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Lim CS, Hoang ET, Viar KE, Stornetta RL, Scott MM, Zhu JJ. Pharmacological rescue of Ras signaling, GluA1-dependent synaptic plasticity, and learning deficits in a fragile X model. Genes Dev 2014; 28:273-89. [PMID: 24493647 PMCID: PMC3923969 DOI: 10.1101/gad.232470.113] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fragile X syndrome, caused by the loss of Fmr1 gene function, is the most common form of inherited mental retardation. Lim et al. find that compounds activating serotonin (5HT) subtype 2B receptors or dopamine (DA) subtype 1-like receptors and those inhibiting 5HT2A-Rs or D2-Rs enhance Ras signaling, GluA1-dependent synaptic plasticity, and learning in Fmr1 knockout mice. Combining 5HT and DA compounds at low doses synergistically restored normal learning. This suggests that properly dosed and combined FDA-approved psychoactive drugs may effectively treat the cognitive impairment associated with fragile X syndrome. Fragile X syndrome, caused by the loss of Fmr1 gene function, is the most common form of inherited mental retardation, with no effective treatment. Using a tractable animal model, we investigated mechanisms of action of a few FDA-approved psychoactive drugs that modestly benefit the cognitive performance in fragile X patients. Here we report that compounds activating serotonin (5HT) subtype 2B receptors (5HT2B-Rs) or dopamine (DA) subtype 1-like receptors (D1-Rs) and/or those inhibiting 5HT2A-Rs or D2-Rs moderately enhance Ras–PI3K/PKB signaling input, GluA1-dependent synaptic plasticity, and learning in Fmr1 knockout mice. Unexpectedly, combinations of these 5HT and DA compounds at low doses synergistically stimulate Ras–PI3K/PKB signal transduction and GluA1-dependent synaptic plasticity and remarkably restore normal learning in Fmr1 knockout mice without causing anxiety-related side effects. These findings suggest that properly dosed and combined FDA-approved psychoactive drugs may effectively treat the cognitive impairment associated with fragile X syndrome.
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Gandhi RM, Kogan CS, Messier C. 2-Methyl-6-(phenylethynyl) pyridine (MPEP) reverses maze learning and PSD-95 deficits in Fmr1 knock-out mice. Front Cell Neurosci 2014; 8:70. [PMID: 24701200 PMCID: PMC3965849 DOI: 10.3389/fncel.2014.00070] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 02/17/2014] [Indexed: 11/22/2022] Open
Abstract
Fragile X Syndrome (FXS) is caused by the lack of expression of the fragile X mental retardation protein (FMRP), which results in intellectual disability and other debilitating symptoms including impairment of visual-spatial functioning. FXS is the only single-gene disorder that is highly co-morbid with autism spectrum disorder and can therefore provide insight into its pathophysiology. Lack of FMRP results in altered group I metabotropic glutamate receptor (mGluR) signaling, which is a target for putative treatments. The Hebb-Williams (H-W) mazes are a set of increasingly complex spatial navigation problems that depend on intact hippocampal and thus mGluR-5 functioning. In the present investigation, we examined whether an antagonist of mGluR-5 would reverse previously described behavioral deficits in fragile X mental retardation 1 knock-out (Fmr1 KO) mice. Mice were trained on a subset of the H-W mazes and then treated with either 20 mg/kg of an mGluR-5 antagonist, 2-Methyl-6-(phenylethynyl) pyridine (MPEP; n = 11) or an equivalent dose of saline (n = 11) prior to running test mazes. Latency and errors were dependent variables recorded during the test phase. Immediately after completing each test, marble-burying behavior was assessed, which confirmed that the drug treatment was pharmacologically active during maze learning. Although latency was not statistically different between the groups, MPEP treated Fmr1 KO mice made significantly fewer errors on mazes deemed more difficult suggesting a reversal of the behavioral deficit. MPEP treated mice were also less perseverative and impulsive when navigating mazes. Furthermore, MPEP treatment reversed post-synaptic density-95 (PSD-95) protein deficits in Fmr1 KO treated mice, whereas levels of a control protein (β-tubulin) remained unchanged. These data further validate MPEP as a potentially beneficial treatment for FXS. Our findings also suggest that adapted H-W mazes may be a useful tool to document alterations in behavioral functioning following pharmacological intervention in FXS.
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Affiliation(s)
- Réno M Gandhi
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | - Cary S Kogan
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | - Claude Messier
- School of Psychology, University of Ottawa Ottawa, ON, Canada
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Braat S, Kooy RF. Fragile X syndrome neurobiology translates into rational therapy. Drug Discov Today 2014; 19:510-9. [PMID: 24508819 DOI: 10.1016/j.drudis.2014.01.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 01/19/2014] [Accepted: 01/27/2014] [Indexed: 12/29/2022]
Abstract
Causal genetic defects have been identified for various neurodevelopmental disorders. A key example in this respect is fragile X syndrome, one of the most frequent genetic causes of intellectual disability and autism. Since the discovery of the causal gene, insights into the underlying pathophysiological mechanisms have increased exponentially. Over the past years, defects were discovered in pathways that are potentially amendable by pharmacological treatment. These findings have inspired the initiation of clinical trials in patients. The targeted pathways converge in part with those of related neurodevelopmental disorders raising hopes that the treatments developed for this specific disorder might be more broadly applicable.
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Affiliation(s)
- Sien Braat
- Department of Medical Genetics, University of Antwerp, Prins Boudewijnlaan 43, Antwerp, Belgium
| | - R Frank Kooy
- Department of Medical Genetics, University of Antwerp, Prins Boudewijnlaan 43, Antwerp, Belgium.
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Franklin AV, King MK, Palomo V, Martinez A, McMahon LL, Jope RS. Glycogen synthase kinase-3 inhibitors reverse deficits in long-term potentiation and cognition in fragile X mice. Biol Psychiatry 2014; 75:198-206. [PMID: 24041505 PMCID: PMC3874248 DOI: 10.1016/j.biopsych.2013.08.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/30/2013] [Accepted: 08/01/2013] [Indexed: 11/30/2022]
Abstract
BACKGROUND Identifying feasible therapeutic interventions is crucial for ameliorating the intellectual disability and other afflictions of fragile X syndrome (FXS), the most common inherited cause of intellectual disability and autism. Hippocampal glycogen synthase kinase-3 (GSK3) is hyperactive in the mouse model of FXS (FX mice), and hyperactive GSK3 promotes locomotor hyperactivity and audiogenic seizure susceptibility in FX mice, raising the possibility that specific GSK3 inhibitors may improve cognitive processes. METHODS We tested if specific GSK3 inhibitors improve deficits in N-methyl-D-aspartate receptor-dependent long-term potentiation at medial perforant path synapses onto dentate granule cells and dentate gyrus-dependent cognitive behavioral tasks. RESULTS GSK3 inhibitors completely rescued deficits in long-term potentiation at medial perforant path-dentate granule cells synapses in FX mice. Furthermore, synaptosomes from the dentate gyrus of FX mice displayed decreased inhibitory serine-phosphorylation of GSK3β compared with wild-type littermates. The potential therapeutic utility of GSK3 inhibitors was further tested on dentate gyrus-dependent cognitive behaviors. In vivo administration of GSK3 inhibitors completely reversed impairments in several cognitive tasks in FX mice, including novel object detection, coordinate and categorical spatial processing, and temporal ordering for visual objects. CONCLUSIONS These findings establish that synaptic plasticity and cognitive deficits in FX mice can be improved by intervention with inhibitors of GSK3, which may prove therapeutically beneficial in FXS.
