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Attallah A, Ardourel M, Gallazzini F, Lesne F, De Oliveira A, Togbé D, Briault S, Perche O. Lack of FMRP in the retina: Evidence of a retinal specific transcriptomic profile. Exp Eye Res 2024; 246:110015. [PMID: 39089568 DOI: 10.1016/j.exer.2024.110015] [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: 03/27/2024] [Revised: 07/11/2024] [Accepted: 07/30/2024] [Indexed: 08/04/2024]
Abstract
Fragile X Syndrome (FXS), the most common inherited form of human intellectual disability, is a monogenic neurodevelopmental disorder caused by a loss-of-function mutation of the FMR1 gene. FMR1 is encoding the Fragile X Messenger Ribonucleo Protein (FMRP) an RNA-binding protein that regulates the translation of synaptic proteins. The absence of FMRP expression has many important consequences on synaptic plasticity and function, leading to the FXS clinical phenotype. Over the last decade, a visual neurosensorial phenotype had been described in the FXS patients as well as in the murine model (Fmr1-/ymice), characterized by retinal deficits associated to retinal perception alterations. However, although the transcriptomic profile in the absence of FMRP has been studied in the cerebral part of the central nervous system (CNS), there are no actual data for the retina which is an extension of the CNS. Herein, we investigate the transcriptomic profile of mRNA from whole retinas of Fmr1-/ymice. Interestingly, we found a specific signature of Fmrp absence on retinal mRNA expression with few common genes compared to other brain studies. Gene Ontology on these retinal specific genes demonstrated an enrichment in retinal development genes as well as in synaptic genes. These alterations could be linked to the reported retinal phenotype of the FXS condition. In conclusion, we describe for the first time, retinal-specific transcriptomic changes in the absence of FMRP.
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Affiliation(s)
- Amir Attallah
- Orléans University, University Hospital Center of Orleans, LI(2)RSO, 14, Avenue de l'hôpital, 45100, Orléans, France; Orleans University, CNRS, laboratoire INEM, UMR7355, 3b Rue de la Férollerie, F-45071, Orléans, Cedex 2, France; ART ARNm US55, 14 Avenue de l'Hôpital, 45100, Orléans, France
| | - Maryvonne Ardourel
- Orléans University, University Hospital Center of Orleans, LI(2)RSO, 14, Avenue de l'hôpital, 45100, Orléans, France; ART ARNm US55, 14 Avenue de l'Hôpital, 45100, Orléans, France
| | - Felix Gallazzini
- University Hospital Center of Orleans, Genetic Department, 14 Avenue de l'Hôpital, 45100, Orléans, France
| | - Fabien Lesne
- University Hospital Center of Orléans CAR&IB, Pôle Biopatholgie, 14 Avenue de l'Hôpital, 45100, Orléans, France
| | - Anthony De Oliveira
- University Hospital Center of Orléans CAR&IB, Pôle Biopatholgie, 14 Avenue de l'Hôpital, 45100, Orléans, France
| | - Dieudonnée Togbé
- Orleans University, CNRS, laboratoire INEM, UMR7355, 3b Rue de la Férollerie, F-45071, Orléans, Cedex 2, France
| | - Sylvain Briault
- Orléans University, University Hospital Center of Orleans, LI(2)RSO, 14, Avenue de l'hôpital, 45100, Orléans, France; ART ARNm US55, 14 Avenue de l'Hôpital, 45100, Orléans, France; University Hospital Center of Orleans, Genetic Department, 14 Avenue de l'Hôpital, 45100, Orléans, France
| | - Olivier Perche
- Orléans University, University Hospital Center of Orleans, LI(2)RSO, 14, Avenue de l'hôpital, 45100, Orléans, France; ART ARNm US55, 14 Avenue de l'Hôpital, 45100, Orléans, France; University Hospital Center of Orleans, Genetic Department, 14 Avenue de l'Hôpital, 45100, Orléans, France.
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2
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Zhang Z, Mao H, Li F, Wang D, Liu Y. METTL14-mediated lncRNA-FAS-AS1 promotes osteoarthritis progression by up-regulating ADAM8. Int J Rheum Dis 2024; 27:e15323. [PMID: 39221886 DOI: 10.1111/1756-185x.15323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Revised: 08/02/2024] [Accepted: 08/17/2024] [Indexed: 09/04/2024]
Abstract
BACKGROUND Osteoarthritis (OA) is a prevalent degenerative disease. We explored the role and regulatory mechanisms of lncRNA-FAS-AS1 in OA progression. METHODS We exposed human immortalized chondrocytes to IL-1β for 24 h to induce an OA cell model. The target molecule levels were assessed using western blot and quantitative real-time PCR (RT-qPCR). Cell viability and apoptosis were measured using CCK-8 and flow cytometry. The m6A modification of FAS-AS1 was determined using MeRIP. We examined the binding relationships between FAS-AS1, Fragile X mental retardation 1 (FMR1), and A disintegrin and metalloproteinase 8 (ADAM8) using RIP and RNA pull-down. The OA animal model was established by separating the medial collateral ligament and medial meniscus. Safranin-O staining and Mankin's scale were employed to evaluate pathological changes within the cartilage. RESULTS FAS-AS1, METTL14, and ADAM8 were upregulated, and the JAK/STAT3 signaling pathway was activated in OA mice and IL-1β-induced chondrocytes. FAS-AS1 knockdown inhibited extracellular matrix degradation in IL-1β-induced chondrocytes; however, ADAM8 overexpression reversed this effect. FAS-AS1 maintained the stability of ADAM8 mRNA by recruiting FMR1. METTL14 knockdown repressed FAS-AS1 expression in an m6A-dependent manner. FAS-AS1 overexpression reversed the inhibitory effects of METTL14 knockdown on JAK/STAT3 signaling and cartilage damage in the OA model both in vitro and in vivo. CONCLUSION METTL14-mediated FAS-AS1 promotes OA progression through the FMR1/ADAM8/JAK/STAT3 axis.
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MESH Headings
- Animals
- Humans
- Male
- Mice
- ADAM Proteins/metabolism
- ADAM Proteins/genetics
- Adenosine/analogs & derivatives
- Apoptosis
- Arthritis, Experimental/metabolism
- Arthritis, Experimental/genetics
- Arthritis, Experimental/pathology
- Cartilage, Articular/metabolism
- Cartilage, Articular/pathology
- Cell Line
- Chondrocytes/metabolism
- Chondrocytes/pathology
- Disease Models, Animal
- Disease Progression
- Interleukin-1beta/metabolism
- Membrane Proteins/metabolism
- Membrane Proteins/genetics
- Methyltransferases/metabolism
- Methyltransferases/genetics
- Mice, Inbred C57BL
- Osteoarthritis/metabolism
- Osteoarthritis/genetics
- Osteoarthritis/pathology
- Osteoarthritis, Knee/metabolism
- Osteoarthritis, Knee/genetics
- Osteoarthritis, Knee/pathology
- RNA, Long Noncoding/genetics
- RNA, Long Noncoding/metabolism
- Signal Transduction
- STAT3 Transcription Factor/metabolism
- STAT3 Transcription Factor/genetics
- Up-Regulation
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Affiliation(s)
- Zhehua Zhang
- Department of Orthopedics, The Third Affiliated Hospital of Inner Mongolia Medical University, Inner Mongolia BaoGang Hospital, Baotou, Inner Mongolia, China
| | - Honggang Mao
- Department of Orthopedics, The Third Affiliated Hospital of Inner Mongolia Medical University, Inner Mongolia BaoGang Hospital, Baotou, Inner Mongolia, China
| | - Fang Li
- Department of Experimental Center, The Third Affiliated Hospital of Inner Mongolia Medical University, Inner Mongolia BaoGang Hospital, Baotou, Inner Mongolia, China
| | - Dahai Wang
- Department of Orthopedics, The Third Affiliated Hospital of Inner Mongolia Medical University, Inner Mongolia BaoGang Hospital, Baotou, Inner Mongolia, China
| | - Yan Liu
- Department of Orthopedics, The Third Affiliated Hospital of Inner Mongolia Medical University, Inner Mongolia BaoGang Hospital, Baotou, Inner Mongolia, China
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3
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Mitchell ME, Cook LC, Shiers S, Tavares-Ferreira D, Akopian AN, Dussor G, Price TJ. Characterization of Fragile X Mental Retardation Protein expression in human nociceptors and their axonal projections to the spinal dorsal horn. J Comp Neurol 2023; 531:814-835. [PMID: 36808110 PMCID: PMC10038933 DOI: 10.1002/cne.25463] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 12/20/2022] [Accepted: 01/27/2023] [Indexed: 02/23/2023]
Abstract
Fragile X Mental Retardation Protein (FMRP) regulates activity-dependent RNA localization and local translation to modulate synaptic plasticity throughout the central nervous system. Mutations in the FMR1 gene that hinder or ablate FMRP function cause Fragile X Syndrome (FXS), a disorder associated with sensory processing dysfunction. FXS premutations are associated with increased FMRP expression and neurological impairments including sex dimorphic presentations of chronic pain. In mice, FMRP ablation causes dysregulated dorsal root ganglion (DRG) neuron excitability and synaptic vesicle exocytosis, spinal circuit activity, and decreased translation-dependent nociceptive sensitization. Activity-dependent, local translation is a key mechanism for enhancing primary nociceptor excitability that promotes pain in animals and humans. These works indicate that FMRP likely regulates nociception and pain at the level of the primary nociceptor or spinal cord. Therefore, we sought to better understand FMRP expression in the human DRG and spinal cord using immunostaining in organ donor tissues. We find that FMRP is highly expressed in DRG and spinal neuron subsets with substantia gelatinosa exhibiting the most abundant immunoreactivity in spinal synaptic fields. Here, it is expressed in nociceptor axons. FMRP puncta colocalized with Nav1.7 and TRPV1 receptor signals suggesting a pool of axoplasmic FMRP localizes to plasma membrane-associated loci in these branches. Interestingly, FMRP puncta exhibited notable colocalization with calcitonin gene-related peptide (CGRP) immunoreactivity selectively in female spinal cord. Our results support a regulatory role for FMRP in human nociceptor axons of the dorsal horn and implicate it in the sex dimorphic actions of CGRP signaling in nociceptive sensitization and chronic pain.
