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Ramírez-Cheyne J, López D, Payán-Gómez C, Arcos-Burgos M, Saldarriaga W. Fragile X syndrome in the largest world clustering. I. Genetic epidemiology and founder effect outline. Am J Med Genet A 2024; 194:e63523. [PMID: 38164622 DOI: 10.1002/ajmg.a.63523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 09/19/2023] [Accepted: 12/16/2023] [Indexed: 01/03/2024]
Abstract
The FMR1 5' regulation gene region harbors a CGG trinucleotide repeat expansion (CGG-TRE) that causes Fragile X syndrome (FXS) when it expands to more than 200 repetitions. Ricaurte is a small village in southwestern Colombia, with an FXS prevalence of 1 in 38 men and 1 in 100 women (~100 times higher than the worldwide reported prevalence), defining Ricaurte as the largest FXS cluster in the world. In the present study, using next-generation sequencing of whole exome capture, we genotype 55 individuals from Ricaurte (49 with either full mutation or with premutation), four individuals from neighboring villages (with either the full mutation or with the premutation), and one unaffected woman, native of Ricaurte, who did not belong to any of the affected families. With advanced clustering and haplotype reconstruction, we modeled a common haplotype of 33 SNPs spanning 83,567,899 bp and harboring the FMR1 gene. This reconstructed haplotype was found in all the men from Ricaurte who carried the expansion, demonstrating that the genetic conglomerate of FXS in this population is due to a founder effect. The definition of this founder effect and its population outlining will allow a better prediction, follow-up, precise and personalized characterization of epidemiological parameters, better knowledge of the disease's natural history, and confident improvement of the clinical attention, life quality, and health interventions for this community.
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Affiliation(s)
| | - Diana López
- Department of Biological Science, Faculty of Agricultural Sciences, Universidad Nacional de Colombia, Palmira, Colombia
| | - César Payán-Gómez
- Dirección Académica, Universidad Nacional de Colombia. Sede de La Paz. Cesar, Colombia
| | - Mauricio Arcos-Burgos
- Instituto de Investigaciones Médicas, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
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2
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Svalina MN, Sullivan R, Restrepo D, Huntsman MM. From circuits to behavior: Amygdala dysfunction in fragile X syndrome. Front Integr Neurosci 2023; 17:1128529. [PMID: 36969493 PMCID: PMC10034113 DOI: 10.3389/fnint.2023.1128529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 02/23/2023] [Indexed: 03/12/2023] Open
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a repeat expansion mutation in the promotor region of the FMR1 gene resulting in transcriptional silencing and loss of function of fragile X messenger ribonucleoprotein 1 protein (FMRP). FMRP has a well-defined role in the early development of the brain. Thus, loss of the FMRP has well-known consequences for normal cellular and synaptic development leading to a variety of neuropsychiatric disorders including an increased prevalence of amygdala-based disorders. Despite our detailed understanding of the pathophysiology of FXS, the precise cellular and circuit-level underpinnings of amygdala-based disorders is incompletely understood. In this review, we discuss the development of the amygdala, the role of neuromodulation in the critical period plasticity, and recent advances in our understanding of how synaptic and circuit-level changes in the basolateral amygdala contribute to the behavioral manifestations seen in FXS.
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Affiliation(s)
- Matthew N. Svalina
- Medical Scientist Training Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Regina Sullivan
- Brain Institute, Nathan Kline Institute, Orangeburg, NY, United States
- Child and Adolescent Psychiatry, Child Study Center, New York University School of Medicine, New York, NY, United States
| | - Diego Restrepo
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Molly M. Huntsman
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
- *Correspondence: Molly M. Huntsman,
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3
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Morrill NK, Joly-Amado A, Li Q, Prabhudeva S, Weeber EJ, Nash KR. Reelin central fragment supplementation improves cognitive deficits in a mouse model of Fragile X Syndrome. Exp Neurol 2022; 357:114170. [PMID: 35863501 DOI: 10.1016/j.expneurol.2022.114170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 07/10/2022] [Accepted: 07/14/2022] [Indexed: 11/04/2022]
Abstract
Fragile X Syndrome (FXS) is the most common form of inherited intellectual disability and is characterized by autistic behaviors, childhood seizures, and deficits in learning and memory. FXS has a loss of function of the FMR1 gene that leads to a lack of Fragile X Mental Retardation Protein (FMRP) expression. FMRP is critical for synaptic plasticity, spatial learning, and memory. Reelin is a large extracellular glycoprotein essential for synaptic plasticity and numerous neurodevelopmental processes. Reduction in Reelin signaling is implicated as a contributing factor in disease etiology in several neurological disorders, including schizophrenia, and autism. However, the role of Reelin in FXS is poorly understood. We demonstrate a reduction in Reelin in Fmr1 knock-out (KO) mice, suggesting that a loss of Reelin activity may contribute to FXS. We demonstrate here that Reelin signaling enhancement via a single intracerebroventricular injection of the Reelin central fragment into Fmr1 KO mice can profoundly rescue cognitive deficits in hidden platform water maze and fear conditioning, as well as hyperactivity during the open field. Improvements in behavior were associated with rescued levels of post synaptic marker in Fmr1 KO mice when compared to controls. These data suggest that increasing Reelin signaling in FXS could offer a novel therapeutic for improving cognition in FXS.
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Affiliation(s)
- Nicole K Morrill
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa FL-33612, USA
| | - Aurelie Joly-Amado
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa FL-33612, USA
| | - Qingyou Li
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa FL-33612, USA
| | - Sahana Prabhudeva
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa FL-33612, USA
| | - Edwin J Weeber
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa FL-33612, USA
| | - Kevin R Nash
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B Downs Blvd, Tampa FL-33612, USA.
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4
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Liu X, Kumar V, Tsai NP, Auerbach BD. Hyperexcitability and Homeostasis in Fragile X Syndrome. Front Mol Neurosci 2022; 14:805929. [PMID: 35069112 PMCID: PMC8770333 DOI: 10.3389/fnmol.2021.805929] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/14/2021] [Indexed: 01/13/2023] Open
Abstract
Fragile X Syndrome (FXS) is a leading inherited cause of autism and intellectual disability, resulting from a mutation in the FMR1 gene and subsequent loss of its protein product FMRP. Despite this simple genetic origin, FXS is a phenotypically complex disorder with a range of physical and neurocognitive disruptions. While numerous molecular and cellular pathways are affected by FMRP loss, there is growing evidence that circuit hyperexcitability may be a common convergence point that can account for many of the wide-ranging phenotypes seen in FXS. The mechanisms for hyperexcitability in FXS include alterations to excitatory synaptic function and connectivity, reduced inhibitory neuron activity, as well as changes to ion channel expression and conductance. However, understanding the impact of FMR1 mutation on circuit function is complicated by the inherent plasticity in neural circuits, which display an array of homeostatic mechanisms to maintain activity near set levels. FMRP is also an important regulator of activity-dependent plasticity in the brain, meaning that dysregulated plasticity can be both a cause and consequence of hyperexcitable networks in FXS. This makes it difficult to separate the direct effects of FMR1 mutation from the myriad and pleiotropic compensatory changes associated with it, both of which are likely to contribute to FXS pathophysiology. Here we will: (1) review evidence for hyperexcitability and homeostatic plasticity phenotypes in FXS models, focusing on similarities/differences across brain regions, cell-types, and developmental time points; (2) examine how excitability and plasticity disruptions interact with each other to ultimately contribute to circuit dysfunction in FXS; and (3) discuss how these synaptic and circuit deficits contribute to disease-relevant behavioral phenotypes like epilepsy and sensory hypersensitivity. Through this discussion of where the current field stands, we aim to introduce perspectives moving forward in FXS research.
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Affiliation(s)
- Xiaopeng Liu
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science & Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Vipendra Kumar
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Nien-Pei Tsai
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Benjamin D. Auerbach
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science & Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- *Correspondence: Benjamin D. Auerbach
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5
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Bleuzé L, Triaca V, Borreca A. FMRP-Driven Neuropathology in Autistic Spectrum Disorder and Alzheimer's disease: A Losing Game. Front Mol Biosci 2021; 8:699613. [PMID: 34760921 PMCID: PMC8573832 DOI: 10.3389/fmolb.2021.699613] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/24/2021] [Indexed: 12/28/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) is an RNA binding protein (RBP) whose absence is essentially associated to Fragile X Syndrome (FXS). As an RNA Binding Protein (RBP), FMRP is able to bind and recognize different RNA structures and the control of specific mRNAs is important for neuronal synaptic plasticity. Perturbations of this pathway have been associated with the autistic spectrum. One of the FMRP partners is the APP mRNA, the main protagonist of Alzheimer’s disease (AD), thereby regulating its protein level and metabolism. Therefore FMRP is associated to two neurodevelopmental and age-related degenerative conditions, respectively FXS and AD. Although these pathologies are characterized by different features, they have been reported to share a number of common molecular and cellular players. The aim of this review is to describe the double-edged sword of FMRP in autism and AD, possibly allowing the elucidation of key shared underlying mechanisms and neuronal circuits. As an RBP, FMRP is able to regulate APP expression promoting the production of amyloid β fragments. Indeed, FXS patients show an increase of amyloid β load, typical of other neurological disorders, such as AD, Down syndrome, Parkinson’s Disease, etc. Beyond APP dysmetabolism, the two neurodegenerative conditions share molecular targets, brain circuits and related cognitive deficits. In this review, we will point out the potential common neuropathological pattern which needs to be addressed and we will hopefully contribute to clarifying the complex phenotype of these two neurorological disorders, in order to pave the way for a novel, common disease-modifying therapy.