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Affiliation(s)
- Aimee V. Franklin
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Margaret K. King
- Departments of Psychiatry and Behavioral Sciences and Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136
| | - Valle Palomo
- Instituto Quimica Medica-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
| | - Ana Martinez
- Instituto Quimica Medica-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
| | - Lori L. McMahon
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Richard S. Jope
- Departments of Psychiatry and Behavioral Sciences and Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136,Corresponding author: Richard S. Jope, Miller School of Medicine, University of Miami, 1011 NW 15th Street, Gautier Building room 416, Miami, Florida 33136, phone: 305-243-0262,
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Jacquemont S, Berry-Kravis E, Hagerman R, von Raison F, Gasparini F, Apostol G, Ufer M, Des Portes V, Gomez-Mancilla B. The challenges of clinical trials in fragile X syndrome. Psychopharmacology (Berl) 2014; 231:1237-50. [PMID: 24173622 PMCID: PMC3932172 DOI: 10.1007/s00213-013-3289-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 09/05/2013] [Indexed: 11/28/2022]
Abstract
RATIONALE Advances in understanding the underlying mechanisms of conditions such as fragile X syndrome (FXS) and autism spectrum disorders have revealed heterogeneous populations. Recent trials of novel FXS therapies have highlighted several challenges including subpopulations with possibly differential therapeutic responses, the lack of specific outcome measures capturing the full range of improvements of patients with FXS, and a lack of biomarkers that can track whether a specific mechanism is responsive to a new drug and whether the response correlates with clinical improvement. OBJECTIVES We review the phenotypic heterogeneity of FXS and the implications for clinical research in FXS and other neurodevelopmental disorders. RESULTS Residual levels of fragile X mental retardation protein (FMRP) expression explain in part the heterogeneity in the FXS phenotype; studies indicate a correlation with both cognitive and behavioral deficits. However, this does not fully explain the extent of phenotypic variance observed or the variability of drug response. Post hoc analyses of studies involving the selective mGluR5 antagonist mavoglurant and the GABAB agonist arbaclofen have uncovered significant therapeutic responses following patient stratification according to FMR1 promoter methylation patterns or baseline severity of social withdrawal, respectively. Future studies designed to quantify disease modification will need to develop new strategies to track changes effectively over time and in multiple symptom domains. CONCLUSION Appropriate selection of patients and outcome measures is central to optimizing future clinical investigations of these complex disorders.
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Affiliation(s)
- Sébastien Jacquemont
- Service de Génétique Médicale, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland
| | - Elizabeth Berry-Kravis
- Departments of Pediatrics, Neurological Sciences and Biochemistry, Rush University Medical Center, Chicago, IL 60612 USA
| | - Randi Hagerman
- MIND Institute and Department of Pediatrics, UC Davis Health System, Sacramento, CA 95817 USA
| | | | - Fabrizio Gasparini
- Novartis Institutes for BioMedical Research Basel, Forum 1, Novartis Campus, 4056 Basel, Switzerland
| | - George Apostol
- Neuroscience Development, Novartis Pharma AG, 4056 Basel, Switzerland
| | - Mike Ufer
- Novartis Institutes for BioMedical Research Basel, Forum 1, Novartis Campus, 4056 Basel, Switzerland
| | - Vincent Des Portes
- National Reference Center for Fragile X and Other XLMR, Hospices Civils de Lyon, Université de Lyon and CNRS UMR 5304 (L2C2), Bron, France
| | - Baltazar Gomez-Mancilla
- Novartis Institutes for BioMedical Research Basel, Forum 1, Novartis Campus, 4056 Basel, Switzerland
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Farshbaf MJ, Ghaedi K, Shirani M, Nasr-Esfahani MH. Peroxisome proliferator activated receptor gamma (PPARγ) as a therapeutic target for improvement of cognitive performance in Fragile-X. Med Hypotheses 2013; 82:291-4. [PMID: 24456944 DOI: 10.1016/j.mehy.2013.12.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 12/03/2013] [Accepted: 12/18/2013] [Indexed: 02/07/2023]
Abstract
Rare disorders leading to intellectual disability, such as Fragile X syndrome (FXS) alter synaptic plasticity. Ligand identification of orphan nuclear receptors has led to the discovery of many signaling pathways and has revealed a direct link of nuclear receptors with human conditions such as mental retardation and neurodegenerative diseases. PPARγ agonists can act as neuroprotective agents, promoting synaptic plasticity and neurite outgrowth. Therefore, selective PPARγ agonists are good candidates for therapeutic evaluation in intellectual disabilities. Preliminary results suggest that PPARγ agonists such as Pioglitazone, Rosiglitazone and synthetic agonist, GW1929, are used as the therapeutic agent in neurological disorders. These components interact with intracellular transduction signals (e.g. GSK3β, PI3K/Akt, Wnt/β-Catenin, Rac1 and MMP-9). It seems that interaction with these pathways can improve memory recognition in FXS animal models. The present hypothesis consists of enhancing synaptic plasticity that may then rescue the learning and memory in FXS. This will open many new therapeutic avenues for a variety of human diseases.
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Affiliation(s)
- Mohammad Jodeiri Farshbaf
- Department of Biology, School of Sciences, University of Isfahan, Isfahan, Iran; Department of Cellular Biotechnology at Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran
| | - Kamran Ghaedi
- Department of Biology, School of Sciences, University of Isfahan, Isfahan, Iran; Department of Cellular Biotechnology at Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran.
| | - Mahsa Shirani
- Department of Biology, School of Sciences, University of Isfahan, Isfahan, Iran
| | - Mohammad Hossein Nasr-Esfahani
- Department of Cellular Biotechnology at Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran.
