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Falcão M, Monteiro P, Jacinto L. Tactile sensory processing deficits in genetic mouse models of autism spectrum disorder. J Neurochem 2024; 168:2105-2123. [PMID: 38837765 DOI: 10.1111/jnc.16135] [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: 04/21/2024] [Revised: 05/04/2024] [Accepted: 05/07/2024] [Indexed: 06/07/2024]
Abstract
Altered sensory processing is a common feature in autism spectrum disorder (ASD), as recognized in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Although altered responses to tactile stimuli are observed in over 60% of individuals with ASD, the neurobiological basis of this phenomenon is poorly understood. ASD has a strong genetic component and genetic mouse models can provide valuable insights into the mechanisms underlying tactile abnormalities in ASD. This review critically addresses recent findings regarding tactile processing deficits found in mouse models of ASD, with a focus on behavioral, anatomical, and functional alterations. Particular attention was given to cellular and circuit-level functional alterations, both in the peripheral and central nervous systems, with the objective of highlighting possible convergence mechanisms across models. By elucidating the impact of mutations in ASD candidate genes on somatosensory circuits and correlating them with behavioral phenotypes, this review significantly advances our understanding of tactile deficits in ASD. Such insights not only broaden our comprehension but also pave the way for future therapeutic interventions.
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Affiliation(s)
- Margarida Falcão
- Department of Biomedicine-Experimental Biology Unit, Faculty of Medicine of the University of Porto (FMUP), Porto, Portugal
| | - Patricia Monteiro
- Department of Biomedicine-Experimental Biology Unit, Faculty of Medicine of the University of Porto (FMUP), Porto, Portugal
| | - Luis Jacinto
- Department of Biomedicine-Experimental Biology Unit, Faculty of Medicine of the University of Porto (FMUP), Porto, Portugal
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Boutet I, Collin CA, MacLeod LS, Messier C, Holahan MR, Berry-Kravis E, Gandhi RM, Kogan CS. Utility of the Hebb-Williams Maze Paradigm for Translational Research in Fragile X Syndrome: A Direct Comparison of Mice and Humans. Front Mol Neurosci 2018; 11:99. [PMID: 29643767 PMCID: PMC5882825 DOI: 10.3389/fnmol.2018.00099] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/13/2018] [Indexed: 11/26/2022] Open
Abstract
To generate meaningful information, translational research must employ paradigms that allow extrapolation from animal models to humans. However, few studies have evaluated translational paradigms on the basis of defined validation criteria. We outline three criteria for validating translational paradigms. We then evaluate the Hebb–Williams maze paradigm (Hebb and Williams, 1946; Rabinovitch and Rosvold, 1951) on the basis of these criteria using Fragile X syndrome (FXS) as model disease. We focused on this paradigm because it allows direct comparison of humans and animals on tasks that are behaviorally equivalent (criterion #1) and because it measures spatial information processing, a cognitive domain for which FXS individuals and mice show impairments as compared to controls (criterion #2). We directly compared the performance of affected humans and mice across different experimental conditions and measures of behavior to identify which conditions produce comparable patterns of results in both species. Species differences were negligible for Mazes 2, 4, and 5 irrespective of the presence of visual cues, suggesting that these mazes could be used to measure spatial learning in both species. With regards to performance on the first trial, which reflects visuo-spatial problem solving, Mazes 5 and 9 without visual cues produced the most consistent results. We conclude that the Hebb–Williams mazes paradigm has the potential to be utilized in translational research to measure comparable cognitive functions in FXS humans and animals (criterion #3).
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Affiliation(s)
- Isabelle Boutet
- School of Psychology, University of Ottawa, Ottawa, ON, Canada
| | | | | | - Claude Messier
- School of Psychology, University of Ottawa, Ottawa, ON, Canada
| | | | - Elizabeth Berry-Kravis
- Pediatrics, Biochemistry, and Neurology, Rush University Medical Center, Chicago, IL, United States
| | - Reno M Gandhi
- School of Psychology, University of Ottawa, Ottawa, ON, Canada
| | - Cary S Kogan
- School of Psychology, University of Ottawa, Ottawa, ON, Canada
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Zorio DAR, Jackson CM, Liu Y, Rubel EW, Wang Y. Cellular distribution of the fragile X mental retardation protein in the mouse brain. J Comp Neurol 2017; 525:818-849. [PMID: 27539535 PMCID: PMC5558202 DOI: 10.1002/cne.24100] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 08/10/2016] [Accepted: 08/11/2016] [Indexed: 11/07/2022]
Abstract
The fragile X mental retardation protein (FMRP) plays an important role in normal brain development. Absence of FMRP results in abnormal neuronal morphologies in a selected manner throughout the brain, leading to intellectual deficits and sensory dysfunction in the fragile X syndrome (FXS). Despite FMRP importance for proper brain function, its overall expression pattern in the mammalian brain at the resolution of individual neuronal cell groups is not known. In this study we used FMR1 knockout and isogenic wildtype mice to systematically map the distribution of FMRP expression in the entire mouse brain. Using immunocytochemistry and cellular quantification analyses, we identified a large number of prominent cell groups expressing high levels of FMRP at the subcortical levels, in particular sensory and motor neurons in the brainstem and thalamus. In contrast, many cell groups in the midbrain and hypothalamus exhibit low FMRP levels. More important, we describe differential patterns of FMRP distribution in both cortical and subcortical brain regions. Almost all major brain areas contain high and low levels of FMRP cell groups adjacent to each other or between layers of the same cortical areas. These differential patterns indicate that FMRP expression appears to be specific to individual neuronal cell groups instead of being associated with all neurons in distinct brain regions, as previously considered. Taken together, these findings support the notion of FMRP differential neuronal regulation and strongly implicate the contribution of fundamental sensory and motor processing at subcortical levels to FXS pathology. J. Comp. Neurol. 525:818-849, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Diego A. R. Zorio