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Affiliation(s)
- Molly E Mitchell
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Lauren C Cook
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Stephanie Shiers
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Diana Tavares-Ferreira
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Armen N Akopian
- Department of Endodontics, UT Health San Antonio, San Antonio, Texas, USA
| | - Gregory Dussor
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Theodore J Price
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
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4
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Scarpitti MR, Warrick JE, Yoder EL, Kearse MG. A noncanonical RNA-binding domain of the fragile X protein, FMRP, elicits translational repression independent of mRNA G-quadruplexes. J Biol Chem 2022; 298:102660. [PMID: 36328245 PMCID: PMC9712993 DOI: 10.1016/j.jbc.2022.102660] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 10/12/2022] [Accepted: 10/21/2022] [Indexed: 11/07/2022] Open
Abstract
Loss of functional fragile X mental retardation protein (FMRP) causes fragile X syndrome, the leading form of inherited intellectual disability and the most common monogenic cause of autism spectrum disorders. FMRP is an RNA-binding protein that controls neuronal mRNA localization and translation. FMRP is thought to inhibit translation elongation after being recruited to target transcripts via binding RNA G-quadruplexes (G4s) within the coding sequence. Here, we directly test this model and report that FMRP inhibits translation independent of mRNA G4s. Furthermore, we found that the RGG box motif together with its natural C-terminal domain forms a noncanonical RNA-binding domain (ncRBD) that is essential for translational repression. The ncRBD elicits broad RNA-binding ability and binds to multiple reporter mRNAs and all four homopolymeric RNAs. Serial deletion analysis of the ncRBD identified that the regions required for mRNA binding and translational repression overlap but are not identical. Consistent with FMRP stalling elongating ribosomes and causing the accumulation of slowed 80S ribosomes, transcripts bound by FMRP via the ncRBD cosediment with heavier polysomes and were present in puromycin-resistant ribosome complexes. Together, this work identifies a ncRBD and translational repression domain that shifts our understanding of how FMRP inhibits translation independent of mRNA G4s.
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Affiliation(s)
- MaKenzie R Scarpitti
- The Biomedical Sciences Graduate Program, The Ohio State University, Columbus, Ohio, USA; Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Julia E Warrick
- The Biomedical Sciences Graduate Program, The Ohio State University, Columbus, Ohio, USA; Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Evelyn L Yoder
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Michael G Kearse
- The Biomedical Sciences Graduate Program, The Ohio State University, Columbus, Ohio, USA; Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA.
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5
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Edwards M, Huang M, Joseph S. The Fragile X Protein Disordered Regions Bind a Novel RNA Target. Biochemistry 2022; 61:1199-1212. [PMID: 35653700 DOI: 10.1021/acs.biochem.2c00228] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fragile X proteins (FXPs) are a family of RNA-binding proteins that regulate mRNA translation to promote proper neural development and cognition in mammals. Of particular interest to researchers is the fragile X mental retardation protein (FMRP), as its absence leads to a neurodevelopmental disorder: fragile X syndrome (FXS), the leading monogenetic cause of autism spectrum disorders. A primary focus of research has been to determine mRNA targets of the FXPs in vivo through pull-down techniques, and to validate them through in vitro binding studies; another approach has been to perform in vitro selection experiments to identify RNA sequence and structural targets. These mRNA targets can be further investigated as potential targets for FXS therapeutics. The most established RNA structural target of this family of proteins is the G-quadruplex. In this article, we report a 99 nucleotide RNA target that is bound by all three FXPs with nanomolar equilibrium constants. Furthermore, we determined that the last 102 amino acids of FMRP, which includes the RGG motif, were necessary and sufficient to bind this RNA target. To the best of our knowledge, this is one of only a few examples of non-G-quadruplex, non-homopolymer RNAs bound by the RGG motif/C-termini of FMRP.
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Affiliation(s)
- Madison Edwards
- Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0314 United States
| | - Molly Huang
- Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0314 United States
| | - Simpson Joseph
- Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0314 United States
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6
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Khlebodarova TM. The molecular view of mechanical stress of brain cells, local translation, and neurodegenerative diseases. Vavilovskii Zhurnal Genet Selektsii 2021; 25:92-100. [PMID: 34901706 PMCID: PMC8629365 DOI: 10.18699/vj21.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 12/03/2022] Open
Abstract
The assumption that chronic mechanical stress in brain cells stemming from intracranial hypertension,
arterial hypertension, or mechanical injury is a risk factor for neurodegenerative diseases was put forward in the
1990s and has since been supported. However, the molecular mechanisms that underlie the way from cell exposure to mechanical stress to disturbances in synaptic plasticity followed by changes in behavior, cognition, and
memory are still poorly understood. Here we review (1) the current knowledge of molecular mechanisms regulating local translation and the actin cytoskeleton state at an activated synapse, where they play a key role in the
formation of various sorts of synaptic plasticity and long-term memory, and (2) possible pathways of mechanical
stress intervention. The roles of the mTOR (mammalian target of rapamycin) signaling pathway; the RNA-binding
FMRP protein; the CYFIP1 protein, interacting with FMRP; the family of small GTPases; and the WAVE regulatory
complex in the regulation of translation initiation and actin cytoskeleton rearrangements in dendritic spines of the
activated synapse are discussed. Evidence is provided that chronic mechanical stress may result in aberrant activation of mTOR signaling and the WAVE regulatory complex via the YAP/TAZ system, the key sensor of mechanical
signals, and influence the associated pathways regulating the formation of F actin filaments and the dendritic spine
structure. These consequences may be a risk factor for various neurological conditions, including autistic spectrum
disorders and epileptic encephalopathy. In further consideration of the role of the local translation system in the
development of neuropsychic and neurodegenerative diseases, an original hypothesis was put forward that one
of the possible causes of synaptopathies is impaired proteome stability associated with mTOR hyperactivity and
formation of complex dynamic modes of de novo protein synthesis in response to synapse-stimulating factors,
including chronic mechanical stress.
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Affiliation(s)
- T M Khlebodarova
- Institute of Cytology and Genetics of Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia Kurchatov Genomic Center of the Institute of Cytology and Genetics of Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
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7
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Richter JD, Zhao X. The molecular biology of FMRP: new insights into fragile X syndrome. Nat Rev Neurosci 2021; 22:209-222. [PMID: 33608673 PMCID: PMC8094212 DOI: 10.1038/s41583-021-00432-0] [Citation(s) in RCA: 166] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2021] [Indexed: 01/31/2023]
Abstract
Fragile X mental retardation protein (FMRP) is the product of the fragile X mental retardation 1 gene (FMR1), a gene that - when epigenetically inactivated by a triplet nucleotide repeat expansion - causes the neurodevelopmental disorder fragile X syndrome (FXS). FMRP is a widely expressed RNA-binding protein with activity that is essential for proper synaptic plasticity and architecture, aspects of neural function that are known to go awry in FXS. Although the neurophysiology of FXS has been described in remarkable detail, research focusing on the molecular biology of FMRP has only scratched the surface. For more than two decades, FMRP has been well established as a translational repressor; however, recent whole transcriptome and translatome analyses in mouse and human models of FXS have shown that FMRP is involved in the regulation of nearly all aspects of gene expression. The emerging mechanistic details of the mechanisms by which FMRP regulates gene expression may offer ways to design new therapies for FXS.
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Affiliation(s)
- Joel D Richter
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
| | - Xinyu Zhao
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA. .,Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA.
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8
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Majumder M, Johnson RH, Palanisamy V. Fragile X-related protein family: a double-edged sword in neurodevelopmental disorders and cancer. Crit Rev Biochem Mol Biol 2020; 55:409-424. [PMID: 32878499 DOI: 10.1080/10409238.2020.1810621] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The fragile X-related (FXR) family proteins FMRP, FXR1, and FXR2 are RNA binding proteins that play a critical role in RNA metabolism, neuronal plasticity, and muscle development. These proteins share significant homology in their protein domains, which are functionally and structurally similar to each other. FXR family members are known to play an essential role in causing fragile X mental retardation syndrome (FXS), the most common genetic form of autism spectrum disorder. Recent advances in our understanding of this family of proteins have occurred in tandem with discoveries of great importance to neurological disorders and cancer biology via the identification of their novel RNA and protein targets. Herein, we review the FXR family of proteins as they pertain to FXS, other mental illnesses, and cancer. We emphasize recent findings and analyses that suggest contrasting functions of this protein family in FXS and tumorigenesis based on their expression patterns in human tissues. Finally, we discuss current gaps in our knowledge regarding the FXR protein family and their role in FXS and cancer and suggest future studies to facilitate bench to bedside translation of the findings.
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Affiliation(s)
- Mrinmoyee Majumder
- Department of Biochemistry and Molecular Biology, School of Medicine, Medical University of South Carolina, Charleston, SC, USA
| | - Roger H Johnson
- Hollings Cancer Center, Medical University of South Carolina, Charleston, SC, USA
| | - Viswanathan Palanisamy
- Department of Biochemistry and Molecular Biology, School of Medicine, Medical University of South Carolina, Charleston, SC, USA
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9
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Kulkarni A, Lopez DH, Extavour CG. Shared Cell Biological Functions May Underlie Pleiotropy of Molecular Interactions in the Germ Lines and Nervous Systems of Animals. Front Ecol Evol 2020. [DOI: 10.3389/fevo.2020.00215] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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10
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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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11
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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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12
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Huang G, Zhu H, Wu S, Cui M, Xu T. Long Noncoding RNA Can Be a Probable Mechanism and a Novel Target for Diagnosis and Therapy in Fragile X Syndrome. Front Genet 2019; 10:446. [PMID: 31191598 PMCID: PMC6541098 DOI: 10.3389/fgene.2019.00446] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 04/30/2019] [Indexed: 01/06/2023] Open
Abstract
Fragile X syndrome (FXS) is the most common congenital hereditary disease of low intelligence after Down syndrome. Its main pathogenic gene is fragile X mental retardation 1 (FMR1) gene associated with intellectual disability, autism, and fragile X-related primary ovarian insufficiency (FXPOI) and fragile X-associated tremor/ataxia syndrome (FXTAS). FMR1 gene transcription leads to the absence of fragile X mental retardation protein (FMRP). How to relieve or cure disorders associated with FXS has also become a clinically disturbing problem. Previous studies have recently shown that long noncoding RNAs (lncRNAs) contribute to the pathogenesis. And it has been identified that several lncRNAs including FMR4, FMR5, and FMR6 contribute to developing FXPOI/FXTAS, originating from the FMR1 gene locus. FMR4 is a product of RNA polymerase II and can regulate the expression of relevant genes during differentiation of human neural precursor cells. FMR5 is a sense-oriented transcript while FMR6 is an antisense lncRNA produced by the 3' UTR of FMR1. FMR6 is likely to contribute to developing FXPOI, and it overlaps exons 15-17 of FMR1 as well as two microRNA binding sites. Additionally, BC1 can bind FMRP to form an inhibitory complex and lncRNA TUG1 also can control axonal development by directly interacting with FMRP through modulating SnoN-Ccd1 pathway. Therefore, these lncRNAs provide pharmaceutical targets and novel biomarkers. This review will: (1) describe the clinical manifestations and traditional pathogenesis of FXS and FXTAS/FXPOI; (2) summarize what is known about the role of lncRNAs in the pathogenesis of FXS and FXTAS/FXPOI; and (3) provide an outlook of potential effects and future directions of lncRNAs in FXS and FXTAS/FXPOI researches.