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Scaffold hopping approach towards various AFQ-056 analogs as potent metabotropic glutamate receptor 5 negative allosteric modulators. Bioorg Med Chem Lett 2013; 23:6370-6. [DOI: 10.1016/j.bmcl.2013.09.059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/17/2013] [Accepted: 09/21/2013] [Indexed: 11/23/2022]
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Wheeler A, Raspa M, Bann C, Bishop E, Hessl D, Sacco P, Bailey DB. Anxiety, attention problems, hyperactivity, and the Aberrant Behavior Checklist in fragile X syndrome. Am J Med Genet A 2013; 164A:141-55. [PMID: 24352914 DOI: 10.1002/ajmg.a.36232] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 07/28/2013] [Indexed: 11/07/2022]
Abstract
Behavior problems are a common challenge for individuals with fragile X syndrome (FXS) and constitute the primary clinical outcome domain in trials testing new FXS medications. However, little is known about the relationship between caregiver-reported behavior problems and co-occurring conditions such as anxiety and attention problems. In this study, 350 caregivers, each with at least one son or daughter with full-mutation FXS, rated one of their children with FXS using the Aberrant Behavior Checklist-Community Version (ABC-C); the Anxiety subscale of the Anxiety, Depression, and Mood Scale; and the Attention/Hyperactivity Items from the Symptom Inventories. In addition to examining family consequences of these behaviors, this study also sought to replicate psychometric findings for the ABC-C in FXS, to provide greater confidence for its use in clinical trials with this population. Psychometric properties and baseline ratings of problem behavior were consistent with other recent studies, further establishing the profile of problem behavior in FXS. Cross-sectional analyses suggest that selected dimensions of problem behavior, anxiety, and hyperactivity are age related; thus, age should serve as an important control in any studies of problem behavior in FXS. Measures of anxiety, attention, and hyperactivity were highly associated with behavior problems, suggesting that these factors at least coincide with problem behavior. However, these problems generally did not add substantially to variance in caregiver burden predicted by elevated behavior problems. The results provide further evidence of the incidence of problem behaviors and co-occurring conditions in FXS and the impact of these behaviors on the family.
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Affiliation(s)
- Anne Wheeler
- Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Fernández E, Rajan N, Bagni C. The FMRP regulon: from targets to disease convergence. Front Neurosci 2013; 7:191. [PMID: 24167470 PMCID: PMC3807044 DOI: 10.3389/fnins.2013.00191] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 10/04/2013] [Indexed: 01/08/2023] Open
Abstract
The fragile X mental retardation protein (FMRP) is an RNA-binding protein that regulates mRNA metabolism. FMRP has been largely studied in the brain, where the absence of this protein leads to fragile X syndrome, the most frequent form of inherited intellectual disability. Since the identification of the FMRP gene in 1991, many studies have primarily focused on understanding the function/s of this protein. Hundreds of potential FMRP mRNA targets and several interacting proteins have been identified. Here, we report the identification of FMRP mRNA targets in the mammalian brain that support the key role of this protein during brain development and in regulating synaptic plasticity. We compared the genes from databases and genome-wide association studies with the brain FMRP transcriptome, and identified several FMRP mRNA targets associated with autism spectrum disorders, mood disorders and schizophrenia, showing a potential common pathway/s for these apparently different disorders.
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Affiliation(s)
- Esperanza Fernández
- Center for the Biology of Disease, Vlaams Institut voor Biotechnologie Leuven, Belgium ; Center for Human Genetics, Leuven Institute for Neuroscience and Disease, KU Leuven Leuven, Belgium
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Schmit TL, Dowell JA, Maes ME, Wilhelm M. c-Jun N-terminal kinase regulates mGluR-dependent expression of post-synaptic FMRP target proteins. J Neurochem 2013; 127:772-81. [PMID: 24047560 PMCID: PMC3992883 DOI: 10.1111/jnc.12453] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/11/2013] [Accepted: 09/12/2013] [Indexed: 12/01/2022]
Abstract
Fragile X syndrome (FXS) is caused by the loss of functional fragile X mental retardation protein (FMRP). Loss of FMRP results in an elevated basal protein expression profile of FMRP targeted mRNAs, a loss of local metabotropic glutamate receptor (mGluR)-regulated protein synthesis, exaggerated long-term depression and corresponding learning and behavioral deficits. Evidence shows that blocking mGluR signaling in FXS models ameliorates these deficits. Therefore, understanding the signaling mechanisms downstream of mGluR stimulation may provide additional therapeutic targets for FXS. Kinase cascades are an integral mechanism regulating mGluR-dependent protein translation. The c-Jun N-terminal kinase (JNK) pathway has been shown to regulate mGluR-dependent nuclear transcription; however, the involvement of JNK in local, synaptic signaling has not been explored. Here, we show that JNK is both necessary and sufficient for mGluR-dependent expression of a subset of FMRP target proteins. In addition, JNK activity is basally elevated in fmr1 knockout mouse synapses, and blocking JNK activity reduces the over-expression of post-synaptic proteins in these mice. Together, these data suggest that JNK may be an important signaling mechanism downstream of mGluR stimulation, regulating FMRP-dependent protein synthesis. Furthermore, local, post-synaptic dysregulation of JNK activity may provide a viable target to ameliorate the deficits involved in FXS. Expression of many FMRP target proteins is enhanced in FXS. Here, we evaluated the role of JNKs in FXS. We found that JNK signaling is activated upon mGluR stimulation in wild-type neurons. Conversely, JNK activity is basally elevated in fmr1 knockout. Inhibiting JNK reduced the expression of FMRP target proteins and driving JNK activity increased the expression of these proteins.
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Affiliation(s)
- Travis L Schmit
- Department of Pediatrics and the Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
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61
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Rangasamy S, D’Mello SR, Narayanan V. Epigenetics, autism spectrum, and neurodevelopmental disorders. Neurotherapeutics 2013; 10:742-56. [PMID: 24104594 PMCID: PMC3805864 DOI: 10.1007/s13311-013-0227-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Epigenetic marks are modifications of DNA and histones. They are considered to be permanent within a single cell during development, and are heritable across cell division. Programming of neurons through epigenetic mechanisms is believed to be critical in neural development. Disruption or alteration in this process causes an array of neurodevelopmental disorders, including autism spectrum disorders (ASDs). Recent studies have provided evidence for an altered epigenetic landscape in ASDs and demonstrated the central role of epigenetic mechanisms in their pathogenesis. Many of the genes linked to the ASDs encode proteins that are involved in transcriptional regulation and chromatin remodeling. In this review we highlight selected neurodevelopmental disorders in which epigenetic dysregulation plays an important role. These include Rett syndrome, fragile X syndrome, Prader-Willi syndrome, Angelman syndrome, and Kabuki syndrome. For each of these disorders, we discuss how advances in our understanding of epigenetic mechanisms may lead to novel therapeutic approaches.
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Affiliation(s)
- Sampathkumar Rangasamy
- />Developmental Neurogenetics Laboratory, Barrow Neurological Institute, Phoenix, AZ 85013 USA
| | | | - Vinodh Narayanan
- />Developmental Neurogenetics Laboratory, Barrow Neurological Institute, Phoenix, AZ 85013 USA
- />Developmental Neurogenetic Laboratory, Barrow Neurological Institute, Phoenix, AZ 85013 USA
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Bagni C, Oostra BA. Fragile X syndrome: From protein function to therapy. Am J Med Genet A 2013; 161A:2809-21. [PMID: 24115651 DOI: 10.1002/ajmg.a.36241] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 08/28/2013] [Indexed: 12/23/2022]
Abstract
Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and autism. The FMR1 gene contains a CGG repeat present in the 5'-untranslated region which can be unstable upon transmission to the next generation. The repeat is up to 55 CGGs long in the normal population. In patients with fragile X syndrome (FXS), a repeat length exceeding 200 CGGs generally leads to methylation of the repeat and the promoter region, which is accompanied by silencing of the FMR1 gene. The disease is a result of lack of expression of the fragile X mental retardation protein leading to severe symptoms, including intellectual disability, hyperactivity, and autistic-like behavior. The FMR1 protein (FMRP) has a number of functions. The translational dysregulation of a subset of mRNAs targeted by FMRP is probably the major contribution to FXS. FMRP is also involved in mRNA transport to synapses where protein synthesis occurs. For some FMRP-bound mRNAs, FMRP is a direct modulator of mRNA stability either by sustaining or preventing mRNA decay. Increased knowledge about the role of FMRP has led to the identification of potential treatments for fragile X syndrome that were often tested first in the different animal models. This review gives an overview about the present knowledge of the function of FMRP and the therapeutic strategies in mouse and man.