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Christine M. Jackson
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Yong Liu
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
| | - Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Box 357923, Seattle, WA 98195, USA
| | - Yuan Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
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Franklin AV, King MK, Palomo V, Martinez A, McMahon LL, Jope RS. Glycogen synthase kinase-3 inhibitors reverse deficits in long-term potentiation and cognition in fragile X mice. Biol Psychiatry 2014; 75:198-206. [PMID: 24041505 PMCID: PMC3874248 DOI: 10.1016/j.biopsych.2013.08.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/30/2013] [Accepted: 08/01/2013] [Indexed: 11/30/2022]
Abstract
BACKGROUND Identifying feasible therapeutic interventions is crucial for ameliorating the intellectual disability and other afflictions of fragile X syndrome (FXS), the most common inherited cause of intellectual disability and autism. Hippocampal glycogen synthase kinase-3 (GSK3) is hyperactive in the mouse model of FXS (FX mice), and hyperactive GSK3 promotes locomotor hyperactivity and audiogenic seizure susceptibility in FX mice, raising the possibility that specific GSK3 inhibitors may improve cognitive processes. METHODS We tested if specific GSK3 inhibitors improve deficits in N-methyl-D-aspartate receptor-dependent long-term potentiation at medial perforant path synapses onto dentate granule cells and dentate gyrus-dependent cognitive behavioral tasks. RESULTS GSK3 inhibitors completely rescued deficits in long-term potentiation at medial perforant path-dentate granule cells synapses in FX mice. Furthermore, synaptosomes from the dentate gyrus of FX mice displayed decreased inhibitory serine-phosphorylation of GSK3β compared with wild-type littermates. The potential therapeutic utility of GSK3 inhibitors was further tested on dentate gyrus-dependent cognitive behaviors. In vivo administration of GSK3 inhibitors completely reversed impairments in several cognitive tasks in FX mice, including novel object detection, coordinate and categorical spatial processing, and temporal ordering for visual objects. CONCLUSIONS These findings establish that synaptic plasticity and cognitive deficits in FX mice can be improved by intervention with inhibitors of GSK3, which may prove therapeutically beneficial in FXS.
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Affiliation(s)
- Aimee V. Franklin
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Margaret K. King
- Departments of Psychiatry and Behavioral Sciences and Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136
| | - Valle Palomo
- Instituto Quimica Medica-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
| | - Ana Martinez
- Instituto Quimica Medica-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
| | - Lori L. McMahon
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Richard S. Jope
- Departments of Psychiatry and Behavioral Sciences and Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136,Corresponding author: Richard S. Jope, Miller School of Medicine, University of Miami, 1011 NW 15th Street, Gautier Building room 416, Miami, Florida 33136, phone: 305-243-0262,
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Fish EW, Krouse MC, Stringfield SJ, DiBerto JF, Robinson JE, Malanga CJ. Changes in sensitivity of reward and motor behavior to dopaminergic, glutamatergic, and cholinergic drugs in a mouse model of fragile X syndrome. PLoS One 2013; 8:e77896. [PMID: 24205018 PMCID: PMC3799757 DOI: 10.1371/journal.pone.0077896] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 09/05/2013] [Indexed: 12/22/2022] Open
Abstract
Fragile X syndrome (FXS) is a leading cause of intellectual disability. FXS is caused by loss of function of the FMR1 gene, and mice in which Fmr1 has been inactivated have been used extensively as a preclinical model for FXS. We investigated the behavioral pharmacology of drugs acting through dopaminergic, glutamatergic, and cholinergic systems in fragile X (Fmr1 (-/Y)) mice with intracranial self-stimulation (ICSS) and locomotor activity measurements. We also measured brain expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in dopamine biosynthesis. Fmr1 (-/Y) mice were more sensitive than wild type mice to the rewarding effects of cocaine, but less sensitive to its locomotor stimulating effects. Anhedonic but not motor depressant effects of the atypical neuroleptic, aripiprazole, were reduced in Fmr1 (-/Y) mice. The mGluR5-selective antagonist, 6-methyl-2-(phenylethynyl)pyridine (MPEP), was more rewarding and the preferential M1 antagonist, trihexyphenidyl, was less rewarding in Fmr1 (-/Y) than wild type mice. Motor stimulation by MPEP was unchanged, but stimulation by trihexyphenidyl was markedly increased, in Fmr1 (-/Y) mice. Numbers of midbrain TH+ neurons in the ventral tegmental area were unchanged, but were lower in the substantia nigra of Fmr1 (-/Y) mice, although no changes in TH levels were found in their forebrain targets. The data are discussed in the context of known changes in the synaptic physiology and pharmacology of limbic motor systems in the Fmr1 (-/Y) mouse model. Preclinical findings suggest that drugs acting through multiple neurotransmitter systems may be necessary to fully address abnormal behaviors in individuals with FXS.
