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Volianskis R, Lundbye CJ, Petroff GN, Jane DE, Georgiou J, Collingridge GL. Cage effects on synaptic plasticity and its modulation in a mouse model of fragile X syndrome. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230484. [PMID: 38853552 DOI: 10.1098/rstb.2023.0484] [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: 02/01/2024] [Accepted: 04/08/2024] [Indexed: 06/11/2024] Open
Abstract
Fragile X syndrome (FXS) is characterized by impairments in executive function including different types of learning and memory. Long-term potentiation (LTP), thought to underlie the formation of memories, has been studied in the Fmr1 mouse model of FXS. However, there have been many discrepancies in the literature with inconsistent use of littermate and non-littermate Fmr1 knockout (KO) and wild-type (WT) control mice. Here, the influence of the breeding strategy (cage effect) on short-term potentiation (STP), LTP, contextual fear conditioning (CFC), expression of N-methyl-d-aspartate receptor (NMDAR) subunits and the modulation of NMDARs, were examined. The largest deficits in STP, LTP and CFC were found in KO mice compared with non-littermate WT. However, the expression of NMDAR subunits was unchanged in this comparison. Rather, NMDAR subunit (GluN1, 2A, 2B) expression was sensitive to the cage effect, with decreased expression in both WT and KO littermates compared with non-littermates. Interestingly, an NMDAR-positive allosteric modulator, UBP714, was only effective in potentiating the induction of LTP in non-littermate KO mice and not the littermate KO mice. These results suggest that commonly studied phenotypes in Fmr1 KOs are sensitive to the cage effect and therefore the breeding strategy may contribute to discrepancies in the literature.This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Rasa Volianskis
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Camilla J Lundbye
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Gillian N Petroff
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - David E Jane
- Hello Bio Limited, Cabot Park, Avonmouth, Bristol BS11 0QL, UK
| | - John Georgiou
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
- TANZ Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Graham L Collingridge
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health System, Toronto, Ontario M5G 1X5, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- TANZ Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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Feuge J, Scharkowski F, Michaelsen-Preusse K, Korte M. FMRP Modulates Activity-Dependent Spine Plasticity by Binding Cofilin1 mRNA and Regulating Localization and Local Translation. Cereb Cortex 2020; 29:5204-5216. [PMID: 30953439 DOI: 10.1093/cercor/bhz059] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 02/14/2019] [Accepted: 02/27/2019] [Indexed: 11/13/2022] Open
Abstract
Multiple variants of intellectual disability, e.g., the Fragile X Syndrome are associated with alterations in dendritic spine morphology, thereby pointing to dysregulated actin dynamics during development and processes of synaptic plasticity. Surprisingly, although the necessity of spine actin remodeling was demonstrated repeatedly, the importance and precise role of actin regulators is often undervalued. Here, we provide evidence that structural and functional plasticity are severely impaired after NMDAR-dependent LTP in the hippocampus of Fmr1 KO mice. We can link these defects to an aberrant activity-dependent regulation of Cofilin 1 (cof1) as activity-dependent modulations of local cof1 mRNA availability, local cof1 translation as well as total cof1 expression are impaired in the absence of FMRP. Finally, we can rescue activity-dependent structural plasticity in KO neurons by mimicking the regulation of cof1 observed in WT cells, thereby illustrating the potential of actin modulators to provide novel treatment strategies for the Fragile X Syndrome.
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Affiliation(s)
- Jonas Feuge
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, Germany
| | | | | | - Martin Korte
- Division of Cellular Neurobiology, Zoological Institute, TU Braunschweig, Germany.,Helmholtz Center for Infection Research, Research group Neuroinflammation and Neurodegeneration, Braunschweig, Germany
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3
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Zhang H, Bramham CR. Bidirectional Dysregulation of AMPA Receptor-Mediated Synaptic Transmission and Plasticity in Brain Disorders. Front Synaptic Neurosci 2020; 12:26. [PMID: 32754026 PMCID: PMC7366028 DOI: 10.3389/fnsyn.2020.00026] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 05/28/2020] [Indexed: 12/11/2022] Open
Abstract
AMPA receptors (AMPARs) are glutamate-gated ion channels that mediate the majority of fast excitatory synaptic transmission throughout the brain. Changes in the properties and postsynaptic abundance of AMPARs are pivotal mechanisms in synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD) of synaptic transmission. A wide range of neurodegenerative, neurodevelopmental and neuropsychiatric disorders, despite their extremely diverse etiology, pathogenesis and symptoms, exhibit brain region-specific and AMPAR subunit-specific aberrations in synaptic transmission or plasticity. These include abnormally enhanced or reduced AMPAR-mediated synaptic transmission or plasticity. Bidirectional reversal of these changes by targeting AMPAR subunits or trafficking ameliorates drug-seeking behavior, chronic pain, epileptic seizures, or cognitive deficits. This indicates that bidirectional dysregulation of AMPAR-mediated synaptic transmission or plasticity may contribute to the expression of many brain disorders and therefore serve as a therapeutic target. Here, we provide a synopsis of bidirectional AMPAR dysregulation in animal models of brain disorders and review the preclinical evidence on the therapeutic targeting of AMPARs.
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Affiliation(s)
- Hongyu Zhang
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Clive R Bramham
- Department of Biomedicine, University of Bergen, Bergen, Norway
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4
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Dendritic Spine Dynamics after Peripheral Nerve Injury: An Intravital Structural Study. J Neurosci 2020; 40:4297-4308. [PMID: 32371602 DOI: 10.1523/jneurosci.2858-19.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 02/10/2020] [Accepted: 02/28/2020] [Indexed: 11/21/2022] Open
Abstract
Neuropathic pain is an intractable medical condition with few or no options for effective treatment. Emerging evidence shows a strong structure-function relationship between dendritic spine dysgenesis and the presence of neuropathic pain. Postmortem tissue analyses can only imply dynamic structural changes associated with injury-induced pain. Here, we profiled the in vivo dynamics of dendritic spines over time on the same superficial dorsal horn (lamina II) neurons before and after peripheral nerve injury-induced pain. We used a two-photon, whole-animal imaging paradigm that permitted repeat imaging of the same dendritic branches of these neurons in C57/Bl6 Thy1-YFP male mice. Our study demonstrates, for the first time, the ongoing, steady-state changes in dendritic spine dynamics in the dorsal horn associated with peripheral nerve injury and pain. Ultimately, the relationship between altered dendritic spine dynamics and neuropathic pain may serve as a structure-based opportunity to investigate mechanisms of pain following injury and disease.SIGNIFICANCE STATEMENT This work is important because it demonstrates for the first time: (1) the powerful utility of intravital study of dendritic spine dynamics in the superficial dorsal horn; (2) that nerve injury-induced pain triggers changes in dendritic spine steady-state behavior in the spinal cord dorsal horn; and (3) this work opens the door to further investigations in vivo of spinal cord dendritic spine dynamics in the context of injury and disease.
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Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder that causes intellectual disability. It is a leading known genetic cause of autism. In addition to cognitive, social, and communication deficits, humans with FXS demonstrate abnormal sensory processing including sensory hypersensitivity. Sensory hypersensitivity commonly manifests as auditory, tactile, or visual defensiveness or avoidance. Clinical, behavioral, and electrophysiological studies consistently show auditory hypersensitivity, impaired habituation to repeated sounds, and reduced auditory attention in humans with FXS. Children with FXS also exhibit significant visuospatial impairments. Studies in infants and toddlers with FXS have documented impairments in processing texture-defined motion stimuli, temporal flicker, perceiving ordinal numerical sequence, and the ability to maintain the identity of dynamic object information during occlusion. Consistent with the observations in humans with FXS, fragile X mental retardation 1 ( Fmr1) gene knockout (KO) rodent models of FXS also show seizures, abnormal visual-evoked responses, auditory hypersensitivity, and abnormal processing at multiple levels of the auditory system, including altered acoustic startle responses. Among other sensory symptoms, individuals with FXS exhibit tactile defensiveness. Fmr1 KO mice also show impaired encoding of tactile stimulation frequency and larger size of receptive fields in the somatosensory cortex. Since sensory deficits are relatively more tractable from circuit mechanisms and developmental perspectives than more complex social behaviors, the focus of this review is on clinical, functional, and structural studies that outline the auditory, visual, and somatosensory processing deficits in FXS. The similarities in sensory phenotypes between humans with FXS and animal models suggest a likely conservation of basic sensory processing circuits across species and may provide a translational platform to not just develop biomarkers but also to understand underlying mechanisms. We argue that preclinical studies in animal models of FXS can facilitate the ongoing search for new therapeutic approaches in FXS by understanding mechanisms of basic sensory processing circuits and behaviors that are conserved across species.
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Affiliation(s)
- Maham Rais
- 1 Division of Biomedical Sciences, University of California Riverside School of Medicine, CA, USA.,2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA
| | - Devin K Binder
- 1 Division of Biomedical Sciences, University of California Riverside School of Medicine, CA, USA.,2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA.,3 Neuroscience Graduate Program, University of California Riverside, CA, USA
| | - Khaleel A Razak
- 2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA.,3 Neuroscience Graduate Program, University of California Riverside, CA, USA.,4 Psychology Department, University of California Riverside, CA, USA
| | - Iryna M Ethell
- 1 Division of Biomedical Sciences, University of California Riverside School of Medicine, CA, USA.,2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA.,3 Neuroscience Graduate Program, University of California Riverside, CA, USA
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Kang S, Cox CL, Gulley JM. High frequency stimulation-induced plasticity in the prelimbic cortex of rats emerges during adolescent development and is associated with an increase in dopamine receptor function. Neuropharmacology 2018; 141:158-166. [PMID: 30165079 DOI: 10.1016/j.neuropharm.2018.08.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 08/13/2018] [Accepted: 08/26/2018] [Indexed: 01/10/2023]
Abstract
Recent studies in rats suggest that high frequency stimulation (HFS) in the ventral hippocampus induces long-term depression (LTD) in the deep layer of the medial prefrontal cortex (mPFC), but only after the prefrontal GABA system has sufficiently developed during early-to mid-adolescence. It is not clear whether this LTD is specific to the hippocampus-mPFC circuit or is instead an intrinsitc regulatory mechanism for the developed mPFC neuro-network. The potential mechanisms underlying this HFS-induced LTD are also largely unknown. In the current study, naïve male Sprague Dawley rats were sacrificed during peri-adolescence or young adulthood for in vitro extracellular recording to determine if HFS delivered in the prelimbic cortex (PLC) would induce LTD in an age-dependent manner and if dopamine receptors are involved in the expression of this LTD. We found four trains of stimulation at 50 Hz induced an LTD in the PFC of adult, but not peri-adolescent, rats. This LTD required intact GABAA receptor functioning and could also be blocked by dopamine D1 or D2 receptor antagonists. Bath application of selective D1 or D2 receptor agonists produced a significant facilitation or suppression in the field potential, respectively, and these effects were only observed in the adult PLC. Furthermore, neither D1 nor D2 stimualtion prior to HFS was able to facilitate LTD in the peri-adolescent PLC. Together, these results suggest dopamine receptor functionality in the PLC increases during adolescent development and it plays an important role in this late-maturating form of plasticity.
