions at genetic, cellular, and molecular levels since dFMR1 mutants have many phenotypes in common with the wide spectrum of FMR1 functions that underlay the disease. In this review, we present very recent Drosophila studies investigating FMRP functions at genetic, cellular, molecular, and electrophysiological levels in addition to research on pharmacological treatments in the fly model. These studies have the potential to aid the discovery of pharmacological therapies for FXS.
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Affiliation(s)
- Małgorzata Drozd
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France.,CNRS LIA (Neogenex), Valbonne, France
| | - Barbara Bardoni
- CNRS LIA (Neogenex), Valbonne, France.,Université Côte d'Azur, INSERM, CNRS, IPMC, Valbonne, France
| | - Maria Capovilla
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France.,CNRS LIA (Neogenex), Valbonne, France
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28
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Dahlhaus R. Of Men and Mice: Modeling the Fragile X Syndrome. Front Mol Neurosci 2018; 11:41. [PMID: 29599705 PMCID: PMC5862809 DOI: 10.3389/fnmol.2018.00041] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 01/31/2018] [Indexed: 12/26/2022] Open
Abstract
The Fragile X Syndrome (FXS) is one of the most common forms of inherited intellectual disability in all human societies. Caused by the transcriptional silencing of a single gene, the fragile x mental retardation gene FMR1, FXS is characterized by a variety of symptoms, which range from mental disabilities to autism and epilepsy. More than 20 years ago, a first animal model was described, the Fmr1 knock-out mouse. Several other models have been developed since then, including conditional knock-out mice, knock-out rats, a zebrafish and a drosophila model. Using these model systems, various targets for potential pharmaceutical treatments have been identified and many treatments have been shown to be efficient in preclinical studies. However, all attempts to turn these findings into a therapy for patients have failed thus far. In this review, I will discuss underlying difficulties and address potential alternatives for our future research.
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Affiliation(s)
- Regina Dahlhaus
- Institute for Biochemistry, Emil-Fischer Centre, University of Erlangen-Nürnberg, Erlangen, Germany
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29
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O'Donnell C, Gonçalves JT, Portera-Cailliau C, Sejnowski TJ. Beyond excitation/inhibition imbalance in multidimensional models of neural circuit changes in brain disorders. eLife 2017; 6:26724. [PMID: 29019321 PMCID: PMC5663477 DOI: 10.7554/elife.26724] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Accepted: 10/04/2017] [Indexed: 11/28/2022] Open
Abstract
A leading theory holds that neurodevelopmental brain disorders arise from imbalances in excitatory and inhibitory (E/I) brain circuitry. However, it is unclear whether this one-dimensional model is rich enough to capture the multiple neural circuit alterations underlying brain disorders. Here, we combined computational simulations with analysis of in vivo two-photon Ca2+ imaging data from somatosensory cortex of Fmr1 knock-out (KO) mice, a model of Fragile-X Syndrome, to test the E/I imbalance theory. We found that: (1) The E/I imbalance model cannot account for joint alterations in the observed neural firing rates and correlations; (2) Neural circuit function is vastly more sensitive to changes in some cellular components over others; (3) The direction of circuit alterations in Fmr1 KO mice changes across development. These findings suggest that the basic E/I imbalance model should be updated to higher dimensional models that can better capture the multidimensional computational functions of neural circuits. In many brain disorders, from autism to schizophrenia, the anatomy of the brain appears remarkably unchanged. This implies that the problem may reside in how neurons communicate with one another. Unfortunately, neuroscientists know little about how brain activity might differ from normal in these disorders, or how specific changes in activity give rise to symptoms. One leading theory, first proposed over a decade ago, is that these disorders reflect an imbalance in the activity of excitatory and inhibitory neurons. Excitatory neurons activate their targets, whereas inhibitory neurons suppress or silence them. While studies in mice have lent support to this theory, they have not yet culminated in new treatments for brain disorders. One limitation of the excitation-inhibition imbalance theory is that it is one-dimensional. It assumes that there is an optimal balance of excitation and inhibition, and that brain disorders can be arranged in an imaginary line on either side of this optimum. Disorders to the right of the optimum, such as epilepsy and some forms of autism, feature too much excitation. Disorders to the left, such as the developmental disorder Rett syndrome, feature too much inhibition. But can diverse brain disorders really be classified on the basis of a single property, or do scientists need to consider other factors? To find out, O’Donnell et al. analyzed recordings of brain activity from genetically modified mice with the mutation that causes fragile X syndrome, the most common form of inherited learning disability and autism. The mice showed changes in their overall brain activity compared to control animals. Their neurons also tended to fire in a more synchronized manner. A computer simulation revealed that an imbalance in excitation and inhibition alone could not explain these changes. Yet, a more complex simulation incorporating extra properties of neural circuits did a better job of explaining the altered neural activity seen in the mice. O’Donnell et al. propose that this more advanced multi-dimensional model of changes in neural circuits could be used to screen candidate drugs before testing them in patients. In principle, the model could even help with designing drugs or other interventions by making it easier for researchers to target more precisely the changes in neural circuits that occur in brain disorders.