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Affiliation(s)
- Eric W. Fish
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Michael C. Krouse
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Sierra J. Stringfield
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Jeffrey F. DiBerto
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - J. Elliott Robinson
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - C. J. Malanga
- Department of Neurology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Carolina Institute for Developmental Disabilities, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail:
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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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King MK, Jope RS. Lithium treatment alleviates impaired cognition in a mouse model of fragile X syndrome. GENES BRAIN AND BEHAVIOR 2013; 12:723-31. [PMID: 23941202 DOI: 10.1111/gbb.12071] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 07/20/2013] [Accepted: 08/08/2013] [Indexed: 02/04/2023]
Abstract
Fragile X syndrome (FXS) is caused by suppressed expression of fragile X mental retardation protein (FMRP), which results in intellectual disability accompanied by many variably manifested characteristics, such as hyperactivity, seizures and autistic-like behaviors. Treatment of mice that lack FMRP, Fmr1 knockout (KO) mice, with lithium has been reported to ameliorate locomotor hyperactivity, prevent hypersensitivity to audiogenic seizures, improve passive avoidance behavior and attenuate sociability deficits. To focus on the defining characteristic of FXS, which is cognitive impairment, we tested if lithium treatment ameliorated impairments in four cognitive tasks in Fmr1 KO mice, tested if the response to lithium differed in adolescent and adult mice and tested if therapeutic effects persisted after discontinuation of lithium administration. Fmr1 KO mice displayed impaired cognition in the novel object detection task, temporal ordering for objects task and coordinate and categorical spatial processing tasks. Chronic lithium treatment of adolescent (from 4 to 8 weeks of age) and adult (from 8 to 12 weeks of age) mice abolished cognitive impairments in all four cognitive tasks. Cognitive deficits returned after lithium treatment was discontinued for 4 weeks. These results show that Fmr1 KO mice exhibit severe impairments in these cognitive tasks, that lithium is equally effective in normalizing cognition in these tasks whether it is administered to young or adult mice and that lithium administration must be continued for the cognitive improvements to be sustained. These findings provide further evidence that lithium administration may be beneficial for individuals with FXS.
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Affiliation(s)
- M K King
- Department of Psychiatry and Behavioral Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA
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8
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Unstable Repeat Expansion in Neurodegenerative Dementias: Mechanisms of Disease. Dement Neurocogn Disord 2012. [DOI: 10.12779/dnd.2012.11.1.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Veeraragavan S, Bui N, Perkins JR, Yuva-Paylor LA, Paylor R. The modulation of fragile X behaviors by the muscarinic M4 antagonist, tropicamide. Behav Neurosci 2011; 125:783-90. [PMID: 21942438 PMCID: PMC3183989 DOI: 10.1037/a0025202] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Muscarinic acetylcholine receptors (mAChR) are G protein-coupled receptors (M1-M5), grouped together into two functional classes, based on their G protein interaction. Although ubiquitously expressed in the CNS, the M4 protein shows highest expression in the neostriatum, cortex, and hippocampus. Electrophysiological and biochemical studies have provided evidence for overactive mAChR signaling in the fragile X knock-out (Fmr1KO) mouse model, and this has been hypothesized to contribute to the phenotypes seen in Fmr1KO mice. To address this hypothesis we used an M4 antagonist, tropicamide, to reduce the activity through the M4 mAChR and investigated the behavioral response in the Fmr1KO animals. Data from the marble-burying assay have shown that tropicamide treatment resulted in a decreased number of marbles buried in the wild-type (WT) and in the knockout (KO) animals. Results from the open field assay indicated that tropicamide increases activity in both the WT and KO mice. In the passive avoidance assay, tropicamide treatment resulted in the improvement of performance in both the WT and the KO animals at the lower doses (2 and 5 mg/kg), and the drug was shown to be important for the acquisition and not the consolidation process. Lastly, we observed that tropicamide causes a significant decrease in the percentage of audiogenic seizures in the Fmr1KO animals. These results suggest that pharmacological antagonism of the M4 receptor modulates select behavioral responses in the Fmr1KO mice.
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Affiliation(s)
- Surabi Veeraragavan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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Modulation of behavioral phenotypes by a muscarinic M1 antagonist in a mouse model of fragile X syndrome. Psychopharmacology (Berl) 2011; 217:143-51. [PMID: 21487657 DOI: 10.1007/s00213-011-2276-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 03/14/2011] [Indexed: 12/12/2022]
Abstract
RATIONALE Muscarinic acetylcholine receptors (mAChR) are G protein-coupled receptors, widely expressed in the CNS. Electrophysiological and molecular studies have provided evidence for overactive M1 receptor signaling in the fragile X knockout (Fmr1 KO) mouse model, suggesting the involvement of the M1 receptors in fragile X syndrome. Overactive signaling through the M1 receptor has been hypothesized to contribute to the phenotypes seen in fragile X mice. OBJECTIVE We investigated the modulation of behavioral responses in the Fmr1 KO animals by reducing the activity through the muscarinic M1 receptor using the pharmacological agent dicyclomine, an M1 antagonist. METHODS The behavioral assays used to investigate the pharmacological effects include marble burying (perseverative behavior), open-field exploration (activity), passive avoidance (learning and memory), prepulse inhibition (sensorimotor gating), and audiogenic seizures. RESULTS Data from the marble-burying assay suggests that treatment with dicyclomine results in a decrease in the number of marbles buried in the wild-type and in the KO animals. To examine the possibility of drug-induced sedation, overall activity was measured in an open-field chamber. Dicyclomine only increases activity at a dose of 20 mg/kg in the wild-type mice but did not affect exploration in the KO animals. Lastly, we observed that dicyclomine causes a significant decrease in the percentage of audiogenic seizures in the Fmr1 KO animals. CONCLUSION Our findings suggest that pharmacologically reducing the activity through the mAChR M1 alters select behavioral responses in the Fmr1 KO mice.