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Affiliation(s)
- Claudia Bagni
- VIB Center for the Biology of Disease, Catholic University of Leuven, Leuven, Belgium; Department of Biomedicine and Prevention, University of Rome, Tor Vergata, Italy
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63
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Lucá R, Averna M, Zalfa F, Vecchi M, Bianchi F, La Fata G, Del Nonno F, Nardacci R, Bianchi M, Nuciforo P, Munck S, Parrella P, Moura R, Signori E, Alston R, Kuchnio A, Farace MG, Fazio VM, Piacentini M, De Strooper B, Achsel T, Neri G, Neven P, Evans DG, Carmeliet P, Mazzone M, Bagni C. The fragile X protein binds mRNAs involved in cancer progression and modulates metastasis formation. EMBO Mol Med 2013; 5:1523-36. [PMID: 24092663 PMCID: PMC3799577 DOI: 10.1002/emmm.201302847] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 08/01/2013] [Accepted: 08/06/2013] [Indexed: 01/30/2023] Open
Abstract
The role of the fragile X mental retardation protein (FMRP) is well established in brain, where its absence leads to the fragile X syndrome (FXS). FMRP is almost ubiquitously expressed, suggesting that, in addition to its effects in brain, it may have fundamental roles in other organs. There is evidence that FMRP expression can be linked to cancer. FMR1 mRNA, encoding FMRP, is overexpressed in hepatocellular carcinoma cells. A decreased risk of cancer has been reported in patients with FXS while a patient-case with FXS showed an unusual decrease of tumour brain invasiveness. However, a role for FMRP in regulating cancer biology, if any, remains unknown. We show here that FMRP and FMR1 mRNA levels correlate with prognostic indicators of aggressive breast cancer, lung metastases probability and triple negative breast cancer (TNBC). We establish that FMRP overexpression in murine breast primary tumours enhances lung metastasis while its reduction has the opposite effect regulating cell spreading and invasion. FMRP binds mRNAs involved in epithelial mesenchymal transition (EMT) and invasion including E-cadherin and Vimentin mRNAs, hallmarks of EMT and cancer progression.
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Affiliation(s)
- Rossella Lucá
- VIB Center for the Biology of Disease, Leuven, Belgium; Center for Human Genetics, KU Leuven, Belgium
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Brendel C, Mielke B, Hillebrand M, Gärtner J, Huppke P. Methotrexate treatment of FraX fibroblasts results in FMR1 transcription but not in detectable FMR1 protein levels. J Neurodev Disord 2013; 5:23. [PMID: 24020679 PMCID: PMC3846751 DOI: 10.1186/1866-1955-5-23] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 08/21/2013] [Indexed: 11/23/2022] Open
Abstract
Background Fragile X syndrome is caused by the loss of FMRP expression due to methylation of the FMR1 promoter. Treatment of fragile X syndrome patients’ lymphoblastoid cells with 5-azadeoxycytidine results in demethylation of the promoter and reactivation of the gene. The aim of the study was to analyze if methotrexate, an agent which also reduces DNA methylation but with less toxicity than 5-azadeoxycytidine, has therapeutic potential in fragile X syndrome. Methods Fibroblasts of fragile X syndrome patients were treated with methotrexate in concentrations ranging from 1 to 4 μg/ml for up to 14 days. FMR1 and FMRP expression were analyzed by quantitative PCR and western blotting. Results FMR1 mRNA was detected and levels correlated positively with methotrexate concentrations and time of treatment, but western blotting did not show detectable FMRP levels. Conclusions We show that it is possible to reactivate FMR1 transcription in fibroblasts of fragile X syndrome patients by treatment with methotrexate. However, we were not able to show FMRP expression, possibly due to the reduced translation efficacy caused by the triplet repeat extension. Unless FMR1 reactivation is more effective in vivo our results indicate that methotrexate has no role in the treatment of fragile X syndrome.
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Affiliation(s)
- Cornelia Brendel
- Department of Pediatrics and Pediatric Neurology, Georg August University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
| | - Benjamin Mielke
- Department of Anesthetics, Georg August University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
| | - Merle Hillebrand
- Department of Pediatrics and Pediatric Neurology, Georg August University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
| | - Jutta Gärtner
- Department of Pediatrics and Pediatric Neurology, Georg August University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
| | - Peter Huppke
- Department of Pediatrics and Pediatric Neurology, Georg August University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany.,Department of Pediatrics and Pediatric Neurology, University Medical Center Göttingen, Georg August University, Robert-Koch-Strasse 40, 37075 Göttingen, Germany
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Friedman SH, Dani N, Rushton E, Broadie K. Fragile X mental retardation protein regulates trans-synaptic signaling in Drosophila. Dis Model Mech 2013; 6:1400-13. [PMID: 24046358 PMCID: PMC3820263 DOI: 10.1242/dmm.012229] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Fragile X syndrome (FXS), the most common inherited determinant of intellectual disability and autism spectrum disorders, is caused by loss of the fragile X mental retardation 1 (FMR1) gene product (FMRP), an mRNA-binding translational repressor. A number of conserved FMRP targets have been identified in the well-characterized Drosophila FXS disease model, but FMRP is highly pleiotropic in function and the full spectrum of FMRP targets has yet to be revealed. In this study, screens for upregulated neural proteins in Drosophila fmr1 (dfmr1) null mutants reveal strong elevation of two synaptic heparan sulfate proteoglycans (HSPGs): GPI-anchored glypican Dally-like protein (Dlp) and transmembrane Syndecan (Sdc). Our recent work has shown that Dlp and Sdc act as co-receptors regulating extracellular ligands upstream of intracellular signal transduction in multiple trans-synaptic pathways that drive synaptogenesis. Consistently, dfmr1 null synapses exhibit altered WNT signaling, with changes in both Wingless (Wg) ligand abundance and downstream Frizzled-2 (Fz2) receptor C-terminal nuclear import. Similarly, a parallel anterograde signaling ligand, Jelly belly (Jeb), and downstream ERK phosphorylation (dpERK) are depressed at dfmr1 null synapses. In contrast, the retrograde BMP ligand Glass bottom boat (Gbb) and downstream signaling via phosphorylation of the transcription factor MAD (pMAD) seem not to be affected. To determine whether HSPG upregulation is causative for synaptogenic defects, HSPGs were genetically reduced to control levels in the dfmr1 null background. HSPG correction restored both (1) Wg and Jeb trans-synaptic signaling, and (2) synaptic architecture and transmission strength back to wild-type levels. Taken together, these data suggest that FMRP negatively regulates HSPG co-receptors controlling trans-synaptic signaling during synaptogenesis, and that loss of this regulation causes synaptic structure and function defects characterizing the FXS disease state.