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Affiliation(s)
- Ge Huang
- The Second Hospital of Jilin University, Changchun, China
| | - He Zhu
- The Second Hospital of Jilin University, Changchun, China
| | - Shuying Wu
- The Second Hospital of Jilin University, Changchun, China
| | - Manhua Cui
- The Second Hospital of Jilin University, Changchun, China
| | - Tianmin Xu
- The Second Hospital of Jilin University, Changchun, China
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13
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Pal R, Bhattacharya A. Modelling Protein Synthesis as A Biomarker in Fragile X Syndrome Patient-Derived Cells. Brain Sci 2019; 9:E59. [PMID: 30862080 PMCID: PMC6468675 DOI: 10.3390/brainsci9030059] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 02/27/2019] [Accepted: 03/06/2019] [Indexed: 12/26/2022] Open
Abstract
The most conserved molecular phenotype of Fragile X Syndrome (FXS) is aberrant protein synthesis. This has been validated in a variety of experimental model systems from zebrafish to rats, patient-derived lymphoblasts and fibroblasts. With the advent of personalized medicine paradigms, patient-derived cells and their derivatives are gaining more translational importance, not only to model disease in a dish, but also for biomarker discovery. Here we review past and current practices of measuring protein synthesis in FXS, studies in patient derived cells and the inherent challenges in measuring protein synthesis in them to offer usable avenues of modeling this important metabolic metric for further biomarker development.
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Affiliation(s)
- Rakhi Pal
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, GKVK Post, Bellary Road, Bengaluru 560065, India.
| | - Aditi Bhattacharya
- Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, GKVK Post, Bellary Road, Bengaluru 560065, India.
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Wang C, Ge L, Wu J, Wang X, Yuan L. MiR-219 represses expression of dFMR1 in Drosophila melanogaster. Life Sci 2018; 218:31-37. [PMID: 30528775 DOI: 10.1016/j.lfs.2018.12.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/27/2018] [Accepted: 12/05/2018] [Indexed: 11/19/2022]
Abstract
AIMS Fragile X mental retardation protein (FMRP) plays a vital role in mRNA trafficking and translation inhibition to regulate the synthesis of local proteins in neuronal axons and dendritic terminals. However, there are no reports on microRNA (miRNA)-mediated regulation of FMRP levels in Drosophila. Here, we aimed to identify miRNAs regulating FMRP levels in Drosophila. MAIN METHODS Using online software, we predicted and selected 11 miRNAs potentially acting on the Drosophila fragile X mental retardation 1 (dFMR1) transcript. These candidates were screened for modulation of dFMR1 transcript levels at the cellular level using a dual luciferase reporter system. In addition, we constructed a transgenic Drosophila model overexpressing miR-219 in the nervous system and quantified dFMRP by western blotting. The neuromuscular junction phenotype in the model was studied by immunofluorescence staining. KEY FINDINGS Among the 11 miRNAs screened, miR-219 and miR-960 reduced luciferase gene activity by binding to the 3'-UTR of the dFMR1 transcript. Mutation of the miR-219 or miR-960 binding sites on the transcript resulted in complete or partial elimination of the miRNA-induced repression. Western blots revealed that dFMRP expression was decreased in the miR-219 overexpression model (Elav>miR-219). Drosophila larvae overexpressing miR-219 showed morphological abnormalities at the neuromuscular junction (increased synaptic boutons and synaptic branches). This finding is consistent with some phenotypes observed in dfmr1 mutants. SIGNIFICANCE Our results suggest that miR-219 regulates dFMR1 expression in Drosophila and is involved in fragile X syndrome pathogenesis. Collectively, these findings expand the current understanding of miRNA-mediated regulation of target molecule-related functions.
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Affiliation(s)
- Chao Wang
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China; State Key Laboratory for Pharmaceutical Biotechnology, Nanjing University, Nanjing 210023, China
| | - Liang Ge
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Jianban Wu
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Xuan Wang
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Liudi Yuan
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China; School of Medicine, Southeast University, Nanjing 210009, China.
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Ferro D, Yao S, Zarnescu DC. Dynamic duo - FMRP and TDP-43: Regulating common targets, causing different diseases. Brain Res 2018; 1693:37-42. [PMID: 29715444 PMCID: PMC5997554 DOI: 10.1016/j.brainres.2018.04.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 04/24/2018] [Accepted: 04/26/2018] [Indexed: 10/17/2022]
Abstract
RNA binding proteins play essential roles during development and aging, and are also involved in disease pathomechanisms. RNA sequencing and omics analyses have provided a window into systems level alterations in neurological disease, and have identified RNA processing defects among notable disease mechanisms. This review focuses on two seemingly distinct neurological disorders, the RNA binding proteins they are linked to, and their newly discovered functional relationship. When deficient, Fragile X Mental Retardation Protein (FMRP) causes developmental deficits and autistic behaviors while TAR-DNA Binding Protein (TDP-43) dysregulation causes age dependent neuronal degeneration. Recent findings that FMRP and TDP-43 associate in ribonuclear protein particles and share mRNA targets in neurons highlight the critical importance of translation regulation in synaptic plasticity and provide new perspectives on neuronal vulnerability during lifespan.
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Affiliation(s)
- Diana Ferro
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States
| | - Stephen Yao
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States
| | - Daniela C Zarnescu
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States; Department of Neuroscience, University of Arizona, Tucson, AZ, United States; Department of Neurology, University of Arizona, Tucson AZ, United States.
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Beke A, Piko H, Haltrich I, Karcagi V, Rigo J, Molnar MJ, Fekete G. Study of patterns of inheritance of premature ovarian failure syndrome carrying maternal and paternal premutations. BMC MEDICAL GENETICS 2018; 19:113. [PMID: 29986653 PMCID: PMC6038184 DOI: 10.1186/s12881-018-0634-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 06/26/2018] [Indexed: 12/21/2022]
Abstract
BACKGROUND Premature ovarian failure / primary ovarian insufficiency (POF/POI) associated with the mutations of the FMR1 (Fragile-X Mental Retardation 1) gene belongs to the group of the so-called trinucleotide expansion diseases. Our aim was to analyse the relationship between the paternally inherited premutation (PIP) and the maternally inherited premutation (MIP) by the examination of the family members of women with POF, carrying the premutation allele confirmed by molecular genetic testing. METHODS Molecular genetic testing was performed in the patients of the 1st Department of Obstetrics and Gynecology with suspected premature ovarian failure. First we performed the southern blot analyses and for the certified premutation cases we used the Repeat Primed PCR. RESULTS Due to POF/POI, a total of 125 patients underwent genetic testing. The FMR1 gene trinucleotide repeat number was examined in the DNA samples of the patients, and in 15 cases (12%) deviations (CGG repeat number corresponding to premutation or gray zone) were detected. In 6 cases out of the 15 cases the CGG repeat number fell within the range of the so-called gray zone (41-54 CGG repeat) (4.8%, 6/125), and the FMR1 premutation (55-200 CGG repeat) ratio was 7.2% (9/125). In 4 out of the 15 cases we found differences in both alleles, one was a premutation allele, and the other allele showed a repeat number belonging to the gray zone. Out of 15 cases, only maternal inheritance (MIP) was detected in 2 cases, in one case the premutation allele (91 CGG repeat number), while in the other case an allele belonging to the gray zone (41 CGG repeat number) were inherited from their mothers. In 10 out of 15 cases, the patient inherited the premutation allele only from the father (PIP). In 5 out of the 10 cases (50%) the premutation allele was inherited from the father, and the repeat number ranged from 55 to 133. Out of 125 cases, 9 patients had detectable cytogenetic abnormalities (7.2%). CONCLUSIONS The RP-PCR method can be used to define the smaller premutations and the exact CGG number. Due to the quantitative nature of the RP-PCR, it is possible to detect the mosaicism as well.
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Affiliation(s)
- Artur Beke
- 1st Department of Obstetrics and Gynecology, Semmelweis University, Baross u. 27, Budapest, 1428, Hungary.
| | - Henriett Piko
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Budapest, Hungary
| | - Iren Haltrich
- 2nd Department of Pediatrics, Semmelweis University fekete, Budapest, Hungary
| | - Veronika Karcagi
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Budapest, Hungary
| | - Janos Rigo
- 1st Department of Obstetrics and Gynecology, Semmelweis University, Baross u. 27, Budapest, 1428, Hungary
| | - Maria Judit Molnar
- Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Budapest, Hungary
| | - György Fekete
- 2nd Department of Pediatrics, Semmelweis University fekete, Budapest, Hungary
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Deregulation of RNA Metabolism in Microsatellite Expansion Diseases. ADVANCES IN NEUROBIOLOGY 2018; 20:213-238. [PMID: 29916021 DOI: 10.1007/978-3-319-89689-2_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RNA metabolism impacts different steps of mRNA life cycle including splicing, polyadenylation, nucleo-cytoplasmic export, translation, and decay. Growing evidence indicates that defects in any of these steps lead to devastating diseases in humans. This chapter reviews the various RNA metabolic mechanisms that are disrupted in Myotonic Dystrophy-a trinucleotide repeat expansion disease-due to dysregulation of RNA-Binding Proteins. We also compare Myotonic Dystrophy to other microsatellite expansion disorders and describe how some of these mechanisms commonly exert direct versus indirect effects toward disease pathologies.