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Early continuous inhibition of group 1 mGlu signaling partially rescues dendritic spine abnormalities in the Fmr1 knockout mouse model for fragile X syndrome. Psychopharmacology (Berl) 2011; 215:291-300. [PMID: 21181121 DOI: 10.1007/s00213-010-2130-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 12/01/2010] [Indexed: 12/17/2022]
Abstract
RATIONALE Abnormal dendritic spine morphology is a significant neuroanatomical defect in fragile X mental retardation. It has been suggested that overactive group 1 metabotropic glutamate receptor (mGlu) signaling is associated with the spine dysmorphology occurring in fragile X syndrome (FXS). Thus, group 1 mGlu became a new therapeutic target for the treatment of FXS. OBJECTIVE The purpose of this study was to identify the effect of inhibition of mGlu signaling in FXS. METHODS We observed the changes in dendritic spines after pharmacological modulation of mGlu signaling in an Fmr1 knockout (KO) mouse model. RESULTS The activation of group 1 mGlu resulted in elongation of dendritic spines in the cultured neurons derived from Fmr1 KO mice and wild-type (WT) mice. Antagonism of group 1 mGlu reduced the average spine length of Fmr1 KO neurons. Furthermore, systemic administration of the selective group 1 mGlu5 antagonist 2-methyl-6-phenylethynyl pyridine (MPEP) reduced the average spine length and density in the cortical neurons of Fmr1 KO mice at developmental age. For the adult mice, MPEP administration was less effective for the restoration of spine length. The percentage of immature spines showed a similar reduction in parallel to the changes of spine length. Temporary MPEP intervention with single-dose treatment did not show any effect. CONCLUSION These results show that MPEP administration could partially rescue the morphological deficits of dendritic spines in Fmr1 KO mice at developmental age.
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Spencer CM, Alekseyenko O, Hamilton SM, Thomas AM, Serysheva E, Yuva-Paylor LA, Paylor R. Modifying behavioral phenotypes in Fmr1KO mice: genetic background differences reveal autistic-like responses. Autism Res 2011; 4:40-56. [PMID: 21268289 DOI: 10.1002/aur.168] [Citation(s) in RCA: 157] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 10/12/2010] [Indexed: 01/07/2023]
Abstract
Fragile X syndrome (FXS) is the most common inherited form of intellectual disability in humans. In addition to cognitive impairment, patients may exhibit hyperactivity, attention deficits, social difficulties and anxiety, and autistic-like behaviors. The degree to which patients display these behaviors varies considerably and is influenced by family history, suggesting that genetic modifiers play a role in the expression of behaviors in FXS. Several studies have examined behavior in a mouse model of FXS in which the Fmr1 gene has been ablated. Most of those studies were done in Fmr1 knockout mice on a pure C57BL/6 or FVB strain background. To gain a better understanding of the effects of genetic background on behaviors resulting from the loss of Fmr1 gene expression, we generated F1 hybrid lines from female Fmr1 heterozygous mice on a pure C57BL/6J background bred with male Fmr1 wild-type (WT) mice of various background strains (A/J, DBA/2J, FVB/NJ, 129S1/SvImJ and CD-1). Male Fmr1 knockout and WT littermates from each line were examined in an extensive behavioral test battery. Results clearly indicate that multiple behavioral responses are dependent on genetic background, including autistic-like traits that are present on limited genetic backgrounds. This approach has allowed us to identify improved models for different behavioral symptoms present in FXS including autistic-like traits.
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Affiliation(s)
- Corinne M Spencer
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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Harris JC. Advances in understanding behavioral phenotypes in neurogenetic syndromes. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2010; 154C:389-99. [DOI: 10.1002/ajmg.c.30276] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Moon J, Ota KT, Driscoll LL, Levitsky DA, Strupp BJ. A mouse model of fragile X syndrome exhibits heightened arousal and/or emotion following errors or reversal of contingencies. Dev Psychobiol 2008; 50:473-85. [PMID: 18551464 DOI: 10.1002/dev.20308] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This study was designed to further assess cognitive and affective functioning in a mouse model of Fragile X syndrome (FXS), the Fmr1(tm1Cgr) or Fmr1 "knockout" (KO) mouse. Male KO mice and wild-type littermate controls were tested on learning set and reversal learning tasks. The KO mice were not impaired in associative learning, transfer of learning, or reversal learning, based on measures of learning rate. Analyses of videotapes of the reversal learning task revealed that both groups of mice exhibited higher levels of activity and wall-climbing during the initial sessions of the task than during the final sessions, a pattern also seen for trials following an error relative to those following a correct response. Notably, the increase in both behavioral measures seen early in the task was significantly more pronounced for the KO mice than for controls, as was the error-induced increase in activity level. This pattern of effects suggests that the KO mice reacted more strongly than controls to the reversal of contingencies and pronounced drop in reinforcement rate, and to errors in general. This pattern of effects is consistent with the heightened emotional reactivity frequently described for humans with FXS.
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Affiliation(s)
- J Moon
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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15
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Larson J, Kim D, Patel RC, Floreani C. Olfactory discrimination learning in mice lacking the fragile X mental retardation protein. Neurobiol Learn Mem 2008; 90:90-102. [PMID: 18289890 DOI: 10.1016/j.nlm.2008.01.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/02/2008] [Accepted: 01/08/2008] [Indexed: 01/17/2023]
Abstract
An automated training system was used to compare the behavior of knockout (KO) mice lacking the fragile X mental retardation protein with that of wild-type (WT) mice (C57Bl/6 strain) in the acquisition and retention of olfactory discriminations. KO and WT mice did not differ in the acquisition of a four-stage nose poke shaping procedure. In two separate experiments, mutant mice required substantially more training to acquire a series of novel olfactory discrimination problems than did control mice. The KO mice required significantly more sessions to reach criterion performance, made significantly more errors during training, and more often failed to acquire discriminations. Both KO and WT mice showed similar error patterns when learning novel discriminations and both groups showed evidence of more rapid learning of later discriminations in the problem series. Both groups showed significant long-term memory two or four weeks after training but WT and KO mice did not differ in this regard. A group of well-trained mice were given training on novel odors in sessions limited to 20-80 trials. Memory of these problems at two day delays did not differ between WT and KO mice. Tests using ethyl acetate demonstrated that WT and KO mice had similar odor detection thresholds.