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Affiliation(s)
- Louis Bleuzé
- University de Rennes 1, Rennes, France.,Humanitas Clinical and Research Center-IRCCS, Rozzano (Mi), Italy
| | - Viviana Triaca
- Institute of Biochemistry and Cell Biology, National Research Council (CNR-IBBC), International Campus A. Buzzati Traverso, Monterotondo, Italy
| | - Antonella Borreca
- Humanitas Clinical and Research Center-IRCCS, Rozzano (Mi), Italy.,Institute of Neuroscience-National Research Council (CNR-IN), Milan, Italy
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6
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Adayev T, LaFauci G, Xu W, Dobkin C, Kascsak R, Brown WT, Goodman JH. Development of a Quantitative FMRP Assay for Mouse Tissue Applications. Genes (Basel) 2021; 12:genes12101516. [PMID: 34680911 PMCID: PMC8535242 DOI: 10.3390/genes12101516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/24/2021] [Accepted: 09/24/2021] [Indexed: 11/20/2022] Open
Abstract
Fragile X syndrome results from the absence of the FMR1 gene product—Fragile X Mental Retardation Protein (FMRP). Fragile X animal research has lacked a reliable method to quantify FMRP. We report the development of an array of FMRP-specific monoclonal antibodies and their application for quantitative assessment of FMRP (qFMRPm) in mouse tissue. To characterize the assay, we determined the normal variability of FMRP expression in four brain structures of six different mouse strains at seven weeks of age. There was a hierarchy of FMRP expression: neocortex > hippocampus > cerebellum > brainstem. The expression of FMRP was highest and least variable in the neocortex, whereas it was most variable in the hippocampus. Male C57Bl/6J and FVB mice were selected to determine FMRP developmental differences in the brain at 3, 7, 10, and 14 weeks of age. We examined the four structures and found a developmental decline in FMRP expression with age, except for the brainstem where it remained stable. qFMRPm assay of blood had highest values in 3 week old animals and dropped by 2.5-fold with age. Sex differences were not significant. The results establish qFMRPm as a valuable tool due to its ease of methodology, cost effectiveness, and accuracy.
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Affiliation(s)
- Tatyana Adayev
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
- Correspondence: ; Tel.: +1-718-494-5314
| | - Giuseppe LaFauci
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
| | - Weimin Xu
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
| | - Carl Dobkin
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
| | - Richard Kascsak
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
| | - W. Ted Brown
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
- Perkins Center, University of Sydney Camperdown, Sydney, NSW 2006, Australia
| | - Jeffrey H. Goodman
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY 10314, USA; (G.L.); (W.X.); (C.D.); (R.K.); (W.T.B.); (J.H.G.)
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7
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Kshatri A, Cerrada A, Gimeno R, Bartolomé-Martín D, Rojas P, Giraldez T. Differential regulation of BK channels by fragile X mental retardation protein. J Gen Physiol 2021; 152:151651. [PMID: 32275741 PMCID: PMC7266151 DOI: 10.1085/jgp.201912502] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 03/12/2020] [Indexed: 01/28/2023] Open
Abstract
Fragile X mental retardation protein (FMRP) is an RNA-binding protein prominently expressed in neurons. Missense mutations or complete loss of FMRP can potentially lead to fragile X syndrome, a common form of inherited intellectual disability. In addition to RNA regulation, FMRP was also proposed to modulate neuronal function by direct interaction with the large conductance Ca2+- and voltage-activated potassium channel (BK) β4 regulatory subunits (BKβ4). However, the molecular mechanisms underlying FMRP regulation of BK channels were not studied in detail. We have used electrophysiology and super-resolution stochastic optical reconstruction microscopy (STORM) to characterize the effects of FMRP on pore-forming BKα subunits, as well as the association with regulatory subunits BKβ4. Our data indicate that, in the absence of coexpressed β4, FMRP alters the steady-state properties of BKα channels by decreasing channel activation and deactivation rates. Analysis using the Horrigan-Aldrich model revealed alterations in the parameters associated with channel opening (L0) and voltage sensor activation (J0). Interestingly, FMRP also altered the biophysical properties of BKαβ4 channels favoring channel opening, although not as dramatically as BKα. STORM experiments revealed clustered multi-protein complexes, consistent with FMRP interacting not only to BKαβ4 but also to BKα. Lastly, we found that a partial loss-of-function mutation in FMRP (R138Q) counteracts many of its functional effects on BKα and BKαβ4 channels. In summary, our data show that FMRP modulates the function of both BKα and BKαβ4 channels.
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Affiliation(s)
- Aravind Kshatri
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Alejandro Cerrada
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Roger Gimeno
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - David Bartolomé-Martín
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Patricio Rojas
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile
| | - Teresa Giraldez
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
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8
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Fyke W, Velinov M. FMR1 and Autism, an Intriguing Connection Revisited. Genes (Basel) 2021; 12:genes12081218. [PMID: 34440392 PMCID: PMC8394635 DOI: 10.3390/genes12081218] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 12/27/2022] Open
Abstract
Autism Spectrum Disorder (ASD) represents a distinct phenotype of behavioral dysfunction that includes deficiencies in communication and stereotypic behaviors. ASD affects about 2% of the US population. It is a highly heritable spectrum of conditions with substantial genetic heterogeneity. To date, mutations in over 100 genes have been reported in association with ASD phenotypes. Fragile X syndrome (FXS) is the most common single-gene disorder associated with ASD. The gene associated with FXS, FMR1 is located on chromosome X. Accordingly, the condition has more severe manifestations in males. FXS results from the loss of function of FMR1 due to the expansion of an unstable CGG repeat located in the 5'' untranslated region of the gene. About 50% of the FXS males and 20% of the FXS females meet the Diagnostic Statistical Manual 5 (DSM-5) criteria for ASD. Among the individuals with ASD, about 3% test positive for FXS. FMRP, the protein product of FMR1, is a major gene regulator in the central nervous system. Multiple pathways regulated by FMRP are found to be dysfunctional in ASD patients who do not have FXS. Thus, FXS presents the opportunity to study cellular phenomena that may have wider applications in the management of ASD and to develop new strategies for ASD therapy.
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Affiliation(s)
- William Fyke
- SUNY Downstate Medical Center, SUNY Downstate College of Medicine, Brooklyn, NY 11203, USA;
- Graduate Program in Neural and Behavioral Science, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Milen Velinov
- Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
- Correspondence:
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9
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Park E, Lau AG, Arendt KL, Chen L. FMRP Interacts with RARα in Synaptic Retinoic Acid Signaling and Homeostatic Synaptic Plasticity. Int J Mol Sci 2021; 22:ijms22126579. [PMID: 34205274 PMCID: PMC8235556 DOI: 10.3390/ijms22126579] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/16/2021] [Accepted: 06/17/2021] [Indexed: 01/08/2023] Open
Abstract
The fragile X syndrome (FXS) is an X-chromosome-linked neurodevelopmental disorder with severe intellectual disability caused by inactivation of the fragile X mental retardation 1 (FMR1) gene and subsequent loss of the fragile X mental retardation protein (FMRP). Among the various types of abnormal synaptic function and synaptic plasticity phenotypes reported in FXS animal models, defective synaptic retinoic acid (RA) signaling and subsequent defective homeostatic plasticity have emerged as a major synaptic dysfunction. However, the mechanism underlying the defective synaptic RA signaling in the absence of FMRP is unknown. Here, we show that RARα, the RA receptor critically involved in synaptic RA signaling, directly interacts with FMRP. This interaction is enhanced in the presence of RA. Blocking the interaction between FMRP and RARα with a small peptide corresponding to the critical binding site in RARα abolishes RA-induced increases in excitatory synaptic transmission, recapitulating the phenotype seen in the Fmr1 knockout mouse. Taken together, these data suggest that not only are functional FMRP and RARα necessary for RA-dependent homeostatic synaptic plasticity, but that the interaction between these two proteins is essential for proper transcription-independent RA signaling. Our results may provide further mechanistic understanding into FXS synaptic pathophysiology.
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Abstract
Fragile X syndrome (FXS) is the most common inherited form of intellectual disability and the leading monogenic cause of autism. The condition stems from loss of fragile X mental retardation protein (FMRP), which regulates a wide range of ion channels via translational control, protein-protein interactions and second messenger pathways. Rapidly increasing evidence demonstrates that loss of FMRP leads to numerous ion channel dysfunctions (that is, channelopathies), which in turn contribute significantly to FXS pathophysiology. Consistent with this, pharmacological or genetic interventions that target dysregulated ion channels effectively restore neuronal excitability, synaptic function and behavioural phenotypes in FXS animal models. Recent studies further support a role for direct and rapid FMRP-channel interactions in regulating ion channel function. This Review lays out the current state of knowledge in the field regarding channelopathies and the pathogenesis of FXS, including promising therapeutic implications.
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Svalina MN, Guthman EM, Cea-Del Rio CA, Kushner JK, Baca SM, Restrepo D, Huntsman MM. Hyperexcitability and Loss of Feedforward Inhibition Contribute to Aberrant Plasticity in the Fmr1KO Amygdala. eNeuro 2021; 8:ENEURO.0113-21.2021. [PMID: 33893168 PMCID: PMC8121259 DOI: 10.1523/eneuro.0113-21.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 04/05/2021] [Accepted: 04/09/2021] [Indexed: 12/15/2022] Open
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder (NDD) characterized by intellectual disability, autism spectrum disorders (ASDs), and anxiety disorders. The disruption in the function of the FMR1 gene results in a range of alterations in cellular and synaptic function. Previous studies have identified dynamic alterations in inhibitory neurotransmission in early postnatal development in the amygdala of the mouse model of FXS. However, little is known about how these changes alter microcircuit development and plasticity in the lateral amygdala (LA). Using whole-cell patch clamp electrophysiology, we demonstrate that principal neurons (PNs) in the LA exhibit hyperexcitability with a concomitant increase in the synaptic strength of excitatory synapses in the BLA. Further, reduced feed-forward inhibition appears to enhance synaptic plasticity in the FXS amygdala. These results demonstrate that plasticity is enhanced in the amygdala of the juvenile Fmr1 knock-out (KO) mouse and that E/I imbalance may underpin anxiety disorders commonly seen in FXS and ASDs.
