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Wang H, Wu LJ, Kim SS, Lee FJS, Gong B, Toyoda H, Ren M, Shang YZ, Xu H, Liu F, Zhao MG, Zhuo M. FMRP acts as a key messenger for dopamine modulation in the forebrain. Neuron 2008; 59:634-47. [PMID: 18760699 DOI: 10.1016/j.neuron.2008.06.027] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/14/2008] [Accepted: 06/13/2008] [Indexed: 11/17/2022]
Abstract
The fragile X mental retardation protein (FMRP) is an RNA-binding protein that controls translational efficiency and regulates synaptic plasticity. Here, we report that FMRP is involved in dopamine (DA) modulation of synaptic potentiation. AMPA glutamate receptor subtype 1 (GluR1) surface expression and phosphorylation in response to D1 receptor stimulation were reduced in cultured Fmr1(-/-) prefrontal cortex (PFC) neurons. Furthermore, D1 receptor signaling was impaired, accompanied by D1 receptor hyperphosphorylation at serine sites and subcellular redistribution of G protein-coupled receptor kinase 2 (GRK2) in both PFC and striatum of Fmr1(-/-) mice. FMRP interacted with GRK2, and pharmacological inhibition of GRK2 rescued D1 receptor signaling in Fmr1(-/-) neurons. Finally, D1 receptor agonist partially rescued hyperactivity and enhanced the motor function of Fmr1(-/-) mice. Our study has identified FMRP as a key messenger for DA modulation in the forebrain and may provide insights into the cellular and molecular mechanisms underlying 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 M5S1A8, Canada
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302
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Hoeft F, Lightbody AA, Hazlett HC, Patnaik S, Piven J, Reiss AL. Morphometric spatial patterns differentiating boys with fragile X syndrome, typically developing boys, and developmentally delayed boys aged 1 to 3 years. ACTA ACUST UNITED AC 2008; 65:1087-97. [PMID: 18762595 DOI: 10.1001/archpsyc.65.9.1087] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT Brain maturation starts well before birth and occurs as a unified process with developmental interaction among different brain regions. Gene and environment play large roles in such a process. Studies of individuals with genetic disorders such as fragile X syndrome (FXS), which is a disorder caused by a single gene mutation resulting in abnormal dendritic and synaptic pruning, together with healthy individuals may provide valuable information. OBJECTIVE To examine morphometric spatial patterns that differentiate between FXS and controls in early childhood. DESIGN A cross-sectional in vivo neuroimaging study. SETTING Academic medical centers. PARTICIPANTS A total of 101 children aged 1 to 3 years, comprising 51 boys with FXS, 32 typically developing boys, and 18 boys with idiopathic developmental delay. MAIN OUTCOME MEASURES Regional gray matter volume as measured by voxel-based morphometry and manual tracing, supplemented by permutation analyses; regression analyses between gray and white matter volumes, IQ, and fragile X mental retardation protein level; and linear support vector machine analyses to classify group membership. RESULTS In addition to aberrant brain structures reported previously in older individuals with FXS, we found reduced gray matter volumes in regions such as the hypothalamus, insula, and medial and lateral prefrontal cortices. These findings are consistent with the cognitive and behavioral phenotypes of FXS. Further, multivariate pattern classification analyses discriminated FXS from typical development and developmental delay with more than 90% prediction accuracy. The spatial patterns that classified FXS from typical development and developmental delay included those that may have been difficult to identify previously using other methods. These included a medial to lateral gradient of increased and decreased regional brain volumes in the posterior vermis, amygdala, and hippocampus. CONCLUSIONS These findings are critical in understanding interplay among genes, environment, brain, and behavior. They signify the importance of examining detailed spatial patterns of healthy and perturbed brain development.
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Affiliation(s)
- Fumiko Hoeft
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 401 Quarry Rd, Stanford, CA 94305-5795, USA.