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Affiliation(s)
- John Larson
- Psychiatric Institute, Department of Psychiatry (M/C 912), College of Medicine, University of Illinois at Chicago, 1601 W. Taylor Street, Chicago, IL 60612, USA.
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Abstract
Autism is a neurodevelopmental syndrome with markedly high heritability. The diagnostic indicators of autism are core behavioral symptoms, rather than definitive neuropathological markers. Etiology is thought to involve complex, multigenic interactions and possible environmental contributions. In this review, we focus on genetic pathways with multiple members represented in autism candidate gene lists. Many of these pathways can also be impinged upon by environmental risk factors associated with the disorder. The mouse model system provides a method to experimentally manipulate candidate genes for autism susceptibility, and to use environmental challenges to drive aberrant gene expression and cell pathology early in development. Mouse models for fragile X syndrome, Rett syndrome and other disorders associated with autistic-like behavior have elucidated neuropathology that might underlie the autism phenotype, including abnormalities in synaptic plasticity. Mouse models have also been used to investigate the effects of alterations in signaling pathways on neuronal migration, neurotransmission and brain anatomy, relevant to findings in autistic populations. Advances have included the evaluation of mouse models with behavioral assays designed to reflect disease symptoms, including impaired social interaction, communication deficits and repetitive behaviors, and the symptom onset during the neonatal period. Research focusing on the effect of gene-by-gene interactions or genetic susceptibility to detrimental environmental challenges may further understanding of the complex etiology for autism.
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Affiliation(s)
- S S Moy
- Neurodevelopmental Disorders Research Center, Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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17
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Brennan FX, Albeck DS, Paylor R. Fmr1 knockout mice are impaired in a leverpress escape/avoidance task. GENES BRAIN AND BEHAVIOR 2006; 5:467-71. [PMID: 16923151 DOI: 10.1111/j.1601-183x.2005.00183.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Fragile X syndrome (FXS) is the most common form of inherited mental retardation (MR). FXS is typically caused by a mutation of the Fmr1 gene (Verkerk et al. 1991, Cell 65, 905-914). To better understand the role of Fmr1 and its gene product fragile X mental-retardation protein (FMRP) in central nervous system function, researchers have turned to the use of animal model systems to generate an Fmr1 knockout (KO) mouse that is deficient in FMRP (Bakker et al. 1994, Cell 78, 23-33). Unfortunately, a number of studies have found no consistent, robust learning and memory impairment in the Fmr1 KO mice. We conducted a study to assess the performance of Fmr1 KO and wildtype (WT) animals in a leverpress escape/avoidance paradigm. Fmr1 KO and WT littermates were studied in four daily 1-h sessions. The Fmr1 KO mice performed fewer avoidance and total responses than WT mice. The KO animals were not simply deficient in avoidance, but a within-factor ANOVA revealed that they did not acquire the leverpress response to any appreciable degree. Observation during the sessions indicated that the Fmr1 KO animals clearly responded to the shock, eliminating an obvious sensory explanation for the deficit. The fact that other studies have found that the KO mice displayed increased exploratory and locomotor activity compared with WT controls argues against a motoric deficit. Future studies will attempt to delineate the nature of the behavioral deficit as well as attempt to rescue the response with glutamatergic or dopaminergic agents.
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Affiliation(s)
- F X Brennan
- Medical Research, VA Medical Center, Philadelphia, PA 19104, USA.
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18
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Moy SS, Nadler JJ, Magnuson TR, Crawley JN. Mouse models of autism spectrum disorders: The challenge for behavioral genetics. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2006; 142C:40-51. [PMID: 16419099 DOI: 10.1002/ajmg.c.30081] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Autism is a severe neurodevelopmental disorder, which typically emerges early in childhood. The core symptoms of autism include deficits in social interaction, impaired communication, and aberrant repetitive behavior, including self-injury. Despite the strong genetic component for the disease, most cases of autism have not been linked to mutations in a specific gene, and the etiology of the disorder has yet to be established. At the present time, there is no generally accepted therapeutic strategy to treat the core symptoms of autism, and there remains a critical need for appropriate animal models and relevant behavioral assays to promote the understanding and treatment of the clinical syndrome. Challenges for the development of valid mouse models include complex genetic interactions underlying the high heritability of the disease in humans, diagnosis based on deficits in social interaction and communication, and the lack of confirmatory neuropathological markers to provide validation for genetic models of the disorder. Research focusing on genes that mediate social behavior in mice may help identify neural circuitry essential for normal social interaction, and lead to novel genetic animal models of the autism behavioral phenotype.
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Affiliation(s)
- Sheryl S Moy
- Neurodevelopmental Disorders Research Center, CB #7146, University of North Carolina, Chapel Hill, NC 27599, USA.