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Affiliation(s)
- Matthew N Svalina
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Medical Scientist Training Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - E Mae Guthman
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Christian A Cea-Del Rio
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Centro de Investigación Biomédica y Aplicada, Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Santiago 9160000, Chile
| | - J Keenan Kushner
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Serapio M Baca
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Diego Restrepo
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Molly M Huntsman
- Neuroscience Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
- Department of Pediatrics, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
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12
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Kramvis I, van Westen R, Lammertse HCA, Riga D, Heistek TS, Loebel A, Spijker S, Mansvelder HD, Meredith RM. Dysregulated Prefrontal Cortex Inhibition in Prepubescent and Adolescent Fragile X Mouse Model. Front Mol Neurosci 2020; 13:88. [PMID: 32528248 PMCID: PMC7264168 DOI: 10.3389/fnmol.2020.00088] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/28/2020] [Indexed: 11/13/2022] Open
Abstract
Changes in excitation and inhibition are associated with the pathobiology of neurodevelopmental disorders of intellectual disability and autism and are widely described in Fragile X syndrome (FXS). In the prefrontal cortex (PFC), essential for cognitive processing, excitatory connectivity and plasticity are found altered in the FXS mouse model, however, little is known about the state of inhibition. To that end, we investigated GABAergic signaling in the Fragile X Mental Retardation 1 (FMR1) knock out (Fmr1-KO) mouse medial PFC (mPFC). We report changes at the molecular, and functional levels of inhibition at three (prepubescence) and six (adolescence) postnatal weeks. Functional changes were most prominent during early postnatal development, resulting in stronger inhibition, through increased synaptic inhibitory drive and amplitude, and reduction of inhibitory short-term synaptic depression. Noise analysis of prepubescent post-synaptic currents demonstrated an increased number of receptors opening during peak current in Fmr1-KO inhibitory synapses. During adolescence amplitudes and plasticity changes normalized, however, the inhibitory drive was now reduced in Fmr1-KO, while synaptic kinetics were prolonged. Finally, adolescent GABAA receptor subunit α2 and GABAB receptor subtype B1 expression levels were different in Fmr1-KOs than WT littermate controls. Together these results extend the degree of synaptic GABAergic alterations in FXS, now to the mPFC of Fmr1-KO mice, a behaviourally relevant brain region in neurodevelopmental disorder pathology.
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Affiliation(s)
- Ioannis Kramvis
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Rhodé van Westen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Hanna C A Lammertse
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Danai Riga
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Tim S Heistek
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Alex Loebel
- Department of Neurobiology, Ludwig-Maximilians Universitat, Munich, Germany
| | - Sabine Spijker
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Huibert D Mansvelder
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
| | - Rhiannon M Meredith
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, Netherlands
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13
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Suardi GAM, Haddad LA. FMRP ribonucleoprotein complexes and RNA homeostasis. ADVANCES IN GENETICS 2020; 105:95-136. [PMID: 32560791 DOI: 10.1016/bs.adgen.2020.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The Fragile Mental Retardation 1 gene (FMR1), at Xq27.3, encodes the fragile mental retardation protein (FMRP), and displays in its 5'-untranslated region a series of polymorphic CGG triplet repeats that may undergo dynamic mutation. Fragile X syndrome (FXS) is the leading cause of inherited intellectual disability among men, and is most frequently due to FMR1 full mutation and consequent transcription repression. FMR1 premutations may associate with at least two other clinical conditions, named fragile X-associated primary ovarian insufficiency (FXPOI) and tremor and ataxia syndrome (FXTAS). While FXPOI and FXTAS appear to be mediated by FMR1 mRNA accumulation, relative reduction of FMRP, and triplet repeat translation, FXS is due to the lack of the RNA-binding protein FMRP. Besides its function as mRNA translation repressor in neuronal and stem/progenitor cells, RNA editing roles have been assigned to FMRP. In this review, we provide a brief description of FMR1 transcribed microsatellite and associated clinical disorders, and discuss FMRP molecular roles in ribonucleoprotein complex assembly and trafficking, as well as aspects of RNA homeostasis affected in FXS cells.
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Affiliation(s)
- Gabriela Aparecida Marcondes Suardi
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Luciana Amaral Haddad
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
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14
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Cataloguing and Selection of mRNAs Localized to Dendrites in Neurons and Regulated by RNA-Binding Proteins in RNA Granules. Biomolecules 2020; 10:biom10020167. [PMID: 31978946 PMCID: PMC7072219 DOI: 10.3390/biom10020167] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/18/2020] [Accepted: 01/20/2020] [Indexed: 12/15/2022] Open
Abstract
Spatiotemporal translational regulation plays a key role in determining cell fate and function. Specifically, in neurons, local translation in dendrites is essential for synaptic plasticity and long-term memory formation. To achieve local translation, RNA-binding proteins in RNA granules regulate target mRNA stability, localization, and translation. To date, mRNAs localized to dendrites have been identified by comprehensive analyses. In addition, mRNAs associated with and regulated by RNA-binding proteins have been identified using various methods in many studies. However, the results obtained from these numerous studies have not been compiled together. In this review, we have catalogued mRNAs that are localized to dendrites and are associated with and regulated by the RNA-binding proteins fragile X mental retardation protein (FMRP), RNA granule protein 105 (RNG105, also known as Caprin1), Ras-GAP SH3 domain binding protein (G3BP), cytoplasmic polyadenylation element binding protein 1 (CPEB1), and staufen double-stranded RNA binding proteins 1 and 2 (Stau1 and Stau2) in RNA granules. This review provides comprehensive information on dendritic mRNAs, the neuronal functions of mRNA-encoded proteins, the association of dendritic mRNAs with RNA-binding proteins in RNA granules, and the effects of RNA-binding proteins on mRNA regulation. These findings provide insights into the mechanistic basis of protein-synthesis-dependent synaptic plasticity and memory formation and contribute to future efforts to understand the physiological implications of local regulation of dendritic mRNAs in neurons.
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15
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Bagni C, Zukin RS. A Synaptic Perspective of Fragile X Syndrome and Autism Spectrum Disorders. Neuron 2019; 101:1070-1088. [PMID: 30897358 PMCID: PMC9628679 DOI: 10.1016/j.neuron.2019.02.041] [Citation(s) in RCA: 186] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/25/2019] [Accepted: 02/27/2019] [Indexed: 12/28/2022]
Abstract
Altered synaptic structure and function is a major hallmark of fragile X syndrome (FXS), autism spectrum disorders (ASDs), and other intellectual disabilities (IDs), which are therefore classified as synaptopathies. FXS and ASDs, while clinically and genetically distinct, share significant comorbidity, suggesting that there may be a common molecular and/or cellular basis, presumably at the synapse. In this article, we review brain architecture and synaptic pathways that are dysregulated in FXS and ASDs, including spine architecture, signaling in synaptic plasticity, local protein synthesis, (m)RNA modifications, and degradation. mRNA repression is a powerful mechanism for the regulation of synaptic structure and efficacy. We infer that there is no single pathway that explains most of the etiology and discuss new findings and the implications for future work directed at improving our understanding of the pathogenesis of FXS and related ASDs and the design of therapeutic strategies to ameliorate these disorders.
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Affiliation(s)
- Claudia Bagni
- Department of Fundamental Neurosciences, University of Lausanne, Lausanne, Switzerland; Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.
| | - R Suzanne Zukin
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York City, NY, USA.
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16
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Zarudnaya MI, Kolomiets IM, Potyahaylo AL, Hovorun DM. Structural transitions in poly(A), poly(C), poly(U), and poly(G) and their possible biological roles. J Biomol Struct Dyn 2018; 37:2837-2866. [PMID: 30052138 DOI: 10.1080/07391102.2018.1503972] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The homopolynucleotide (homo-oligonucleotide) tracts function as regulatory elements at various stages of mRNAs life cycle. Numerous cellular proteins specifically bind to these tracts. Among them are the different poly(A)-binding proteins, poly(C)-binding proteins, multifunctional fragile X mental retardation protein which binds specifically both to poly(G) and poly(U) and others. Molecular mechanisms of regulation of gene expression mediated by homopolynucleotide tracts in RNAs are not fully understood and the structural diversity of these tracts can contribute substantially to this regulation. This review summarizes current knowledge on different forms of homoribopolynucleotides, in particular, neutral and acidic forms of poly(A) and poly(C), and also biological relevance of homoribopolynucleotide (homoribo-oligonucleotide) tracts is discussed. Under physiological conditions, the acidic forms of poly(A) and poly(C) can be induced by proton transfer from acidic amino acids of proteins to adenine and cytosine bases. Finally, we present potential mechanisms for the regulation of some biological processes through the formation of intramolecular poly(A) duplexes.
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Affiliation(s)
- Margarita I Zarudnaya
- a Department of Molecular and Quantum Biophysics , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , Kyiv , Ukraine
| | - Iryna M Kolomiets
- a Department of Molecular and Quantum Biophysics , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , Kyiv , Ukraine
| | - Andriy L Potyahaylo
- a Department of Molecular and Quantum Biophysics , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , Kyiv , Ukraine
| | - Dmytro M Hovorun
- a Department of Molecular and Quantum Biophysics , Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine , Kyiv , Ukraine.,b Department of Molecular Biotechnology and Bioinformatics , Institute of High Technologies, Taras Shevchenko National University of Kyiv , Kyiv , Ukraine
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17
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Castagnola S, Delhaye S, Folci A, Paquet A, Brau F, Duprat F, Jarjat M, Grossi M, Béal M, Martin S, Mantegazza M, Bardoni B, Maurin T. New Insights Into the Role of Ca v2 Protein Family in Calcium Flux Deregulation in Fmr1-KO Neurons. Front Mol Neurosci 2018; 11:342. [PMID: 30319351 PMCID: PMC6170614 DOI: 10.3389/fnmol.2018.00342] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 08/30/2018] [Indexed: 12/31/2022] Open
Abstract
Fragile X syndrome (FXS), the most common form of inherited intellectual disability (ID) and a leading cause of autism, results from the loss of expression of the Fmr1 gene which encodes the RNA-binding protein Fragile X Mental Retardation Protein (FMRP). Among the thousands mRNA targets of FMRP, numerous encode regulators of ion homeostasis. It has also been described that FMRP directly interacts with Ca2+ channels modulating their activity. Collectively these findings suggest that FMRP plays critical roles in Ca2+ homeostasis during nervous system development. We carried out a functional analysis of Ca2+ regulation using a calcium imaging approach in Fmr1-KO cultured neurons and we show that these cells display impaired steady state Ca2+ concentration and an altered entry of Ca2+ after KCl-triggered depolarization. Consistent with these data, we show that the protein product of the Cacna1a gene, the pore-forming subunit of the Cav2.1 channel, is less expressed at the plasma membrane of Fmr1-KO neurons compared to wild-type (WT). Thus, our findings point out the critical role that Cav2.1 plays in the altered Ca2+ flux in Fmr1-KO neurons, impacting Ca2+ homeostasis of these cells. Remarkably, we highlight a new phenotype of cultured Fmr1-KO neurons that can be considered a novel cellular biomarker and is amenable to small molecule screening and identification of new drugs to treat FXS.