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Affiliation(s)
- Shuo Kang
- Neuroscience Program, University of Illinois, Urbana-Champaign, USA
| | - Charles L Cox
- Neuroscience Program, University of Illinois, Urbana-Champaign, USA; Department of Molecular and Integrative Physiology, University of Illinois, Urbana-Champaign, USA; Department of Pharmacology, University of Illinois, Urbana-Champaign, USA; Beckman Institute for Advanced Science, University of Illinois, Urbana-Champaign, USA.
| | - Joshua M Gulley
- Neuroscience Program, University of Illinois, Urbana-Champaign, USA; Department of Psychology, University of Illinois, Urbana-Champaign, USA; Institute for Genomic Biology, University of Illinois, Urbana-Champaign, USA.
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7
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Westmark PR, Dekundy A, Gravius A, Danysz W, Westmark CJ. Rescue of Fmr1 KO phenotypes with mGluR 5 inhibitors: MRZ-8456 versus AFQ-056. Neurobiol Dis 2018; 119:190-198. [PMID: 30125640 DOI: 10.1016/j.nbd.2018.08.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 08/08/2018] [Accepted: 08/13/2018] [Indexed: 12/23/2022] Open
Abstract
Metabotropic glutamate receptor 5 (mGluR5) is a drug target for central nervous system disorders such as fragile X syndrome that involve excessive glutamate-induced excitation. We tested the efficacy of a novel negative allosteric modulator of mGluR5 developed by Merz Pharmaceuticals, MRZ-8456, in comparison to MPEP and AFQ-056 (Novartis, a.k.a. mavoglurant) in both in vivo and in vitro assays in a mouse model of fragile X syndrome, Fmr1KO mice. The in vivo assays included susceptibility to audiogenic-induced seizures and pharmacokinetic measurements of drug availability. The in vitro assays included dose response assessments of biomarker expression and dendritic spine length and density in cultured primary neurons. Both MRZ-8456 and AFQ-056 attenuated wild running and audiogenic-induced seizures in Fmr1KO mice with similar pharmacokinetic profiles. Both drugs significantly reduced dendritic expression of amyloid-beta protein precursor (APP) and rescued the ratio of mature to immature dendritic spines. These findings demonstrate that MRZ-8456, a drug being developed for the treatment of motor complications of L-DOPA in Parkinson's disease and which completed a phase I clinical trial, is effective in attenuating both well-established (seizures and dendritic spine maturity) and exploratory biomarker (APP expression) phenotypes in a mouse model of fragile X syndrome.
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Affiliation(s)
- Pamela R Westmark
- University of Wisconsin-Madison, Department of Neurology, Madison, WI, USA; University of Wisconsin-Madison, Department of Medicine, Madison, WI, USA
| | - Andrzej Dekundy
- Merz Pharmaceuticals GmbH, Eckenheimer Landstrasse 100, 60318 Frankfurt am Main, Germany
| | - Andreas Gravius
- Merz Pharmaceuticals GmbH, Eckenheimer Landstrasse 100, 60318 Frankfurt am Main, Germany
| | - Wojciech Danysz
- Merz Pharmaceuticals GmbH, Eckenheimer Landstrasse 100, 60318 Frankfurt am Main, Germany
| | - Cara J Westmark
- University of Wisconsin-Madison, Department of Neurology, Madison, WI, USA.
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Michaelsen‐Preusse K, Feuge J, Korte M. Imbalance of synaptic actin dynamics as a key to fragile X syndrome? J Physiol 2018; 596:2773-2782. [PMID: 29380377 PMCID: PMC6046079 DOI: 10.1113/jp275571] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 01/09/2018] [Indexed: 11/08/2022] Open
Abstract
Our experiences and memories define who we are, and evidence has accumulated that memory formation is dependent on functional and structural adaptations of synaptic structures in our brain. Especially dendritic spines, the postsynaptic compartments of synapses show a strong structure-to-function relationship and a high degree of structural plasticity. Although the molecular mechanisms are not completely understood, it is known that these modifications are highly dependent on the actin cytoskeleton, the major cytoskeletal component of the spine. Given the crucial involvement of actin in these mechanisms, dysregulations of spine actin dynamics (reflected by alterations in dendritic spine morphology) can be found in a variety of neurological disorders ranging from schizophrenia to several forms of autism spectrum disorders such as fragile X syndrome (FXS). FXS is caused by a single mutation leading to an inactivation of the X-linked fragile X mental retardation 1 gene and loss of its gene product, the RNA-binding protein fragile X mental retardation protein 1 (FMRP), which normally can be found both pre- and postsynaptically. FMRP is involved in mRNA transport as well as regulation of local translation at the synapse, and although hundreds of FMRP-target mRNAs could be identified only a very few interactions between FMRP and actin-regulating proteins have been reported and validated. In this review we give an overview of recent work by our lab and others providing evidence that dysregulated actin dynamics might indeed be at the very base of a deeper understanding of neurological disorders ranging from cognitive impairment to the autism spectrum.
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Affiliation(s)
- Kristin Michaelsen‐Preusse
- Zoological Institute, Division of Cellular NeurobiologyTU BraunschweigSpielmannstr. 7Braunschweig38106Germany
| | - Jonas Feuge
- Zoological Institute, Division of Cellular NeurobiologyTU BraunschweigSpielmannstr. 7Braunschweig38106Germany
| | - Martin Korte
- Zoological Institute, Division of Cellular NeurobiologyTU BraunschweigSpielmannstr. 7Braunschweig38106Germany
- Helmholtz Centre for Infection ResearchAG NINDInhoffenstr. 7Braunschweig38124Germany
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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: 77] [Impact Index Per Article: 12.8] [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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10
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Gilbert J, Man HY. Fundamental Elements in Autism: From Neurogenesis and Neurite Growth to Synaptic Plasticity. Front Cell Neurosci 2017; 11:359. [PMID: 29209173 PMCID: PMC5701944 DOI: 10.3389/fncel.2017.00359] [Citation(s) in RCA: 161] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 10/31/2017] [Indexed: 01/12/2023] Open
Abstract
Autism spectrum disorder (ASD) is a set of neurodevelopmental disorders with a high prevalence and impact on society. ASDs are characterized by deficits in both social behavior and cognitive function. There is a strong genetic basis underlying ASDs that is highly heterogeneous; however, multiple studies have highlighted the involvement of key processes, including neurogenesis, neurite growth, synaptogenesis and synaptic plasticity in the pathophysiology of neurodevelopmental disorders. In this review article, we focus on the major genes and signaling pathways implicated in ASD and discuss the cellular, molecular and functional studies that have shed light on common dysregulated pathways using in vitro, in vivo and human evidence. HighlightsAutism spectrum disorder (ASD) has a prevalence of 1 in 68 children in the United States. ASDs are highly heterogeneous in their genetic basis. ASDs share common features at the cellular and molecular levels in the brain. Most ASD genes are implicated in neurogenesis, structural maturation, synaptogenesis and function.
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Affiliation(s)
- James Gilbert
- Department of Biology, Boston University, Boston, MA, United States
| | - Heng-Ye Man
- Department of Biology, Boston University, Boston, MA, United States.,Department of Pharmacology & Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
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Borrie SC, Brems H, Legius E, Bagni C. Cognitive Dysfunctions in Intellectual Disabilities: The Contributions of the Ras-MAPK and PI3K-AKT-mTOR Pathways. Annu Rev Genomics Hum Genet 2017; 18:115-142. [DOI: 10.1146/annurev-genom-091416-035332] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sarah C. Borrie
- Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
| | - Hilde Brems
- Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
| | - Eric Legius
- Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
| | - Claudia Bagni
- Department of Human Genetics, KU Leuven, 3000 Leuven, Belgium
- Department of Fundamental Neuroscience, University of Lausanne, 1005 Lausanne, Switzerland
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, 00173 Rome, Italy
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12
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Cheng GR, Li XY, Xiang YD, Liu D, McClintock SM, Zeng Y. The implication of AMPA receptor in synaptic plasticity impairment and intellectual disability in fragile X syndrome. Physiol Res 2017; 66:715-727. [PMID: 28730825 DOI: 10.33549/physiolres.933473] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Fragile X syndrome (FXS) is the most frequently inherited form of intellectual disability and prevalent single-gene cause of autism. A priority of FXS research is to determine the molecular mechanisms underlying the cognitive and social functioning impairments in humans and the FXS mouse model. Glutamate ionotropic alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (AMPARs) mediate a majority of fast excitatory neurotransmission in the central nervous system and are critically important for nearly all aspects of brain function, including neuronal development, synaptic plasticity, and learning and memory. Both preclinical and clinical studies have indicated that expression, trafficking, and functions of AMPARs are altered and result in altered synapse development and plasticity, cognitive impairment, and poor mental health in FXS. In this review, we discuss the contribution of AMPARs to disorders of FXS by highlighting recent research advances with a specific focus on change in AMPARs expression, trafficking, and dependent synaptic plasticity. Since changes in synaptic strength underlie the basis of learning, development, and disease, we suggest that the current knowledge base of AMPARs has reached a unique point to permit a comprehensive re-evaluation of their roles in FXS.
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Affiliation(s)
- Gui-Rong Cheng
- Brain and Cognition Research Institute, School of Medicine, Wuhan University of Science and Technology, Wuhan, China, Hubei Key Laboratory of Hazard Identification and Control for Occupational Disease, Wuhan, China.