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19
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Mineur YS, Huynh LX, Crusio WE. Social behavior deficits in the Fmr1 mutant mouse. Behav Brain Res 2005; 168:172-5. [PMID: 16343653 DOI: 10.1016/j.bbr.2005.11.004] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2005] [Revised: 10/31/2005] [Accepted: 11/07/2005] [Indexed: 11/23/2022]
Abstract
Mice exhibiting deficits in social behavior may provide valuable models for autistic-like behavioral problems. We tested social interactions in male mice from three inbred strains: C57BL/6J (B6), BALB/cJ (C) and DBA/2J (D2). All three strains showed gradual habituation of the number of social interactions with an ovariectomized female over four subsequent 2min sessions, returning to initial levels when presented with another stimulus mouse. Next, we studied males with a knockout mutation in the Fmr1 gene on a B6 background. KO animals showed strongly reduced levels of social interaction, which were about similar as those of habituated controls. This social behavior deficit suggests that Fmr1 KO mice could possibly be used as models for autistic behaviors.
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Affiliation(s)
- Yann S Mineur
- Brudnick Neuropsychiatric Research Institute, University of Massachusetts Medical School, Worcester, MA, USA
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20
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Yan QJ, Asafo-Adjei PK, Arnold HM, Brown RE, Bauchwitz RP. A phenotypic and molecular characterization of the fmr1-tm1Cgr Fragile X mouse. GENES BRAIN AND BEHAVIOR 2004; 3:337-59. [PMID: 15544577 DOI: 10.1111/j.1601-183x.2004.00087.x] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fragile X Syndrome is the most common form of inherited mental retardation. It is also known for having a substantial behavioral morbidity, including autistic features. In humans, Fragile X Syndrome is almost always caused by inactivation of the X-linked FMR1 gene. A single knockout mouse model, fmr1-tm1Cgr, exists. In this report we further characterize the cognitive and behavioral phenotype of the fmr1-tm1Cgr Fragile X mouse through the use of F1 hybrid mice derived from two inbred strains (FVB/NJ and C57BL/6J). Use of F1 hybrids allows focus on the effects of the fmr1-tm1Cgr allele with reduced influence from recessive alleles present in the parental inbred strains. We find that the cognitive phenotype of fmr1-tm1Cgr mice, including measures of working memory and learning set formation that are known to be seriously impacted in humans with Fragile X Syndrome, are essentially normal. Further testing of inbred strains supports this conclusion. Thus, any fmr1-tm1Cgr cognitive deficit is surprisingly mild or absent. There is, however, clear support presented for a robust audiogenic seizure phenotype in all strains tested, as well as increased entries into the center of an open field. Finally, a molecular examination of the fmr1-tm1Cgr mouse shows that, contrary to common belief, it is not a molecular null. Implications of this finding for interpretation of the phenotype are discussed.
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Affiliation(s)
- Q J Yan
- Department of Neurology, St. Luke's-Roosevelt Institute for Health Sciences, Columbia University, New York, NY, USA
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21
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Frankland PW, Wang Y, Rosner B, Shimizu T, Balleine BW, Dykens EM, Ornitz EM, Silva AJ. Sensorimotor gating abnormalities in young males with fragile X syndrome and Fmr1-knockout mice. Mol Psychiatry 2004; 9:417-25. [PMID: 14981523 DOI: 10.1038/sj.mp.4001432] [Citation(s) in RCA: 225] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fragile X syndrome (FXS) is the most common single gene (FMR1) disorder affecting cognitive and behavioral function in humans. This syndrome is characterized by a cluster of abnormalities including lower IQ, attention deficits, impairments in adaptive behavior and increased incidence of autism. Here, we show that young males with FXS have profound deficits in prepulse inhibition (PPI), a basic marker of sensorimotor gating that has been extensively studied in rodents. Importantly, the magnitude of the PPI impairments in the fragile X children predicted the severity of their IQ, attention, adaptive behavior and autistic phenotypes. Additionally, these measures were highly correlated with each other, suggesting that a shared mechanism underlies this complex phenotypic cluster. Studies in Fmr1-knockout mice also revealed sensorimotor gating and learning abnormalities. However, PPI and learning were enhanced rather than reduced in the mutants. Therefore, these data show that mutations of the FMR1 gene impact equivalent processes in both humans and mice. However, since these phenotypic changes are opposite in direction, they also suggest that murine compensatory mechanisms following loss of FMR1 function differ from those in humans.
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Affiliation(s)
- P W Frankland
- Department of Neurobiology, UCLA, Los Angeles, CA 90095, USA
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22
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Segal M, Kreher U, Greenberger V, Braun K. Is fragile X mental retardation protein involved in activity-induced plasticity of dendritic spines? Brain Res 2003; 972:9-15. [PMID: 12711073 DOI: 10.1016/s0006-8993(03)02410-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Dendritic morphology of 2-week-old cultured neurons, taken from postnatal day 1 fragile X mental retardation gene1 knock out (FMR1-/-) mice hippocampus, were compared with cells taken from wild type mice. Under control conditions the FMR1-/- neurons displayed significantly lower spine densities compared to wild type neurons. Pharmacological stimulation of electrical activity, induced by bicuculline, caused a reduction in dendritic spine density in both the FMR1-/- and the wild type cells. In both groups, bicuculline induced a significant shrinkage of spines that were occupied by one or more synaptophysin-immunoreactive presynaptic terminals. The concentration of FMR1 in the wild type cultures was not affected by bicuculline treatment. These experiments indicate that FMR1 is not likely to be an essential factor in activity-modulated morphological plasticity of dendritic spines in cultured hippocampal neurons.
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Affiliation(s)
- Menahem Segal
- Department of Neurobiology, The Weizmann Institute, Rehovot 76100, Israel.