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Affiliation(s)
- Sara Castagnola
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France.,CNRS LIA "Neogenex", Valbonne, France
| | - Sébastien Delhaye
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France.,CNRS LIA "Neogenex", Valbonne, France
| | | | - Agnès Paquet
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France
| | - Frédéric Brau
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France
| | - Fabrice Duprat
- Université Côte d'Azur, INSERM, CNRS UMR7275, IPMC, Valbonne, France
| | - Marielle Jarjat
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France.,CNRS LIA "Neogenex", Valbonne, France
| | - Mauro Grossi
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France.,CNRS LIA "Neogenex", Valbonne, France
| | - Méline Béal
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France.,CNRS LIA "Neogenex", Valbonne, France
| | - Stéphane Martin
- Université Côte d'Azur, INSERM, CNRS UMR7275, IPMC, Valbonne, France
| | | | - Barbara Bardoni
- CNRS LIA "Neogenex", Valbonne, France.,Université Côte d'Azur, INSERM, CNRS UMR7275, IPMC, Valbonne, France
| | - Thomas Maurin
- Université Côte d'Azur, CNRS UMR7275, IPMC, Valbonne, France.,CNRS LIA "Neogenex", Valbonne, France
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18
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Melancia F, Trezza V. Modelling fragile X syndrome in the laboratory setting: A behavioral perspective. Behav Brain Res 2018; 350:149-163. [DOI: 10.1016/j.bbr.2018.04.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/24/2018] [Accepted: 04/24/2018] [Indexed: 12/13/2022]
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19
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Zhang Z, Marro SG, Zhang Y, Arendt KL, Patzke C, Zhou B, Fair T, Yang N, Südhof TC, Wernig M, Chen L. The fragile X mutation impairs homeostatic plasticity in human neurons by blocking synaptic retinoic acid signaling. Sci Transl Med 2018; 10:eaar4338. [PMID: 30068571 PMCID: PMC6317709 DOI: 10.1126/scitranslmed.aar4338] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 07/12/2018] [Indexed: 11/02/2022]
Abstract
Fragile X syndrome (FXS) is an X chromosome-linked disease leading to severe intellectual disabilities. FXS is caused by inactivation of the fragile X mental retardation 1 (FMR1) gene, but how FMR1 inactivation induces FXS remains unclear. Using human neurons generated from control and FXS patient-derived induced pluripotent stem (iPS) cells or from embryonic stem cells carrying conditional FMR1 mutations, we show here that loss of FMR1 function specifically abolished homeostatic synaptic plasticity without affecting basal synaptic transmission. We demonstrated that, in human neurons, homeostatic plasticity induced by synaptic silencing was mediated by retinoic acid, which regulated both excitatory and inhibitory synaptic strength. FMR1 inactivation impaired homeostatic plasticity by blocking retinoic acid-mediated regulation of synaptic strength. Repairing the genetic mutation in the FMR1 gene in an FXS patient cell line restored fragile X mental retardation protein (FMRP) expression and fully rescued synaptic retinoic acid signaling. Thus, our study reveals a robust functional impairment caused by FMR1 mutations that might contribute to neuronal dysfunction in FXS. In addition, our results suggest that FXS patient iPS cell-derived neurons might be useful for studying the mechanisms mediating functional abnormalities in FXS.
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Affiliation(s)
- Zhenjie Zhang
- Departments of Neurosurgery, and Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305-5453, USA
| | - Samuele G Marro
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Yingsha Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Kristin L Arendt
- Departments of Neurosurgery, and Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305-5453, USA
| | - Christopher Patzke
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Bo Zhou
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Tyler Fair
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Nan Yang
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA.
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Marius Wernig
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA.
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Lu Chen
- Departments of Neurosurgery, and Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305-5453, USA.
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20
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Drozd M, Bardoni B, Capovilla M. Modeling Fragile X Syndrome in Drosophila. Front Mol Neurosci 2018; 11:124. [PMID: 29713264 PMCID: PMC5911982 DOI: 10.3389/fnmol.2018.00124] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/29/2018] [Indexed: 01/18/2023] Open
Abstract
Intellectual disability (ID) and autism are hallmarks of Fragile X Syndrome (FXS), a hereditary neurodevelopmental disorder. The gene responsible for FXS is Fragile X Mental Retardation gene 1 (FMR1) encoding the Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein involved in RNA metabolism and modulating the expression level of many targets. Most cases of FXS are caused by silencing of FMR1 due to CGG expansions in the 5'-UTR of the gene. Humans also carry the FXR1 and FXR2 paralogs of FMR1 while flies have only one FMR1 gene, here called dFMR1, sharing the same level of sequence homology with all three human genes, but functionally most similar to FMR1. This enables a much easier approach for FMR1 genetic studies. Drosophila has been widely used to investigate FMR1 functions at genetic, cellular, and molecular levels since dFMR1 mutants have many phenotypes in common with the wide spectrum of FMR1 functions that underlay the disease. In this review, we present very recent Drosophila studies investigating FMRP functions at genetic, cellular, molecular, and electrophysiological levels in addition to research on pharmacological treatments in the fly model. These studies have the potential to aid the discovery of pharmacological therapies for FXS.
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Affiliation(s)
- Małgorzata Drozd
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France.,CNRS LIA (Neogenex), Valbonne, France
| | - Barbara Bardoni
- CNRS LIA (Neogenex), Valbonne, France.,Université Côte d'Azur, INSERM, CNRS, IPMC, Valbonne, France
| | - Maria Capovilla
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France.,CNRS LIA (Neogenex), Valbonne, France
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21
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Altered surface mGluR5 dynamics provoke synaptic NMDAR dysfunction and cognitive defects in Fmr1 knockout mice. Nat Commun 2017; 8:1103. [PMID: 29062097 PMCID: PMC5653653 DOI: 10.1038/s41467-017-01191-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 08/24/2017] [Indexed: 12/20/2022] Open
Abstract
Metabotropic glutamate receptor subtype 5 (mGluR5) is crucially implicated in the pathophysiology of Fragile X Syndrome (FXS); however, its dysfunction at the sub-cellular level, and related synaptic and cognitive phenotypes are unexplored. Here, we probed the consequences of mGluR5/Homer scaffold disruption for mGluR5 cell-surface mobility, synaptic N-methyl-D-aspartate receptor (NMDAR) function, and behavioral phenotypes in the second-generation Fmr1 knockout (KO) mouse. Using single-molecule tracking, we found that mGluR5 was significantly more mobile at synapses in hippocampal Fmr1 KO neurons, causing an increased synaptic surface co-clustering of mGluR5 and NMDAR. This correlated with a reduced amplitude of synaptic NMDAR currents, a lack of their mGluR5-activated long-term depression, and NMDAR/hippocampus dependent cognitive deficits. These synaptic and behavioral phenomena were reversed by knocking down Homer1a in Fmr1 KO mice. Our study provides a mechanistic link between changes of mGluR5 dynamics and pathological phenotypes of FXS, unveiling novel targets for mGluR5-based therapeutics. Dysfunction of mGluR5 has been implicated in Fragile X syndrome. Here, using a single-molecule tracking technique, the authors found an increased lateral mobility of mGluR5 at the synaptic site in Fmr1 KO hippocampal neurons, leading to abnormal NMDAR-mediated synaptic plasticity and cognitive deficits.
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22
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Davis JK, Broadie K. Multifarious Functions of the Fragile X Mental Retardation Protein. Trends Genet 2017; 33:703-714. [PMID: 28826631 PMCID: PMC5610095 DOI: 10.1016/j.tig.2017.07.008] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/20/2017] [Accepted: 07/24/2017] [Indexed: 01/01/2023]
Abstract
Fragile X syndrome (FXS), a heritable intellectual and autism spectrum disorder (ASD), results from the loss of Fragile X mental retardation protein (FMRP). This neurodevelopmental disease state exhibits neural circuit hyperconnectivity and hyperexcitability. Canonically, FMRP functions as an mRNA-binding translation suppressor, but recent findings have enormously expanded its proposed roles. Although connections between burgeoning FMRP functions remain unknown, recent advances have extended understanding of its involvement in RNA, channel, and protein binding that modulate calcium signaling, activity-dependent critical period development, and the excitation-inhibition (E/I) neural circuitry balance. In this review, we contextualize 3 years of FXS model research. Future directions extrapolated from recent advances focus on discovering links between FMRP roles to determine whether FMRP has a multitude of unrelated functions or whether combinatorial mechanisms can explain its multifaceted existence.
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Affiliation(s)
- Jenna K Davis
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA
| | - Kendal Broadie
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA.
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23
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Abdelsayed MM, Ho BT, Vu MMK, Polanco J, Spitale RC, Lupták A. Multiplex Aptamer Discovery through Apta-Seq and Its Application to ATP Aptamers Derived from Human-Genomic SELEX. ACS Chem Biol 2017; 12:2149-2156. [PMID: 28661647 DOI: 10.1021/acschembio.7b00001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Laboratory-evolved RNAs bind a wide variety of targets and serve highly diverse functions, including as diagnostic and therapeutic aptamers. The majority of aptamers have been identified using in vitro selection (SELEX), a molecular evolution technique based on selecting target-binding RNAs from highly diverse pools through serial rounds of enrichment and amplification. In vitro selection typically yields multiple distinct motifs of highly variable abundance and target-binding affinities. The discovery of new aptamers is often limited by the difficulty of characterizing the selected motifs, because testing of individual sequences tends to be a tedious process. To facilitate the discovery of new aptamers within in vitro selected pools, we developed Apta-Seq, a multiplex analysis based on quantitative, ligand-dependent 2' acylation of solvent-accessible regions of the selected RNA pools, followed by reverse transcription (SHAPE) and deep sequencing. The method reveals, in a single sequencing experiment, the identity, structural features, and target dissociation constants for aptamers present in the selected pool. Application of Apta-Seq to a human genomic pool enriched for ATP-binding RNAs yielded three new aptamers, which together with previously identified human aptamers suggest that ligand-binding RNAs may be common in mammals.
