51
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Pellerin D, Çaku A, Fradet M, Bouvier P, Dubé J, Corbin F. Lovastatin corrects ERK pathway hyperactivation in fragile X syndrome: potential of platelet’s signaling cascades as new outcome measures in clinical trials. Biomarkers 2016; 21:497-508. [DOI: 10.3109/1354750x.2016.1160289] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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52
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Sun MK, Hongpaisan J, Alkon DL. Rescue of Synaptic Phenotypes and Spatial Memory in Young Fragile X Mice. ACTA ACUST UNITED AC 2016; 357:300-10. [PMID: 26941170 DOI: 10.1124/jpet.115.231100] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/02/2016] [Indexed: 01/01/2023]
Abstract
Fragile X syndrome (FXS) is characterized by synaptic immaturity, cognitive impairment, and behavioral changes. The disorder is caused by transcriptional shutdown in neurons of thefragile X mental retardation 1gene product, fragile X mental retardation protein. Fragile X mental retardation protein is a repressor of dendritic mRNA translation and its silencing leads to dysregulation of synaptically driven protein synthesis and impairments of intellect, cognition, and behavior, and FXS is a disorder that currently has no effective therapeutics. Here, young fragile X mice were treated with chronic bryostatin-1, a relatively selective protein kinase Cεactivator, which induces synaptogenesis and synaptic maturation/repair. Chronic treatment with bryostatin-1 rescues young fragile X mice from the disorder phenotypes, including normalization of most FXS abnormalities in 1) hippocampal brain-derived neurotrophic factor expression, 2) postsynaptic density-95 levels, 3) transformation of immature dendritic spines to mature synapses, 4) densities of the presynaptic and postsynaptic membranes, and 5) spatial learning and memory. The therapeutic effects were achieved without downregulation of metabotropic glutamate receptor (mGluR) 5 in the hippocampus and are more dramatic than those of a late-onset treatment in adult fragile X mice. mGluR5 expression was in fact lower in fragile X mice and its expression was restored with the bryostatin-1 treatment. Our results show that synaptic and cognitive function of young FXS mice can be normalized through pharmacological treatment without downregulation of mGluR5 and that bryostatin-1-like agents may represent a novel class of drugs to treat fragile X mental retardation at a young age and in adults.
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Affiliation(s)
- Miao-Kun Sun
- Blanchette Rockefeller Neurosciences Institute, Morgantown, West Virginia
| | - Jarin Hongpaisan
- Blanchette Rockefeller Neurosciences Institute, Morgantown, West Virginia
| | - Daniel L Alkon
- Blanchette Rockefeller Neurosciences Institute, Morgantown, West Virginia
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53
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Subramanian M, Timmerman CK, Schwartz JL, Pham DL, Meffert MK. Characterizing autism spectrum disorders by key biochemical pathways. Front Neurosci 2015; 9:313. [PMID: 26483618 PMCID: PMC4586332 DOI: 10.3389/fnins.2015.00313] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Accepted: 08/20/2015] [Indexed: 12/29/2022] Open
Abstract
The genetic and phenotypic heterogeneity of autism spectrum disorders (ASD) presents a substantial challenge for diagnosis, classification, research, and treatment. Investigations into the underlying molecular etiology of ASD have often yielded mixed and at times opposing findings. Defining the molecular and biochemical underpinnings of heterogeneity in ASD is crucial to our understanding of the pathophysiological development of the disorder, and has the potential to assist in diagnosis and the rational design of clinical trials. In this review, we propose that genetically diverse forms of ASD may be usefully parsed into entities resulting from converse patterns of growth regulation at the molecular level, which lead to the correlates of general synaptic and neural overgrowth or undergrowth. Abnormal brain growth during development is a characteristic feature that has been observed both in children with autism and in mouse models of autism. We review evidence from syndromic and non-syndromic ASD to suggest that entities currently classified as autism may fundamentally differ by underlying pro- or anti-growth abnormalities in key biochemical pathways, giving rise to either excessive or reduced synaptic connectivity in affected brain regions. We posit that this classification strategy has the potential not only to aid research efforts, but also to ultimately facilitate early diagnosis and direct appropriate therapeutic interventions.