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Affiliation(s)
- Samuel H Friedman
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37212, USA
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Discovery, synthesis, and structure–activity relationships of 2-aminoquinazoline derivatives as a novel class of metabotropic glutamate receptor 5 negative allosteric modulators. Bioorg Med Chem Lett 2013; 23:4493-500. [DOI: 10.1016/j.bmcl.2013.06.049] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 06/14/2013] [Accepted: 06/17/2013] [Indexed: 11/18/2022]
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Iscru E, Goddyn H, Ahmed T, Callaerts-Vegh Z, D'Hooge R, Balschun D. Improved spatial learning is associated with increased hippocampal but not prefrontal long-term potentiation in mGluR4 knockout mice. GENES BRAIN AND BEHAVIOR 2013; 12:615-25. [PMID: 23714430 DOI: 10.1111/gbb.12052] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 02/13/2013] [Accepted: 05/21/2013] [Indexed: 01/08/2023]
Abstract
Although much information about metabotropic glutamate receptors (mGluRs) and their role in normal and pathologic brain function has been accumulated during the last decades, the role of group III mGluRs is still scarcely documented. Here, we examined mGluR4 knockout mice for types of behavior and synaptic plasticity that depend on either the hippocampus or the prefrontal cortex (PFC). We found improved spatial short- and long-term memory in the radial arm maze, which was accompanied by enhanced long-term potentiation (LTP) in hippocampal CA1 region. In contrast, LTP in the PFC was unchanged when compared with wild-type controls. Changes in paired-pulse facilitation that became overt in the presence of the GABAA antagonist picrotoxin indicated a function of mGluR4 in maintaining the excitation/inhibition balance, which is of crucial importance for information processing in the brain and the deterioration of these processes in neuropsychological disorders such as autism, epilepsy and schizophrenia.
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Affiliation(s)
- E Iscru
- Laboratory of Biological Psychology, Faculty of Psychology and Educational Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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68
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Lohith TG, Osterweil EK, Fujita M, Jenko KJ, Bear MF, Innis RB. Is metabotropic glutamate receptor 5 upregulated in prefrontal cortex in fragile X syndrome? Mol Autism 2013; 4:15. [PMID: 23706040 PMCID: PMC3679853 DOI: 10.1186/2040-2392-4-15] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 05/08/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Fragile X syndrome (FXS) is a common inherited form of intellectual disability caused by loss of function of the fragile X mental retardation protein. Recent animal studies suggest that upregulated downstream signaling by metabotropic glutamate receptor 5 (mGluR5) might be an important mechanism for cognitive and behavioral abnormalities associated with FXS. However, mGluR5 density in human FXS remains unknown. METHODS Receptor binding and protein expression were measured in the postmortem prefrontal cortex of 14 FXS patients or carriers and 17 age- and sex-matched control subjects without neurological disorders. In-vitro binding assays were performed using [3H]-labeled 3-methoxy-5-pyridin-2-ylethynylpyridine (MPEPy), a selective and high-affinity negative allosteric modulator of mGluR5, to measure receptor density and the radioligand's dissociation constant, which is inversely proportional to affinity. Immunoblotting was also performed, to measure mGluR5 protein expression. RESULTS The mGluR5 density increased with marginal significance (+16%; P = 0.058) in the prefrontal cortex of FXS patients or carriers compared with matched healthy controls. No significant change in dissociation constant (-4%; P = 0.293) was observed. Immunoblotting found a significant elevation (+32%; P = 0.048) in mGluR5 protein expression. CONCLUSIONS Both mGluR5 binding density and protein expression were increased in the brains of FXS patients or carriers, but only expression was significantly different, which could be because of the small sample size and moderate variability. Another important caveat is that the effects of psychotropic medications on mGluR5 expression are largely unknown. Future in-vivo measurement of mGluR5 with positron emission tomography might characterize the role of this receptor in the pathophysiology of FXS and facilitate trials of mGluR5-oriented treatments for this disorder.
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Affiliation(s)
- Talakad G Lohith
- Molecular Imaging Branch, National Institute of Mental Health, 10 Center Drive, Bethesda, MD 20892-1026, USA.
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69
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Abstract
OBJECTIVE There is a great need for valid outcome measures of functional improvement for impending clinical trials of targeted interventions for fragile X syndrome (FXS). Families often report conversational language improvement during clinical treatment, but no validated measures exist to quantify this outcome. This small-scale study sought to determine the feasibility, reproducibility, and clinical validity of highly structured expressive language sampling as an outcome measure reflecting language ability. METHODS Narrative and conversation tasks were administered to 36 verbal participants (25 males and 11 females) with FXS (aged 5-36 years, mean, 18 ± 7 years). Alternate versions were used with randomized task order at 2- to 3-week intervals (mean, 19.6 ± 6.4 days). Audio recordings of sessions were transcribed and analyzed. Dependent measures reflected talkativeness (total number of utterances), utterance planning (proportion of communication [C] units with mazes), articulation (proportion of unintelligible/partly unintelligible C-units), vocabulary (number of different word roots), and syntactic ability (mean length of utterance [MLU] in words). Reproducibility of measures was evaluated with intraclass correlation coefficients (ICC). RESULTS All participants could complete the tasks. Coded data were highly reproducible with Pearson's correlations at p < .01 for all measures and ICC values of .911 to .966 (conversation) and .728 to .940 (narration). Some measures including MLU and different word roots were correlated with expressive language subscale scores from the Vineland Adaptive Behavior Scale. CONCLUSIONS These expressive language sampling tasks appear to be feasible, reproducible, and clinically valid and should be further validated in a larger cohort, as a promising means of assessing functional expressive language outcomes during clinical trials in FXS.
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Abstract
Fragile X syndrome, a common cause of intellectual disability and autism, is thought to occur due to abnormal regulation of neuronal protein synthesis. A study by Osterweil et al. (2013), in this issue, demonstrates that the HMG-CoA reductase inhibitor lovastatin can normalize protein synthesis and also reduce audiogenic seizures in Fmr1 knockout mice.
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Affiliation(s)
- Jonathan Lipton
- F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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71
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Abstract
Brain development in neurodevelopmental disorders has been considered to comprise a sequence of critical periods, and abnormalities occurring during early development have been considered irreversible in adulthood. However, findings in mouse models of neurodevelopmental disorders, including fragile X, Rett syndrome, Down syndrome, and neurofibromatosis type I suggest that it is possible to reverse certain molecular, electrophysiological, and behavioral deficits associated with these disorders in adults by genetic or pharmacological manipulations. Furthermore, recent studies have suggested that critical period-like plasticity can be reactivated in the adult brain by environmental manipulations or by pharmacotherapy. These studies open up a tantalizing possibility that targeted pharmacological treatments in combination with regimes of training or rehabilitation might alleviate or reverse the symptoms of neurodevelopmental disorders even after the end of critical developmental periods. Even though translation from animal experimentation to clinical practice is challenging, these results suggest a rational basis for treatment of neurodevelopmental disorders in adulthood.