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303
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Ras signaling mechanisms underlying impaired GluR1-dependent plasticity associated with fragile X syndrome. J Neurosci 2008; 28:7847-62. [PMID: 18667617 DOI: 10.1523/jneurosci.1496-08.2008] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Fragile X syndrome, caused by the loss of FMR1 gene function and loss of fragile X mental retardation protein (FMRP), is the most commonly inherited form of mental retardation. The syndrome is characterized by associative learning deficits, reduced risk of cancer, dendritic spine dysmorphogenesis, and facial dysmorphism. However, the molecular mechanism that links loss of function of FMR1 to the learning disability remains unclear. Here, we report an examination of small GTPase Ras signaling and synaptic AMPA receptor (AMPA-R) trafficking in cultured slices and intact brains of wild-type and FMR1 knock-out mice. In FMR1 knock-out mice, synaptic delivery of GluR1-, but not GluR2L- and GluR4-containing AMPA-Rs is impaired, resulting in a selective loss of GluR1-dependent long-term synaptic potentiation (LTP). Although Ras activity is upregulated, its downstream MEK (extracellular signal-regulated kinase kinase)-ERK (extracellular signal-regulated kinase) signaling appears normal, and phosphoinositide 3-kinase (PI3K)-protein kinase B (PKB; or Akt) signaling is compromised in FMR1 knock-out mice. Enhancing Ras-PI3K-PKB signaling restores synaptic delivery of GluR1-containing AMPA-Rs and normal LTP in FMR1 knock-out mice. These results suggest aberrant Ras signaling as a novel mechanism for fragile X syndrome and indicate manipulating Ras-PI3K-PKB signaling to be a potentially effective approach for treating patients with fragile X syndrome.
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304
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EphB receptors couple dendritic filopodia motility to synapse formation. Neuron 2008; 59:56-69. [PMID: 18614029 DOI: 10.1016/j.neuron.2008.05.007] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 04/18/2008] [Accepted: 05/08/2008] [Indexed: 12/31/2022]
Abstract
Motile dendritic filopodial processes are thought to be precursors of spine synapses, but how motility relates to cell-surface cues required for axon-dendrite recognition and synaptogenesis remains unclear. We demonstrate with dynamic imaging that loss of EphBs results in reduced motility of filopodia in cultured cortical neurons and brain slice. EphB knockdown and rescue experiments during different developmental time windows show that EphBs are required for synaptogenesis only when filopodia are most abundant and motile. In the context of EphB knockdown and reduced filopodia motility, independent rescue of either motility with PAK or of Eph-ephrin binding with an EphB2 kinase mutant is not sufficient to restore synapse formation. Strikingly, the combination of PAK and kinase-inactive EphB2 rescues synaptogenesis. Deletion of the ephrin-binding domain from EphB2 precludes rescue, indicating that both motility and trans-cellular interactions are required. Our findings provide a mechanistic link between dendritic filopodia motility and synapse differentiation.
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305
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Abstract
OBJECTIVE In fragile X syndrome (FXS), it is hypothesized that absence of the fragile X mental retardation protein (FMRP) disrupts regulation of group 1 metabotropic glutamate receptor (mGluR and mGluR5)-dependent translation in dendrites. Lithium reduces mGluR-activated translation and reverses phenotypes in the dfxr mutant fly and fmr1 knockout mouse. This pilot add-on trial was conducted to evaluate safety and efficacy of lithium in humans with FXS. METHODS Fifteen individuals with FXS, ages 6-23, received lithium titrated to levels of 0.8-1.2 mEq/L. The primary outcome measure, the Aberrant Behavior Checklist --Community Edition (ABC-C) Irritability Subscale, secondary outcome measures (other ABC-C subscales, clinical global improvement scale (CGI), visual analog scale for behavior (VAS), Vineland Adaptive Behavior Scale (VABS)), exploratory cognitive and psychophysiological measures and an extracellular signal-regulated kinase (ERK) activation assay were administered at baseline and 2 months of treatment. Side effects were quantified with a standardized checklist and lithium level, complete blood count (CBC), thyroid stimulating hormone (TSH), and chemistry screen were done at baseline, 2 weeks, 4 weeks and 2 months. RESULTS The only significant treatment-related side effects were polyuria/polydipsia (n = 7) and elevated TSH (n = 4). Although the ABC-C Irritability Subscale showed only a trend toward improvement, there was significant improvement in the Total ABC-C score (p = 0.005), VAS (p = 0.003), CGI (p = 0.002), VABS Maladaptive Behavior Subscale (p = 0.007), and RBANS List Learning (p = 0.03) and an enhanced ERK activation rate (p = 0.007). Several exploratory tasks proved too difficult for lower-functioning FXS subjects. CONCLUSIONS Results from this study are consistent with results in mouse and fly models of FXS, and suggest that lithium is well-tolerated and provides functional benefits in FXS, possibly by modifying the underlying neural defect. A placebo-controlled trial of lithium in FXS is warranted.