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Dynamic landscape of the local translation at activated synapses. Mol Psychiatry 2018; 23:107-114. [PMID: 29203851 PMCID: PMC5754473 DOI: 10.1038/mp.2017.245] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 10/09/2017] [Indexed: 01/17/2023]
Abstract
The mammalian target of rapamycin (mTOR) signaling pathway is the central regulator of cap-dependent translation at the synapse. Disturbances in mTOR pathway have been associated with several neurological diseases, such as autism and epilepsy. RNA-binding protein FMRP, a negative regulator of translation initiation, is one of the key components of the local translation system. Activation and inactivation of FMRP occurs via phosphorylation by S6 kinase and dephosphorylation by PP2A phosphatase, respectively. S6 kinase and PP2A phosphatase are activated in response to mGluR receptor stimulation through different signaling pathways and at different rates. The dynamic aspects of this system are poorly understood. We developed a mathematical model of FMRP-dependent regulation of postsynaptic density (PSD) protein synthesis in response to mGluR receptor stimulation and conducted in silico experiments to study the regulatory circuit functioning. The modeling results revealed the possibility of generating oscillatory (cyclic and quasi-cyclic), chaotic and even hyperchaotic dynamics of postsynaptic protein synthesis as well as the presence of multiple attractors in a wide range of parameters of the local translation system. The results suggest that autistic disorders associated with mTOR pathway hyperactivation may be due to impaired proteome stability associated with the formation of complex dynamic regimes of PSD protein synthesis in response to stimulation of mGluR receptors on the postsynaptic membrane of excitatory synapses on pyramidal hippocampal cells.
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Tseng E, Tang HT, AlOlaby RR, Hickey L, Tassone F. Altered expression of the FMR1 splicing variants landscape in premutation carriers. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2017; 1860:1117-1126. [PMID: 28888471 DOI: 10.1016/j.bbagrm.2017.08.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 08/26/2017] [Accepted: 08/26/2017] [Indexed: 01/17/2023]
Abstract
FMR1 premutation carriers (55-200 CGG repeats) are at risk for developing Fragile X-associated Tremor/Ataxia Syndrome (FXTAS), an adult onset neurodegenerative disorder. Approximately 20% of female carriers will develop Fragile X-associated Primary Ovarian Insufficiency (FXPOI), in addition to a number of clinical problems affecting premutation carriers throughout their life span. Marked elevation in FMR1 mRNA levels have been observed with premutation alleles resulting in RNA toxicity, the leading molecular mechanism proposed for the FMR1 associated disorders observed in premutation carriers. The FMR1 gene undergoes alternative splicing and we have recently reported that the relative abundance of all FMR1 mRNA isoforms is significantly increased in premutation carriers. In this study, we characterized the transcriptional FMR1 isoforms distribution pattern in different tissues and identified a total of 49 isoforms, some of which observed only in premutation carriers and which might play a role in the pathogenesis of FXTAS. Further, we investigated the distribution pattern and expression levels of the FMR1 isoforms in asymptomatic premutation carriers and in those with FXTAS and found no significant differences between the two groups. Our findings suggest that the characterization of the expression levels of the different FMR1 isoforms is fundamental for understanding the regulation of the FMR1 gene as imbalance in their expression could lead to an altered functional diversity with neurotoxic consequences. Their characterization will also help to elucidating the mechanism(s) by which "toxic gain of function" of the FMR1 mRNA may play a role in FXTAS and/or in the other FMR1-associated conditions.
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Affiliation(s)
| | - Hiu-Tung Tang
- Biochemistry and Molecular Medicine, UC Davis, Sacramento, CA 95817, USA
| | - Reem Rafik AlOlaby
- Biochemistry and Molecular Medicine, UC Davis, Sacramento, CA 95817, USA
| | - Luke Hickey
- Pacific Biosciences, Inc., Menlo Park, CA 94025, USA
| | - Flora Tassone
- Biochemistry and Molecular Medicine, UC Davis, Sacramento, CA 95817, USA; MIND Institute, UC Davis, Sacramento, CA 95817, USA.
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ESCRT-III Membrane Trafficking Misregulation Contributes To Fragile X Syndrome Synaptic Defects. Sci Rep 2017; 7:8683. [PMID: 28819289 PMCID: PMC5561180 DOI: 10.1038/s41598-017-09103-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 07/19/2017] [Indexed: 12/12/2022] Open
Abstract
The leading cause of heritable intellectual disability (ID) and autism spectrum disorders (ASD), Fragile X syndrome (FXS), is caused by loss of the mRNA-binding translational suppressor Fragile X Mental Retardation Protein (FMRP). In the Drosophila FXS disease model, we found FMRP binds shrub mRNA (human Chmp4) to repress Shrub expression, causing overexpression during the disease state early-use critical period. The FXS hallmark is synaptic overelaboration causing circuit hyperconnectivity. Testing innervation of a central brain learning/memory center, we found FMRP loss and Shrub overexpression similarly increase connectivity. The ESCRT-III core protein Shrub has a central role in endosome-to-multivesicular body membrane trafficking, with synaptic requirements resembling FMRP. Consistently, we found FMRP loss and Shrub overexpression similarly elevate endosomes and result in the arrested accumulation of enlarged intraluminal vesicles within synaptic boutons. Importantly, genetic correction of Shrub levels in the FXS model prevents synaptic membrane trafficking defects and strongly restores innervation. These results reveal a new molecular mechanism underpinning the FXS disease state.
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Detection and Quantification of the Fragile X Mental Retardation Protein 1 (FMRP). Genes (Basel) 2016; 7:genes7120121. [PMID: 27941672 PMCID: PMC5192497 DOI: 10.3390/genes7120121] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 01/11/2023] Open
Abstract
The final product of FMR1 gene transcription, Fragile X Mental Retardation Protein 1 (FMRP), is an RNA binding protein that acts as a repressor of translation. FMRP is expressed in several tissues and plays important roles in neurogenesis, synaptic plasticity, and ovarian functions and has been implicated in a number of neuropsychological disorders. The loss of FMRP causes Fragile X Syndrome (FXS). In most cases, FXS is due to large expansions of a CGG repeat in FMR1—normally containing 6–54 repeats—to over 200 CGGs and identified as full mutation (FM). Hypermethylation of the repeat induces FMR1 silencing and lack of FMRP expression in FM male. Mosaic FM males express low levels of FMRP and present a less severe phenotype that inversely correlates with FMRP levels. Carriers of pre-mutations (55–200 CGG) show increased mRNA, and normal to reduced FMRP levels. Alternative splicing of FMR1 mRNA results in 24 FMRP predicted isoforms whose expression are tissues and developmentally regulated. Here, we summarize the approaches used by several laboratories including our own to (a) detect and estimate the amount of FMRP in different tissues, developmental stages and various pathologies; and (b) to accurately quantifying FMRP for a direct diagnosis of FXS in adults and newborns.
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22
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Ma Y, Tian S, Wang Z, Wang C, Chen X, Li W, Yang Y, He S. CMP‑N‑acetylneuraminic acid synthetase interacts with fragile X related protein 1. Mol Med Rep 2016; 14:1501-8. [PMID: 27357083 PMCID: PMC4940058 DOI: 10.3892/mmr.2016.5438] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 05/25/2016] [Indexed: 11/30/2022] Open
Abstract
Fragile X mental retardation protein (FMRP), fragile X related 1 protein (FXR1P) and FXR2P are the members of the FMR protein family. These proteins contain two KH domains and a RGG box, which are characteristic of RNA binding proteins. The absence of FMRP, causes fragile X syndrome (FXS), the leading cause of hereditary mental retardation. FXR1P is expressed throughout the body and important for normal muscle development, and its absence causes cardiac abnormality. To investigate the functions of FXR1P, a screen was performed to identify FXR1P-interacting proteins and determine the biological effect of the interaction. The current study identified CMP-N-acetylneuraminic acid synthetase (CMAS) as an interacting protein using the yeast two-hybrid system, and the interaction between FXR1P and CMAS was validated in yeast using a β-galactosidase assay and growth studies with selective media. Furthermore, co-immunoprecipitation was used to analyze the FXR1P/CMAS association and immunofluorescence microscopy was performed to detect expression and intracellular localization of the proteins. The results of the current study indicated that FXR1P and CMAS interact, and colocalize in the cytoplasm and the nucleus of HEK293T and HeLa cells. Accordingly, a fragile X related 1 (FXR1) gene overexpression vector was constructed to investigate the effect of FXR1 overexpression on the level of monosialotetrahexosylganglioside 1 (GM1). The results of the current study suggested that FXR1P is a tissue-specific regulator of GM1 levels in SH-SY5Y cells, but not in HEK293T cells. Taken together, the results initially indicate that FXR1P interacts with CMAS, and that FXR1P may enhance the activation of sialic acid via interaction with CMAS, and increase GM1 levels to affect the development of the nervous system, thus providing evidence for further research into the pathogenesis of FXS.