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13
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Tatti R, Haley MS, Swanson O, Tselha T, Maffei A. Neurophysiology and Regulation of the Balance Between Excitation and Inhibition in Neocortical Circuits. Biol Psychiatry 2017; 81:821-831. [PMID: 27865453 PMCID: PMC5374043 DOI: 10.1016/j.biopsych.2016.09.017] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 08/25/2016] [Accepted: 09/15/2016] [Indexed: 12/18/2022]
Abstract
Brain function relies on the ability of neural networks to maintain stable levels of activity, while experiences sculpt them. In the neocortex, the balance between activity and stability relies on the coregulation of excitatory and inhibitory inputs onto principal neurons. Shifts of excitation or inhibition result in altered excitability impaired processing of incoming information. In many neurodevelopmental and neuropsychiatric disorders, the excitability of local circuits is altered, suggesting that their pathophysiology may involve shifts in synaptic excitation, inhibition, or both. Most studies focused on identifying the cellular and molecular mechanisms controlling network excitability to assess whether they may be altered in animal models of disease. The impact of changes in excitation/inhibition balance on local circuit and network computations is not clear. Here we report findings on the integration of excitatory and inhibitory inputs in healthy cortical circuits and discuss how shifts in excitation/inhibition balance may relate to pathological phenotypes.
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Affiliation(s)
- Roberta Tatti
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Melissa S. Haley
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Olivia Swanson
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Tenzin Tselha
- Dept. of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794
| | - Arianna Maffei
- Department of Neurobiology and Behavior, Stony Brook University, The State University of New York, Stony Brook, New York.
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14
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Lin YC, Frei JA, Kilander MBC, Shen W, Blatt GJ. A Subset of Autism-Associated Genes Regulate the Structural Stability of Neurons. Front Cell Neurosci 2016; 10:263. [PMID: 27909399 PMCID: PMC5112273 DOI: 10.3389/fncel.2016.00263] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 10/28/2016] [Indexed: 12/15/2022] Open
Abstract
Autism spectrum disorder (ASD) comprises a range of neurological conditions that affect individuals’ ability to communicate and interact with others. People with ASD often exhibit marked qualitative difficulties in social interaction, communication, and behavior. Alterations in neurite arborization and dendritic spine morphology, including size, shape, and number, are hallmarks of almost all neurological conditions, including ASD. As experimental evidence emerges in recent years, it becomes clear that although there is broad heterogeneity of identified autism risk genes, many of them converge into similar cellular pathways, including those regulating neurite outgrowth, synapse formation and spine stability, and synaptic plasticity. These mechanisms together regulate the structural stability of neurons and are vulnerable targets in ASD. In this review, we discuss the current understanding of those autism risk genes that affect the structural connectivity of neurons. We sub-categorize them into (1) cytoskeletal regulators, e.g., motors and small RhoGTPase regulators; (2) adhesion molecules, e.g., cadherins, NCAM, and neurexin superfamily; (3) cell surface receptors, e.g., glutamatergic receptors and receptor tyrosine kinases; (4) signaling molecules, e.g., protein kinases and phosphatases; and (5) synaptic proteins, e.g., vesicle and scaffolding proteins. Although the roles of some of these genes in maintaining neuronal structural stability are well studied, how mutations contribute to the autism phenotype is still largely unknown. Investigating whether and how the neuronal structure and function are affected when these genes are mutated will provide insights toward developing effective interventions aimed at improving the lives of people with autism and their families.
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Affiliation(s)
- Yu-Chih Lin
- Laboratory of Neuronal Connectivity, Program in Neuroscience, Hussman Institute for Autism, Baltimore MD, USA
| | - Jeannine A Frei
- Laboratory of Neuronal Connectivity, Program in Neuroscience, Hussman Institute for Autism, Baltimore MD, USA
| | - Michaela B C Kilander
- Laboratory of Neuronal Connectivity, Program in Neuroscience, Hussman Institute for Autism, Baltimore MD, USA
| | - Wenjuan Shen
- Laboratory of Neuronal Connectivity, Program in Neuroscience, Hussman Institute for Autism, Baltimore MD, USA
| | - Gene J Blatt
- Laboratory of Autism Neurocircuitry, Program in Neuroscience, Hussman Institute for Autism, Baltimore MD, USA
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15
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Zhao P, Hill M, Liu S, Chen L, Bangalore L, Waxman SG, Tan AM. Dendritic spine remodeling following early and late Rac1 inhibition after spinal cord injury: evidence for a pain biomarker. J Neurophysiol 2016; 115:2893-910. [PMID: 26936986 DOI: 10.1152/jn.01057.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/01/2016] [Indexed: 12/15/2022] Open
Abstract
Neuropathic pain is a significant complication following spinal cord injury (SCI) with few effective treatments. Drug development for neuropathic pain often fails because preclinical studies do not always translate well to clinical conditions. Identification of biological characteristics predictive of disease state or drug responsiveness could facilitate more effective clinical translation. Emerging evidence indicates a strong correlation between dendritic spine dysgenesis and neuropathic pain. Because dendritic spines are located on dorsal horn neurons within the spinal cord nociceptive system, dendritic spine remodeling provides a unique opportunity to understand sensory dysfunction after SCI. In this study, we provide support for the postulate that dendritic spine profiles can serve as biomarkers for neuropathic pain. We show that dendritic spine profiles after SCI change to a dysgenic state that is characteristic of neuropathic pain in a Rac1-dependent manner. Suppression of the dysgenic state through inhibition of Rac1 activity is accompanied by attenuation of neuropathic pain. Both dendritic spine dysgenesis and neuropathic pain return when inhibition of Rac1 activity is lifted. These findings suggest the utility of dendritic spines as structural biomarkers for neuropathic pain.
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Affiliation(s)
- Peng Zhao
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Myriam Hill
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Shujun Liu
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Lubin Chen
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Lakshmi Bangalore
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Andrew M Tan
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
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16
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Nona CN, Bermejo MK, Ramsey AJ, Nobrega JN. Changes in dendritic spine density in the nucleus accumbens do not underlie ethanol sensitization. Synapse 2015; 69:607-10. [PMID: 26340045 DOI: 10.1002/syn.21862] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 07/31/2015] [Accepted: 08/25/2015] [Indexed: 01/31/2023]
Abstract
Behavioral sensitization to various drugs of abuse has been shown to change dendritic spine density and/or morphology of nucleus accumbens (NAc) medium spiny neurons, an effect seen across drug classes. However, is it not known whether behavioral sensitization to ethanol (EtOH) is also associated with structural changes in this region. Here we compared dendritic spine density and morphology between mice showing High vs. Low levels of EtOH sensitization and found that high levels of EtOH sensitization were not associated with changes in dendritic spine density or spine type. Unexpectedly, however, a significant increase in the density of stubby-type spines was seen in mice that were resistant to sensitization. Since the presence of this spine type has been associated with long-term depression and cognitive/learning deficits this may explain why these mice fail to sensitize and why they show poor performance in conditioning tasks, as previously shown. A possible causal role for structural plasticity in behavioral sensitization to various drugs has been debated. In the case of EtOH sensitization, our results suggest that drug-induced changes in structural plasticity in the accumbens neurons may not be the cause of sensitized behavior.
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Affiliation(s)
- Christina N Nona
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada.,Behavioural Neurobiology Laboratory, Campbell Family Mental Health Research Institute, CAMH, Toronto, Ontario, Canada
| | - Marie Kristel Bermejo
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - Amy J Ramsey
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada
| | - José N Nobrega
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario, Canada.,Behavioural Neurobiology Laboratory, Campbell Family Mental Health Research Institute, CAMH, Toronto, Ontario, Canada.,Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada.,Department of Psychology, University of Toronto, Toronto, Ontario, Canada
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17
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Mottron L, Duret P, Mueller S, Moore RD, Forgeot d'Arc B, Jacquemont S, Xiong L. Sex differences in brain plasticity: a new hypothesis for sex ratio bias in autism. Mol Autism 2015; 6:33. [PMID: 26052415 PMCID: PMC4456778 DOI: 10.1186/s13229-015-0024-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Accepted: 04/27/2015] [Indexed: 01/13/2023] Open
Abstract
Several observations support the hypothesis that differences in synaptic and regional cerebral plasticity between the sexes account for the high ratio of males to females in autism. First, males are more susceptible than females to perturbations in genes involved in synaptic plasticity. Second, sex-related differences in non-autistic brain structure and function are observed in highly variable regions, namely, the heteromodal associative cortices, and overlap with structural particularities and enhanced activity of perceptual associative regions in autistic individuals. Finally, functional cortical reallocations following brain lesions in non-autistic adults (for example, traumatic brain injury, multiple sclerosis) are sex-dependent. Interactions between genetic sex and hormones may therefore result in higher synaptic and consecutively regional plasticity in perceptual brain areas in males than in females. The onset of autism may largely involve mutations altering synaptic plasticity that create a plastic reaction affecting the most variable and sexually dimorphic brain regions. The sex ratio bias in autism may arise because males have a lower threshold than females for the development of this plastic reaction following a genetic or environmental event.