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306
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Fiore R, Siegel G, Schratt G. MicroRNA function in neuronal development, plasticity and disease. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1779:471-8. [DOI: 10.1016/j.bbagrm.2007.12.006] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Revised: 11/22/2007] [Accepted: 12/07/2007] [Indexed: 12/31/2022]
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307
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Penzes P, Jones KA. Dendritic spine dynamics--a key role for kalirin-7. Trends Neurosci 2008; 31:419-27. [PMID: 18597863 PMCID: PMC3973420 DOI: 10.1016/j.tins.2008.06.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 05/23/2008] [Accepted: 06/02/2008] [Indexed: 11/20/2022]
Abstract
Changes in the structure and function of dendritic spines contribute to numerous physiological processes such as synaptic transmission and plasticity, as well as behavior, including learning and memory. Moreover, altered dendritic spine morphogenesis and plasticity is an endophenotype of many neurodevelopmental and neuropsychiatric disorders. Hence, the molecular mechanisms that control spine plasticity and pathology have been under intense investigation over the past few years. A series of recent studies has improved our understanding of spine dynamics by establishing kalirin-7 as an important regulator of dendritic spine development as well as structural and functional plasticity, providing a model for the molecular control of structural plasticity and implicating kalirin-7 in synaptic pathology in several disorders including schizophrenia and Alzheimer's disease.
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Affiliation(s)
- Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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308
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Dictenberg JB, Swanger SA, Antar LN, Singer RH, Bassell GJ. A direct role for FMRP in activity-dependent dendritic mRNA transport links filopodial-spine morphogenesis to fragile X syndrome. Dev Cell 2008; 14:926-39. [PMID: 18539120 DOI: 10.1016/j.devcel.2008.04.003] [Citation(s) in RCA: 382] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 03/19/2008] [Accepted: 04/16/2008] [Indexed: 01/26/2023]
Abstract
The function of local protein synthesis in synaptic plasticity and its dysregulation in fragile X syndrome (FXS) is well studied, however the contribution of regulated mRNA transport to this function remains unclear. We report a function for the fragile X mental retardation protein (FMRP) in the rapid, activity-regulated transport of mRNAs important for synaptogenesis and plasticity. mRNAs were deficient in glutamatergic signaling-induced dendritic localization in neurons from Fmr1 KO mice, and single mRNA particle dynamics in live neurons revealed diminished kinesis. Motor-dependent translocation of FMRP and cognate mRNAs involved the C terminus of FMRP and kinesin light chain, and KO brain showed reduced kinesin-associated mRNAs. Acute suppression of FMRP and target mRNA transport in WT neurons resulted in altered filopodia-spine morphology that mimicked the FXS phenotype. These findings highlight a mechanism for stimulus-induced dendritic mRNA transport and link its impairment in a mouse model of FXS to altered developmental morphologic plasticity.
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Affiliation(s)
- Jason B Dictenberg
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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309
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Abstract
The development and function of neuronal circuits within the brain are orchestrated by sophisticated gene regulatory mechanisms. Recently, microRNAs have emerged as a novel class of small RNAs that fine-tune protein synthesis. microRNAs are abundantly expressed in the vertebrate nervous system, where they contribute to the specification of neuronal cell identity. Moreover, microRNAs also play an important role in mature neurons. This review summarizes the current knowledge about the function of microRNAs in the nervous system with special emphasis on synapse formation and plasticity. The second part of this work will discuss the potential involvement of microRNAs in neurologic diseases. The study of brain microRNAs promises to expand our understanding of the mechanisms underlying higher cognitive functions and neurologic diseases.