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Affiliation(s)
- Yun Ma
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Shuai Tian
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Zongbao Wang
- Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Institute of Pharmaceutical and Biological Sciences, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Changbo Wang
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Xiaowei Chen
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Wei Li
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Yang Yang
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Shuya He
- Department of Biochemistry & Biology, University of South China, Hengyang, Hunan 421001, P.R. China
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RNA Secondary Structure Modulates FMRP's Bi-Functional Role in the MicroRNA Pathway. Int J Mol Sci 2016; 17:ijms17060985. [PMID: 27338369 PMCID: PMC4926514 DOI: 10.3390/ijms17060985] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 05/23/2016] [Accepted: 06/14/2016] [Indexed: 11/28/2022] Open
Abstract
MicroRNAs act by post-transcriptionally regulating the gene expression of 30%–60% of mammalian genomes. MicroRNAs are key regulators in all cellular processes, though the mechanism by which the cell activates or represses microRNA-mediated translational regulation is poorly understood. In this review, we discuss the RNA binding protein Fragile X Mental Retardation Protein (FMRP) and its role in microRNA-mediated translational regulation. Historically, FMRP is known to function as a translational suppressor. However, emerging data suggests that FMRP has both an agonistic and antagonistic role in regulating microRNA-mediated translational suppression. This bi-functional role is dependent on FMRP’s interaction with the RNA helicase Moloney leukemia virus 10 (MOV10), which modifies the structural landscape of bound mRNA, therefore facilitating or inhibiting its association with the RNA-Induced Silencing Complex.
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Crystal structure reveals specific recognition of a G-quadruplex RNA by a β-turn in the RGG motif of FMRP. Proc Natl Acad Sci U S A 2015; 112:E5391-400. [PMID: 26374839 DOI: 10.1073/pnas.1515737112] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fragile X Mental Retardation Protein (FMRP) is a regulatory RNA binding protein that plays a central role in the development of several human disorders including Fragile X Syndrome (FXS) and autism. FMRP uses an arginine-glycine-rich (RGG) motif for specific interactions with guanine (G)-quadruplexes, mRNA elements implicated in the disease-associated regulation of specific mRNAs. Here we report the 2.8-Å crystal structure of the complex between the human FMRP RGG peptide bound to the in vitro selected G-rich RNA. In this model system, the RNA adopts an intramolecular K(+)-stabilized G-quadruplex structure composed of three G-quartets and a mixed tetrad connected to an RNA duplex. The RGG peptide specifically binds to the duplex-quadruplex junction, the mixed tetrad, and the duplex region of the RNA through shape complementarity, cation-π interactions, and multiple hydrogen bonds. Many of these interactions critically depend on a type I β-turn, a secondary structure element whose formation was not previously recognized in the RGG motif of FMRP. RNA mutagenesis and footprinting experiments indicate that interactions of the peptide with the duplex-quadruplex junction and the duplex of RNA are equally important for affinity and specificity of the RGG-RNA complex formation. These results suggest that specific binding of cellular RNAs by FMRP may involve hydrogen bonding with RNA duplexes and that RNA duplex recognition can be a characteristic RNA binding feature for RGG motifs in other proteins.
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Lyons JI, Kerr GR, Mueller PW. Fragile X Syndrome: Scientific Background and Screening Technologies. J Mol Diagn 2015; 17:463-71. [PMID: 26162330 DOI: 10.1016/j.jmoldx.2015.04.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 03/05/2015] [Accepted: 04/02/2015] [Indexed: 11/26/2022] Open
Abstract
Fragile X is the most common inherited cause of mental retardation with a prevalence of 1 in 4000 for males and 1 in 5000 to 8000 for females. The American College of Medical Genetics and Genomics has recommended diagnostic testing for fragile X in symptomatic persons, women with ovarian dysfunction, and persons with tremor/ataxia syndrome. Although medical and scientific professionals do not currently recommend screening nonsymptomatic populations, improvements in current treatment approaches and ongoing clinical trials have generated growing interest in screening for fragile X. Here, we briefly review the relevant molecular basis of fragile X and fragile X testing and compare three different molecular technologies available for fragile X screening in both males and females. These technologic approaches include destabilizing the CGG-repeat region with betaine and using chimeric CGG-targeted PCR primers, using heat pulses to destabilize C-G bonds in the PCR extension step, and using melting curve analysis to differentiate expanded CGG repeats from normals. The first two-step method performed with high sensitivity and specificity. The second method provided agarose gel images that allow identification of males with expanded CGG repeats and females with expanded CGG-repeat bands which are sometimes faint. The third melting curve analysis method would require controls in each run to correct for shifting optimal cutoff values.
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Affiliation(s)
- Justine I Lyons
- Molecular Risk Assessment Laboratory, Newborn Screening and Molecular Biology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Gregory R Kerr
- Molecular Risk Assessment Laboratory, Newborn Screening and Molecular Biology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Patricia W Mueller
- Molecular Risk Assessment Laboratory, Newborn Screening and Molecular Biology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia.
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26
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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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27
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Kazdoba TM, Leach PT, Silverman JL, Crawley JN. Modeling fragile X syndrome in the Fmr1 knockout mouse. Intractable Rare Dis Res 2014; 3:118-33. [PMID: 25606362 PMCID: PMC4298642 DOI: 10.5582/irdr.2014.01024] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 11/28/2014] [Indexed: 11/05/2022] Open
Abstract
Fragile X Syndrome (FXS) is a commonly inherited form of intellectual disability and one of the leading genetic causes for autism spectrum disorder. Clinical symptoms of FXS can include impaired cognition, anxiety, hyperactivity, social phobia, and repetitive behaviors. FXS is caused by a CGG repeat mutation which expands a region on the X chromosome containing the FMR1 gene. In FXS, a full mutation (> 200 repeats) leads to hypermethylation of FMR1, an epigenetic mechanism that effectively silences FMR1 gene expression and reduces levels of the FMR1 gene product, fragile X mental retardation protein (FMRP). FMRP is an RNA-binding protein that is important for the regulation of protein expression. In an effort to further understand how loss of FMR1 and FMRP contribute to FXS symptomology, several FXS animal models have been created. The most well characterized rodent model is the Fmr1 knockout (KO) mouse, which lacks FMRP protein due to a disruption in its Fmr1 gene. Here, we review the behavioral phenotyping of the Fmr1 KO mouse to date, and discuss the clinical relevance of this mouse model to the human FXS condition. While much remains to be learned about FXS, the Fmr1 KO mouse is a valuable tool for understanding the repercussions of functional loss of FMRP and assessing the efficacy of pharmacological compounds in ameliorating the molecular and behavioral phenotypes relevant to FXS.
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Affiliation(s)
- Tatiana M. Kazdoba
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
- Address correspondence to: Dr. Tatiana M. Kazdoba, MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, Research II Building 96, 4625 2nd Avenue, Sacramento, CA 95817, USA. E-mail:
| | - Prescott T. Leach
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
| | - Jill L. Silverman
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
| | - Jacqueline N. Crawley
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, 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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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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Translational regulation of NeuroD1 expression by FMRP: involvement in glutamatergic neuronal differentiation of cultured rat primary neural progenitor cells. Cell Mol Neurobiol 2013; 34:297-305. [PMID: 24338128 DOI: 10.1007/s10571-013-0014-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 11/27/2013] [Indexed: 10/25/2022]
Abstract
Fragile X mental retardation protein (FMRP) is encoded by Fmr1 gene in which mutation is known to cause fragile X syndrome characterized by mental impairment and other psychiatric symptoms similar to autism spectrum disorders. FMRP plays important roles in cellular mRNA biology such as transport, stability, and translation as an RNA-binding protein. In the present study, we identified potential role of FMRP in the neural differentiation, using cortical neural progenitor cells from Sprague-Dawley rat. We newly found NeuroD1, an essential regulator of glutamatergic neuronal differentiation, as a new mRNA target interacting with FMRP in co-immunoprecipitation experiments. We also identified FMRP as a regulator of neuronal differentiation by modulating NeuroD1 expression. Down-regulation of FMRP by siRNA also increased NeuroD1 expression along with increased pre- and post-synaptic development of glutamatergic neuron, as evidenced by Western blot and immunocytochemistry. On the contrary, cells harboring FMRP over-expression construct showed decreased NeuroD1 expression. Treatment of cultured neural precursor cells with a histone deacetylase inhibitor, valproic acid known as an inducer of hyper-glutamatergic neuronal differentiation, down-regulated the expression of FMRP, and induced NeuroD1 expression. Our study suggests that modulation of FMRP expression regulates neuronal differentiation by interaction with its binding target mRNA, and provides an example of the gene and environmental interaction regulating glutamatergic neuronal differentiation.
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Schmit TL, Dowell JA, Maes ME, Wilhelm M. c-Jun N-terminal kinase regulates mGluR-dependent expression of post-synaptic FMRP target proteins. J Neurochem 2013; 127:772-81. [PMID: 24047560 PMCID: PMC3992883 DOI: 10.1111/jnc.12453] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/11/2013] [Accepted: 09/12/2013] [Indexed: 12/01/2022]
Abstract
Fragile X syndrome (FXS) is caused by the loss of functional fragile X mental retardation protein (FMRP). Loss of FMRP results in an elevated basal protein expression profile of FMRP targeted mRNAs, a loss of local metabotropic glutamate receptor (mGluR)-regulated protein synthesis, exaggerated long-term depression and corresponding learning and behavioral deficits. Evidence shows that blocking mGluR signaling in FXS models ameliorates these deficits. Therefore, understanding the signaling mechanisms downstream of mGluR stimulation may provide additional therapeutic targets for FXS. Kinase cascades are an integral mechanism regulating mGluR-dependent protein translation. The c-Jun N-terminal kinase (JNK) pathway has been shown to regulate mGluR-dependent nuclear transcription; however, the involvement of JNK in local, synaptic signaling has not been explored. Here, we show that JNK is both necessary and sufficient for mGluR-dependent expression of a subset of FMRP target proteins. In addition, JNK activity is basally elevated in fmr1 knockout mouse synapses, and blocking JNK activity reduces the over-expression of post-synaptic proteins in these mice. Together, these data suggest that JNK may be an important signaling mechanism downstream of mGluR stimulation, regulating FMRP-dependent protein synthesis. Furthermore, local, post-synaptic dysregulation of JNK activity may provide a viable target to ameliorate the deficits involved in FXS. Expression of many FMRP target proteins is enhanced in FXS. Here, we evaluated the role of JNKs in FXS. We found that JNK signaling is activated upon mGluR stimulation in wild-type neurons. Conversely, JNK activity is basally elevated in fmr1 knockout. Inhibiting JNK reduced the expression of FMRP target proteins and driving JNK activity increased the expression of these proteins.