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Abstract
Substance dependence is characterized by a group of symptoms, according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR). These symptoms include tolerance, withdrawal, drug consumption for alleviating withdrawal, exaggerated consumption beyond original intention, failure to reduce drug consumption, expending a considerable amount of time obtaining or recovering from the substance's effects, disregard of basic aspects of life (for example, family), and maintenance of drug consumption, despite facing adverse consequences. The nucleus accumbens (NAc) is a brain structure located in the basal forebrain of vertebrates, and it has been the target of addictive drugs. Different neurotransmitter systems at the level of the NAc circuitry have been linked to the different problems of drug addiction, like compulsive use and relapse. The glutamate system has been linked mainly to relapse after drug-seeking extinction. The dopamine system has been linked mainly to compulsive drug use. The glutamate homeostasis hypothesis centers around the dynamics of synaptic and extrasynaptic levels of glutamate, and their impact on circuitry from the prefrontal cortex (PFC) to the NAc. After repetitive drug use, deregulation of this homeostasis increases the release of glutamate from the PFC to the NAc during drug relapse. Glial cells also play a fundamental role in this hypothesis; glial cells shape the interactions between the PFC and the NAc by means of altering glutamate levels in synaptic and extrasynaptic spaces. On the other hand, cocaine self-administration and withdrawal increases the surface expression of subunit glutamate receptor 1 (GluA1) of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors at the level of the NAc. Also, cocaine self-administration and withdrawal induce the formation of subunit glutamate receptor 2 (GluA2), lacking the Ca(2+)-permeable AMPA receptors (CP-AMPARs) at the level of the NAc. Antagonism of the CP-AMPARs reduces cravings. It is necessary to pursue further exploration of the AMPA receptor subunit composition and variations at the level of the NAc for a better understanding of glutamatergic plastic changes. It is known that cocaine and morphine are able to induce changes in dendritic spine morphology by modifying actin cycling. These changes include an initial increase in spine head diameter and increases in AMPA receptor expression, followed by a second stage of spine head diameter retraction and reduction of the AMPA receptors' expression in spines. Besides glutamate and dopamine, other factors, like brain-derived neurotrophic factor (BDNF), can influence NAc activity and induce changes in dendritic spine density. BDNF also induces drug-related behaviors like self-administration and relapse. Neither apoptosis nor neurogenesis plays a relevant role in the neurobiological processes subjacent to cocaine addiction in adults (rodent or human). Different therapeutic drugs like N-acetylcysteine (NAC), modafinil, acamprosate, and topiramate have been tested in preclinical and/or clinical models for alleviating drug relapse. Moreover, these therapeutic drugs target the glutamatergic circuitry between the PFC and the NAc. NAC and acamprosate have shown inconsistent results in clinical trials. Modafinil and topiramate have shown some success, but more clinical trials are necessary. Based on the current review findings, it could be recommendable to explore therapeutic approaches that include synergism between different drugs and neurotransmitter systems. The discrepancy in the results of some therapeutic drugs between preclinical versus clinical trials for alleviating relapse or drug dependence could be linked to the scarce exploration of preclinical models that mimic polydrug abuse patterns, for example, cocaine plus alcohol. At the clinical level, the pattern of polydrug consumption is a phenomenon of considerable frequency. Finally, as a complement at the end, an updated summary is included about the role of glutamate in other neuropsychiatric disorders (for example, mood disorders, schizophrenia, and others).
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Affiliation(s)
- Gabriel C Quintero
- Florida State University - Panama, Clayton, Panama ; Medical University of South Carolina, Charleston, South Carolina, USA ; Smithsonian Tropical Research Institute, Ancon, Republic of Panama
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73
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Swanger SA, Bassell GJ. Dendritic protein synthesis in the normal and diseased brain. Neuroscience 2012; 232:106-27. [PMID: 23262237 DOI: 10.1016/j.neuroscience.2012.12.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/21/2012] [Accepted: 12/01/2012] [Indexed: 01/25/2023]
Abstract
Synaptic activity is a spatially limited process that requires a precise, yet dynamic, complement of proteins within the synaptic micro-domain. The maintenance and regulation of these synaptic proteins is regulated, in part, by local mRNA translation in dendrites. Protein synthesis within the postsynaptic compartment allows neurons tight spatial and temporal control of synaptic protein expression, which is critical for proper functioning of synapses and neural circuits. In this review, we discuss the identity of proteins synthesized within dendrites, the receptor-mediated mechanisms regulating their synthesis, and the possible roles for these locally synthesized proteins. We also explore how our current understanding of dendritic protein synthesis in the hippocampus can be applied to new brain regions and to understanding the pathological mechanisms underlying varied neurological diseases.
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Affiliation(s)
- S A Swanger
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - G J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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74
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Wijetunge LS, Chattarji S, Wyllie DJA, Kind PC. Fragile X syndrome: from targets to treatments. Neuropharmacology 2012; 68:83-96. [PMID: 23257237 DOI: 10.1016/j.neuropharm.2012.11.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/27/2012] [Accepted: 11/29/2012] [Indexed: 01/11/2023]
Abstract
Fragile X syndrome (FXS) is one of the most prevalent and well-studied monogenetic causes of intellectual disability and autism and, although rare, its high penetrance makes it a desirable model for the study of neurodevelopmental disorders more generally. Indeed recent studies suggest that there is functional convergence of a number of genes that are implicated in intellectual disability and autism indicating that an understanding of the cellular and biochemical dysfunction that occurs in monogenic forms of these disorders are likely to reveal common targets for therapeutic intervention. Fundamental research into FXS has provided a wealth of information about how the loss of function of the fragile X mental retardation protein results in biochemical, anatomical and physiological dysfunction leading to the discovery of interventions that correct many of the core pathological phenotypes associated with animal models of FXS. Most promisingly such strategies have led to development of drugs that are now in clinical trials. This review highlights how progress in understanding disorders such as FXS has led to a new era in which targeted molecular treatment towards neurodevelopmental disorders is becoming a reality. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.
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Affiliation(s)
- Lasani S Wijetunge
- Patrick Wild Centre, Centre for Integrative Physiology, University of Edinburgh, EH8 9XD, UK
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75
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FMRP targets distinct mRNA sequence elements to regulate protein expression. Nature 2012; 492:382-6. [PMID: 23235829 PMCID: PMC3528815 DOI: 10.1038/nature11737] [Citation(s) in RCA: 524] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 11/02/2012] [Indexed: 12/16/2022]
Abstract
Fragile-X Syndrome (FXS) is a multi-organ disease leading to mental retardation, macro-orchidism in males, and premature ovarian insufficiency in female carriers. FXS is also a prominent monogenic disease associated with autism spectrum disorders (ASD). FXS is typically caused by the loss of FRAGILE X-MENTAL RETARDATION 1 (FMR1) expression, which encodes for the RNA-binding protein (RBP), FMRP. We report the discovery of distinct RNA recognition elements (RREs) that correspond to the two independent RNA binding domains of FMRP, and the binding sites within the mRNA targets for wild-type and I304N mutant FMRP isoforms and its paralogs, FXR1 and FXR2. RRE frequency, ratio, and distribution determine target mRNA association with FMRP. Among highly-enriched targets, we identified many genes involved in ASD and demonstrate that FMRP affects their protein levels in cell culture, mice, and human brain. Unexpectedly, we discovered that these targets are also dysregulated in Fmr1-/- mouse ovaries, showing signs of premature follicular overdevelopment. These results indicate that FMRP targets shared signaling pathways across different cellular contexts. As it is become increasingly appreciated that signaling pathways are important to FXS and ASD, our results here provide a molecular guide towards the pursuit of novel therapeutic targets for these neurological disorders.