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Affiliation(s)
- Silvia Bicker
- Interdisziplinäes Zentrum fü Neurowissenschaften, SFB488 Junior Group, Universitä Heidelberg, and Institut fü Neuroanatomie, Universitäsklinikum Heidelberg, Heidelberg, Germany
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310
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311
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Smit AE, van der Geest JN, Vellema M, Koekkoek SKE, Willemsen R, Govaerts LCP, Oostra BA, De Zeeuw CI, VanderWerf F. Savings and extinction of conditioned eyeblink responses in fragile X syndrome. GENES BRAIN AND BEHAVIOR 2008; 7:770-7. [PMID: 18616611 PMCID: PMC2613242 DOI: 10.1111/j.1601-183x.2008.00417.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The fragile X syndrome (FRAXA) is the most widespread heritable form of mental retardation caused by the lack of expression of the fragile X mental retardation protein (FMRP). This lack has been related to deficits in cerebellum-mediated acquisition of conditioned eyelid responses in individuals with FRAXA. In the present behavioral study, long-term effects of deficiency of FMRP were investigated by examining the acquisition, savings and extinction of delay eyeblink conditioning in male individuals with FRAXA. In the acquisition experiment, subjects with FRAXA displayed a significantly poor performance compared with controls. In the savings experiment performed at least 6 months later, subjects with FRAXA and controls showed similar levels of savings of conditioned responses. Subsequently, extinction was faster in subjects with FRAXA than in controls. These findings confirm that absence of the FMRP affects cerebellar motor learning. The normal performance in the savings experiment and aberrant performance in the acquisition and extinction experiments of individuals with FRAXA suggest that different mechanisms underlie acquisition, savings and extinction of cerebellar motor learning.
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Affiliation(s)
- A E Smit
- Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
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312
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Thomas CC, Combe CL, Dyar KA, Inglis FM. Modest alterations in patterns of motor neuron dendrite morphology in the Fmr1 knockout mouse model for fragile X. Int J Dev Neurosci 2008; 26:805-11. [PMID: 18638539 DOI: 10.1016/j.ijdevneu.2008.06.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2008] [Revised: 06/14/2008] [Accepted: 06/14/2008] [Indexed: 10/21/2022] Open
Abstract
Fragile X, an inheritable form of mental retardation, is caused by the inactivation of a gene on the X chromosome, FMR1 which codes for an RNA binding protein, fragile X mental retardation protein. Loss of this protein is associated with reduced complexities of neuronal dendrites and alterations in spine morphology in a number of cortical brain regions, and these deficits may underlie the cognitive impairment observed in fragile X patients. Among the many symptoms of fragile X are altered motor functions, although the neuronal basis for these remains unclear. In this study we investigated whether knockout of Fmr1 in the mouse model of fragile X altered dendrite morphology in developing spinal cord motor neurons. We find that Fmr1 knockout leads to modest alterations in the distribution of dendritic arbor across the span of the motor neuron dendritic tree in 2- and 4-week-old mice, compared to wild-type controls, consistent with slower rates of extension and abnormal pruning of intermediate dendritic segments. These studies suggest that some motor deficits in fragile X patients may be due to abnormal maturation of dendritic patterning within spinal motor neurons, and suggest that strategies aimed at preventing motor impairment in fragile X patients may be targeted at motor functions during early development.
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Affiliation(s)
- Christina C Thomas
- Undergraduate Neuroscience Program, Tulane University, New Orleans, LA 70118, USA
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313
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Genome-wide screen reveals APC-associated RNAs enriched in cell protrusions. Nature 2008; 453:115-9. [PMID: 18451862 DOI: 10.1038/nature06888] [Citation(s) in RCA: 243] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Accepted: 03/05/2008] [Indexed: 01/17/2023]
Abstract
RNA localization is important for the establishment and maintenance of polarity in multiple cell types. Localized RNAs are usually transported along microtubules or actin filaments and become anchored at their destination to some underlying subcellular structure. Retention commonly involves actin or actin-associated proteins, although cytokeratin filaments and dynein anchor certain RNAs. RNA localization is important for diverse processes ranging from cell fate determination to synaptic plasticity; however, so far there have been few comprehensive studies of localized RNAs in mammalian cells. Here we have addressed this issue, focusing on migrating fibroblasts that polarize to form a leading edge and a tail in a process that involves asymmetric distribution of RNAs. We used a fractionation scheme combined with microarrays to identify, on a genome-wide scale, RNAs that localize in protruding pseudopodia of mouse fibroblasts in response to migratory stimuli. We find that a diverse group of RNAs accumulates in such pseudopodial protrusions. Through their 3' untranslated regions these transcripts are anchored in granules concentrated at the plus ends of detyrosinated microtubules. RNAs in the granules associate with the adenomatous polyposis coli (APC) tumour suppressor and the fragile X mental retardation protein (FMRP). APC is required for the accumulation of transcripts in protrusions. Our results suggest a new type of RNA anchoring mechanism as well as a new, unanticipated function for APC in localizing RNAs.