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23
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Qin M, Kang J, Smith CB. Increased rates of cerebral glucose metabolism in a mouse model of fragile X mental retardation. Proc Natl Acad Sci U S A 2002; 99:15758-63. [PMID: 12427968 PMCID: PMC137789 DOI: 10.1073/pnas.242377399] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In humans, failure to express the fragile X mental retardation protein (FMRP) gives rise to fragile X syndrome, the most common form of inherited mental retardation. A fragile X knockout (fmr1 KO) mouse has been described that has some of the characteristics of patients with fragile X syndrome, including immature dendritic spines and subtle behavioral deficits. In our behavioral studies, fmr1 KO mice exhibited hyperactivity and a higher rate of entrance into the center of an open field compared with controls, suggesting decreased levels of anxiety. Our finding of impaired performance of fmr1 KO mice on a passive avoidance task is suggestive of a deficit in learning and memory. In an effort to understand what brain regions are involved in the behavioral abnormalities, we applied the [(14)C]deoxyglucose method for the determination of cerebral metabolic rates for glucose (CMR(glc)). We measured CMR(glc) in 38 regions in adult male fmr1 KO and WT littermates. We found CMR(glc) was higher in all 38 regions in fmr1 KO mice, and in 26 of the regions, differences were statistically significant. Differences in CMR(glc) ranged from 12% to 46%, and the greatest differences occurred in regions of the limbic system and primary sensory and posterior parietal cortical areas. Regions most affected are consistent with behavioral deficiencies and regions in which FMRP expression is highest. Higher CMR(glc) in fragile X mice may be a function of abnormalities found in dendritic spines.
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Affiliation(s)
- Mei Qin
- Unit on Neurobiology, Laboratory of Cerebral Metabolism, National Institute of Mental Health, Bethesda, MD, USA
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24
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Abstract
Fragile X syndrome is one of the most common forms of inherited mental retardation. In most cases the disease is caused by the methylation-induced transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene that occurs as a result of the expansion of a CGG repeat in the gene's 5'UTR and leads to the loss of protein product fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that associates with translating polyribosomes as part of a large messenger ribonucleoprotein (mRNP) and modulates the translation of its RNA ligands. Pathological studies from the brains of patients and from Fmr1 knockout mice show abnormal dendritic spines implicating FMRP in synapse formation and function. Evidence from both in vitro and in vivo neuronal studies indicates that FMRP is located at the synapse and the loss of FMRP alters synaptic plasticity. As synaptic plasticity has been implicated in learning and memory, analysis of synapse abnormalities in patients and Fmr1 knockout mice should prove useful in studying the pathogenesis of fragile X syndrome and understanding learning and cognition in general. If an appreciable portion of the total variance (in IQ) is due to sex linked genes, it is of more importance that a boy should have a clever mother than a clever father. Hogben 1932 (quoted in Lehrke 1974)
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Affiliation(s)
- William T O'Donnell
- Howard Hughes Medical Institute and Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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25
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Barnes AP, Milgram SL. Signals from the X: signal transduction and X-linked mental retardation. Int J Dev Neurosci 2002; 20:397-406. [PMID: 12175880 DOI: 10.1016/s0736-5748(02)00016-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The dramatic increase in genomic information is allowing the rapid identification of genes that are altered in mental retardation (MR). It is necessary to place their resulting gene products in their cellular context to understand how they may have contributed to a patient's cognitive deficits. This review will consider signaling molecules that have been implicated in X-linked MR and the known pathways by which these proteins covey information will be delineated. The proteins discussed include four distinct classes: transmembrane receptors, guanine nucleotide related proteins, kinases, and translational regulators.
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Affiliation(s)
- Anthony P Barnes
- Department of Cell and Developmental Biology, UNC-Neurodevelopmental Disorders Research Center, University of North Carolina, Chapel Hill, NC 27599, USA
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26
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Hoogeveen AT, Willemsen R, Oostra BA. Fragile X syndrome, the Fragile X related proteins, and animal models. Microsc Res Tech 2002; 57:148-55. [PMID: 12112450 DOI: 10.1002/jemt.10064] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Fragile X syndrome (FraX), which is characterized among other physical and neurologic impairments by mental retardation, is caused by the absence of the product of the FMR1 gene. The Fragile X Mental Retardation Protein (FMRP) is a member of a novel family of RNA-binding proteins. The latter includes two other proteins highly homologous with FMRP: the fragile X related proteins 1 and 2 (FXRP1 and FXRP2). Characterization of FXRPs, including their interaction with FMRP, will provide critical information about the mechanisms of action of FMRP and the role of this group of proteins in FMRP-deficient conditions such as FraX. Genetic manipulations of FMRP and the FXRPs should also provide valuable tools for investigating pathophysiology and gene therapies in FraX. The present review summarizes the strategies used for identifying the FXRPs, their chromosomal localization, molecular structure, and tissue distribution. It also reviews interactions between different members of this family of RNA-binding proteins. Animal models, both knockout and transgenic, of FMRP and the FXRPs are discussed. Phenotypic features of the FMR1 knockout mouse, the FMR1 transgenic rescue mouse, and other novel strategies for manipulating and delivering FMRP and FXRPs to the brain and other tissues are described.
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Affiliation(s)
- André T Hoogeveen
- Department of Clinical Genetics, Erasmus University, 3000 DR Rotterdam, The Netherlands.