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Affiliation(s)
- Michael M. Abdelsayed
- Department
of Molecular Biology and Biochemistry, University of California—Irvine, Irvine, California 92697, United States
| | - Bao T. Ho
- Department
of Pharmaceutical Sciences, University of California—Irvine, Irvine, California 92697, United States
| | - Michael M. K. Vu
- Department
of Chemistry, University of California—Irvine, Irvine, California 92697, United States
| | - Julio Polanco
- Department
of Molecular Biology and Biochemistry, University of California—Irvine, Irvine, California 92697, United States
| | - Robert C. Spitale
- Department
of Pharmaceutical Sciences, University of California—Irvine, Irvine, California 92697, United States
- Department
of Chemistry, University of California—Irvine, Irvine, California 92697, United States
| | - Andrej Lupták
- Department
of Molecular Biology and Biochemistry, University of California—Irvine, Irvine, California 92697, United States
- Department
of Pharmaceutical Sciences, University of California—Irvine, Irvine, California 92697, United States
- Department
of Chemistry, University of California—Irvine, Irvine, California 92697, United States
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24
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Schaefer TL, Davenport MH, Grainger LM, Robinson CK, Earnheart AT, Stegman MS, Lang AL, Ashworth AA, Molinaro G, Huber KM, Erickson CA. Acamprosate in a mouse model of fragile X syndrome: modulation of spontaneous cortical activity, ERK1/2 activation, locomotor behavior, and anxiety. J Neurodev Disord 2017; 9:6. [PMID: 28616095 PMCID: PMC5467053 DOI: 10.1186/s11689-017-9184-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 01/13/2017] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Fragile X Syndrome (FXS) occurs as a result of a silenced fragile X mental retardation 1 gene (FMR1) and subsequent loss of fragile X mental retardation protein (FMRP) expression. Loss of FMRP alters excitatory/inhibitory signaling balance, leading to increased neuronal hyperexcitability and altered behavior. Acamprosate (the calcium salt of N-acetylhomotaurinate), a drug FDA-approved for relapse prevention in the treatment of alcohol dependence in adults, is a novel agent with multiple mechanisms that may be beneficial for people with FXS. There are questions regarding the neuroactive effects of acamprosate and the significance of the molecule's calcium moiety. Therefore, the electrophysiological, cellular, molecular, and behavioral effects of acamprosate were assessed in the Fmr1-/y (knock out; KO) mouse model of FXS controlling for the calcium salt in several experiments. METHODS Fmr1 KO mice and their wild-type (WT) littermates were utilized to assess acamprosate treatment on cortical UP state parameters, dendritic spine density, and seizure susceptibility. Brain extracellular-signal regulated kinase 1/2 (ERK1/2) activation was used to investigate this signaling molecule as a potential biomarker for treatment response. Additional adult mice were used to assess chronic acamprosate treatment and any potential effects of the calcium moiety using CaCl2 treatment on behavior and nuclear ERK1/2 activation. RESULTS Acamprosate attenuated prolonged cortical UP state duration, decreased elevated ERK1/2 activation in brain tissue, and reduced nuclear ERK1/2 activation in the dentate gyrus in KO mice. Acamprosate treatment modified behavior in anxiety and locomotor tests in Fmr1 KO mice in which control-treated KO mice were shown to deviate from control-treated WT mice. Mice treated with CaCl2 were not different from saline-treated mice in the adult behavior battery or nuclear ERK1/2 activation. CONCLUSIONS These data indicate that acamprosate, and not calcium, improves function reminiscent of reduced anxiety-like behavior and hyperactivity in Fmr1 KO mice and that acamprosate attenuates select electrophysiological and molecular dysregulation that may play a role in the pathophysiology of FXS. Differences between control-treated KO and WT mice were not evident in a recognition memory test or in examination of acoustic startle response/prepulse inhibition which impeded conclusions from being made about the treatment effects of acamprosate in these instances.
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Affiliation(s)
- Tori L Schaefer
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA
| | - Matthew H Davenport
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA
| | - Lindsay M Grainger
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA
| | - Chandler K Robinson
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA
| | - Anthony T Earnheart
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA
| | - Melinda S Stegman
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA.,Present address: Division of Nephrology and Hypertension, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229 USA
| | - Anna L Lang
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA.,Present address: Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY 40202 USA
| | - Amy A Ashworth
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA.,Present address: BlackbookHR, Cincinnati, OH 45202 USA
| | - Gemma Molinaro
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390 USA
| | - Kimberly M Huber
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390 USA
| | - Craig A Erickson
- Division of Psychiatry, MLC 7004, Cincinnati Children's Research Foundation, 3333 Burnet Ave., Cincinnati, OH 45229-3039 USA
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Jeon SJ, Ryu JH, Bahn GH. Altered Translational Control of Fragile X Mental Retardation Protein on Myelin Proteins in Neuropsychiatric Disorders. Biomol Ther (Seoul) 2017; 25:231-238. [PMID: 27829268 PMCID: PMC5424632 DOI: 10.4062/biomolther.2016.042] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Revised: 06/28/2016] [Accepted: 07/28/2016] [Indexed: 01/07/2023] Open
Abstract
Myelin is a specialized structure of the nervous system that both enhances electrical conductance and insulates neurons from external risk factors. In the central nervous system, polarized oligodendrocytes form myelin by wrapping processes in a spiral pattern around neuronal axons through myelin-related gene regulation. Since these events occur at a distance from the cell body, post-transcriptional control of gene expression has strategic advantage to fine-tune the overall regulation of protein contents in situ. Therefore, many research interests have been focused to identify RNA binding proteins and their regulatory mechanism in myelinating compartments. Fragile X mental retardation protein (FMRP) is one such RNA binding protein, regulating its target expression by translational control. Although the majority of works on FMRP have been performed in neurons, it is also found in the developing or mature glial cells including oligodendrocytes, where its function is not well understood. Here, we will review evidences suggesting abnormal translational regulation of myelin proteins with accompanying white matter problem and neurological deficits in fragile X syndrome, which can have wider mechanistic and pathological implication in many other neurological and psychiatric disorders.
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Affiliation(s)
- Se Jin Jeon
- Department of Life and Nanopharmaceutical Science, College of Pharmacy, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Jong Hoon Ryu
- Department of Life and Nanopharmaceutical Science, College of Pharmacy, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Geon Ho Bahn
- Department of Neuropsychiatry, School of Medicine, Kyung Hee University, Seoul 02447, Republic of Korea
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26
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Terasaka N, Futai K, Katoh T, Suga H. A human microRNA precursor binding to folic acid discovered by small RNA transcriptomic SELEX. RNA (NEW YORK, N.Y.) 2016; 22:1918-1928. [PMID: 27852928 PMCID: PMC5113211 DOI: 10.1261/rna.057737.116] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 09/12/2016] [Indexed: 05/17/2023]
Abstract
RNA aptamers are structured motifs that bind to specific molecules. A growing number of RNAs bearing aptamer elements, whose functions are modulated by direct binding of metabolites, have been found in living cells. Recent studies have suggested that more small RNAs binding to metabolites likely exist and may be involved in diverse cellular processes. However, conventional methods are not necessarily suitable for the discovery of such RNA aptamer elements in small RNAs with lengths ranging from 50 to 200 nucleotides, due to the far more abundant tRNAs in this size range. Here, we describe a new in vitro selection method to uncover naturally occurring small RNAs capable of binding to a ligand of interest, referred to as small RNA transcriptomic SELEX (smaRt-SELEX). By means of this method, we identified a motif in human precursor microRNA 125a (hsa-pre-miR-125a) that interacts with folic acid. Mutation studies revealed that the terminal loop region of hsa-pre-miR-125a is important for this binding interaction. This method has potential for the discovery of new RNA aptamer elements or catalytic motifs in biological small RNA fractions.
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Affiliation(s)
- Naohiro Terasaka
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Kazuki Futai
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takayuki Katoh
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
- JST, CREST, The University of Tokyo, Tokyo 113-0033, Japan
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27
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Basu S, Bahadur RP. A structural perspective of RNA recognition by intrinsically disordered proteins. Cell Mol Life Sci 2016; 73:4075-84. [PMID: 27229125 PMCID: PMC7079799 DOI: 10.1007/s00018-016-2283-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 05/13/2016] [Accepted: 05/20/2016] [Indexed: 11/24/2022]
Abstract
Protein-RNA recognition is essential for gene expression and its regulation, which is indispensable for the survival of the living organism at one hand, on the other hand, misregulation of this recognition may lead to their extinction. Polymorphic conformation of both the interacting partners is a characteristic feature of such molecular recognition that promotes the assembly. Many RNA binding proteins (RBP) or regions in them are found to be intrinsically disordered, and this property helps them to play a central role in the regulatory processes. Sequence composition and the length of the flexible linkers between RNA binding domains in RBPs are crucial in making significant contacts with its partner RNA. Polymorphic conformations of RBPs can provide thermodynamic advantage to its binding partner while acting as a chaperone. Prolonged extensions of the disordered regions in RBPs also contribute to the stability of the large cellular machines including ribosome and viral assemblies. The involvement of these disordered regions in most of the significant cellular processes makes RBPs highly associated with various human diseases that arise due to their misregulation.
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Affiliation(s)
- Sushmita Basu
- Computational Structural Biology Lab, Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Ranjit Prasad Bahadur
- Computational Structural Biology Lab, Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
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28
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Anderson BR, Chopra P, Suhl JA, Warren ST, Bassell GJ. Identification of consensus binding sites clarifies FMRP binding determinants. Nucleic Acids Res 2016; 44:6649-59. [PMID: 27378784 PMCID: PMC5001617 DOI: 10.1093/nar/gkw593] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 06/17/2016] [Indexed: 12/30/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) is a multifunctional RNA-binding protein with crucial roles in neuronal development and function. Efforts aimed at elucidating how FMRP target mRNAs are selected have produced divergent sets of target mRNA and putative FMRP-bound motifs, and a clear understanding of FMRP's binding determinants has been lacking. To clarify FMRP's binding to its target mRNAs, we produced a shared dataset of FMRP consensus binding sequences (FCBS), which were reproducibly identified in two published FMRP CLIP sequencing datasets. This comparative dataset revealed that of the various sequence and structural motifs that have been proposed to specify FMRP binding, the short sequence motifs TGGA and GAC were corroborated, and a novel TAY motif was identified. In addition, the distribution of the FCBS set demonstrates that FMRP preferentially binds to the coding region of its targets but also revealed binding along 3' UTRs in a subset of target mRNAs. Beyond probing these putative motifs, the FCBS dataset of reproducibly identified FMRP binding sites is a valuable tool for investigating FMRP targets and function.