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Affiliation(s)
- Laurent Mottron
- Centre d'excellence en Troubles envahissants du dévelopement de l'Université de Montréal (CETEDUM), Montréal, Canada.,Hôpital Rivière-des-Prairies, Département de Psychiatrie, Montréal, Canada.,Centre de Recherche de l'Institut Universitaire en Santé Mentale de Montréal, Québec, Canada.,Department of Psychiatry, University of Montreal, Québec, Canada
| | - Pauline Duret
- Centre d'excellence en Troubles envahissants du dévelopement de l'Université de Montréal (CETEDUM), Montréal, Canada.,Hôpital Rivière-des-Prairies, Département de Psychiatrie, Montréal, Canada.,Centre de Recherche de l'Institut Universitaire en Santé Mentale de Montréal, Québec, Canada.,Department of Psychiatry, University of Montreal, Québec, Canada.,Département de Biologie, École Normale Supérieure de Lyon, Lyon, CEDEX 07 France
| | - Sophia Mueller
- Institute of Clinical Radiology, University Hospitals, Munich, Germany.,Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA 02129 USA.,Harvard University, Center for Brain Science, Cambridge, MA 02138 USA
| | - Robert D Moore
- Department of Psychiatry, University of Montreal, Québec, Canada.,Department of Health Sciences, University of Montreal, Montreal, Canada.,College of Applied Health Sciences, University of Illinois, Urbana-Champaign, USA
| | - Baudouin Forgeot d'Arc
- Centre d'excellence en Troubles envahissants du dévelopement de l'Université de Montréal (CETEDUM), Montréal, Canada.,Hôpital Rivière-des-Prairies, Département de Psychiatrie, Montréal, Canada.,Centre de Recherche de l'Institut Universitaire en Santé Mentale de Montréal, Québec, Canada.,Department of Psychiatry, University of Montreal, Québec, Canada
| | - Sebastien Jacquemont
- Department of Psychiatry, University of Montreal, Québec, Canada.,Centre de recherche, Centre Hospitalier Universitaire Sainte Justine, Montréal, Canada.,Service of Medical Genetics, University Hospital of Lausanne, University of Lausanne, Lausanne, 1011 Switzerland
| | - Lan Xiong
- Centre de Recherche de l'Institut Universitaire en Santé Mentale de Montréal, Québec, Canada.,Department of Psychiatry, University of Montreal, Québec, Canada
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18
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Neuhofer D, Henstridge CM, Dudok B, Sepers M, Lassalle O, Katona I, Manzoni OJ. Functional and structural deficits at accumbens synapses in a mouse model of Fragile X. Front Cell Neurosci 2015; 9:100. [PMID: 25859182 PMCID: PMC4374460 DOI: 10.3389/fncel.2015.00100] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/07/2015] [Indexed: 12/26/2022] Open
Abstract
Fragile X is the most common cause of inherited intellectual disability and a leading cause of autism. The disease is caused by mutation of a single X-linked gene called fmr1 that codes for the Fragile X mental retardation protein (FMRP), a 71 kDa protein, which acts mainly as a translation inhibitor. Fragile X patients suffer from cognitive and emotional deficits that coincide with abnormalities in dendritic spines. Changes in spine morphology are often associated with altered excitatory transmission and long-term plasticity, the most prominent deficit in fmr1-/y mice. The nucleus accumbens, a central part of the mesocortico-limbic reward pathway, is now considered as a core structure in the control of social behaviors. Although the socio-affective impairments observed in Fragile X suggest dysfunctions in the accumbens, the impact of the lack of FMRP on accumbal synapses has scarcely been studied. Here we report for the first time a new spike timing-dependent plasticity paradigm that reliably triggers NMDAR-dependent long-term potentiation (LTP) of excitatory afferent inputs of medium spiny neurons (MSN) in the nucleus accumbens core region. Notably, we discovered that this LTP was completely absent in fmr1-/y mice. In the fmr1-/y accumbens intrinsic membrane properties of MSNs and basal excitatory neurotransmission remained intact in the fmr1-/y accumbens but the deficit in LTP was accompanied by an increase in evoked AMPA/NMDA ratio and a concomitant reduction of spontaneous NMDAR-mediated currents. In agreement with these physiological findings, we found significantly more filopodial spines in fmr1-/y mice by using an ultrastructural electron microscopic analysis of accumbens core medium spiny neuron spines. Surprisingly, spine elongation was specifically due to the longer longitudinal axis and larger area of spine necks, whereas spine head morphology and postsynaptic density size on spine heads remained unaffected in the fmr1-/y accumbens. These findings together reveal new structural and functional synaptic deficits in Fragile X.
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Affiliation(s)
- Daniela Neuhofer
- INSERM U901 Marseille, France ; INMED Marseille, France ; Université de Aix-Marseille, UMR S901 Marseille, France
| | - Christopher M Henstridge
- Momentum Laboratory of Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary
| | - Barna Dudok
- Momentum Laboratory of Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary ; School of Ph.D. Studies, Semmelweis University Budapest, Hungary
| | - Marja Sepers
- Department of Psychiatry, University of British Columbia Vancouver, Canada
| | - Olivier Lassalle
- INSERM U901 Marseille, France ; INMED Marseille, France ; Université de Aix-Marseille, UMR S901 Marseille, France
| | - István Katona
- Momentum Laboratory of Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary
| | - Olivier J Manzoni
- INSERM U901 Marseille, France ; INMED Marseille, France ; Université de Aix-Marseille, UMR S901 Marseille, France
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19
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Tan AM. Dendritic spine dysgenesis in neuropathic pain. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 131:385-408. [PMID: 25744680 DOI: 10.1016/bs.pmbts.2014.12.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The failure of neuropathic pain to abate even years after trauma suggests that adverse changes to synaptic function must exist in a chronic pathological state in nociceptive pathways. The chronicity of neuropathic pain therefore underscores the importance of understanding the contribution of dendritic spines--micron-sized postsynaptic structures that represent modifiable sites of synaptic contact. Historically, dendritic spines have been of great interest to the learning and memory field. More recent evidence points to the exciting implication that abnormal dendritic spine structure following disease or injury may represent a "molecular memory" for maintaining chronic pain. Dendritic spine dysgenesis in dorsal horn neurons contributes to nociceptive hyperexcitability associated with neuropathic pain, as demonstrated in multiple pain models, i.e., spinal cord injury, peripheral nerve injury, diabetic neuropathy, and thermal burn injury. Because of the relationship between dendritic spine structure and neuronal function, a thorough investigation of dendritic spine behavior in the spinal cord is a unique opportunity to better understand the mechanisms of sensory dysfunction after injury or disease. At a conceptual level, a spinal memory mechanism that engages dendritic spine remodeling would also contribute to a broad range of intractable neurological conditions. Molecules involved in regulating dendritic spine plasticity may offer novel targets for the development of effective and durable therapies for neurological disease.
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Affiliation(s)
- Andrew Michael Tan
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut, USA; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut, USA; Hopkins School, New Haven, Connecticut, USA.
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20
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Phillips M, Pozzo-Miller L. Dendritic spine dysgenesis in autism related disorders. Neurosci Lett 2015; 601:30-40. [PMID: 25578949 DOI: 10.1016/j.neulet.2015.01.011] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 12/31/2014] [Accepted: 01/04/2015] [Indexed: 01/22/2023]
Abstract
The activity-dependent structural and functional plasticity of dendritic spines has led to the long-standing belief that these neuronal compartments are the subcellular sites of learning and memory. Of relevance to human health, central neurons in several neuropsychiatric illnesses, including autism related disorders, have atypical numbers and morphologies of dendritic spines. These so-called dendritic spine dysgeneses found in individuals with autism related disorders are consistently replicated in experimental mouse models. Dendritic spine dysgenesis reflects the underlying synaptopathology that drives clinically relevant behavioral deficits in experimental mouse models, providing a platform for testing new therapeutic approaches. By examining molecular signaling pathways, synaptic deficits, and spine dysgenesis in experimental mouse models of autism related disorders we find strong evidence for mTOR to be a critical point of convergence and promising therapeutic target.
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Affiliation(s)
- Mary Phillips
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Lucas Pozzo-Miller
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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21
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Francis SM, Sagar A, Levin-Decanini T, Liu W, Carter CS, Jacob S. Oxytocin and vasopressin systems in genetic syndromes and neurodevelopmental disorders. Brain Res 2014; 1580:199-218. [PMID: 24462936 PMCID: PMC4305432 DOI: 10.1016/j.brainres.2014.01.021] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/08/2013] [Accepted: 01/15/2014] [Indexed: 10/25/2022]
Abstract
Oxytocin (OT) and arginine vasopressin (AVP) are two small, related neuropeptide hormones found in many mammalian species, including humans. Dysregulation of these neuropeptides have been associated with changes in behavior, especially social interactions. We review how the OT and AVP systems have been investigated in Autism Spectrum Disorder (ASD), Prader-Willi Syndrome (PWS), Williams Syndrome (WS) and Fragile X syndrome (FXS). All of these neurodevelopmental disorders (NDD) are marked by social deficits. While PWS, WS and FXS have identified genetic mutations, ASD stems from multiple genes with complex interactions. Animal models of NDD are invaluable for studying the role and relatedness of OT and AVP in the developing brain. We present data from a FXS mouse model affecting the fragile X mental retardation 1 (Fmr1) gene, resulting in decreased OT and AVP staining cells in some brain regions. Reviewing the research about OT and AVP in these NDD suggests that altered OT pathways may be downstream from different etiological factors and perturbations in development. This has implications for ongoing studies of the therapeutic application of OT in NDD. This article is part of a Special Issue entitled Oxytocin and Social Behav.
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Affiliation(s)
- S M Francis
- University of Minnesota, Department of Psychiatry, Minneapolis, MN, USA
| | - A Sagar
- University of California at Irvine, Department of Psychiatry and Human Behavior, USA
| | - T Levin-Decanini
- University of Minnesota, Department of Psychiatry, Minneapolis, MN, USA
| | - W Liu
- Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
| | - C S Carter
- University of North Carolina, Department of Psychiatry, Chapel Hill, NC, USA
| | - S Jacob
- University of Minnesota, Department of Psychiatry, Minneapolis, MN, USA.
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22
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Yang S, Yang S, Park JS, Kirkwood A, Bao S. Failed stabilization for long-term potentiation in the auditory cortex of FMR1 knockout mice. PLoS One 2014; 9:e104691. [PMID: 25115962 PMCID: PMC4130563 DOI: 10.1371/journal.pone.0104691] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/10/2014] [Indexed: 01/27/2023] Open
Abstract
Fragile X syndrome is a developmental disorder that affects sensory systems. A null mutation of the Fragile X Mental Retardation protein 1 (Fmr1) gene in mice has varied effects on developmental plasticity in different sensory systems, including normal barrel cortical plasticity, altered ocular dominance plasticity and grossly impaired auditory frequency map plasticity. The mutation also has different effects on long-term synaptic plasticity in somatosensory and visual cortical neurons, providing insights on how it may differentially affect the sensory systems. Here we present evidence that long-term potentiation (LTP) is impaired in the developing auditory cortex of the Fmr1 knockout (KO) mice. This impairment of synaptic plasticity is consistent with impaired frequency map plasticity in the Fmr1 KO mouse. Together, these results suggest a potential role of LTP in sensory map plasticity during early sensory development.