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314
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Post-transcriptional regulation of myelin formation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1779:486-94. [PMID: 18590840 DOI: 10.1016/j.bbagrm.2008.06.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2008] [Revised: 05/15/2008] [Accepted: 06/03/2008] [Indexed: 12/21/2022]
Abstract
Myelin is a specialized structure of the nervous system that both enhances electrical conductance and protects neurons from degeneration. In the central nervous system, extensively polarized oligodendrocytes form myelin by wrapping cellular processes in a spiral pattern around neuronal axons. Myelin formation requires the oligodendrocyte to regulate gene expression in response to changes in its extracellular environment. Because these changes occur at a distance from the cell body, post-transcriptional control of gene expression allows the cell to fine-tune its response. Here, we review the RNA-binding proteins that control myelin formation in the brain, highlighting the molecular mechanisms by which they control gene expression and drawing parallels from studies in other cell types.
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315
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Roles of calcium-stimulated adenylyl cyclase and calmodulin-dependent protein kinase IV in the regulation of FMRP by group I metabotropic glutamate receptors. J Neurosci 2008; 28:4385-97. [PMID: 18434517 DOI: 10.1523/jneurosci.0646-08.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The fragile X syndrome is caused by the lack of fragile X mental retardation protein (FMRP) attributable to silencing of the FMR1 gene. The metabotropic glutamate receptors (mGluRs) in the CNS contribute to different brain functions, including learning/memory, mental disorders, drug addiction, and persistent pain. Most of the previous studies have been focused on downstream targets of FMRP in hippocampal neurons, and fewer studies have been reported for the second-messenger signaling pathways between group I mGluRs and FMRP. Furthermore, no molecular study has been performed in the anterior cingulate cortex (ACC), a key region involved in high brain cognitive and executive functions. In this study, we demonstrate that activation of group I mGluR upregulated FMRP in ACC neurons of adult mice through the Ca(2+)-dependent signaling pathways. Using genetic approaches, we found that Ca(2+)/calmodulin-stimulated adenylyl cyclase 1 (AC1) and calcium/calmodulin-dependent kinase IV (CaMKIV) contribute to the upregulation of FMRP induced by stimulating group I mGluRs. The upregulation of FMRP occurs at the transcriptional level. The cAMP-dependent protein kinase is activated by stimulating group I mGluRs through AC1 in ACC neurons. Both AC1 and CaMKIV contribute to the regulation of FMRP by group I mGluRs probably through cAMP response element-binding protein activation. Our study has provided the first evidence for a molecular link between group I mGluRs and FMRP in ACC neurons and may help us to understand the pathogenesis of fragile X syndrome.
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316
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Centonze D, Rossi S, Mercaldo V, Napoli I, Ciotti MT, De Chiara V, Musella A, Prosperetti C, Calabresi P, Bernardi G, Bagni C. Abnormal striatal GABA transmission in the mouse model for the fragile X syndrome. Biol Psychiatry 2008; 63:963-73. [PMID: 18028882 DOI: 10.1016/j.biopsych.2007.09.008] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 08/10/2007] [Accepted: 09/12/2007] [Indexed: 11/27/2022]
Abstract
BACKGROUND Structural and functional neuroimaging studies suggest abnormal activity in the striatum of patients with the fragile X syndrome (FXS), the most common form of inherited mental retardation. METHODS Neurophysiological and immunofluorescence experiments in striatal brain slices. We studied the synaptic transmission in a mouse model for FXS, as well as the subcellular localization of fragile X mental retardation protein (FMRP) and brain cytoplasmic (BC1) RNA in striatal axons. RESULTS Our results show that absence of FMRP is associated with apparently normal striatal glutamate-mediated transmission, but abnormal gamma-aminobutyric acid (GABA) transmission. This effect is likely secondary to increased transmitter release from GABAergic nerve terminals. We detected the presence of FMRP in axons of striatal neurons and observed a selective increase in the frequency of spontaneous and miniature inhibitory postsynaptic currents (sIPSCs, mIPSCs) in fmr1-knockout mice. We also observed reduced paired-pulse ratio of evoked IPSCs, a finding that is consistent with the idea that transmitter release probability from striatal GABAergic nerve terminals is higher than normal in these mutants. Finally, we have identified the small noncoding BC1 RNA as a critical coplayer of FMRP in the regulation of striatal synaptic transmission. CONCLUSIONS Understanding the physiologic action of FMRP and the synaptic defects associated with GABA transmission might be useful to design appropriate pharmacologic interventions for FXS.