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76
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Wang H, Zhuo M. Group I metabotropic glutamate receptor-mediated gene transcription and implications for synaptic plasticity and diseases. Front Pharmacol 2012; 3:189. [PMID: 23125836 PMCID: PMC3485740 DOI: 10.3389/fphar.2012.00189] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 10/11/2012] [Indexed: 12/05/2022] Open
Abstract
Stimulation of group I metabotropic glutamate receptors (mGluRs) initiates a wide variety of signaling pathways. Group I mGluR activation can regulate gene expression at both translational and transcriptional levels, and induces translation or transcription-dependent synaptic plastic changes in neurons. The group I mGluR-mediated translation-dependent neural plasticity has been well reviewed. In this review, we will highlight group I mGluR-induced gene transcription and its role in synaptic plasticity. The signaling pathways (PKA, CaMKs, and MAPKs) which have been shown to link group I mGluRs to gene transcription, the relevant transcription factors (CREB and NF-κB), and target proteins (FMRP and ARC) will be documented. The significance and future direction for characterizing group I mGluR-mediated gene transcription in fragile X syndrome, schizophrenia, drug addiction, and other neurological disorders will also be discussed.
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Affiliation(s)
- Hansen Wang
- Department of Physiology, Faculty of Medicine, University of Toronto Toronto, ON, Canada
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77
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Genetic removal of p70 S6 kinase 1 corrects molecular, synaptic, and behavioral phenotypes in fragile X syndrome mice. Neuron 2012; 76:325-37. [PMID: 23083736 DOI: 10.1016/j.neuron.2012.07.022] [Citation(s) in RCA: 238] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2012] [Indexed: 01/21/2023]
Abstract
Fragile X syndrome (FXS) is the leading inherited cause of autism and intellectual disability. Aberrant synaptic translation has been implicated in the etiology of FXS, but most lines of research on therapeutic strategies have targeted protein synthesis indirectly, far upstream of the translation machinery. We sought to perturb p70 ribosomal S6 kinase 1 (S6K1), a key translation initiation and elongation regulator, in FXS model mice. We found that genetic reduction of S6K1 prevented elevated phosphorylation of translational control molecules, exaggerated protein synthesis, enhanced mGluR-dependent long-term depression (LTD), weight gain, and macro-orchidism in FXS model mice. In addition, S6K1 deletion prevented immature dendritic spine morphology and multiple behavioral phenotypes, including social interaction deficits, impaired novel object recognition, and behavioral inflexibility. Our results support the model that dysregulated protein synthesis is the key causal factor in FXS and that restoration of normal translation can stabilize peripheral and neurological function in FXS.
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78
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Gürkan CK, Hagerman RJ. TARGETED TREATMENTS IN AUTISM AND FRAGILE X SYNDROME. RESEARCH IN AUTISM SPECTRUM DISORDERS 2012; 6:1311-1320. [PMID: 23162607 PMCID: PMC3498468 DOI: 10.1016/j.rasd.2012.05.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Autism is a neurodevelopmental disorder consisting of a constellation of symptoms that sometimes occur as part of a complex disorder characterized by impairments in social interaction, communication and behavioral domains. It is a highly disabling disorder and there is a need for treatment targeting the core symptoms. Although autism is accepted as highly heritable, there is no genetic cure at this time. Autism is shown to be linked to several genes and is a feature of some complex genetic disorders, including fragile X syndrome (FXS), fragile X premutation involvement, tuberous sclerosis and Rett syndrome. The term autism spectrum disorders (ASDs) covers autism, Asperger syndrome and pervasive developmental disorders (PDD-NOS) and the etiologies are heterogeneous. In recent years, targeted treatments have been developed for several disorders that have a known specific genetic cause leading to autism. Since there are significant molecular and neurobiological overlaps among disorders, targeted treatments developed for a specific disorder may be helpful in ASD of unknown etiology. Examples of this are two drug classes developed to treat FXS, Arbaclofen, a GABA(B) agonist, and mGluR5 antagonists, and both may be helpful in autism without FXS. The mGluR5 antagonists are also likely to have a benefit in the aging problems of fragile X premutation carriers, the fragile X -associated tremor ataxia syndrome (FXTAS) and the Parkinsonism that can occur in aging patients with fragile X syndrome. Targeted treatments in FXS which has a well known genetic etiology may lead to new targeted treatments in autism.
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Affiliation(s)
- C. Kağan Gürkan
- Department of Pediatrics and the MIND Institute, UC Davis Medical Center, Adress: MIND Institute at UC Davis Medical Center, 2825 50th Street, Sacramento, California 95817
| | - Randi J. Hagerman
- Department of Pediatrics and the MIND Institute, UC Davis Medical Center, Adress: MIND Institute at UC Davis Medical Center, 2825 50th Street, Sacramento, California 95817
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Discovery of 1H-pyrrolo[2,3-c]pyridine-7-carboxamides as novel, allosteric mGluR5 antagonists. Bioorg Med Chem Lett 2012; 22:6454-9. [DOI: 10.1016/j.bmcl.2012.08.053] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 08/10/2012] [Accepted: 08/13/2012] [Indexed: 11/21/2022]
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80
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Bhattacharya A, Klann E. The molecular basis of cognitive deficits in pervasive developmental disorders. Learn Mem 2012; 19:434-43. [PMID: 22904374 DOI: 10.1101/lm.025007.111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Persons with pervasive developmental disorders (PDD) exhibit a range of cognitive deficits that hamper their quality of life, including difficulties involving communication, sociability, and perspective-taking. In recent years, a variety of studies in mice that model genetic syndromes with a high risk of PDD have provided insights into the underlying molecular mechanisms associated with these disorders. What is less appreciated is how the molecular anomalies affect neuronal and circuit function to give rise to the cognitive deficits associated with PDD. In this review, we describe genetic mutations that cause PDD and discuss how they alter fundamental social and cognitive processes. We then describe efforts to correct cognitive impairments associated with these disorders and identify areas of further inquiry in the search for molecular targets for therapeutics for PDD.