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Affiliation(s)
- Bart R Anderson
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Pankaj Chopra
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Joshua A Suhl
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Stephen T Warren
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Pediatrics, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA
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29
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Basu S, Bahadur RP. A structural perspective of RNA recognition by intrinsically disordered proteins. CELLULAR AND MOLECULAR LIFE SCIENCES : CMLS 2016. [PMID: 27229125 DOI: 10.1007/s00018‐016‐2283‐1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Protein-RNA recognition is essential for gene expression and its regulation, which is indispensable for the survival of the living organism at one hand, on the other hand, misregulation of this recognition may lead to their extinction. Polymorphic conformation of both the interacting partners is a characteristic feature of such molecular recognition that promotes the assembly. Many RNA binding proteins (RBP) or regions in them are found to be intrinsically disordered, and this property helps them to play a central role in the regulatory processes. Sequence composition and the length of the flexible linkers between RNA binding domains in RBPs are crucial in making significant contacts with its partner RNA. Polymorphic conformations of RBPs can provide thermodynamic advantage to its binding partner while acting as a chaperone. Prolonged extensions of the disordered regions in RBPs also contribute to the stability of the large cellular machines including ribosome and viral assemblies. The involvement of these disordered regions in most of the significant cellular processes makes RBPs highly associated with various human diseases that arise due to their misregulation.
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Affiliation(s)
- Sushmita Basu
- Computational Structural Biology Lab, Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Ranjit Prasad Bahadur
- Computational Structural Biology Lab, Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
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30
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Neuron class-specific requirements for Fragile X Mental Retardation Protein in critical period development of calcium signaling in learning and memory circuitry. Neurobiol Dis 2016; 89:76-87. [PMID: 26851502 DOI: 10.1016/j.nbd.2016.02.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 01/27/2016] [Accepted: 02/02/2016] [Indexed: 01/22/2023] Open
Abstract
Neural circuit optimization occurs through sensory activity-dependent mechanisms that refine synaptic connectivity and information processing during early-use developmental critical periods. Fragile X Mental Retardation Protein (FMRP), the gene product lost in Fragile X syndrome (FXS), acts as an activity sensor during critical period development, both as an RNA-binding translation regulator and channel-binding excitability regulator. Here, we employ a Drosophila FXS disease model to assay calcium signaling dynamics with a targeted transgenic GCaMP reporter during critical period development of the mushroom body (MB) learning/memory circuit. We find FMRP regulates depolarization-induced calcium signaling in a neuron-specific manner within this circuit, suppressing activity-dependent calcium transients in excitatory cholinergic MB input projection neurons and enhancing calcium signals in inhibitory GABAergic MB output neurons. Both changes are restricted to the developmental critical period and rectified at maturity. Importantly, conditional genetic (dfmr1) rescue of null mutants during the critical period corrects calcium signaling defects in both neuron classes, indicating a temporally restricted FMRP requirement. Likewise, conditional dfmr1 knockdown (RNAi) during the critical period replicates constitutive null mutant defects in both neuron classes, confirming cell-autonomous requirements for FMRP in developmental regulation of calcium signaling dynamics. Optogenetic stimulation during the critical period enhances depolarization-induced calcium signaling in both neuron classes, but this developmental change is eliminated in dfmr1 null mutants, indicating the activity-dependent regulation requires FMRP. These results show FMRP shapes neuron class-specific calcium signaling in excitatory vs. inhibitory neurons in developing learning/memory circuitry, and that FMRP mediates activity-dependent regulation of calcium signaling specifically during the early-use critical period.
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31
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Zfrp8 forms a complex with fragile-X mental retardation protein and regulates its localization and function. Dev Biol 2016; 410:202-212. [PMID: 26772998 DOI: 10.1016/j.ydbio.2015.12.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 11/13/2015] [Accepted: 12/09/2015] [Indexed: 11/21/2022]
Abstract
Fragile-X syndrome is the most commonly inherited cause of autism and mental disabilities. The Fmr1 (Fragile-X Mental Retardation 1) gene is essential in humans and Drosophila for the maintenance of neural stem cells, and Fmr1 loss results in neurological and reproductive developmental defects in humans and flies. FMRP (Fragile-X Mental Retardation Protein) is a nucleo-cytoplasmic shuttling protein, involved in mRNA silencing and translational repression. Both Zfrp8 and Fmr1 have essential functions in the Drosophila ovary. In this study, we identified FMRP, Nufip (Nuclear Fragile-X Mental Retardation Protein-interacting Protein) and Tral (Trailer Hitch) as components of a Zfrp8 protein complex. We show that Zfrp8 is required in the nucleus, and controls localization of FMRP in the cytoplasm. In addition, we demonstrate that Zfrp8 genetically interacts with Fmr1 and tral in an antagonistic manner. Zfrp8 and FMRP both control heterochromatin packaging, also in opposite ways. We propose that Zfrp8 functions as a chaperone, controlling protein complexes involved in RNA processing in the nucleus.
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32
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Suhl JA, Warren ST. Single-Nucleotide Mutations in FMR1 Reveal Novel Functions and Regulatory Mechanisms of the Fragile X Syndrome Protein FMRP. J Exp Neurosci 2015; 9:35-41. [PMID: 26819560 PMCID: PMC4720182 DOI: 10.4137/jen.s25524] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 11/04/2015] [Accepted: 11/08/2015] [Indexed: 11/05/2022] Open
Abstract
Fragile X syndrome is a monogenic disorder and a common cause of intellectual disability. Despite nearly 25 years of research on FMR1, the gene underlying the syndrome, very few pathological mutations other than the typical CGG-repeat expansion have been reported. This is in contrast to other X-linked, monogenic, intellectual disability disorders, such as Rett syndrome, where many point mutations have been validated as causative of the disorder. As technology has improved and significantly driven down the cost of sequencing, allowing for whole genes to be sequenced with relative ease, in-depth sequencing studies on FMR1 have recently been performed. These studies have led to the identification of novel variants in FMR1, where some of which have been functionally evaluated and are likely pathogenic. In this review, we discuss recently identified FMR1 variants, the ways these novel variants cause dysfunction, and how they reveal new regulatory mechanisms and functionalities of the gene.
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Affiliation(s)
- Joshua A Suhl
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - Stephen T Warren
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.; Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA.; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
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33
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Abstract
Fragile X syndrome (FXS) results from a genetic mutation in a single gene yet produces a phenotypically complex disorder with a range of neurological and psychiatric problems. Efforts to decipher how perturbations in signaling pathways lead to the myriad alterations in synaptic and cellular functions have provided insights into the molecular underpinnings of this disorder. From this large body of data, the theme of circuit hyperexcitability has emerged as a potential explanation for many of the neurological and psychiatric symptoms in FXS. The mechanisms for hyperexcitability range from alterations in the expression or activity of ion channels to changes in neurotransmitters and receptors. Contributions of these processes are often brain region and cell type specific, resulting in complex effects on circuit function that manifest as altered excitability. Here, we review the current state of knowledge of the molecular, synaptic, and circuit-level mechanisms underlying hyperexcitability and their contributions to the FXS phenotypes.
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34
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Sosińska P, Mikuła-Pietrasik J, Książek K. The double-edged sword of long non-coding RNA: The role of human brain-specific BC200 RNA in translational control, neurodegenerative diseases, and cancer. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 766:58-67. [DOI: 10.1016/j.mrrev.2015.08.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 07/29/2015] [Accepted: 08/28/2015] [Indexed: 12/14/2022]
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35
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Fatemi SH, Folsom TD. GABA receptor subunit distribution and FMRP-mGluR5 signaling abnormalities in the cerebellum of subjects with schizophrenia, mood disorders, and autism. Schizophr Res 2015; 167:42-56. [PMID: 25432637 PMCID: PMC5301472 DOI: 10.1016/j.schres.2014.10.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 10/06/2014] [Accepted: 10/08/2014] [Indexed: 12/24/2022]
Abstract
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain. GABAergic receptor abnormalities have been documented in several major psychiatric disorders including schizophrenia, mood disorders, and autism. Abnormal expression of mRNA and protein for multiple GABA receptors has also been observed in multiple brain regions leading to alterations in the balance between excitatory/inhibitory signaling in the brain with potential profound consequences for normal cognition and maintenance of mood and perception. Altered expression of GABAA receptor subunits has been documented in fragile X mental retardation 1 (FMR1) knockout mice, suggesting that loss of its protein product, fragile X mental retardation protein (FMRP), impacts GABAA subunit expression. Recent postmortem studies from our laboratory have shown reduced expression of FMRP in the brains of subjects with schizophrenia, bipolar disorder, major depression, and autism. FMRP acts as a translational repressor and, under normal conditions, inhibits metabotropic glutamate receptor 5 (mGluR5)-mediated signaling. In fragile X syndrome (FXS), the absence of FMRP is hypothesized to lead to unregulated mGluR5 signaling, ultimately resulting in the behavioral and intellectual impairments associated with this disorder. Our laboratory has identified changes in mGluR5 expression in autism, schizophrenia, and mood disorders. In the current review article, we discuss our postmortem data on GABA receptors, FMRP, and mGluR5 levels and compare our results with other laboratories. Finally, we discuss the interactions between these molecules and the potential for new therapeutic interventions that target these interconnected signaling systems.
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Affiliation(s)
- S Hossein Fatemi
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, 420 Delaware St SE, MMC 392, Minneapolis, MN 55455, USA; Department of Neuroscience, University of Minnesota Medical School, 321 Church St. SE, Minneapolis, MN 55455, USA.
| | - Timothy D Folsom
- Department of Psychiatry, Division of Neuroscience Research, University of Minnesota Medical School, 420 Delaware St SE, MMC 392, Minneapolis, MN 55455, USA.