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Affiliation(s)
- Sungchil Yang
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
| | - Sunggu Yang
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jae-Sung Park
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Alfredo Kirkwood
- Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Shaowen Bao
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
- * E-mail:
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23
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Chen T, Lu JS, Song Q, Liu MG, Koga K, Descalzi G, Li YQ, Zhuo M. Pharmacological rescue of cortical synaptic and network potentiation in a mouse model for fragile X syndrome. Neuropsychopharmacology 2014; 39:1955-67. [PMID: 24553731 PMCID: PMC4059905 DOI: 10.1038/npp.2014.44] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 01/21/2014] [Accepted: 02/04/2014] [Indexed: 12/29/2022]
Abstract
Fragile X syndrome, caused by the mutation of the Fmr1 gene, is characterized by deficits of attention and learning ability. In the hippocampus of Fmr1 knockout mice (KO), long-term depression is enhanced whereas long-term potentiation (LTP) including late-phase LTP (L-LTP) is reduced or unaffected. Here we examined L-LTP in the anterior cingulate cortex (ACC) in Fmr1 KO mice by using a 64-electrode array recording system. In wild-type mice, theta-burst stimulation induced L-LTP that does not occur in all active electrodes/channels within the cingulate circuit and is typically detected in ∼75% of active channels. Furthermore, L-LTP recruited new responses from previous inactive channels. Both L-LTP and the recruitment of inactive responses were blocked in the ACC slices of Fmr1 KO mice. Bath application of metabotropic glutamate receptor 5 (mGluR5) antagonist or glycogen synthase kinase-3 (GSK3) inhibitors rescued the L-LTP and network recruitment. Our results demonstrate that loss of FMRP will greatly impair L-LTP and recruitment of cortical network in the ACC that can be rescued by pharmacological inhibition of mGluR5 or GSK3. This study is the first report of the network properties of L-LTP in the ACC, and provides basic mechanisms for future treatment of cortex-related cognitive defects in fragile X patients.
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Affiliation(s)
- Tao Chen
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China,Department of Anatomy and KK Leung Brain Research Center, Fourth Military Medical University, Xi'an, China
| | - Jing-Shan Lu
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China
| | - Qian Song
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China
| | - Ming-Gang Liu
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China,Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Kohei Koga
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China,Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Giannina Descalzi
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Yun-Qing Li
- Department of Anatomy and KK Leung Brain Research Center, Fourth Military Medical University, Xi'an, China,Department of Anatomy and KK Leung Brain Research Center, Fourth Military Medical University, Xi'an 710032, China, Tel: +86 29 84774501, Fax: +86 29 83283229, E-mail:
| | - Min Zhuo
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China,Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada,Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada, Tel: +1 416 978 4018, Fax: +1 416 978 7398, E-mail:
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24
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Abekhoukh S, Bardoni B. CYFIP family proteins between autism and intellectual disability: links with Fragile X syndrome. Front Cell Neurosci 2014; 8:81. [PMID: 24733999 PMCID: PMC3973919 DOI: 10.3389/fncel.2014.00081] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 02/27/2014] [Indexed: 12/14/2022] Open
Abstract
Intellectual disability (ID) and autism spectrum disorders (ASDs) have in common alterations in some brain circuits and brain abnormalities, such as synaptic transmission and dendritic spines morphology. Recent studies have indicated a differential expression for specific categories of genes as a cause for both types of disease, while an increasing number of genes is recognized to produce both disorders. An example is the Fragile X mental retardation gene 1 (FMR1), whose silencing causes the Fragile X syndrome, the most common form of ID and autism, also characterized by physical hallmarks. Fragile X mental retardation protein (FMRP), the protein encoded by FMR1, is an RNA-binding protein with an important role in translational control. Among the interactors of FMRP, CYFIP1/2 (cytoplasmic FMRP interacting protein) proteins are good candidates for ID and autism, on the bases of their genetic implication and functional properties, even if the precise functional significance of the CYFIP/FMRP interaction is not understood yet. CYFIP1 and CYFIP2 represent a link between Rac1, the WAVE (WAS protein family member) complex and FMRP, favoring the cross talk between actin polymerization and translational control.
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Affiliation(s)
- Sabiha Abekhoukh
- CNRS, Institute of Molecular and Cellular Pharmacology, UMR 7275 Valbonne, France ; University of Nice Sophia-Antipolis Nice, France ; CNRS, International Associated Laboratories-NEOGENEX Valbonne, France
| | - Barbara Bardoni
- CNRS, Institute of Molecular and Cellular Pharmacology, UMR 7275 Valbonne, France ; University of Nice Sophia-Antipolis Nice, France ; CNRS, International Associated Laboratories-NEOGENEX Valbonne, France
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25
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Schneider A, Ligsay A, Hagerman RJ. Fragile X syndrome: an aging perspective. ACTA ACUST UNITED AC 2014; 18:68-74. [PMID: 23949830 DOI: 10.1002/ddrr.1129] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 04/24/2012] [Accepted: 06/19/2012] [Indexed: 11/11/2022]
Abstract
Cognitive and behavioral correlates of molecular variations related to the FMR1 gene have been studied rather extensively, but research about the long-term outcome in individuals with fragile X spectrum disorders remains sparse. In this review, we present an overview of aging research and recent findings in regard to cellular and clinical manifestations of aging in fragile X syndrome, and the FMR1 premutation.
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Affiliation(s)
- Andrea Schneider
- MIND Institute, University of California at Davis Medical Center, Sacramento, California, USA.
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26
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Maurin T, Zongaro S, Bardoni B. Fragile X Syndrome: from molecular pathology to therapy. Neurosci Biobehav Rev 2014; 46 Pt 2:242-55. [PMID: 24462888 DOI: 10.1016/j.neubiorev.2014.01.006] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 01/12/2014] [Accepted: 01/14/2014] [Indexed: 02/09/2023]
Abstract
Fragile X Syndrome (FXS) is the most common form of inherited intellectual disability due to the silencing of the FMR1 gene encoding FMRP (Fragile X Mental Retardation Protein), an RNA-binding protein involved in different steps of RNA metabolism. Of particular interest is the key role of FMRP in translational regulation. Since the first functional characterizations of FMRP, its role has been underlined by its association with actively translating polyribosomes. Furthermore, a plethora of mRNA targets of FMRP have been identified. In the absence of FMRP the deregulation of translation/transport/stability of these mRNAs has a cascade effect on many pathways, resulting into the final phenotype. We review here a set of targets of FMRP (mRNAs and proteins) that may have an impact on the FXS phenotype by deregulating some key cellular processes, such as translation, cytoskeleton remodeling and oxidative stress. The manipulation of these abnormal pathways by specific drugs may represent new therapeutic opportunities for FXS patients.
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Affiliation(s)
- Thomas Maurin
- Institute of Molecular and Cellular Pharmacology, CNRS UMR7275, University of Nice Sophia Antipolis, Route des Lucioles, 06560 Valbonne, France
| | - Samantha Zongaro
- Institute of Molecular and Cellular Pharmacology, CNRS UMR7275, University of Nice Sophia Antipolis, Route des Lucioles, 06560 Valbonne, France
| | - Barbara Bardoni
- Institute of Molecular and Cellular Pharmacology, CNRS UMR7275, University of Nice Sophia Antipolis, Route des Lucioles, 06560 Valbonne, France.
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27
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Sethna F, Moon C, Wang H. From FMRP function to potential therapies for fragile X syndrome. Neurochem Res 2013; 39:1016-31. [PMID: 24346713 DOI: 10.1007/s11064-013-1229-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 12/03/2013] [Accepted: 12/12/2013] [Indexed: 12/12/2022]
Abstract
Fragile X syndrome (FXS) is caused by mutations in the fragile X mental retardation 1 (FMR1) gene. Most FXS cases occur due to the expansion of the CGG trinucleotide repeats in the 5' un-translated region of FMR1, which leads to hypermethylation and in turn silences the expression of FMRP (fragile X mental retardation protein). Numerous studies have demonstrated that FMRP interacts with both coding and non-coding RNAs and represses protein synthesis at dendritic and synaptic locations. In the absence of FMRP, the basal protein translation is enhanced and not responsive to neuronal stimulation. The altered protein translation may contribute to functional abnormalities in certain aspects of synaptic plasticity and intracellular signaling triggered by Gq-coupled receptors. This review focuses on the current understanding of FMRP function and potential therapeutic strategies that are mainly based on the manipulation of FMRP targets and knowledge gained from FXS pathophysiology.
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Affiliation(s)
- Ferzin Sethna
- Genetics Program, Michigan State University, East Lansing, MI, 48824, USA
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Abstract
Fragile X syndrome, the most common form of heritable mental retardation, is a developmental disorder with known effects within sensory systems. Altered developmental plasticity has been reported in the visual and somatosensory systems in Fmr1 knock-out (KO) mice. Behavioral studies have revealed maladaptive auditory responses in fragile X syndrome patients and Fmr1 KO mice, suggesting that adaptive plasticity may also be impaired in the auditory system. Here we show that, whereas tonotopic frequency representation develops normally in Fmr1 KO mice, developmental plasticity in primary auditory cortex is grossly impaired. This deficit can be rescued by pharmacological blockade of mGluR5 receptors. These results support the mGluR hypothesis of fragile X mental retardation and suggest that deficient developmental plasticity may contribute to maladaptive auditory processing in fragile X syndrome.
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29
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Burn injury-induced mechanical allodynia is maintained by Rac1-regulated dendritic spine dysgenesis. Exp Neurol 2013; 248:509-19. [DOI: 10.1016/j.expneurol.2013.07.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/16/2013] [Accepted: 07/26/2013] [Indexed: 11/22/2022]
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Cook D, Nuro E, Murai KK. Increasing our understanding of human cognition through the study of Fragile X Syndrome. Dev Neurobiol 2013; 74:147-77. [PMID: 23723176 PMCID: PMC4216185 DOI: 10.1002/dneu.22096] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 05/17/2013] [Indexed: 12/16/2022]
Abstract
Fragile X Syndrome (FXS) is considered the most common form of inherited intellectual disability. It is caused by reductions in the expression level or function of a single protein, the Fragile X Mental Retardation Protein (FMRP), a translational regulator which binds to approximately 4% of brain messenger RNAs. Accumulating evidence suggests that FXS is a complex disorder of cognition, involving interactions between genetic and environmental influences, leading to difficulties in acquiring key life skills including motor skills, language, and proper social behaviors. Since many FXS patients also present with one or more features of autism spectrum disorders (ASDs), insights gained from studying the monogenic basis of FXS could pave the way to a greater understanding of underlying features of multigenic ASDs. Here we present an overview of the FXS and FMRP field with the goal of demonstrating how loss of a single protein involved in translational control affects multiple stages of brain development and leads to debilitating consequences on human cognition. We also focus on studies which have rescued or improved FXS symptoms in mice using genetic or therapeutic approaches to reduce protein expression. We end with a brief description of how deficits in translational control are implicated in FXS and certain cases of ASDs, with many recent studies demonstrating that ASDs are likely caused by increases or decreases in the levels of certain key synaptic proteins. The study of FXS and its underlying single genetic cause offers an invaluable opportunity to study how a single gene influences brain development and behavior.