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Affiliation(s)
- Diego Centonze
- Clinica Neurologica, Dipartimento di Neuroscienze, Università Tor Vergata, Rome, Italy.
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317
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de Vrij FMS, Levenga J, van der Linde HC, Koekkoek SK, De Zeeuw CI, Nelson DL, Oostra BA, Willemsen R. Rescue of behavioral phenotype and neuronal protrusion morphology in Fmr1 KO mice. Neurobiol Dis 2008; 31:127-32. [PMID: 18571098 DOI: 10.1016/j.nbd.2008.04.002] [Citation(s) in RCA: 217] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 04/01/2008] [Accepted: 04/17/2008] [Indexed: 10/22/2022] Open
Abstract
Lack of fragile X mental retardation protein (FMRP) causes Fragile X Syndrome, the most common form of inherited mental retardation. FMRP is an RNA-binding protein and is a component of messenger ribonucleoprotein complexes, associated with brain polyribosomes, including dendritic polysomes. FMRP is therefore thought to be involved in translational control of specific mRNAs at synaptic sites. In mice lacking FMRP, protein synthesis-dependent synaptic plasticity is altered and structural malformations of dendritic protrusions occur. One hypothesized cause of the disease mechanism is based on exaggerated group I mGluR receptor activation. In this study, we examined the effect of the mGluR5 antagonist MPEP on Fragile X related behavior in Fmr1 KO mice. Our results demonstrate a clear defect in prepulse inhibition of startle in Fmr1 KO mice, that could be rescued by MPEP. Moreover, we show for the first time a structural rescue of Fragile X related protrusion morphology with two independent mGluR5 antagonists.
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Affiliation(s)
- Femke M S de Vrij
- Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
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318
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Characterization of potential outcome measures for future clinical trials in fragile X syndrome. J Autism Dev Disord 2008; 38:1751-7. [PMID: 18369716 DOI: 10.1007/s10803-008-0564-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Accepted: 02/27/2008] [Indexed: 10/22/2022]
Abstract
Clinical trials targeting recently elucidated synaptic defects in fragile X syndrome (FXS) will require outcome measures capable of assessing short-term changes in cognitive functioning. Potentially useful measures for FXS were evaluated here in a test-retest setting in males and females with FXS (N = 46). Good reproducibility, determined by an interclass correlation (ICC) or weighted kappa (kappa) of 0.7-0.9 was seen for RBANS List and Story Memory, NEPSY Tower, Woodcock-Johnson Spatial Relations and the commissions score from the Carolina Fragile X Project Continuous Performance Test (CPT). This study demonstrates the feasibility of generating test profiles containing reliability data, ability levels required for test performance, and refusal rates to assist with choice of outcome measures in FXS and other cohorts with cognitive disability.
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319
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Wirojanan J, Kraff J, Hawkins DS, Laird C, Gane LW, Angkustsiri K, Tassone F, Hagerman RJ. Two boys with fragile x syndrome and hepatic tumors. J Pediatr Hematol Oncol 2008; 30:239-41. [PMID: 18376289 DOI: 10.1097/mph.0b013e31815f88c9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hepatic tumors are rare childhood neoplasms with uncertain etiology. We report the cooccurrence of hepatic tumors in 2 boys with fragile X syndrome, one with hepatoblastoma and another with desmoplastic nested spindle cell tumor of liver. The pathogenesis of fragile X syndrome involves silencing of the fragile X mental retardation 1 gene and consequent loss of FMR1 protein. We speculate regarding molecular pathways that might explain the cooccurrence of the 2 conditions. Further examination of a possible functional link between hepatic neoplasia and loss of FMRP is warranted.