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Affiliation(s)
- Travis L Schmit
- Department of Pediatrics and the Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Comprehensive analysis of the transcriptional landscape of the human FMR1 gene reveals two new long noncoding RNAs differentially expressed in Fragile X syndrome and Fragile X-associated tremor/ataxia syndrome. Hum Genet 2013; 133:59-67. [PMID: 24005575 PMCID: PMC3898532 DOI: 10.1007/s00439-013-1356-6] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 08/25/2013] [Indexed: 01/23/2023]
Abstract
The majority of the human genome is transcribed but not translated, giving rise to noncoding RNAs (ncRNAs), including long ncRNAs (lncRNAs, >200 nt) that perform a wide range of functions in gene regulation. The Fragile X mental retardation 1 (FMR1) gene is a microsatellite locus that in the general population contains <55 CGG repeats in its 5′-untranslated region. Expansion of this repeat region to a size of 55-200 CGG repeats, known as premutation, is associated with Fragile X tremor and ataxia syndrome (FXTAS). Further expansion beyond 200 CGG repeats, or full mutation, leads to FMR1 gene silencing and results in Fragile X syndrome (FXS). Using a novel technology called “Deep-RACE”, which combines rapid amplification of cDNA ends (RACE) with next generation sequencing, we systematically interrogated the FMR1 gene locus for the occurrence of novel lncRNAs. We discovered two transcripts, FMR5 and FMR6. FMR5 is a sense lncRNA transcribed upstream of the FMR1 promoter, whereas FMR6 is an antisense transcript overlapping the 3′ region of FMR1. FMR5 was expressed in several human brain regions from unaffected individuals and from full and premutation patients. FMR6 was silenced in full mutation and, unexpectedly, in premutation carriers suggesting abnormal transcription and/or chromatin remodeling prior to transition to the full mutation. These lncRNAs may thus be useful as biomarkers, allowing for early detection and therapeutic intervention in FXS and FXTAS. Finally we show that FMR5 and FMR6 are expressed in peripheral blood leukocytes and propose future studies that correlate lncRNA expression with clinical outcomes.
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Mahboubi H, Seganathy E, Kong D, Stochaj U. Identification of Novel Stress Granule Components That Are Involved in Nuclear Transport. PLoS One 2013; 8:e68356. [PMID: 23826389 PMCID: PMC3694919 DOI: 10.1371/journal.pone.0068356] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 05/31/2013] [Indexed: 11/30/2022] Open
Abstract
Background Importin-α1 belongs to a subfamily of nuclear transport adaptors and participates in diverse cellular functions. Best understood for its role in protein transport, importin-α1 also contributes to other biological processes. For instance, arsenite treatment causes importin-α1 to associate with cytoplasmic stress granules (SGs) in mammalian cells. These stress-induced compartments contain translationally arrested mRNAs, small ribosomal subunits and numerous proteins involved in mRNA transport and metabolism. At present, it is not known whether members of all three importin-α subfamilies locate to SGs in response to stress. Results Here, we demonstrate that the oxidant diethyl maleate (DEM), arsenite and heat shock, promote the formation of cytoplasmic SGs that contain nuclear transport factors. Specifically, importin-α1, α4 and α5, which belong to distinct subfamilies, and importin-β1 were targeted by all of these stressors to cytoplasmic SGs, but not to P-bodies. Importin-α family members have been implicated in transcriptional regulation, which prompted us to analyze their ability to interact with poly(A)-RNA in growing cells. Our studies show that importin-α1, but not α4, α5, importin-β1 or CAS, associated with poly(A)-RNA under nonstress conditions. Notably, this interaction was significantly reduced when cells were treated with DEM. Additional studies suggest that importin-α1 is likely connected to poly(A)-RNA through an indirect interaction, as the adaptor did not bind homopolymer RNA specifically in vitro. Significance Our studies establish that members of three importin-α subfamilies are bona fide SG components under different stress conditions. Furthermore, importin-α1 is unique in its ability to interact with poly(A)-RNA in a stress-dependent fashion, and in vitro experiments indicate that this association is indirect. Collectively, our data emphasize that nuclear transport factors participate in a growing number of cellular activities that are modulated by stress.
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Affiliation(s)
- Hicham Mahboubi
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | | | - Dekun Kong
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Ursula Stochaj
- Department of Physiology, McGill University, Montreal, Quebec, Canada
- * E-mail:
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Long-lasting effects of minocycline on behavior in young but not adult Fragile X mice. Neuroscience 2013; 246:186-98. [PMID: 23660195 DOI: 10.1016/j.neuroscience.2013.04.058] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 04/26/2013] [Accepted: 04/27/2013] [Indexed: 12/18/2022]
Abstract
Fragile X Syndrome (FXS) is the most common single-gene inherited form of intellectual disability with behaviors characteristic of autism. People with FXS display childhood seizures, hyperactivity, anxiety, developmental delay, attention deficits, and visual-spatial memory impairment, as well as a propensity for obsessive-compulsive disorder. Several of these aberrant behaviors and FXS-associated synaptic irregularities also occur in "fragile X mental retardation gene" knock-out (Fmr1 KO) mice. We previously reported that minocycline promotes the maturation of dendritic spines - postsynaptic sites for excitatory synapses - in the developing hippocampus of Fmr1 KO mice, which may underlie the beneficial effects of minocycline on anxiolytic behavior in young Fmr1 KO mice. In this study, we compared the effectiveness of minocycline treatment in young and adult Fmr1 KO mice, and determined the dependence of behavioral improvements on short-term versus long-term minocycline administration. We found that 4- and 8-week-long treatments significantly reduced locomotor activity in both young and adult Fmr1 KO mice. Some behavioral improvements persisted in young mice post-treatment, but in adults the beneficial effects were lost soon after minocycline treatment was stopped. We also show, for the first time, that minocycline treatment partially attenuates the number and severity of audiogenic seizures in Fmr1 KO mice. This report provides further evidence that minocycline treatment has immediate and long-lasting benefits on FXS-associated behaviors in the Fmr1 KO mouse model.
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Di Marino D, Achsel T, Lacoux C, Falconi M, Bagni C. Molecular dynamics simulations show how the FMRP Ile304Asn mutation destabilizes the KH2 domain structure and affects its function. J Biomol Struct Dyn 2013; 32:337-50. [PMID: 23527791 DOI: 10.1080/07391102.2013.768552] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mutations or deletions of FMRP, involved in the regulation of mRNA metabolism in brain, lead to the Fragile X syndrome (FXS), the most frequent form of inherited intellectual disability. A severe manifestation of the disease has been associated with the Ile304Asn mutation, located on the KH2 domain of the protein. Several hypotheses have been proposed to explain the possible molecular mechanism responsible for the drastic effect of this mutation in humans. Here, we performed a molecular dynamics simulation and show that the Ile304Asn mutation destabilizes the hydrophobic core producing a partial unfolding of two α-helices and a displacement of a third one. The affected regions show increased residue flexibility and motion. Molecular docking analysis revealed strongly reduced binding to a model single-stranded nucleic acid in agreement with known data that the two partially unfolded helices form the RNA-binding surface. The third helix, which we show here to be also affected, is involved in the PAK1 protein interaction. These two functional binding sites on the KH2 domain do not overlap spatially, and therefore, they can simultaneously bind their targets. Since the Ile304Asn mutation affects both binding sites, this may justify the severe clinical manifestation observed in the patient in which both mRNA metabolism activity and cytoskeleton remodeling would be affected.
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Affiliation(s)
- Daniele Di Marino
- a VIB Center for the Biology of Disease, Catholic University of Leuven , Herestraat 49, 3000 Leuven , Belgium
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Brackett DM, Qing F, Amieux PS, Sellers DL, Horner PJ, Morris DR. FMR1 transcript isoforms: association with polyribosomes; regional and developmental expression in mouse brain. PLoS One 2013; 8:e58296. [PMID: 23505481 PMCID: PMC3591412 DOI: 10.1371/journal.pone.0058296] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 02/01/2013] [Indexed: 12/31/2022] Open
Abstract
The primary transcript of the mammalian Fragile X Mental Retardation-1 gene (Fmr1), like many transcripts in the central nervous system, is alternatively spliced to yield mRNAs encoding multiple proteins, which can possess quite different biochemical properties. Despite the fact that the relative levels of the 12 Fmr1 transcript isoforms examined here vary by as much as two orders of magnitude amongst themselves in both adult and embryonic mouse brain, all are associated with polyribosomes, consistent with translation into the corresponding isoforms of the protein product, FMRP (Fragile X Mental Retardation Protein). Employing the RiboTag methodology developed in our laboratory, the relative proportions of the 7 most abundant transcript isoforms were measured specifically in neurons and found to be similar to those identified in whole brain. Measurements of isoform profiles across 11 regions of adult brain yielded similar distributions, with the exceptions of the hippocampus and the olfactory bulb. These two regions differ from most of the brain in relative amounts of transcripts encoding an alternate form of one of the KH RNA binding domains. A possible relationship between patterns of expression in the hippocampus and olfactory bulb and the presence of neuroblasts in these two regions is suggested by the isoform patterns in early embryonic brain and in cultured neural progenitor cells. These results demonstrate that the relative levels of the Fmr1 isoforms are modulated according to developmental stage, highlighting the complex ramifications of losing all the protein isoforms in individuals with Fragile X Syndrome. It should also be noted that, of the eight most prominent FMRP isoforms (1–3, 6–9 and 12) in mouse, only two have the major site of phosphorylation at Ser-499, which is thought to be involved in some of the regulatory interactions of this protein.