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Affiliation(s)
- Denise Cook
- Department of Neurology and Neurosurgery, Centre for Research in Neuroscience, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, Quebec, Canada
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31
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Bassani S, Zapata J, Gerosa L, Moretto E, Murru L, Passafaro M. The neurobiology of X-linked intellectual disability. Neuroscientist 2013; 19:541-52. [PMID: 23820068 DOI: 10.1177/1073858413493972] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
X-linked intellectual disability (XLID) affects 1% to 3% of the population. XLID subsumes several heterogeneous conditions, all of which are marked by cognitive impairment and reduced adaptive skills. XLID arises from mutations on the X chromosome; to date, 102 XLID genes have been identified. The proteins encoded by XLID genes are involved in higher brain functions, such as cognition, learning and memory, and their molecular role is the subject of intense investigation. Here, we review recent findings concerning a representative group of XLID proteins: the fragile X mental retardation protein; methyl-CpG-binding protein 2 and cyclin-dependent kinase-like 5 proteins, which are involved in Rett syndrome; the intracellular signaling molecules of the Rho guanosine triphosphatases family; and the class of cell adhesion molecules. We discuss how XLID gene mutations affect the structure and function of synapses.
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Affiliation(s)
- Silvia Bassani
- CNR Institute of Neuroscience, Department BIOMETRA, University of Milan, Milan, Italy
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32
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Homeostatic responses fail to correct defective amygdala inhibitory circuit maturation in fragile X syndrome. J Neurosci 2013; 33:7548-58. [PMID: 23616559 DOI: 10.1523/jneurosci.2764-12.2013] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Fragile X syndrome (FXS) is a debilitating neurodevelopmental disorder thought to arise from disrupted synaptic communication in several key brain regions, including the amygdala, a central processing center for information with emotional and social relevance. Recent studies reveal defects in both excitatory and inhibitory neurotransmission in mature amygdala circuits in Fmr1(-/y) mutants, the animal model of FXS. However, whether these defects are the result of altered synaptic development or simply faulty mature circuits remains unknown. Using a combination of electrophysiological and genetic approaches, we show the development of both presynaptic and postsynaptic components of inhibitory neurotransmission in the FXS amygdala is dynamically altered during critical stages of neural circuit formation. Surprisingly, we observe that there is a homeostatic correction of defective inhibition, which, despite transiently restoring inhibitory synaptic efficacy to levels at or beyond those of control, ultimately fails to be maintained. Using inhibitory interneuron-specific conditional knock-out and rescue mice, we further reveal that fragile X mental retardation protein function in amygdala inhibitory microcircuits can be segregated into distinct presynaptic and postsynaptic components. Collectively, these studies reveal a previously unrecognized complexity of disrupted neuronal development in FXS and therefore have direct implications for establishing novel temporal and region-specific targeted therapies to ameliorate core amygdala-based behavioral symptoms.
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Sidorov MS, Auerbach BD, Bear MF. Fragile X mental retardation protein and synaptic plasticity. Mol Brain 2013; 6:15. [PMID: 23566911 PMCID: PMC3636002 DOI: 10.1186/1756-6606-6-15] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/25/2013] [Indexed: 12/20/2022] Open
Abstract
Loss of the translational repressor FMRP causes Fragile X syndrome. In healthy neurons, FMRP modulates the local translation of numerous synaptic proteins. Synthesis of these proteins is required for the maintenance and regulation of long-lasting changes in synaptic strength. In this role as a translational inhibitor, FMRP exerts profound effects on synaptic plasticity.
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Affiliation(s)
- Michael S Sidorov
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 46-3301, USA
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Ng MC, Yang YL, Lu KT. Behavioral and synaptic circuit features in a zebrafish model of fragile X syndrome. PLoS One 2013; 8:e51456. [PMID: 23536755 PMCID: PMC3594205 DOI: 10.1371/journal.pone.0051456] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 11/01/2012] [Indexed: 01/08/2023] Open
Abstract
Fragile X syndrome (FXS) is the most frequent inherited form of human mental retardation. It is characterized by cognitive impairment and physical and behavioral problems and is caused by the silencing of fmr1 transcription and the absence of the fmr1 protein (FMRP). Recently, animal models of FXS have greatly facilitated the investigation of the molecular and cellular mechanisms of this loss-of-function disorder. The present study was aimed to further characterize the role of FMRP in behavior and synaptic function by using fmr1 knockout zebrafish. In adult zebrafish, we found that fmr1 knockout produces the anxiolytic-like responses of increased exploratory behavior in light/dark and open-field tests and avoidance learning impairment. Furthermore, electrophysiological recordings from telencephalic slice preparations of knockout fish displayed markedly reduced long-term potentiation and enhanced long-term depression compared to wild-type fish; however, basal glutamatergic transmission and presynaptic function at the lateral (Dl) and medial (Dm) division of the dorsal telencephalon synapse remained normal. Taken together, our study not only evaluates the mechanism of FRMP but also suggests that zebrafish have valuable potential as a complementary vertebrate model in studying the molecular pathogenesis of human fragile X syndrome.
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Affiliation(s)
- Ming-Chong Ng
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Yi-Ling Yang
- Department of Biochemical Science and Technology, National Chia-Yi University, Chia-Yi, Taiwan
- * E-mail: (YLY); (KTL)
| | - Kwok-Tung Lu
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
- * E-mail: (YLY); (KTL)
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35
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Chung L, Bey AL, Jiang YH. Synaptic plasticity in mouse models of autism spectrum disorders. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2012; 16:369-78. [PMID: 23269898 PMCID: PMC3526740 DOI: 10.4196/kjpp.2012.16.6.369] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 10/27/2012] [Accepted: 10/28/2012] [Indexed: 12/03/2022]
Abstract
Analysis of synaptic plasticity together with behavioral and molecular studies have become a popular approach to model autism spectrum disorders in order to gain insight into the pathosphysiological mechanisms and to find therapeutic targets. Abnormalities of specific types of synaptic plasticity have been revealed in numerous genetically modified mice that have molecular construct validity to human autism spectrum disorders. Constrained by the feasibility of technique, the common regions analyzed in most studies are hippocampus and visual cortex. The relevance of the synaptic defects in these regions to the behavioral abnormalities of autistic like behaviors is still a subject of debate. Because the exact regions or circuits responsible for the core features of autistic behaviors in humans are still poorly understood, investigation using region-specific conditional mutant mice may help to provide the insight into the neuroanatomical basis of autism in the future.
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Affiliation(s)
- Leeyup Chung
- Department of Pediatrics, Duke University School of Medicine, Durham, NC 27710, USA
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36
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Lee HY, Jan LY. Fragile X syndrome: mechanistic insights and therapeutic avenues regarding the role of potassium channels. Curr Opin Neurobiol 2012; 22:887-94. [PMID: 22483378 PMCID: PMC3393774 DOI: 10.1016/j.conb.2012.03.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 03/15/2012] [Indexed: 12/31/2022]
Abstract
Fragile X syndrome (FXS) is a common form of mental disability and one of the known causes of autism. The mutation responsible for FXS is a large expansion of the trinucleotide CGG repeats that leads to DNA methylation of the fragile X mental retardation gene 1 (FMR1) and transcriptional silencing, resulting in the absence of fragile X mental retardation protein (FMRP), an mRNA binding protein. Although it is widely known that FMRP is critical for metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD), which has provided a general theme for developing pharmacological drugs for FXS, specific downstream targets of FMRP may also be of therapeutic value. Since alterations in potassium channel expression level or activity could underlie neuronal network defects in FXS, here we describe recent findings on how these channels might be altered in mouse models of FXS and the possible therapeutic avenues for treating FXS.
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Affiliation(s)
- Hye Young Lee
- Howard Hughes Medical Institute, Departments of Physiology, Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA
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37
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Gocel J, Larson J. Synaptic NMDA receptor-mediated currents in anterior piriform cortex are reduced in the adult fragile X mouse. Neuroscience 2012; 221:170-81. [PMID: 22750206 PMCID: PMC3424403 DOI: 10.1016/j.neuroscience.2012.06.052] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/05/2012] [Accepted: 06/21/2012] [Indexed: 01/16/2023]
Abstract
Fragile X syndrome is a neurodevelopmental condition caused by the transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene. The Fmr1 knockout (KO) mouse exhibits age-dependent deficits in long term potentiation (LTP) at association (ASSN) synapses in anterior piriform cortex (APC). To investigate the mechanisms for this, whole-cell voltage-clamp recordings of ASSN stimulation-evoked synaptic currents were made in APC of slices from adult Fmr1-KO and wild-type (WT) mice, using the competitive N-methyl-D-aspartate (NMDA) receptor antagonist, CPP, to distinguish currents mediated by NMDA and AMPA receptors. NMDA/AMPA current ratios were lower in Fmr1-KO mice than in WT mice, at ages ranging from 3-18months. Since amplitude and frequency of miniature excitatory postsynaptic currents (mEPSCs) mediated by AMPA receptors were no different in Fmr1-KO and WT mice at these ages, the results suggest that NMDA receptor-mediated currents are selectively reduced in Fmr1-KO mice. Analyses of voltage-dependence and decay kinetics of NMDA receptor-mediated currents did not reveal differences between Fmr1-KO and WT mice, suggesting that reduced NMDA currents in Fmr1-KO mice are due to fewer synaptic receptors rather than differences in receptor subunit composition. Reduced NMDA receptor signaling may help to explain the LTP deficit seen at APC ASSN synapses in Fmr1-KO mice at 6-18months of age, but does not explain normal LTP at these synapses in mice 3-6months old. Evoked currents and mEPSCs were also examined in senescent Fmr1-KO and WT mice at 24-28months of age. NMDA/AMPA ratios were similar in senescent WT and Fmr1-KO mice, due to a decrease in the ratio in the WT mice, without significant change in AMPA receptor-mediated mEPSCs.