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Affiliation(s)
- Juthamas Wirojanan
- Medical Investigation of Neurodevelopmental Disorders , University of California Davis Health System, Sacramento, CA 95817, USA
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320
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Ronesi JA, Huber KM. Metabotropic glutamate receptors and fragile x mental retardation protein: partners in translational regulation at the synapse. Sci Signal 2008; 1:pe6. [PMID: 18272470 DOI: 10.1126/stke.15pe6] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Fragile X syndrome (FXS) mental retardation is caused by loss-of-function mutations in an RNA-binding protein, fragile X mental retardation protein (FMRP). Previous studies in patients or animal models of FXS have identified alterations in dendritic spine structure, as well as synaptic plasticity induced by metabotropic glutamate receptors (mGluRs). The translation of multiple messenger RNA (mRNA) targets of FMRP is regulated by mGluRs at synapses. Here, we incorporate data from several studies into a working model of how FMRP regulates mGluR-stimulated protein synthesis and, in turn, regulates protein synthesis-dependent synaptic plasticity. Understanding the complex functions of FMRP at the synapse will lead to a better understanding of the neurobiological underpinnings of mental retardation.
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Affiliation(s)
- Jennifer A Ronesi
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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321
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Koldewyn K, Hessl D, Adams J, Tassone F, Hagerman PJ, Hagerman RJ, Rivera SM. Reduced Hippocampal Activation During Recall is Associated with Elevated FMR1 mRNA and Psychiatric Symptoms in Men with the Fragile X Premutation. Brain Imaging Behav 2008; 2:105-116. [PMID: 19430586 DOI: 10.1007/s11682-008-9020-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent studies reveal that young carriers of the fragile X premutation are at increased risk for psychiatric conditions, memory problems and executive deficits. Post mortem and structural MRI studies suggest the hippocampus is preferentially affected by the premutation. The current study utilized magnetic resonance imaging (MRI) to explore the relationship between hippocampal structure and function as well as molecular/genetic and psychiatric measures in men with the fragile X premutation. Although the groups did not differ in hippocampal volume, the premutation group showed reduced left hippocampal activation and increased right parietal activation during a recall task relative to controls. These results suggest that brain function underlying memory recall is affected by premutation status. Left hippocampal activation was negatively correlated with both FMR1 mRNA level and psychiatric symptomology in the premutation group. These associations support the theory that increased levels of FMR1 mRNA affect brain function and contribute to psychiatric symptoms.
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Affiliation(s)
- Kami Koldewyn
- Medical Investigation of Neurodevelopmental, Disorders (M.I.N.D.) Institute, University of California-Davis, Medical Center, Sacramento, USA
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322
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Mechanistic relationships between Drosophila fragile X mental retardation protein and metabotropic glutamate receptor A signaling. Mol Cell Neurosci 2008; 37:747-60. [PMID: 18280750 DOI: 10.1016/j.mcn.2008.01.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Revised: 12/20/2007] [Accepted: 01/03/2008] [Indexed: 11/23/2022] Open
Abstract
Fragile X syndrome is caused by loss of the FMRP translational regulator. A current hypothesis proposes that FMRP functions downstream of mGluR signaling to regulate synaptic connections. Using the Drosophila disease model, we test relationships between dFMRP and the sole Drosophila mGluR (DmGluRA) by assaying protein expression, behavior and neuron structure in brain and NMJ; in single mutants, double mutants and with an mGluR antagonist. At the protein level, dFMRP is upregulated in dmGluRA mutants, and DmGluRA is upregulated in dfmr1 mutants, demonstrating mutual negative feedback. Null dmGluRA mutants display defects in coordinated movement behavior, which are rescued by removing dFMRP expression. Null dfmr1 mutants display increased NMJ presynaptic structural complexity and elevated presynaptic vesicle pools, which are rescued by blocking mGluR signaling. Null dfmr1 brain neurons similarly display increased presynaptic architectural complexity, which is rescued by blocking mGluR signaling. These data show that DmGluRA and dFMRP convergently regulate presynaptic properties.