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Affiliation(s)
- Cian O'Donnell
- Department of Computer Science, University of Bristol, Bristol, United Kingdom.,Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, United States
| | - J Tiago Gonçalves
- Dominick Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, United States.,Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Carlos Portera-Cailliau
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, United States.,Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, United States
| | - Terrence J Sejnowski
- Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, United States.,Division of Biological Sciences, University of California at San Diego, La Jolla, United States
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30
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Davis JK, Broadie K. Multifarious Functions of the Fragile X Mental Retardation Protein. Trends Genet 2017; 33:703-714. [PMID: 28826631 PMCID: PMC5610095 DOI: 10.1016/j.tig.2017.07.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/20/2017] [Accepted: 07/24/2017] [Indexed: 01/01/2023]
Abstract
Fragile X syndrome (FXS), a heritable intellectual and autism spectrum disorder (ASD), results from the loss of Fragile X mental retardation protein (FMRP). This neurodevelopmental disease state exhibits neural circuit hyperconnectivity and hyperexcitability. Canonically, FMRP functions as an mRNA-binding translation suppressor, but recent findings have enormously expanded its proposed roles. Although connections between burgeoning FMRP functions remain unknown, recent advances have extended understanding of its involvement in RNA, channel, and protein binding that modulate calcium signaling, activity-dependent critical period development, and the excitation-inhibition (E/I) neural circuitry balance. In this review, we contextualize 3 years of FXS model research. Future directions extrapolated from recent advances focus on discovering links between FMRP roles to determine whether FMRP has a multitude of unrelated functions or whether combinatorial mechanisms can explain its multifaceted existence.
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Affiliation(s)
- Jenna K Davis
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA
| | - Kendal Broadie
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA.
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31
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Tian Y, Yang C, Shang S, Cai Y, Deng X, Zhang J, Shao F, Zhu D, Liu Y, Chen G, Liang J, Sun Q, Qiu Z, Zhang C. Loss of FMRP Impaired Hippocampal Long-Term Plasticity and Spatial Learning in Rats. Front Mol Neurosci 2017; 10:269. [PMID: 28894415 PMCID: PMC5581399 DOI: 10.3389/fnmol.2017.00269] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Accepted: 08/09/2017] [Indexed: 11/13/2022] Open
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by mutations in the FMR1 gene that inactivate expression of the gene product, the fragile X mental retardation 1 protein (FMRP). In this study, we used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology to generate Fmr1 knockout (KO) rats by disruption of the fourth exon of the Fmr1 gene. Western blotting analysis confirmed that the FMRP was absent from the brains of the Fmr1 KO rats (Fmr1exon4-KO ). Electrophysiological analysis revealed that the theta-burst stimulation (TBS)-induced long-term potentiation (LTP) and the low-frequency stimulus (LFS)-induced long-term depression (LTD) were decreased in the hippocampal Schaffer collateral pathway of the Fmr1exon4-KO rats. Short-term plasticity, measured as the paired-pulse ratio, remained normal in the KO rats. The synaptic strength mediated by the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) was also impaired. Consistent with previous reports, the Fmr1exon4-KO rats demonstrated an enhanced 3,5-dihydroxyphenylglycine (DHPG)-induced LTD in the present study, and this enhancement is insensitive to protein translation. In addition, the Fmr1exon4-KO rats showed deficits in the probe trial in the Morris water maze test. These results demonstrate that deletion of the Fmr1 gene in rats specifically impairs long-term synaptic plasticity and hippocampus-dependent learning in a manner resembling the key symptoms of FXS. Furthermore, the Fmr1exon4-KO rats displayed impaired social interaction and macroorchidism, the results consistent with those observed in patients with FXS. Thus, Fmr1exon4-KO rats constitute a novel rat model of FXS that complements existing mouse models.
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Affiliation(s)
- Yonglu Tian
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University-IDG/McGovern Institute for Brain Research, Peking UniversityBeijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking UniversityBeijing, China
| | - Chaojuan Yang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University-IDG/McGovern Institute for Brain Research, Peking UniversityBeijing, China
| | - Shujiang Shang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University-IDG/McGovern Institute for Brain Research, Peking UniversityBeijing, China
| | - Yijun Cai
- CAS Key Laboratory of Primate Neurobiology, Institute of Neuroscience, Chinese Academy of SciencesShanghai, China
| | - Xiaofei Deng
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of SciencesBeijing, China
| | - Jian Zhang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University-IDG/McGovern Institute for Brain Research, Peking UniversityBeijing, China
| | - Feng Shao
- Department of Psychology, Peking UniversityBeijing, China
| | - Desheng Zhu
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University-IDG/McGovern Institute for Brain Research, Peking UniversityBeijing, China
| | - Yunbo Liu
- Institute of Laboratory Animal Science, Peking Union Medical College/Chinese Academy of Medical SciencesBeijing, China
| | - Guiquan Chen
- MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Nanjing UniversityNanjing, China
| | - Jing Liang
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of SciencesBeijing, China
| | - Qiang Sun
- CAS Key Laboratory of Primate Neurobiology, Institute of Neuroscience, Chinese Academy of SciencesShanghai, China
| | - Zilong Qiu
- CAS Key Laboratory of Primate Neurobiology, Institute of Neuroscience, Chinese Academy of SciencesShanghai, China
| | - Chen Zhang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University-IDG/McGovern Institute for Brain Research, Peking UniversityBeijing, China.,Key Laboratory for Neuroscience, Ministry of Education/National Health and Family Planning Commission, Peking UniversityBeijing, China
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