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Affiliation(s)
- James Gocel
- Psychiatric Institute, Department of Psychiatry, College of Medicine, University of Illinois, Chicago, IL 60612, USA
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38
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Abstract
Diabetic neuropathic pain imposes a huge burden on individuals and society, and represents a major public health problem. Despite aggressive efforts, diabetic neuropathic pain is generally refractory to available clinical treatments. A structure-function link between maladaptive dendritic spine plasticity and pain has been demonstrated previously in CNS and PNS injury models of neuropathic pain. Here, we reasoned that if dendritic spine remodeling contributes to diabetic neuropathic pain, then (1) the presence of malformed spines should coincide with the development of pain, and (2) disrupting maladaptive spine structure should reduce chronic pain. To determine whether dendritic spine remodeling contributes to neuropathic pain in streptozotocin (STZ)-induced diabetic rats, we analyzed dendritic spine morphology and electrophysiological and behavioral signs of neuropathic pain. Our results show changes in dendritic spine shape, distribution, and shape on wide-dynamic-range (WDR) neurons within lamina IV-V of the dorsal horn in diabetes. These diabetes-induced changes were accompanied by WDR neuron hyperexcitability and decreased pain thresholds at 4 weeks. Treatment with NSC23766 (N(6)-[2-[[4-(diethylamino)-1-methylbutyl]amino]-6-methyl-4-pyrimidinyl]-2-methyl-4,6-quinolinediamine trihydrochloride), a Rac1-specific inhibitor known to interfere with spine plasticity, decreased the presence of malformed spines in diabetes, attenuated neuronal hyperresponsiveness to peripheral stimuli, reduced spontaneous firing activity from WDR neurons, and improved nociceptive mechanical pain thresholds. At 1 week after STZ injection, animals with hyperglycemia with no evidence of pain had few or no changes in spine morphology. These results demonstrate that diabetes-induced maladaptive dendritic spine remodeling has a mechanistic role in neuropathic pain. Molecular pathways that control spine morphogenesis and plasticity may be promising future targets for treatment.
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39
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Pathological plasticity in fragile X syndrome. Neural Plast 2012; 2012:275630. [PMID: 22811939 PMCID: PMC3395158 DOI: 10.1155/2012/275630] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 05/21/2012] [Indexed: 01/17/2023] Open
Abstract
Deficits in neuronal plasticity are common hallmarks of many neurodevelopmental disorders. In the case of fragile-X syndrome (FXS), disruption in the function of a single gene, FMR1, results in a variety of neurological consequences directly related to problems with the development, maintenance, and capacity of plastic neuronal networks. In this paper, we discuss current research illustrating the mechanisms underlying plasticity deficits in FXS. These processes include synaptic, cell intrinsic, and homeostatic mechanisms both dependent on and independent of abnormal metabotropic glutamate receptor transmission. We place particular emphasis on how identified deficits may play a role in developmental critical periods to produce neuronal networks with permanently decreased capacity to dynamically respond to changes in activity central to learning, memory, and cognition in patients with FXS. Characterizing early developmental deficits in plasticity is fundamental to develop therapies that not only treat symptoms but also minimize the developmental pathology of the disease.
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Xu ZH, Yang Q, Feng B, Liu SB, Zhang N, Xing JH, Li XQ, Wu YM, Gao GD, Zhao MG. Group I mGluR antagonist rescues the deficit of D1-induced LTP in a mouse model of fragile X syndrome. Mol Neurodegener 2012; 7:24. [PMID: 22640474 PMCID: PMC3467183 DOI: 10.1186/1750-1326-7-24] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 04/17/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Fragile X syndrome (FXS) is caused by the absence of the mRNA-binding protein Fragile X mental retardation protein (FMRP), encoded by the Fmr1 gene. Overactive signaling by group 1 metabotropic glutamate receptor (Grp1 mGluR) could contribute to slowed synaptic development and other symptoms of FXS. Our previous study has identified that facilitation of synaptic long-term potentiation (LTP) by D1 receptor is impaired in Fmr1 knockout (KO) mice. However, the contribution of Grp1 mGluR to the facilitation of synaptic plasticity by D1 receptor stimulation in the prefrontal cortex has been less extensively studied. RESULTS Here we demonstrated that DL-AP3, a Grp1 mGluR antagonist, rescued LTP facilitation by D1 receptor agonist SKF81297 in Fmr1KO mice. Grp1 mGluR inhibition restored the GluR1-subtype AMPA receptors surface insertion by D1 activation in the cultured Fmr1KO neurons. Simultaneous treatment of Grp1 mGluR antagonist with D1 agonist recovered the D1 receptor signaling by reversing the subcellular redistribution of G protein-coupled receptor kinase 2 (GRK2) in the Fmr1KO neurons. Treatment of SKF81297 alone failed to increase the phosphorylation of NR2B-containing N-methyl D-aspartate receptors (NMDARs) at Tyr-1472 (p-NR2B-Tyr1472) in the cultures from KO mice. However, simultaneous treatment of DL-AP3 could rescue the level of p-NR2B-Tyr1472 by SKF81297 in the cultures from KO mice. Furthermore, behavioral tests indicated that simultaneous treatment of Grp1 mGluR antagonist with D1 agonist inhibited hyperactivity and improved the learning ability in the Fmr1KO mice. CONCLUSION The findings demonstrate that mGluR1 inhibition is a useful strategy to recover D1 receptor signaling in the Fmr1KO mice, and combination of Grp1 mGluR antagonist and D1 agonist is a potential drug therapy for the FXS.
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Affiliation(s)
- Zhao-Hui Xu
- Department of Neurosurgery, Tangdu Hospital, Fourth Military Medical University, 17 Changle West Road, Xi'an, 710032, China
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41
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Peebles KA, Price TJ. Self-injurious behaviour in intellectual disability syndromes: evidence for aberrant pain signalling as a contributing factor. JOURNAL OF INTELLECTUAL DISABILITY RESEARCH : JIDR 2012; 56:441-52. [PMID: 21917053 PMCID: PMC3272540 DOI: 10.1111/j.1365-2788.2011.01484.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
BACKGROUND In most individuals, injury results in activation of peripheral nociceptors (pain-sensing neurons of the peripheral nervous system) and amplification of central nervous system (CNS) pain pathways that serve as a disincentive to continue harmful behaviour; however, this may not be the case in some developmental disorders that cause intellectual disability (ID). Moreover, individuals affected by ID disorders may initiate self-injurious behaviour to address irritating or painful sensations. In normal individuals, a negative feedback loop decreases sensation of pain, which involves descending inhibitory neurons in the CNS that attenuate spinal nociceptive processing. If spinal nociceptive signalling is impaired in these developmental disorders, an exaggerated painful stimulus may be required in order to engage descending anti-nociceptive signals. METHODS Using electronic databases, we conducted a review of publications regarding the incidence of chronic pain or altered pain sensation in ID patients or corresponding preclinical models. RESULTS There is a body of evidence indicating that individuals with fragile X mental retardation and/or Rett syndrome have altered pain sensation. These findings in humans are supported by mechanistic studies using genetically modified mice harbouring mutations consistent with the human disease. Thus, once self-injurious behaviour is initiated, the signal to stop may be missing. Several developmental disorders that cause ID are associated with increased incidence of gastroesophageal reflux disease (GERD), which can cause severe visceral pain. Individuals affected by these disorders who also have GERD may self-injure as a mechanism to engage descending inhibitory circuits to quell visceral pain. In keeping with this hypothesis, pharmacological treatment of GERD has been shown to be effective for reducing self-injurious behaviour in some patients. Hence, multiple lines of evidence suggest aberrant nociceptive processing in developmental disorders that cause ID. CONCLUSIONS There is evidence that pain pathways and pain amplification mechanisms are altered in several preclinical models of developmental disorders that cause ID. We present hypotheses regarding how impaired pain pathways or chronic pain might contribute to self-injurious behaviour. Studies evaluating the relationship between pain and self-injurious behaviour will provide better understanding of the mechanisms underlying self-injurious behaviour in the ID population and may lead to more effective treatments.
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Affiliation(s)
- K A Peebles
- Department of Pharmacology, University of Arizona, Tucson, Arizona 85724, USA
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42
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Panaccione I, King R, Molinaro G, Riozzi B, Battaglia G, Nicoletti F, Bashir ZI. Constitutively active group I mGlu receptors and PKMzeta regulate synaptic transmission in developing perirhinal cortex. Neuropharmacology 2012; 66:143-50. [PMID: 23357951 DOI: 10.1016/j.neuropharm.2012.03.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/13/2012] [Accepted: 03/15/2012] [Indexed: 10/28/2022]
Abstract
Synaptic transmission is essential for early development of the central nervous system. However, the mechanisms that regulate early synaptic transmission in the cerebral cortex are unclear. PKMζ is a kinase essential for the maintenance of LTP. We show for the first time that inhibition of PKMζ produces a profound depression of basal synaptic transmission in neonatal, but not adult, rat perirhinal cortex. This suggests that synapses in early development are in a constitutive LTP-like state. Furthermore, basal synaptic transmission in immature, but not mature, perirhinal cortex relies on persistent activity of metabotropic glutamate (mGlu) receptor, PI3Kinase and mammalian target of rapamycin (mTOR). Thus early in development, cortical synapses exist in an LTP-like state maintained by tonically active mGlu receptor-, mTOR- and PKMζ- dependent cascades. These results provide new understanding of the molecular mechanisms that control synapses during development and may aid our understanding of developmental disorders such as autism and schizophrenia. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.