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36
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Gross C, Hoffmann A, Bassell GJ, Berry-Kravis EM. Therapeutic Strategies in Fragile X Syndrome: From Bench to Bedside and Back. Neurotherapeutics 2015; 12:584-608. [PMID: 25986746 PMCID: PMC4489963 DOI: 10.1007/s13311-015-0355-9] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Fragile X syndrome (FXS), an inherited intellectual disability often associated with autism, is caused by the loss of expression of the fragile X mental retardation protein. Tremendous progress in basic, preclinical, and translational clinical research has elucidated a variety of molecular-, cellular-, and system-level defects in FXS. This has led to the development of several promising therapeutic strategies, some of which have been tested in larger-scale controlled clinical trials. Here, we will summarize recent advances in understanding molecular functions of fragile X mental retardation protein beyond the well-known role as an mRNA-binding protein, and will describe current developments and emerging limitations in the use of the FXS mouse model as a preclinical tool to identify therapeutic targets. We will review the results of recent clinical trials conducted in FXS that were based on some of the preclinical findings, and discuss how the observed outcomes and obstacles will inform future therapy development in FXS and other autism spectrum disorders.
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Affiliation(s)
- Christina Gross
- />Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229 USA
| | - Anne Hoffmann
- />Department of Pediatrics, Rush University Medical Center, Chicago, IL 60612 USA
| | - Gary J. Bassell
- />Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322 USA
| | - Elizabeth M. Berry-Kravis
- />Departments of Pediatrics, Neurological Sciences, Biochemistry, Rush University Medical Center, Chicago, IL 60612 USA
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37
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Weisz ED, Monyak RE, Jongens TA. Deciphering discord: How Drosophila research has enhanced our understanding of the importance of FMRP in different spatial and temporal contexts. Exp Neurol 2015; 274:14-24. [PMID: 26026973 DOI: 10.1016/j.expneurol.2015.05.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 05/18/2015] [Accepted: 05/23/2015] [Indexed: 01/06/2023]
Abstract
Fragile X Syndrome (FXS) is the most common heritable form of intellectual impairment as well as the leading monogenetic cause of autism. In addition to its canonical definition as a neurodevelopmental disease, recent findings in the clinic suggest that FXS is a systemic disorder that is characterized by a variety of heterogeneous phenotypes. Efforts to study FXS pathogenesis have been aided by the development and characterization of animal models of the disease. Research efforts in Drosophila melanogaster have revealed key insights into the mechanistic underpinnings of FXS. While much remains unknown, it is increasingly apparent that FXS involves a myriad of spatially and temporally specific alterations in cellular function. Consequently, the literature is filled with numerous discordant findings. Researchers and clinicians alike must be cognizant of this dissonance, as it will likely be important for the design of preclinical studies to assess the efficacy of therapeutic strategies to improve the lives of FXS patients.
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Affiliation(s)
- Eliana D Weisz
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States
| | - Rachel E Monyak
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States
| | - Thomas A Jongens
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States.
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38
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Braat S, D'Hulst C, Heulens I, De Rubeis S, Mientjes E, Nelson DL, Willemsen R, Bagni C, Van Dam D, De Deyn PP, Kooy RF. The GABAA receptor is an FMRP target with therapeutic potential in fragile X syndrome. Cell Cycle 2015; 14:2985-95. [PMID: 25790165 PMCID: PMC4827888 DOI: 10.4161/15384101.2014.989114] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 04/11/2015] [Indexed: 01/08/2023] Open
Abstract
Previous research indicates that the GABAAergic system is involved in the pathophysiology of the fragile X syndrome, a frequent form of inherited intellectual disability and associated with autism spectrum disorder. However, the molecular mechanism underlying GABAAergic deficits has remained largely unknown. Here, we demonstrate reduced mRNA expression of GABAA receptor subunits in the cortex and cerebellum of young Fmr1 knockout mice. In addition, we show that the previously reported underexpression of specific subunits of the GABAA receptor can be corrected in YAC transgenic rescue mice, containing the full-length human FMR1 gene in an Fmr1 knockout background. Moreover, we demonstrate that FMRP directly binds several GABAA receptor mRNAs. Finally, positive allosteric modulation of GABAA receptors with the neurosteroid ganaxolone can modulate specific behaviors in Fmr1 knockout mice, emphasizing the therapeutic potential of the receptor.
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Affiliation(s)
- Sien Braat
- Department of Medical Genetics; University of Antwerp; Antwerp, Belgium
| | - Charlotte D'Hulst
- Department of Medical Genetics; University of Antwerp; Antwerp, Belgium
- Present address: Department of Biological Sciences; Hunter College; City University of New York; New York, NY USA
| | - Inge Heulens
- Department of Medical Genetics; University of Antwerp; Antwerp, Belgium
| | - Silvia De Rubeis
- VIB Department of Molecular and Developmental Genetics; Molecular Neurobiology; Catholic University Leuven; Leuven, Belgium
- Present address: Seaver Autism Centre for Research and Treatment; Icahn School of Medicine at Mount Sinai; New York, NY USA
| | - Edwin Mientjes
- Department of Clinical Genetics; Erasmus MC Rotterdam; Rotterdam, The Netherlands
| | - David L Nelson
- Department of Molecular and Human Genetics; Baylor College of Medicine; One Baylor Plaza; Houston, TX USA
| | - Rob Willemsen
- Department of Clinical Genetics; Erasmus MC Rotterdam; Rotterdam, The Netherlands
| | - Claudia Bagni
- VIB Department of Molecular and Developmental Genetics; Molecular Neurobiology; Catholic University Leuven; Leuven, Belgium
- Department of Biomedicine and Prevention; University of Rome Tor Vergata; Rome, Italy
| | - Debby Van Dam
- Laboratory of Neurochemistry and Behaviour; Institute Born-Bunge; Department of Biomedical Sciences; University of Antwerp; Antwerp, Belgium
| | - Peter P De Deyn
- Laboratory of Neurochemistry and Behaviour; Institute Born-Bunge; Department of Biomedical Sciences; University of Antwerp; Antwerp, Belgium
- Memory clinic; Department of Neurology; Middelheim General Hospital; ZNA; Antwerp, Belgium
- Department of Neurology and Alzheimer Research Centre; University Medical Centre; Groningen, The Netherlands
| | - R Frank Kooy
- Department of Medical Genetics; University of Antwerp; Antwerp, Belgium
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Kenny PJ, Zhou H, Kim M, Skariah G, Khetani RS, Drnevich J, Arcila ML, Kosik KS, Ceman S. MOV10 and FMRP regulate AGO2 association with microRNA recognition elements. Cell Rep 2014; 9:1729-1741. [PMID: 25464849 DOI: 10.1016/j.celrep.2014.10.054] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 10/09/2014] [Accepted: 10/18/2014] [Indexed: 10/24/2022] Open
Abstract
The fragile X mental retardation protein FMRP regulates translation of its bound mRNAs through incompletely defined mechanisms. FMRP has been linked to the microRNA pathway, and we show here that it associates with the RNA helicase MOV10, also associated with the microRNA pathway. FMRP associates with MOV10 directly and in an RNA-dependent manner and facilitates MOV10's association with RNAs in brain and cells, suggesting a cooperative interaction. We identified the RNAs recognized by MOV10 using RNA immunoprecipitation and iCLIP. Examination of the fate of MOV10 on RNAs revealed a dual function for MOV10 in regulating translation: it facilitates microRNA-mediated translation of some RNAs, but it also increases expression of other RNAs by preventing AGO2 function. The latter subset was also bound by FMRP in close proximity to the MOV10 binding site, suggesting that FMRP prevents MOV10-mediated microRNA suppression. We have identified a mechanism for FMRP-mediated translational regulation through its association with MOV10.
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Affiliation(s)
- Phillip J Kenny
- Cell and Developmental Biology, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
| | - Hongjun Zhou
- Neuroscience Research Institute and Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Miri Kim
- College of Medicine, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA; Neuroscience Program, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
| | - Geena Skariah
- Neuroscience Program, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
| | - Radhika S Khetani
- High-Performance Biological Computing, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
| | - Jenny Drnevich
- High-Performance Biological Computing, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA
| | - Mary Luz Arcila
- Neuroscience Research Institute and Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Kenneth S Kosik
- Neuroscience Research Institute and Molecular, Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Stephanie Ceman
- Cell and Developmental Biology, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA; College of Medicine, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA; Neuroscience Program, Roy J. Carver Biotechnology Center, University of Illinois-Urbana Champaign, Urbana, IL 61801, USA.
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40
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Campos-Melo D, Droppelmann CA, Volkening K, Strong MJ. RNA-binding proteins as molecular links between cancer and neurodegeneration. Biogerontology 2014; 15:587-610. [PMID: 25231915 DOI: 10.1007/s10522-014-9531-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 09/11/2014] [Indexed: 12/12/2022]
Abstract
For many years, epidemiological studies have suggested an association between cancer and neurodegenerative disorders-two disease processes that seemingly have little in common. Although these two disease processes share disruptions in a wide range of cellular pathways, including cell survival, cell death and the cell cycle, the end result is very divergent: uncontrolled cell survival and proliferation in cancer and progressive neuronal cell death in neurodegeneration. Despite the clinical data connecting these two disease processes, little is known about the molecular links between them. Among the mechanisms affected in cancer and neurodegenerative diseases, alterations in RNA metabolism are obtaining significant attention given the critical role for RNA transcription, maturation, transport, stability, degradation and translation in normal cellular function. RNA-binding proteins (RBPs) are integral to each stage of RNA metabolism through their participation in the formation of ribonucleoprotein complexes (RNPs). RBPs have a broad range of functions including posttranscriptional regulation of mRNA stability, splicing, editing and translation, mRNA export and localization, mRNA polyadenylation and miRNA biogenesis, ultimately impacting the expression of every single gene in the cell. In this review, we examine the evidence for RBPs as being key a molecular linkages between cancer and neurodegeneration.