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Affiliation(s)
- Aditi Bhattacharya
- Center for Neural Science, New York University, New York, New York 10003, USA
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81
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Wang H, Morishita Y, Miura D, Naranjo JR, Kida S, Zhuo M. Roles of CREB in the regulation of FMRP by group I metabotropic glutamate receptors in cingulate cortex. Mol Brain 2012; 5:27. [PMID: 22867433 PMCID: PMC3478997 DOI: 10.1186/1756-6606-5-27] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Accepted: 08/02/2012] [Indexed: 12/04/2022] Open
Abstract
Background Fragile X syndrome is caused by lack of fragile X mental retardation protein (FMRP) due to silencing of the FMR1 gene. The metabotropic glutamate receptors (mGluRs) in the central nervous system contribute to higher brain functions including learning/memory, mental disorders and persistent pain. The transcription factor cyclic AMP-responsive element binding protein (CREB) is involved in important neuronal functions, such as synaptic plasticity and neuronal survival. Our recent study has shown that stimulation of Group I mGluRs upregulated FMRP and activated CREB in anterior cingulate cortex (ACC), a key region for brain cognitive and executive functions, suggesting that activation of Group I mGluRs may upregulate FMRP through CREB signaling pathway. Results In this study, we demonstrate that CREB contributes to the regulation of FMRP by Group I mGluRs. In ACC neurons of adult mice overexpressing dominant active CREB mutant, the upregulation of FMRP by stimulating Group I mGluR is enhanced compared to wild-type mice. However, the regulation of FMRP by Group I mGluRs is not altered by overexpression of Ca2+-insensitive mutant form of downstream regulatory element antagonist modulator (DREAM), a transcriptional repressor involved in synaptic transmission and plasticity. Conclusion Our study has provided further evidence for CREB involvement in regulation of FMRP by Group I mGluRs in ACC neurons, and may help to elucidate the pathogenesis of fragile X syndrome.
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Affiliation(s)
- Hansen Wang
- Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
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82
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Gross C, Bassell GJ. Excess protein synthesis in FXS patient lymphoblastoid cells can be rescued with a p110β-selective inhibitor. Mol Med 2012; 18:336-45. [PMID: 22207187 DOI: 10.2119/molmed.2011.00363] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2011] [Accepted: 12/05/2011] [Indexed: 02/06/2023] Open
Abstract
The fragile X mental retardation protein (FMRP) plays a key role for neurotransmitter-mediated signaling upstream of neuronal protein synthesis. Functional loss of FMRP causes the inherited intellectual disability fragile X syndrome (FXS), and leads to increased and stimulus-insensitive neuronal protein synthesis in FXS animal models. Previous studies suggested that excess protein synthesis mediated by dysregulated signal transduction contributes to the majority of neurological defects in FXS, and might be a promising target for therapeutic strategies in patients. However, possible impairments in receptor-dependent protein synthesis have not been evaluated in patient cells so far. Using quantitative fluorescent metabolic labeling, we demonstrate that protein synthesis is exaggerated and cannot be further increased by cytokine stimulation in human fragile X lymphoblastoid cells. Our previous work suggested that loss of FMRP-mediated regulation of protein expression and enzymatic function of the PI3K catalytic subunit p110β contributes to dysregulated protein synthesis in a mouse model of FXS. Here, we demonstrate that these molecular mechanisms are recapitulated in FXS patient cells. Furthermore, we show that treatment with a p110β-selective antagonist rescues excess protein synthesis in synaptoneurosomes from an FXS mouse model and in patient cells. Our work suggests that dys-regulated protein synthesis and PI3K activity in patient cells might be suitable biomarkers to quantify the efficacy of drugs to ameliorate molecular mechanisms underlying FXS, and could be used for drug screens to refine treatment strategies for individual patients. Moreover, we provide rationale to pursue p110β-targeting treatments as potential therapy in FXS, and possibly other autism spectrum disorders.
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Affiliation(s)
- Christina Gross
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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84
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He CX, Portera-Cailliau C. The trouble with spines in fragile X syndrome: density, maturity and plasticity. Neuroscience 2012; 251:120-8. [PMID: 22522472 DOI: 10.1016/j.neuroscience.2012.03.049] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 02/14/2012] [Accepted: 03/04/2012] [Indexed: 01/15/2023]
Abstract
Dendritic spines are the principal recipients of excitatory synaptic inputs and the basic units of neural computation in the mammalian brain. Alterations in the density, size, shape, and turnover of mature spines, or defects in how spines are generated and establish synapses during brain development, could all result in neuronal dysfunction and lead to cognitive and/or behavioral impairments. That spines are abnormal in fragile X syndrome (FXS) and in the best-studied animal model of this disorder, the Fmr1 knockout mouse, is an undeniable fact. But the trouble with spines in FXS is that the exact nature of their defect is still controversial. Here, we argue that the most consistent abnormality of spines in FXS may be a subtle defect in activity-dependent spine plasticity and maturation. We also propose some future directions for research into spine plasticity in FXS at the cellular and ultrastructural levels that could help solve a two-decade-long riddle about the integrity of synapses in this prototypical neurodevelopmental disorder.
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Affiliation(s)
- C X He
- Department of Neurology, David Geffen School of Medicine at UCLA, 710 Westwood Plaza, Los Angeles, CA 90095, USA
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85
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Affiliation(s)
- Gwenn S Smith
- Division of Geriatric Psychiatry and Neuropsychiatry, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Johns Hopkins Bayview Medical Center, Baltimore, MD, USA
| | - Xiaohua Li
- Department of Psychiatry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - P Jeffrey Conn
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
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86
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Guo W, Murthy AC, Zhang L, Johnson EB, Schaller EG, Allan AM, Zhao X. Inhibition of GSK3β improves hippocampus-dependent learning and rescues neurogenesis in a mouse model of fragile X syndrome. Hum Mol Genet 2011; 21:681-91. [PMID: 22048960 DOI: 10.1093/hmg/ddr501] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Fragile X syndrome (FXS), a common inherited form of intellectual disability with learning deficits, results from a loss of fragile X mental retardation protein (FMRP). Despite extensive research, treatment options for FXS remain limited. Since FMRP is known to play an important role in adult hippocampal neurogenesis and hippocampus-dependent learning and FMRP regulates the adult neural stem cell fate through the translational regulation of glycogen synthase kinase 3β (GSK3β), we investigated the effects of a GSK3β inhibitor, SB216763, on Fmr1 knockout mice (Fmr1 KO). We found that the inhibition of GSK3β could reverse the hippocampus-dependent learning deficits and rescue adult hippocampal neurogenesis at multiple stages in Fmr1 KO mice. Our results point to GSK3β inhibition as a potential treatment for the learning deficits seen in FXS.
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Affiliation(s)
- Weixiang Guo
- Waisman Center and Department of Neuroscience, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53705, USA
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87
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Swanger SA, Yao X, Gross C, Bassell GJ. Automated 4D analysis of dendritic spine morphology: applications to stimulus-induced spine remodeling and pharmacological rescue in a disease model. Mol Brain 2011; 4:38. [PMID: 21982080 PMCID: PMC3213078 DOI: 10.1186/1756-6606-4-38] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Accepted: 10/07/2011] [Indexed: 12/22/2022] Open
Abstract
Uncovering the mechanisms that regulate dendritic spine morphology has been limited, in part, by the lack of efficient and unbiased methods for analyzing spines. Here, we describe an automated 3D spine morphometry method and its application to spine remodeling in live neurons and spine abnormalities in a disease model. We anticipate that this approach will advance studies of synapse structure and function in brain development, plasticity, and disease.
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Affiliation(s)
- Sharon A Swanger
- Department of Cell Biology, Emory University, 615 Michael St, NE, Atlanta, GA 30322, USA
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