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Affiliation(s)
- Isabella Panaccione
- MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, BS8 1TD, United Kingdom
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43
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Hagerman R, Lauterborn J, Au J, Berry-Kravis E. Fragile X syndrome and targeted treatment trials. Results Probl Cell Differ 2012; 54:297-335. [PMID: 22009360 PMCID: PMC4114775 DOI: 10.1007/978-3-642-21649-7_17] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Work in recent years has revealed an abundance of possible new treatment targets for fragile X syndrome (FXS). The use of animal models, including the fragile X knockout mouse which manifests a phenotype very similar to FXS in humans, has resulted in great strides in this direction of research. The lack of Fragile X Mental Retardation Protein (FMRP) in FXS causes dysregulation and usually overexpression of a number of its target genes, which can cause imbalances of neurotransmission and deficits in synaptic plasticity. The use of metabotropic glutamate receptor (mGluR) blockers and gamma amino-butyric acid (GABA) agonists have been shown to be efficacious in reversing cellular and behavioral phenotypes, and restoring proper brain connectivity in the mouse and fly models. Proposed new pharmacological treatments and educational interventions are discussed in this chapter. In combination, these various targeted treatments show promising preliminary results in mitigating or even reversing the neurobiological abnormalities caused by loss of FMRP, with possible translational applications to other neurodevelopmental disorders including autism.
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Affiliation(s)
- Randi Hagerman
- Department of Pediatrics, University of California, Sacramento, CA, USA.
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Price TJ, Melemedjian OK. Fragile X mental retardation protein (FMRP) and the spinal sensory system. Results Probl Cell Differ 2012; 54:41-59. [PMID: 22009347 DOI: 10.1007/978-3-642-21649-7_4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The purpose of this chapter is to discuss the role of the fragile X mental retardation protein (FMRP) in the spinal sensory system and the potential for use of the mouse model of fragile X syndrome to better understand some aspects of the human syndrome as well as advance knowledge in other areas of investigation, such as pain amplification, an important aspect of clinical pain disorders. We describe how the Fmr1 knockout mouse can be used to better understand the role of Fmrp in axons using cultures of sensory neurons and using manipulations to these neurons in vivo. We also discuss the established evidence for a role of Fmrp in nociceptive sensitization and how this evidence relates to an emerging role of translation control as a key process in pain amplification. Finally, we explore opportunities centered on the Fmr1 KO mouse for gaining further insight into the role of translation control in pain amplification and how this model may be used to identify novel therapeutic targets. We conclude that the study of the spinal sensory system in the Fmr1 KO mouse presents several unique prospects for gaining better insight into the human disorder and other clinical issues, such as chronic pain disorders, that affect millions of people worldwide.
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Affiliation(s)
- Theodore J Price
- Department of Pharmacology, The University of Arizona School of Medicine, Tucson, AZ, USA.
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45
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Liu ZH, Huang T, Smith CB. Lithium reverses increased rates of cerebral protein synthesis in a mouse model of fragile X syndrome. Neurobiol Dis 2011; 45:1145-52. [PMID: 22227453 DOI: 10.1016/j.nbd.2011.12.037] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 12/07/2011] [Accepted: 12/19/2011] [Indexed: 12/18/2022] Open
Abstract
Individuals with fragile X syndrome (FXS), an inherited form of cognitive disability, have a wide range of symptoms including hyperactivity, autistic behavior, seizures and learning deficits. FXS is caused by silencing of FMR1 and the consequent absence of fragile X mental retardation protein (FMRP). FMRP is an RNA-binding protein that associates with polyribosomes and negatively regulates translation. In a previous study of a mouse model of FXS (Fmr1 knockout (KO)) we demonstrated that in vivo rates of cerebral protein synthesis (rCPS) were elevated in selective brain regions suggesting that the absence of FMRP in FXS may result in dysregulation of cerebral protein synthesis. Lithium, a drug used clinically to treat bipolar disorder, has been used to improve mood dysregulation in individuals with FXS. We reported previously that in the Fmr1 KO mouse chronic dietary lithium treatment reversed or ameliorated both behavioral and morphological abnormalities. Herein we report that chronic dietary lithium treatment reversed the increased rCPS in Fmr1 KO mice with little effect on wild type mice. We also report our results of analyses of key signaling molecules involved in regulation of mRNA translation. Our analyses indicate that neither effects on the PI3K/Akt nor the MAPK/ERK 1/2 pathway fully account for the effects of lithium treatment on rCPS. Collectively our findings and those from other laboratories on the efficacy of lithium treatment in animal models support further studies in patients with FXS.
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Affiliation(s)
- Zhong-Hua Liu
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
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Tan AM, Chang YW, Zhao P, Hains BC, Waxman SG. Rac1-regulated dendritic spine remodeling contributes to neuropathic pain after peripheral nerve injury. Exp Neurol 2011; 232:222-33. [DOI: 10.1016/j.expneurol.2011.08.028] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 08/11/2011] [Accepted: 08/18/2011] [Indexed: 10/17/2022]
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Bray S, Hirt M, Jo B, Hall SS, Lightbody AA, Walter E, Chen K, Patnaik S, Reiss AL. Aberrant frontal lobe maturation in adolescents with fragile X syndrome is related to delayed cognitive maturation. Biol Psychiatry 2011; 70:852-8. [PMID: 21802660 PMCID: PMC3191299 DOI: 10.1016/j.biopsych.2011.05.038] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 05/21/2011] [Accepted: 05/24/2011] [Indexed: 10/17/2022]
Abstract
BACKGROUND Fragile X syndrome (FXS) is the most common known heritable cause of intellectual disability. Prior studies in FXS have observed a plateau in cognitive and adaptive behavioral development in early adolescence, suggesting that brain development in FXS may diverge from typical development during this period. METHODS In this study, we examined adolescent brain development using structural magnetic resonance imaging data acquired from 59 individuals with FXS and 83 typically developing control subjects aged 9 to 22, a subset of whom were followed up longitudinally (1-5 years; typically developing: 17, FXS: 19). Regional volumes were modeled to obtain estimates of age-related change. RESULTS We found that while structures such as the caudate showed consistent volume differences from control subjects across adolescence, prefrontal cortex (PFC) gyri showed significantly aberrant maturation. Furthermore, we found that PFC-related measures of cognitive functioning followed a similarly aberrant developmental trajectory in FXS. CONCLUSIONS Our findings suggest that aberrant maturation of the PFC during adolescence may contribute to persistent or increasing intellectual deficits in FXS.
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Affiliation(s)
- Signe Bray
- Department of Psychiatry, Hotchkiss Brain Institute, University of Calgary, 1403 - 29 Street NW Calgary, Alberta, T2N 2T9, Canada,Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Melissa Hirt
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Booil Jo
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Scott S. Hall
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Amy A. Lightbody
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Elizabeth Walter
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Kelly Chen
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Swetapadma Patnaik
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA
| | - Allan L. Reiss
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Palo Alto, CA, 94305, USA,Corresponding Author: Allan L. Reiss, Center for Interdisciplinary Brain Sciences Research, Stanford University School of Medicine, 401 Quarry Rd., Palo Alto, CA, 94305, Phone: 650 498 4538, Fax: 650 724 4761,
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Paluszkiewicz SM, Martin BS, Huntsman MM. Fragile X syndrome: the GABAergic system and circuit dysfunction. Dev Neurosci 2011; 33:349-64. [PMID: 21934270 DOI: 10.1159/000329420] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Accepted: 03/10/2011] [Indexed: 12/18/2022] Open
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder characterized by intellectual disability, sensory hypersensitivity, and high incidences of autism spectrum disorders and epilepsy. These phenotypes are suggestive of defects in neural circuit development and imbalances in excitatory glutamatergic and inhibitory GABAergic neurotransmission. While alterations in excitatory synapse function and plasticity are well-established in Fmr1 knockout (KO) mouse models of FXS, a number of recent electrophysiological and molecular studies now identify prominent defects in inhibitory GABAergic transmission in behaviorally relevant forebrain regions such as the amygdala, cortex, and hippocampus. In this review, we summarize evidence for GABAergic system dysfunction in FXS patients and Fmr1 KO mouse models alike. We then discuss some of the known developmental roles of GABAergic signaling, as well as the development and refinement of GABAergic synapses as a framework for understanding potential causes of mature circuit dysfunction. Finally, we highlight the GABAergic system as a relevant target for the treatment of FXS.
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Affiliation(s)
- Scott M Paluszkiewicz
- Center for Neuroscience Research, Children's National Medical Center, Washington, DC 20010, USA
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Suvrathan A, Chattarji S. Fragile X syndrome and the amygdala. Curr Opin Neurobiol 2011; 21:509-15. [DOI: 10.1016/j.conb.2011.04.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 04/14/2011] [Accepted: 04/18/2011] [Indexed: 12/29/2022]
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Klemmer P, Meredith RM, Holmgren CD, Klychnikov OI, Stahl-Zeng J, Loos M, van der Schors RC, Wortel J, de Wit H, Spijker S, Rotaru DC, Mansvelder HD, Smit AB, Li KW. Proteomics, ultrastructure, and physiology of hippocampal synapses in a fragile X syndrome mouse model reveal presynaptic phenotype. J Biol Chem 2011; 286:25495-504. [PMID: 21596744 DOI: 10.1074/jbc.m110.210260] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Fragile X syndrome (FXS), the most common form of hereditary mental retardation, is caused by a loss-of-function mutation of the Fmr1 gene, which encodes fragile X mental retardation protein (FMRP). FMRP affects dendritic protein synthesis, thereby causing synaptic abnormalities. Here, we used a quantitative proteomics approach in an FXS mouse model to reveal changes in levels of hippocampal synapse proteins. Sixteen independent pools of Fmr1 knock-out mice and wild type mice were analyzed using two sets of 8-plex iTRAQ experiments. Of 205 proteins quantified with at least three distinct peptides in both iTRAQ series, the abundance of 23 proteins differed between Fmr1 knock-out and wild type synapses with a false discovery rate (q-value) <5%. Significant differences were confirmed by quantitative immunoblotting. A group of proteins that are known to be involved in cell differentiation and neurite outgrowth was regulated; they included Basp1 and Gap43, known PKC substrates, and Cend1. Basp1 and Gap43 are predominantly expressed in growth cones and presynaptic terminals. In line with this, ultrastructural analysis in developing hippocampal FXS synapses revealed smaller active zones with corresponding postsynaptic densities and smaller pools of clustered vesicles, indicative of immature presynaptic maturation. A second group of proteins involved in synaptic vesicle release was up-regulated in the FXS mouse model. In accordance, paired-pulse and short-term facilitation were significantly affected in these hippocampal synapses. Together, the altered regulation of presynaptically expressed proteins, immature synaptic ultrastructure, and compromised short-term plasticity points to presynaptic changes underlying glutamatergic transmission in FXS at this stage of development.
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Affiliation(s)
- Patricia Klemmer
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, 1081 HV Amsterdam, The Netherlands
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