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Affiliation(s)
- David M. Brackett
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Feng Qing
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Paul S. Amieux
- Department of Pharmacology; University of Washington, Seattle, Washington, United States of America
| | - Drew L. Sellers
- Department of Neurological Surgery, University of Washington, Seattle, Washington, United States of America
| | - Philip J. Horner
- Department of Neurological Surgery, University of Washington, Seattle, Washington, United States of America
| | - David R. Morris
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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Charalambous DC, Pasciuto E, Mercaldo V, Pilo Boyl P, Munck S, Bagni C, Santama N. KIF1Bβ transports dendritically localized mRNPs in neurons and is recruited to synapses in an activity-dependent manner. Cell Mol Life Sci 2013; 70:335-56. [PMID: 22945799 PMCID: PMC11113723 DOI: 10.1007/s00018-012-1108-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 07/17/2012] [Accepted: 07/24/2012] [Indexed: 12/15/2022]
Abstract
KIF1Bβ is a kinesin-like, microtubule-based molecular motor protein involved in anterograde axonal vesicular transport in vertebrate and invertebrate neurons. Certain KIF1Bβ isoforms have been implicated in different forms of human neurodegenerative disease, with characterization of their functional integration and regulation in the context of synaptic signaling still ongoing. Here, we characterize human KIF1Bβ (isoform NM015074), whose expression we show to be developmentally regulated and elevated in cortical areas of the CNS (including the motor cortex), in the hippocampus, and in spinal motor neurons. KIF1Bβ localizes to the cell body, axon, and dendrites, overlapping with synaptic-vesicle and postsynaptic-density structures. Correspondingly, in purified cortical synaptoneurosomes, KIF1Bβ is enriched in both pre- and postsynaptic structures, forming detergent-resistant complexes. Interestingly, KIF1Bβ forms RNA-protein complexes, containing the dendritically localized Arc and Calmodulin mRNAs, proteins previously shown to be part of RNA transport granules such as Purα, FMRP and FXR2P, and motor protein KIF3A, as well as Calmodulin. The interaction between KIF1Bβ and Calmodulin is Ca(+2)-dependent and takes place through a domain mapped at the carboxy-terminal tail of the motor. Live imaging of cortical neurons reveals active movement by KIF1Bβ at dendritic processes, suggesting that it mediates the transport of dendritically localized mRNAs. Finally, we show that synaptic recruitment of KIF1Bβ is activity-dependent and increased by stimulation of metabotropic or ionotropic glutamate receptors. The activity-dependent synaptic recruitment of KIF1Bβ, its interaction with Ca(2+) sensor Calmodulin, and its new role as a dendritic motor of ribonucleoprotein complexes provide a novel basis for understanding the concerted co-ordination of motor protein mobilization and synaptic signaling pathways.
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Affiliation(s)
- Despina C. Charalambous
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678 Nicosia, Cyprus
| | - Emanuela Pasciuto
- VIB Center for Biology of Disease, Katholieke Universiteit Leuven, Heresraat 49, 3000 Leuven, Belgium
| | - Valentina Mercaldo
- VIB Center for Biology of Disease, Katholieke Universiteit Leuven, Heresraat 49, 3000 Leuven, Belgium
- Present Address: Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Pietro Pilo Boyl
- VIB Center for Biology of Disease, Katholieke Universiteit Leuven, Heresraat 49, 3000 Leuven, Belgium
- Present Address: Institute of Genetics, University of Bonn, Karlrobert-Kreiten Str. 13, 53115 Bonn, Germany
| | - Sebastian Munck
- VIB Center for Biology of Disease, Katholieke Universiteit Leuven, Heresraat 49, 3000 Leuven, Belgium
| | - Claudia Bagni
- VIB Center for Biology of Disease, Katholieke Universiteit Leuven, Heresraat 49, 3000 Leuven, Belgium
- Department of Biomedicine and Prevention, Faculty of Medicine, University of Rome Tor Vergata, Via Montpellier 1, 00100 Rome, Italy
| | - Niovi Santama
- Department of Biological Sciences, University of Cyprus, University Avenue 1, 1678 Nicosia, Cyprus
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FMRP targets distinct mRNA sequence elements to regulate protein expression. Nature 2012; 492:382-6. [PMID: 23235829 PMCID: PMC3528815 DOI: 10.1038/nature11737] [Citation(s) in RCA: 524] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 11/02/2012] [Indexed: 12/16/2022]
Abstract
Fragile-X Syndrome (FXS) is a multi-organ disease leading to mental retardation, macro-orchidism in males, and premature ovarian insufficiency in female carriers. FXS is also a prominent monogenic disease associated with autism spectrum disorders (ASD). FXS is typically caused by the loss of FRAGILE X-MENTAL RETARDATION 1 (FMR1) expression, which encodes for the RNA-binding protein (RBP), FMRP. We report the discovery of distinct RNA recognition elements (RREs) that correspond to the two independent RNA binding domains of FMRP, and the binding sites within the mRNA targets for wild-type and I304N mutant FMRP isoforms and its paralogs, FXR1 and FXR2. RRE frequency, ratio, and distribution determine target mRNA association with FMRP. Among highly-enriched targets, we identified many genes involved in ASD and demonstrate that FMRP affects their protein levels in cell culture, mice, and human brain. Unexpectedly, we discovered that these targets are also dysregulated in Fmr1-/- mouse ovaries, showing signs of premature follicular overdevelopment. These results indicate that FMRP targets shared signaling pathways across different cellular contexts. As it is become increasingly appreciated that signaling pathways are important to FXS and ASD, our results here provide a molecular guide towards the pursuit of novel therapeutic targets for these neurological disorders.
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Wang H, Morishita Y, Miura D, Naranjo JR, Kida S, Zhuo M. Roles of CREB in the regulation of FMRP by group I metabotropic glutamate receptors in cingulate cortex. Mol Brain 2012; 5:27. [PMID: 22867433 PMCID: PMC3478997 DOI: 10.1186/1756-6606-5-27] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Accepted: 08/02/2012] [Indexed: 12/04/2022] Open
Abstract
Background Fragile X syndrome is caused by lack of fragile X mental retardation protein (FMRP) due to silencing of the FMR1 gene. The metabotropic glutamate receptors (mGluRs) in the central nervous system contribute to higher brain functions including learning/memory, mental disorders and persistent pain. The transcription factor cyclic AMP-responsive element binding protein (CREB) is involved in important neuronal functions, such as synaptic plasticity and neuronal survival. Our recent study has shown that stimulation of Group I mGluRs upregulated FMRP and activated CREB in anterior cingulate cortex (ACC), a key region for brain cognitive and executive functions, suggesting that activation of Group I mGluRs may upregulate FMRP through CREB signaling pathway. Results In this study, we demonstrate that CREB contributes to the regulation of FMRP by Group I mGluRs. In ACC neurons of adult mice overexpressing dominant active CREB mutant, the upregulation of FMRP by stimulating Group I mGluR is enhanced compared to wild-type mice. However, the regulation of FMRP by Group I mGluRs is not altered by overexpression of Ca2+-insensitive mutant form of downstream regulatory element antagonist modulator (DREAM), a transcriptional repressor involved in synaptic transmission and plasticity. Conclusion Our study has provided further evidence for CREB involvement in regulation of FMRP by Group I mGluRs in ACC neurons, and may help to elucidate the pathogenesis of fragile X syndrome.
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Affiliation(s)
- Hansen Wang
- Department of Physiology, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada
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Musiyenko A, Majumdar T, Andrews J, Adams B, Barik S. PRMT1 methylates the single Argonaute of Toxoplasma gondii and is important for the recruitment of Tudor nuclease for target RNA cleavage by antisense guide RNA. Cell Microbiol 2012; 14:882-901. [PMID: 22309152 DOI: 10.1111/j.1462-5822.2012.01763.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Argonaute (Ago) plays a central role in RNA interference in metazoans, but its status in lower organisms remains ill-defined. We report on the Ago complex of the unicellular protozoan, Toxoplasma gondii (Tg), an obligatory pathogen of mammalian hosts. The PIWI-like domain of TgAgo lacked the canonical DDE/H catalytic triad, explaining its weak target RNA cleavage activity. However, TgAgo associated with a stronger RNA slicer, a Tudor staphylococcal nuclease (TSN), and with a protein Arg methyl transferase, PRMT1. Mutational analysis suggested that the N-terminal RGG-repeat domain of TgAgo was methylated by PRMT1, correlating with the recruitment of TSN. The slicer activity of TgAgo was Mg(2+)-dependent and required perfect complementarity between the guide RNA and the target. In contrast, the TSN activity was Ca(2+) -dependent and required an imperfectly paired guide RNA. Ago knockout parasites showed essentially normal growth, but in contrast, the PRMT1 knockouts grew abnormally. Chemical inhibition of Arg-methylation also had an anti-parasitic effect. These results suggest that the parasitic PRMT1 plays multiple roles, and its loss affects the recruitment of a more potent second slicer to the parasitic RNA silencing complex, the exact mechanism of which remains to be determined.
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Affiliation(s)
- Alla Musiyenko
- Department of Biochemistry and Molecular Biology, University of South Alabama, College of Medicine, 307 University Blvd., Mobile, Alabama, USA
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Kindler S, Kreienkamp HJ. The role of the postsynaptic density in the pathology of the fragile X syndrome. Results Probl Cell Differ 2012; 54:61-80. [PMID: 22009348 DOI: 10.1007/978-3-642-21649-7_5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The protein repertoire of excitatory synapses controls dendritic spine morphology, synaptic plasticity and higher brain functions. In brain neurons, the RNA-associated fragile X mental retardation protein (FMRP) binds in vivo to various transcripts encoding key postsynaptic components and may thereby substantially regulate the molecular composition of dendritic spines. In agreement with this notion functional loss of FMRP in patients affected by the fragile X syndrome (FXS) causes cognitive impairment. Here we address our current understanding of the functional role of individual postsynaptic proteins. We discuss how FMRP controls the abundance of select proteins at postsynaptic sites, which signaling pathways regulate the local activity of FMRP at synapses, and how altered levels of postsynaptic proteins may contribute to FXS pathology.