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Affiliation(s)
- Megha Subramanian
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Christina K Timmerman
- Department of Biological Chemistry, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Joshua L Schwartz
- Department of Biological Chemistry, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Daniel L Pham
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Mollie K Meffert
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine Baltimore, MD, USA ; Department of Biological Chemistry, Johns Hopkins University School of Medicine Baltimore, MD, USA
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54
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Sastre A, Campillo NE, Gil C, Martinez A. Therapeutic approaches for the future treatment of Fragile X. Curr Opin Behav Sci 2015. [DOI: 10.1016/j.cobeha.2015.01.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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55
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Kumari D, Bhattacharya A, Nadel J, Moulton K, Zeak NM, Glicksman A, Dobkin C, Brick DJ, Schwartz PH, Smith CB, Klann E, Usdin K. Identification of fragile X syndrome specific molecular markers in human fibroblasts: a useful model to test the efficacy of therapeutic drugs. Hum Mutat 2015; 35:1485-94. [PMID: 25224527 DOI: 10.1002/humu.22699] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 09/04/2014] [Indexed: 11/06/2022]
Abstract
Fragile X syndrome (FXS) is the most frequent cause of inherited intellectual disability and autism. It is caused by the absence of the fragile X mental retardation 1 (FMR1) gene product, fragile X mental retardation protein (FMRP), an RNA-binding protein involved in the regulation of translation of a subset of brain mRNAs. In Fmr1 knockout mice, the absence of FMRP results in elevated protein synthesis in the brain as well as increased signaling of many translational regulators. Whether protein synthesis is also dysregulated in FXS patients is not firmly established. Here, we demonstrate that fibroblasts from FXS patients have significantly elevated rates of basal protein synthesis along with increased levels of phosphorylated mechanistic target of rapamycin (p-mTOR), phosphorylated extracellular signal regulated kinase 1/2, and phosphorylated p70 ribosomal S6 kinase 1 (p-S6K1). The treatment with small molecules that inhibit S6K1 and a known FMRP target, phosphoinositide 3-kinase (PI3K) catalytic subunit p110β, lowered the rates of protein synthesis in both control and patient fibroblasts. Our data thus demonstrate that fibroblasts from FXS patients may be a useful in vitro model to test the efficacy and toxicity of potential therapeutics prior to clinical trials, as well as for drug screening and designing personalized treatment approaches.
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Affiliation(s)
- Daman Kumari
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
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de Esch C, van den Berg W, Buijsen R, Jaafar I, Nieuwenhuizen-Bakker I, Gasparini F, Kushner S, Willemsen R. Fragile X mice have robust mGluR5-dependent alterations of social behaviour in the Automated Tube Test. Neurobiol Dis 2015; 75:31-9. [DOI: 10.1016/j.nbd.2014.12.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 12/08/2014] [Accepted: 12/23/2014] [Indexed: 11/16/2022] Open
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Wang H, Pati S, Pozzo-Miller L, Doering LC. Targeted pharmacological treatment of autism spectrum disorders: fragile X and Rett syndromes. Front Cell Neurosci 2015; 9:55. [PMID: 25767435 PMCID: PMC4341567 DOI: 10.3389/fncel.2015.00055] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 02/05/2015] [Indexed: 12/27/2022] Open
Abstract
Autism spectrum disorders (ASDs) are genetically and clinically heterogeneous and lack effective medications to treat their core symptoms. Studies of syndromic ASDs caused by single gene mutations have provided insights into the pathophysiology of autism. Fragile X and Rett syndromes belong to the syndromic ASDs in which preclinical studies have identified rational targets for drug therapies focused on correcting underlying neural dysfunction. These preclinical discoveries are increasingly translating into exciting human clinical trials. Since there are significant molecular and neurobiological overlaps among ASDs, targeted treatments developed for fragile X and Rett syndromes may be helpful for autism of different etiologies. Here, we review the targeted pharmacological treatment of fragile X and Rett syndromes and discuss related issues in both preclinical studies and clinical trials of potential therapies for the diseases.