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Perrone-Bizzozero N, Bolognani F. Role of HuD and other RNA-binding proteins in neural development and plasticity. J Neurosci Res 2002; 68:121-6. [PMID: 11948657 DOI: 10.1002/jnr.10175] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Transcription factors have traditionally been viewed as the main determinants of gene expression. Yet, in recent years it has become apparent that RNA-binding proteins also play a critical role in determining the levels of expression of a large number of genes. Once mRNAs are transcribed, RNA-binding proteins can control all subsequent steps in their function, from alternative splicing and translation to mRNA transport and stability. In the nervous system, a large number of genes are regulated post-transcriptionally via the interaction of their mRNAs with specific RNA-binding proteins. This type of regulation is particularly important in the control of the temporal and spatial pattern of gene expression during neural development. This review will discuss the function of the embryonic lethal abnormal vision (ELAV)/Hu family of nervous system-specific RNA-binding proteins, with a special emphasis on HuD, a member of this family that controls GAP-43 mRNA stability and expression. In addition, we will present recent findings on other neural RNA-binding proteins: the ribonucleoprotein K homology (KH)-domain proteins, Fragile X mental retardation protein (FMRP), quakinguiable protein (QKI), and Nova-1. Together with the ELAV/Hu family, these proteins are essential for proper neural development and in some cases for plasticity in the mature brain. The biological significance of these proteins is evident not only by their evolutionary conservation but also by the magnitude of problems arising from autoimmune reactions against them or from mutations affecting their expression or function.
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Affiliation(s)
- Nora Perrone-Bizzozero
- Department of Neurosciences, University of New Mexico School of Medicine, 915 Camino de Salud NE, BMSB Rm. 145, Albuquerque, NM 87131-5223, USA.
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Li J, Pelletier MR, Perez Velazquez JL, Carlen PL. Reduced cortical synaptic plasticity and GluR1 expression associated with fragile X mental retardation protein deficiency. Mol Cell Neurosci 2002; 19:138-51. [PMID: 11860268 DOI: 10.1006/mcne.2001.1085] [Citation(s) in RCA: 220] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Lack of expression of the fragile X mental retardation protein (FMRP), due to silencing of the FMR1 gene, causes the Fragile X syndrome. Although FMRP was characterized previously to be an RNA binding protein, little is known about its function or the mechanisms underlying the Fragile X syndrome. Here we report that the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor subunit, GluR1, was decreased in the cortical synapses, but not in the hippocampus or cerebellum, of FMR1 gene knockout mice. Reduced long-term potentiation (LTP) was also found in the cortex but not in the hippocampus. Another RNA binding protein, FXR; the N-methyl-D-aspartate receptor subunit, NR2; and other learning-related proteins including c-fos, synapsin, myelin proteolipid protein, and cAMP response element binding protein were not different between FMR1 gene knockout and wild-type mice. These findings suggest that the depressed cortical GluR1 expression and LTP associated with FMRP deficiency could contribute to the Fragile X phenotype.
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Affiliation(s)
- Jianxue Li
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, University of Toronto, Toronto, Ontario M5T 2S8, Canada
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29
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Abstract
The clinical features of the Fragile X mental retardation syndrome are linked to the absence of the set of protein isoforms, derived from alternative splicing of the Fragile X mental retardation gene 1 (FMR1), and collectively termed FMRP. FMRP is an RNA binding protein that is part of a ribonucleoprotein particle associated to actively translating polyribosomes, and which can shuttle between nucleus and cytoplasm. Two highly homologous human proteins, FXR1P and FXR2P, share the same domain structure as FMRP, and probably similar functions. The properties of FMRP suggested that it is involved in nuclear export, cytoplasmic transport, and/or translational control of target mRNAs. In particular, it may play a role in regulation of protein synthesis at postsynaptic sites of dendrites, and in maturation of dendritic spines. Efforts are underway to identify the putative specific mRNA targets of FMRP, and study the effect of FMRP absence on the corresponding proteins. Other approaches have led to the identification of proteins that interact with FMRP. Some of them discriminate between FMRP and the homologous FXR1/2P proteins, and may thus be important for defining unique functions of FMRP that are deficient in Fragile X patients. The physiological functions of FMRP are notably approached through the study of a FMR1 knock-out mouse model. The recent identification in Drosophila melanogaster of genes encoding homologs of FMRP/FXRP and of their interacting proteins, open the way to use of Drosophila genetics to study FMRP function.
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Affiliation(s)
- B Bardoni
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, Strasbourg, France
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Van Dam D, D'Hooge R, Hauben E, Reyniers E, Gantois I, Bakker CE, Oostra BA, Kooy RF, De Deyn PP. Spatial learning, contextual fear conditioning and conditioned emotional response in Fmr1 knockout mice. Behav Brain Res 2000; 117:127-36. [PMID: 11099766 DOI: 10.1016/s0166-4328(00)00296-5] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fmr1 knockout mice are an animal model for fragile X syndrome, the most common form of heritable mental retardation in humans. Fmr1 knockout mice exhibit macro-orchidism and cognitive and behavioural deficits reminiscent of the human phenotype. In the present study additional behavioural and cognitive testing was performed. Knockouts and control littermates were subjected to a spatial learning test using a plus-shaped water maze. Animals had to learn the position of a hidden escape platform during training trials. The position of this platform was changed during subsequent reversal trials. Previously reported deficits in reversal learning were replicated, but we also observed significant differences during the acquisition trials. A plus-shaped water maze experiment with daily changing platform positions failed to provide clear evidence for a working memory impairment, putatively underlying the spatial learning deficits. Two different test settings were used to examine the reported deficit of Fmr1 knockout mice in fear conditioning. Conditioned fear responses were observed in a contextual fear test, and the ability to acquire an emotional response was tested by means of response suppression in a conditioned emotional response procedure. Neither protocol revealed significant differences between controls and knockouts.
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Affiliation(s)
- D Van Dam
- Laboratory of Neurochemistry and Behaviour, Born-Bunge Foundation, University of Antwerp, Universiteitsplein 1, B2610 Wilrijk, Antwerp, Belgium
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31
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