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Affiliation(s)
- Stefan Kindler
- Institute for Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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42
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Mines MA, Jope RS. Glycogen synthase kinase-3: a promising therapeutic target for fragile x syndrome. Front Mol Neurosci 2011; 4:35. [PMID: 22053151 PMCID: PMC3205455 DOI: 10.3389/fnmol.2011.00035] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2011] [Accepted: 10/08/2011] [Indexed: 12/26/2022] Open
Abstract
Recent advances in understanding the pathophysiological mechanisms contributing to fragile X syndrome (FXS) have increased optimism that drug interventions can provide significant therapeutic benefits. FXS results from inadequate expression of functional fragile X mental retardation protein (FMRP). FMRP may have several functions, but it is most well-established as an RNA binding protein that regulates translation, and it is thought that by this mechanism FMRP is capable of affecting numerous cellular processes by selectively regulating protein levels. The multiple cellular functions regulated by FMRP suggest that multiple interventions may be required for reversing the effects of deficient FMRP. Evidence that inhibitors of glycogen synthase kinase-3 (GSK3) may contribute to the therapeutic treatment of FXS is reviewed here. Lithium, a GSK3 inhibitor, improved function in the Drosophila model of FXS. In mice lacking FMRP expression (FX mice), GSK3 is hyperactive in several brain regions. Significant improvements in several FX-related phenotypes have been obtained in FX mice following the administration of lithium, and in some case other GSK3 inhibitors. These responses include normalization of heightened audiogenic seizure susceptibility and of hyperactive locomotor behavior, enhancement of passive avoidance learning retention and of sociability behaviors, and corrections of macroorchidism, neuronal spine density, and neural plasticity measured electrophysiologically as long term depression. A pilot clinical trial of lithium in patients with FXS also found improvements in several measures of behavior. Taken together, these findings indicate that lithium and other inhibitors of GSK3 are promising candidate therapeutic agents for treating FXS.
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Affiliation(s)
- Marjelo A. Mines
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at BirminghamBirmingham, AL, USA
| | - Richard S. Jope
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at BirminghamBirmingham, AL, USA
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43
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Mattis VB, Svendsen CN. Induced pluripotent stem cells: a new revolution for clinical neurology? Lancet Neurol 2011; 10:383-94. [PMID: 21435601 DOI: 10.1016/s1474-4422(11)70022-9] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Why specific neuronal populations are uniquely susceptible in neurodegenerative diseases remains a mystery. Brain tissue samples from patients are rarely available for testing, and animal models frequently do not recapitulate all features of a specific disorder; therefore, pathophysiological investigations are difficult. An exciting new avenue for neurological research and drug development is the discovery that patients' somatic cells can be reprogrammed to a pluripotent state; these cells are known as induced pluripotent stem cells. Once pluripotency is reinstated, cell colonies can be expanded and differentiated into specific neural populations. The availability of these cells enables the monitoring in vitro of temporal features of disease initiation and progression, and testing of new drug treatments on the patient's own cells. Hence, this swiftly growing area of research has the potential to contribute greatly to our understanding of the pathophysiology of neurodegenerative and neurodevelopmental diseases.
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Affiliation(s)
- Virginia B Mattis
- Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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44
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Ji X, Sun H, Zhou H, Xiang J, Tang Y, Zhao C. Research Progress of RNA Quadruplex. Nucleic Acid Ther 2011; 21:185-200. [DOI: 10.1089/nat.2010.0272] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Xiaohui Ji
- Key Laboratory for Cell Proliferation and Regulation Biology of Ministry of Education, Beijing Key Laboratory of Gene Engineering Drugs and Biological Technology, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Hongxia Sun
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Huaxi Zhou
- Department of Systems Science, School of Management, Beijing Normal University, Beijing, China
| | - Junfeng Xiang
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Yalin Tang
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Changqi Zhao
- Key Laboratory for Cell Proliferation and Regulation Biology of Ministry of Education, Beijing Key Laboratory of Gene Engineering Drugs and Biological Technology, College of Life Sciences, Beijing Normal University, Beijing, China
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45
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Yan X, Denman RB. Conformational-dependent and independent RNA binding to the fragile x mental retardation protein. J Nucleic Acids 2011; 2011:246127. [PMID: 21772992 PMCID: PMC3136132 DOI: 10.4061/2011/246127] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 03/16/2011] [Indexed: 01/13/2023] Open
Abstract
The interaction between the fragile X mental retardation protein (FMRP) and BC1 RNA has been the subject of controversy. We probed the parameters of RNA binding to FMRP in several ways. Nondenaturing agarose gel analysis showed that BC1 RNA transcripts produced by in vitro transcription contain a population of conformers, which can be modulated by preannealing. Accordingly, FMRP differentially binds to the annealed and unannealed conformer populations. Using partial RNase digestion, we demonstrate that annealed BC1 RNA contains a unique conformer that FMRP likely binds. We further demonstrate that this interaction is 100-fold weaker than that the binding of eEF-1A mRNA and FMRP, and that preannealing is not a general requirement for FMRP's interaction with RNA. In addition, binding does not require the N-terminal 204 amino acids of FMRP, methylated arginine residues and can be recapitulated by both fragile X paralogs. Altogether, our data continue to support a model in which BC1 RNA functions independently of FMRP.
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Affiliation(s)
- Xin Yan
- CSI/IBR Center for Developmental Neuroscience, College of Staten Island, City University of New York, Staten Island, NY 10314, USA
| | - Robert B. Denman
- Biochemical Molecular Neurobiology Laboratory, Department of Molecular Biology, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314, USA
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46
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Ji X, Sun H, Zhou H, Xiang J, Tang Y, Zhao C. Research Progress of RNA Quadruplex. Oligonucleotides 2011:121102072334007. [PMID: 21574857 DOI: 10.1089/oli.2010.0272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
RNA/DNA sequences rich in guanine (G) can form a 4-strand structure, G-quadruplex, which has been extensively researched and observed in mammalian, fungi, and plants, with in vivo existence in eukaryotic cells. Compared with DNA quadruplex, the potential existence of RNA quadruplex appears to be generally rare; however, it is believed by some researchers to be more inevitable in vivo and speculated to play an important role where it exists. Recently, researches concerning the function of G-quadruplexes in RNAs commence, making much progress. However, there is no available review particularly focusing on RNA quadruplex till now as we know. Therefore, we decide to give a review to comprehensively summarize research progress on it. This review highlights the diverse topologies for RNA quadruplex structure and its effect factors; outlines the current knowledge of RNA quadruplex's physiological functions in biological systems, especially in gene expression; and presents the prospects of RNA quadruplex.
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Affiliation(s)
- Xiaohui Ji
- 1 Key Laboratory for Cell Proliferation and Regulation Biology of Ministry of Education, Beijing Key Laboratory of Gene Engineering Drugs and Biological Technology, College of Life Sciences, Beijing Normal University , Beijing, China
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Sjekloća L, Pauwels K, Pastore A. On the aggregation properties of FMRP - a link with the FXTAS syndrome? FEBS J 2011; 278:1912-21. [DOI: 10.1111/j.1742-4658.2011.08108.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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48
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Beerman RW, Jongens TA. A non-canonical start codon in the Drosophila fragile X gene yields two functional isoforms. Neuroscience 2011; 181:48-66. [PMID: 21333716 DOI: 10.1016/j.neuroscience.2011.02.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 02/10/2011] [Accepted: 02/12/2011] [Indexed: 02/07/2023]
Abstract
Fragile X syndrome is caused by the loss of expression of the fragile X mental retardation protein (FMRP). As a RNA binding protein, FMRP functions in translational regulation, localization, and stability of its neuronal target transcripts. The Drosophila homologue, dFMR1, is well conserved in sequence and function with respect to human FMRP. Although dFMR1 is known to express two main isoforms, the mechanism behind production of the second, more slowly migrating isoform has remained elusive. Furthermore, it remains unknown whether the two isoforms may also contribute differentially to dFMR1 function. We have found that this second dFMR1 isoform is generated through an alternative translational start site in the dfmr1 5'UTR. This 5'UTR coding sequence is well conserved in the melanogaster group. Translation of the predominant, smaller form of dFMR1 (dFMR1-S(N)) begins at a canonical start codon (ATG), whereas translation of the minor, larger form (dFMR1-L(N)) begins upstream at a non-canonical start codon (CTG). To assess the contribution of the N-terminal extension toward dFMR1 activity, we generated transgenic flies that exclusively express either dFMR1-S(N) or dFMR1-L(N). Expression analyses throughout development revealed that dFMR1-S(N) is required for normal dFMR1-L(N) expression levels in adult brains. In situ expression analyses showed that either dFMR1-S(N) or dFMR1-L(N) is individually sufficient for proper dFMR1 localization in the nervous system. Functional studies demonstrated that both dFMR1-S(N) and dFMR1-L(N) can function independently to rescue dfmr1 null defects in synaptogenesis and axon guidance. Thus, dfmr1 encodes two functional isoforms with respect to expression and activity throughout neuronal development.
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Affiliation(s)
- R W Beerman
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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49
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Fatemi SH, Folsom TD. The role of fragile X mental retardation protein in major mental disorders. Neuropharmacology 2010; 60:1221-6. [PMID: 21108954 DOI: 10.1016/j.neuropharm.2010.11.011] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 11/04/2010] [Accepted: 11/11/2010] [Indexed: 12/14/2022]
Abstract
Fragile X mental retardation protein (FMRP) is highly enriched in neurons and binds to approximately 4% of mRNAs in mammalian brain. Its loss is a hallmark of fragile X syndrome (FXS), the most common form of mental retardation. In this review we discuss the mutation in the fragile X mental retardation-1 gene (FMR1), that leads to FXS, the role FMRP plays in neuronal cells, experiments from our own laboratory that demonstrate reductions of FMRP in additional psychiatric disorders (autism, schizophrenia, bipolar disorder, and major depressive disorder), and potential therapies to ameliorate the loss of FMRP. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.
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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.
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50
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Bhogal B, Jongens TA. Fragile X syndrome and model organisms: identifying potential routes of therapeutic intervention. Dis Model Mech 2010; 3:693-700. [PMID: 20682752 DOI: 10.1242/dmm.002006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fragile X syndrome (FXS) is a cognitive disorder caused by silencing of the fragile X mental retardation 1 gene (FMR1). Since the discovery of the gene almost two decades ago, most scientific contributions have focused on identifying the molecular function of the fragile X mental retardation protein (FMRP) and understanding how absence of FMR1 gene expression gives rise to the disease phenotypes. The use of model organisms has allowed rapid progression in the FXS field and has given insight into the molecular basis of the disease. The mouse and fly FXS models have enabled studies to identify potential targets and pathways for pharmacological treatment. Here, we briefly review the two primary FXS model systems and describe how studies in these organisms have led us closer to therapeutic treatments for patients afflicted with FXS.
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Affiliation(s)
- Balpreet Bhogal
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6145, USA
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