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Affiliation(s)
- Hansen Wang
- Faculty of Medicine, University of Toronto, 1 King's College Circle Toronto, ON, Canada
| | - Sandipan Pati
- Department of Neurology, Epilepsy Division, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Lucas Pozzo-Miller
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham Birmingham, AL, USA
| | - Laurie C Doering
- Faculty of Health Sciences, Department of Pathology and Molecular Medicine, McMaster University Hamilton, ON, Canada
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Faridar A, Jones-Davis D, Rider E, Li J, Gobius I, Morcom L, Richards LJ, Sen S, Sherr EH. Mapk/Erk activation in an animal model of social deficits shows a possible link to autism. Mol Autism 2014; 5:57. [PMID: 25874073 PMCID: PMC4396809 DOI: 10.1186/2040-2392-5-57] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Accepted: 10/08/2014] [Indexed: 01/01/2023] Open
Abstract
Background There is converging preclinical and clinical evidence to suggest that the extracellular signal-regulated kinase (ERK) signaling pathway may be dysregulated in autism spectrum disorders. Method We evaluated Mapk/Erk1/2, cellular proliferation and apoptosis in BTBR mice, as a preclinical model of Autism. We had previously generated 410 F2 mice from the cross of BTBR with B6. At that time, six different social behaviors in all F2 mice were evaluated and scored. In this study, eight mice at each extreme of the social behavioral spectrum were selected and the expression and activity levels of Mapk/Erk in the prefrontal cortex and cerebellum of these mice were compared. Finally, we compared the Mapk/Erk signaling pathway in brain and lymphocytes of the same mice, testing for correlation in the degree of kinase activation across these separate tissues. Results Levels of phosphorylated Erk (p-Erk) were significantly increased in the brains of BTBR versus control mice. We also observed a significant association between juvenile social behavior and phosphorylated mitogen-activated protein kinase kinase (p-Mek) and p-Erk levels in the prefrontal cortex but not in the cerebellum. In contrast, we did not find a significant association between social behavior and total protein levels of either Mek or Erk. We also tested whether steady-state levels of Erk activation in the cerebral cortex in individual animals correlated with levels of Erk activation in lymphocytes, finding a significant relationship for this signaling pathway. Conclusion These observations suggest that dysregulation of the ERK signaling pathway may be an important mediator of social behavior, and that measuring activation of this pathway in peripheral lymphocytes may serve as a surrogate marker for central nervous system (CNS) ERK activity, and possibly autistic behavior. Electronic supplementary material The online version of this article (doi:10.1186/2040-2392-5-57) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alireza Faridar
- Department of Neurology, University of California, 675 Nelson Rising Way, Suite 214B, San Francisco, CA 94158 USA ; Methodist Neurological Institute, 6550 Fannin St, Houston Texas, 77030 USA
| | - Dorothy Jones-Davis
- Department of Neurology, University of California, 675 Nelson Rising Way, Suite 214B, San Francisco, CA 94158 USA
| | - Eric Rider
- Department of Neurology, University of California, 675 Nelson Rising Way, Suite 214B, San Francisco, CA 94158 USA
| | - Jiang Li
- Department of Neurology, University of California, 675 Nelson Rising Way, Suite 214B, San Francisco, CA 94158 USA
| | - Ilan Gobius
- Queensland Brain Institute, The University of Queensland, Brisbane, 4072 Australia
| | - Laura Morcom
- Queensland Brain Institute, The University of Queensland, Brisbane, 4072 Australia
| | - Linda J Richards
- Queensland Brain Institute, The University of Queensland, Brisbane, 4072 Australia ; School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland 4072 Australia
| | - Saunak Sen
- Epidemiology and Biostatistics, University of California, 550 16th Street, San Francisco, CA 94158 USA
| | - Elliott H Sherr
- Department of Neurology, University of California, 675 Nelson Rising Way, Suite 214B, San Francisco, CA 94158 USA
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Gkogkas CG, Khoutorsky A, Cao R, Jafarnejad SM, Prager-Khoutorsky M, Giannakas N, Kaminari A, Fragkouli A, Nader K, Price TJ, Konicek BW, Graff JR, Tzinia AK, Lacaille JC, Sonenberg N. Pharmacogenetic inhibition of eIF4E-dependent Mmp9 mRNA translation reverses fragile X syndrome-like phenotypes. Cell Rep 2014; 9:1742-1755. [PMID: 25466251 PMCID: PMC4294557 DOI: 10.1016/j.celrep.2014.10.064] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 09/30/2014] [Accepted: 10/24/2014] [Indexed: 01/22/2023] Open
Abstract
Fragile X syndrome (FXS) is the leading genetic cause of autism. Mutations in Fmr1 (fragile X mental retardation 1 gene) engender exaggerated translation resulting in dendritic spine dysmorphogenesis, synaptic plasticity alterations, and behavioral deficits in mice, which are reminiscent of FXS phenotypes. Using postmortem brains from FXS patients and Fmr1 knockout mice (Fmr1(-/y)), we show that phosphorylation of the mRNA 5' cap binding protein, eukaryotic initiation factor 4E (eIF4E), is elevated concomitant with increased expression of matrix metalloproteinase 9 (MMP-9) protein. Genetic or pharmacological reduction of eIF4E phosphorylation rescued core behavioral deficits, synaptic plasticity alterations, and dendritic spine morphology defects via reducing exaggerated translation of Mmp9 mRNA in Fmr1(-/y) mice, whereas MMP-9 overexpression produced several FXS-like phenotypes. These results uncover a mechanism of regulation of synaptic function by translational control of Mmp-9 in FXS, which opens the possibility of new treatment avenues for the diverse neurological and psychiatric aspects of FXS.