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Affiliation(s)
- Danae Campos-Melo
- Molecular Medicine Group, Robarts Research Institute, Western University, London, ON, Canada
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41
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Matic K, Eninger T, Bardoni B, Davidovic L, Macek B. Quantitative phosphoproteomics of murine Fmr1-KO cell lines provides new insights into FMRP-dependent signal transduction mechanisms. J Proteome Res 2014; 13:4388-97. [PMID: 25168779 DOI: 10.1021/pr5006372] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Fragile X mental retardation protein (FMRP) is an RNA-binding protein that has a major effect on neuronal protein synthesis. Transcriptional silencing of the FMR1 gene leads to loss of FMRP and development of Fragile X syndrome (FXS), the most common known hereditary cause of intellectual impairment and autism. Here we utilize SILAC-based quantitative phosphoproteomics to analyze murine FMR1(-) and FMR1(+) fibroblastic cell lines derived from FMR1-KO embryos to identify proteins and phosphorylation sites dysregulated as a consequence of FMRP loss. We quantify FMRP-related changes in the levels of 5,023 proteins and 6,133 phosphorylation events and map them onto major signal transduction pathways. Our study confirms global downregulation of the MAPK/ERK pathway and decrease in phosphorylation level of ERK1/2 in the absence of FMRP, which is connected to attenuation of long-term potentiation. We detect differential expression of several key proteins from the p53 pathway, pointing to the involvement of p53 signaling in dysregulated cell cycle control in FXS. Finally, we detect differential expression and phosphorylation of proteins involved in pre-mRNA processing and nuclear transport, as well as Wnt and calcium signaling, such as PLC, PKC, NFAT, and cPLA2. We postulate that calcium homeostasis is likely affected in molecular pathogenesis of FXS.
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Affiliation(s)
- Katarina Matic
- Proteome Center Tübingen and ‡Graduate School of Cellular and Molecular Neuroscience, University of Tübingen , Österbergstrasse 3, 72074 Tübingen, Germany
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Kimura S, Sakakibara Y, Sato K, Ote M, Ito H, Koganezawa M, Yamamoto D. TheDrosophilalingerer protein cooperates with Orb2 in long-term memory formation. J Neurogenet 2014; 29:8-17. [DOI: 10.3109/01677063.2014.917644] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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43
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Suhl JA, Chopra P, Anderson BR, Bassell GJ, Warren ST. Analysis of FMRP mRNA target datasets reveals highly associated mRNAs mediated by G-quadruplex structures formed via clustered WGGA sequences. Hum Mol Genet 2014; 23:5479-91. [PMID: 24876161 DOI: 10.1093/hmg/ddu272] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Fragile X syndrome, a common cause of intellectual disability and a well-known cause of autism spectrum disorder, is the result of loss or dysfunction of fragile X mental retardation protein (FMRP), a highly selective RNA-binding protein and translation regulator. A major research priority has been the identification of the mRNA targets of FMRP, particularly as recent studies suggest an excess of FMRP targets among genes implicated in idiopathic autism and schizophrenia. Several large-scale studies have attempted to identify mRNAs bound by FMRP through several methods, each generating a list of putative target genes, leading to distinct hypotheses by which FMRP recognizes its targets; namely, by RNA structure or sequence. However, no in depth analyses have been performed to identify the level of consensus among the studies. Here, we analyze four large FMRP target datasets to generate high-confidence consensus lists, and examine all datasets for sequence elements within the target RNAs to validate reported FMRP binding motifs (GACR, ACUK and WGGA). We found GACR to be highly enriched in FMRP datasets, while ACUK was not. The WGGA pattern was modestly enriched in several, but not all datasets. The previous association between FMRP and G-quadruplexes prompted the analysis of the distribution of WGGA in the target genes. Consistent with the requirements for G-quadruplex formation, we observed highly clustered WGGA motifs in FMRP targets compared with other genes, implicating both RNA structure and sequence in the recognition motif of FMRP. In addition, we generate a list of the top 40 FMRP targets associated with FXS-related phenotypes.
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Affiliation(s)
| | | | | | | | - Stephen T Warren
- Department of Human Genetics, Departments of Biochemistry and Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
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Fragile X mental retardation protein regulates translation by binding directly to the ribosome. Mol Cell 2014; 54:407-417. [PMID: 24746697 DOI: 10.1016/j.molcel.2014.03.023] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 02/18/2014] [Accepted: 03/10/2014] [Indexed: 11/23/2022]
Abstract
Fragile X syndrome (FXS) is the most common form of inherited mental retardation, and it is caused by loss of function of the fragile X mental retardation protein (FMRP). FMRP is an RNA-binding protein that is involved in the translational regulation of several neuronal mRNAs. However, the precise mechanism of translational inhibition by FMRP is unknown. Here, we show that FMRP inhibits translation by binding directly to the L5 protein on the 80S ribosome. Furthermore, cryoelectron microscopic reconstruction of the 80S ribosome⋅FMRP complex shows that FMRP binds within the intersubunit space of the ribosome such that it would preclude the binding of tRNA and translation elongation factors on the ribosome. These findings suggest that FMRP inhibits translation by blocking the essential components of the translational machinery from binding to the ribosome.
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45
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Brager DH, Johnston D. Channelopathies and dendritic dysfunction in fragile X syndrome. Brain Res Bull 2014; 103:11-7. [PMID: 24462643 DOI: 10.1016/j.brainresbull.2014.01.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/06/2014] [Accepted: 01/13/2014] [Indexed: 11/17/2022]
Abstract
Dendritic spine abnormalities and the metabotropic glutamate receptor theory put the focus squarely on synapses and protein synthesis as the cellular locus of fragile X syndrome. Synapses however, are only partly responsible for information processing in neuronal networks. Neurotransmitter triggered excitatory postsynaptic potentials (EPSPs) are shaped and integrated by dendritic voltage-gated ion channels. These EPSPs, and in some cases the resultant dendritic spikes, are further modified by dendritic voltage-gated ion channels as they propagate to the soma. If the resultant somatic depolarization is large enough, action potential(s) will be triggered and propagate both orthodromically down the axon, where it may trigger neurotransmitter release, and antidromically back into the dendritic tree, where it can activate and modify dendritic voltage-gated and receptor activated ion channels. Several channelopathies, both soma-dendritic (L-type calcium channels, Slack potassium channels, h-channels, A-type potassium channels) and axo-somatic (BK channels and delayed rectifier potassium channels) were identified in the fmr1-/y mouse model of fragile X syndrome. Pathological function of these channels will strongly influence the excitability of individual neurons as well as overall network function. In this chapter we discuss the role of voltage-gated ion channels in neuronal processing and describe how identified channelopathies in models of fragile X syndrome may play a role in dendritic pathophysiology.
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Affiliation(s)
- Darrin H Brager
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712, United States.
| | - Daniel Johnston
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712, United States
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46
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Li Y, Tang W, Zhang LR, Zhang CY. FMRP regulates miR196a-mediated repression of HOXB8 via interaction with the AGO2 MID domain. MOLECULAR BIOSYSTEMS 2014; 10:1757-64. [DOI: 10.1039/c4mb00066h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Nolze A, Schneider J, Keil R, Lederer M, Hüttelmaier S, Kessels MM, Qualmann B, Hatzfeld M. FMRP regulates actin filament organization via the armadillo protein p0071. RNA (NEW YORK, N.Y.) 2013; 19:1483-96. [PMID: 24062571 PMCID: PMC3851716 DOI: 10.1261/rna.037945.112] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Loss of fragile X mental retardation protein (FMRP) causes synaptic dysfunction and intellectual disability. FMRP is an RNA-binding protein that controls the translation or turnover of a subset of mRNAs. Identifying these target transcripts is an important step toward understanding the pathology of the disease. Here, we show that FMRP regulates actin organization and neurite outgrowth via the armadillo protein p0071. In mouse embryonic fibroblasts (MEFs) lacking FMRP (Fmr1-), the actin cytoskeleton was markedly reorganized with reduced stress fibers and F-actin/G-actin ratios compared to fibroblasts re-expressing the protein. FMRP interfered with the translation of the p0071 mRNA in a 3'-UTR-dependent manner. Accordingly, FMRP-depleted cells revealed elevated levels of p0071 protein. The knockdown of p0071 in Fmr1- fibroblasts restored stress fibers and an elongated cell shape, thus rescuing the Fmr1- phenotype, whereas overexpression of p0071 in Fmr1+ cells mimicked the Fmr1- phenotype. Moreover, p0071 and FMRP regulated neurite outgrowth and branching in a diametrically opposed way in agreement with the negative regulation of p0071 by FMRP. These results identify p0071 as an important and novel FMRP target and strongly suggest that impaired actin cytoskeletal functions mediated by an excess of p0071 are key aspects underlying the fragile X syndrome.
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Affiliation(s)
- Alexander Nolze
- Institute of Molecular Medicine, Division of Pathobiochemistry, Martin-Luther-University of Halle, 06114 Halle, Germany
| | - Jacqueline Schneider
- Institute for Biochemistry I, Jena University Hospital–Friedrich Schiller University Jena, 07743 Jena, Germany
| | - René Keil
- Institute of Molecular Medicine, Division of Pathobiochemistry, Martin-Luther-University of Halle, 06114 Halle, Germany
| | - Marcell Lederer
- Institute of Molecular Medicine, Division of Cell Biology, Martin-Luther-University of Halle, 06120 Halle, Germany
| | - Stefan Hüttelmaier
- Institute of Molecular Medicine, Division of Cell Biology, Martin-Luther-University of Halle, 06120 Halle, Germany
| | - Michael M. Kessels
- Institute for Biochemistry I, Jena University Hospital–Friedrich Schiller University Jena, 07743 Jena, Germany
| | - Britta Qualmann
- Institute for Biochemistry I, Jena University Hospital–Friedrich Schiller University Jena, 07743 Jena, Germany
| | - Mechthild Hatzfeld
- Institute of Molecular Medicine, Division of Pathobiochemistry, Martin-Luther-University of Halle, 06114 Halle, Germany
- Corresponding authorE-mail
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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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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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LaFauci G, Adayev T, Kascsak R, Kascsak R, Nolin S, Mehta P, Brown WT, Dobkin C. Fragile X Screening by Quantification of FMRP in Dried Blood Spots by a Luminex Immunoassay. J Mol Diagn 2013; 15:508-17. [DOI: 10.1016/j.jmoldx.2013.02.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 02/11/2013] [Accepted: 02/20/2013] [Indexed: 02/03/2023] Open
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