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Affiliation(s)
- Christos G Gkogkas
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada.
| | - Arkady Khoutorsky
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada
| | - Ruifeng Cao
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada
| | - Seyed Mehdi Jafarnejad
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada
| | - Masha Prager-Khoutorsky
- Center for Research in Neuroscience, McGill University, Montréal General Hospital, Montréal, QC H3G 1A4, Canada
| | - Nikolaos Giannakas
- Institute of Biosciences and Applications, National Center for Scientific Research Demokritos, Agia Paraskevi, 15310 Athens, Greece
| | - Archontia Kaminari
- Institute of Biosciences and Applications, National Center for Scientific Research Demokritos, Agia Paraskevi, 15310 Athens, Greece
| | - Apostolia Fragkouli
- Institute of Biosciences and Applications, National Center for Scientific Research Demokritos, Agia Paraskevi, 15310 Athens, Greece
| | - Karim Nader
- Department of Psychology, McGill University, Montréal, QC H3A 1B1, Canada
| | - Theodore J Price
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Bruce W Konicek
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Jeremy R Graff
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Athina K Tzinia
- Institute of Biosciences and Applications, National Center for Scientific Research Demokritos, Agia Paraskevi, 15310 Athens, Greece
| | - Jean-Claude Lacaille
- GRSNC and Department of Neurosciences, Université de Montréal, Montréal, QC H3C 3J7, Canada
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada.
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60
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de Esch CE, Zeidler S, Willemsen R. Translational endpoints in fragile X syndrome. Neurosci Biobehav Rev 2014; 46 Pt 2:256-69. [DOI: 10.1016/j.neubiorev.2013.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 10/07/2013] [Accepted: 10/09/2013] [Indexed: 01/01/2023]
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Westmark CJ. The quest for fragile X biomarkers. Mol Cell Pediatr 2014; 1:1. [PMID: 26567095 DOI: 10.1186/s40348-014-0001-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 06/18/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Fragile X is the most common form of inherited intellectual disability and the leading known genetic cause of autism. There is currently no cure or approved medication for fragile X although various drugs target specific disease symptoms and a large number of therapeutics are in various stages of clinical development. Multiple recent clinical trials have failed on their primary endpoints indicating that there is a compelling need for validated biomarkers and outcome measures in fragile X. FINDINGS There are currently no validated blood-based biomarkers to assess disease severity or to monitor drug efficacy in fragile X syndrome. Herein, we review candidate blood protein biomarkers including extracellular-regulated kinase, phosphoinositide 3-kinase, matrix metalloproteinase 9, amyloid-beta and amyloid-beta protein precursor. CONCLUSIONS Bench-to-bedside plans for fragile X syndrome are severely limited by the lack of validated outcome measures. The reviewed candidate biomarkers are at early stages of validation and deserve further investigation.
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Affiliation(s)
- Cara J Westmark
- Department of Neurology, University of Wisconsin-Madison, Madison, WI, USA.
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62
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Sun MK, Hongpaisan J, Lim CS, Alkon DL. Bryostatin-1 Restores Hippocampal Synapses and Spatial Learning and Memory in Adult Fragile X Mice. J Pharmacol Exp Ther 2014; 349:393-401. [DOI: 10.1124/jpet.114.214098] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Fragile X syndrome: a preclinical review on metabotropic glutamate receptor 5 (mGluR5) antagonists and drug development. Psychopharmacology (Berl) 2014; 231:1217-26. [PMID: 24232444 DOI: 10.1007/s00213-013-3330-3] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 10/14/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Fragile X syndrome (FXS) is considered the leading inherited cause of intellectual disability and autism. In FXS, the fragile X mental retardation 1 (FMR1) gene is silenced and the fragile X mental retardation protein (FMRP) is not expressed, resulting in the characteristic features of the syndrome. Despite recent advances in understanding the pathophysiology of FXS, there is still no cure for this condition; current treatment is symptomatic. Preclinical research is essential in the development of potential therapeutic agents. OBJECTIVES This review provides an overview of the preclinical evidence supporting metabotropic glutamate receptor 5 (mGluR5) antagonists as therapeutic agents for FXS. RESULTS According to the mGluR theory of FXS, the absence of FMRP leads to enhanced glutamatergic signaling via mGluR5, which leads to increased protein synthesis and defects in synaptic plasticity including enhanced long-term depression. As such, efforts to develop agents that target the underlying pathophysiology of FXS have focused on mGluR5 modulation. Animal models, particularly the Fmr1 knockout mouse model, have become invaluable in exploring therapeutic approaches on an electrophysiological, behavioral, biochemical, and neuroanatomical level. Two direct approaches are currently being investigated for FXS treatment: reactivating the FMR1 gene and compensating for the lack of FMRP. The latter approach has yielded promising results, with mGluR5 antagonists showing efficacy in clinical trials. CONCLUSIONS Targeting mGluR5 is a valid approach for the development of therapeutic agents that target the underlying pathophysiology of FXS. Several compounds are currently in development, with encouraging results.
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64
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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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Castrén ML, Castrén E. BDNF in fragile X syndrome. Neuropharmacology 2013; 76 Pt C:729-36. [PMID: 23727436 DOI: 10.1016/j.neuropharm.2013.05.018] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 05/07/2013] [Accepted: 05/08/2013] [Indexed: 12/12/2022]
Abstract
Fragile X syndrome (FXS) is a monogenic disorder that is caused by the absence of FMR1 protein (FMRP). FXS serves as an excellent model disorder for studies investigating disturbed molecular mechanisms and synapse function underlying cognitive impairment, autism, and behavioral disturbance. Abnormalities in dendritic spines and synaptic transmission in the brain of FXS individuals and mouse models for FXS indicate perturbations in the development, maintenance, and plasticity of neuronal network connectivity. However, numerous alterations are found during the early development in FXS, including abnormal differentiation of neural progenitors and impaired migration of newly born neurons. Several aspects of FMRP function are modulated by brain-derived neurotrophic factor (BDNF) signaling. Here, we review the evidence of the role for BDNF in the developing and adult FXS brain. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.
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Affiliation(s)
- Maija L Castrén
- Institute of Biomedicine/Physiology, University of Helsinki, P.O. Box 63, FIN-00014 Helsinki, Finland; Rinnekoti Foundation, Rinnekodintie 10, FIN-02980 Espoo, Finland.
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Curia G, Gualtieri F, Bartolomeo R, Vezzali R, Biagini G. Resilience to audiogenic seizures is associated with p-ERK1/2 dephosphorylation in the subiculum of Fmr1 knockout mice. Front Cell Neurosci 2013; 7:46. [PMID: 23630463 PMCID: PMC3635025 DOI: 10.3389/fncel.2013.00046] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 04/03/2013] [Indexed: 12/30/2022] Open
Abstract
Young, but not adult, fragile X mental retardation gene (Fmr1) knockout (KO) mice display audiogenic seizures (AGS) that can be prevented by inhibiting extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation. In order to identify the cerebral regions involved in these phenomena, we characterized the response to AGS in Fmr1 KO mice and wild type (WT) controls at postnatal day (P) 45 and P90. To characterize the diverse response to AGS in various cerebral regions, we evaluated the activity markers FosB/ΔFosB and phosphorylated ERK1/2 (p-ERK1/2). Wild running (100% of tested mice) followed by clonic/tonic seizures (30%) were observed in P45 Fmr1 KO mice, but not in WT mice. In P90 Fmr1 KO mice, wild running was only present in 25% of tested animals. Basal FosB/ΔFosB immunoreactivity was higher (P < 0.01 vs. WT) in the CA1 and subiculum of P45 Fmr1 KO mice. Following the AGS test, FosB/ΔFosB expression consistently increased in most of the analyzed regions in both groups at P45, but not at P90. Interestingly, FosB/ΔFosB immunoreactivity was significantly higher in P45 Fmr1 KO mice in the medial geniculate body (P < 0.05 vs. WT) and CA3 (P < 0.01). Neurons presenting with immunopositivity to p-ERK1/2 were more abundant in the subiculum of Fmr1 KO mice in control condition (P < 0.05 vs. WT, in both age groups). In this region, p-ERK1/2-immunopositive cells significantly decreased (–75%, P < 0.01) in P90 Fmr1 KO mice exposed to the AGS test, but no changes were found in P45 mice or in other brain regions. In both age groups of WT mice, p-ERK1/2-immunopositive cells increased in the subiculum after exposure to the acoustic test. Our findings illustrate that FosB/ΔFosB markers are overexpressed in the medial geniculate body and CA3 in Fmr1 KO mice experiencing AGS, and that p-ERK1/2 is markedly decreased in the subiculum of Fmr1 KO mice resistant to AGS induction. These findings suggest that resilience to AGS is associated with dephosphorylation of p-ERK1/2 in the subiculum of mature Fmr1 KO mice.
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Affiliation(s)
- Giulia Curia
- Laboratory of Experimental Epileptology, Department of Biomedical, Metabolic, and Neural Sciences, University of Modena and Reggio Emilia Modena, Italy
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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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