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323
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Decreased nociceptive sensitization in mice lacking the fragile X mental retardation protein: role of mGluR1/5 and mTOR. J Neurosci 2008; 27:13958-67. [PMID: 18094233 DOI: 10.1523/jneurosci.4383-07.2007] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Fragile X mental retardation is caused by silencing of the gene (FMR1) that encodes the RNA-binding protein (FMRP) that influences translation in neurons. A prominent feature of the human disorder is self-injurious behavior, suggesting an abnormality in pain processing. Moreover, FMRP regulates group I metabotropic glutamate receptor (mGluR1/5)-dependent plasticity, which is known to contribute to nociceptive sensitization. We demonstrate here, using the Fmr1 knock-out (KO) mouse, that FMRP plays an important role in pain processing because Fmr1 KO mice showed (1) decreased (approximately 50%) responses to ongoing nociception (phase 2, formalin test), (2) a 3 week delay in the development of peripheral nerve injury-induced allodynia, and (3) a near absence of wind-up responses in ascending sensory fibers after repetitive C-fiber stimulation. We provide evidence that the behavioral deficits are related to a mGluR1/5- and mammalian target of rapamycin (mTOR)-mediated mechanism because (1) spinal mGluR5 antagonism failed to inhibit the second phase of the formalin test, and we observed a marked reduction in nociceptive response to an intrathecal injection of an mGluR1/5 agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) in Fmr1 KO mice; (2) peripheral DHPG injection had no effect in KO mice yet evoked thermal hyperalgesia in wild types; and (3) the mTOR inhibitor rapamycin inhibited formalin- and DHPG-induced nociception in wild-type but not Fmr1 KO mice. These experiments show that translation regulation via FMRP and mTOR is an important feature of nociceptive plasticity. These observations also support the hypothesis that the persistence of self-injurious behavior observed in fragile X mental retardation patients could be related to deficits in nociceptive sensitization.
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324
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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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325
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Kaufmann WE, Capone GT, Clarke M, Budimirovic DB. Autism in Genetic Intellectual Disability. AUTISM : THE INTERNATIONAL JOURNAL OF RESEARCH AND PRACTICE 2008. [DOI: 10.1007/978-1-60327-489-0_4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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326
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Dahm R, Zeitelhofer M, Götze B, Kiebler MA, Macchi P. Visualizing mRNA localization and local protein translation in neurons. Methods Cell Biol 2008; 85:293-327. [PMID: 18155468 DOI: 10.1016/s0091-679x(08)85013-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Fluorescent proteins (FPs) have been successfully used to study the localization and interactions of proteins in living cells. They have also been instrumental in analyzing the proteins involved in the localization of RNAs in different cell types, including neurons. With the development of methods that also tag RNAs via fluorescent proteins, researchers now have a powerful tool to covisualize RNAs and associated proteins in living neurons. Here, we review the current status of the use of FPs in the study of transport and localization of ribonucleoprotein particles (RNPs) in neurons and provide key protocols used to introduce transgenes into cultured neurons, including calcium-phosphate-based transfection and nucleofection. These methods allow the fast and efficient expression of fluorescently tagged fusion proteins in neurons at different stages of differentiation and form the basis for fluorescent protein-based live cell imaging in neuronal cultures. Additional protocols are given that allow the simultaneous visualization of RNP proteins and cargo RNAs in living neurons and aspects of the visualization of fluorescently tagged proteins in neurons, such as colocalization studies, are discussed. Finally, we review approaches to visualize the local synthesis of proteins in distal dendrites and axons.
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Affiliation(s)
- Ralf Dahm
- Center for Brain Research, Division of Neuronal Cell Biology, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria
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327
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Fossella J, Fan J, Liu X, Guise K, Brocki K, Hof PR, Kittappa R, McKay R, Posner M. Provisional hypotheses for the molecular genetics of cognitive development: imaging genetic pathways in the anterior cingulate cortex. Biol Psychol 2007; 79:23-9. [PMID: 18261834 DOI: 10.1016/j.biopsycho.2007.12.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 12/16/2007] [Accepted: 12/18/2007] [Indexed: 10/22/2022]
Abstract
Brain imaging genetic research involves a multitude of methods and spans many traditional levels of analysis. Given the vast permutations among several million common genetic variants with thousands of brain tissue voxels and a wide array of cognitive tasks that activate specific brain systems, we are prompted to develop specific hypotheses that synthesize converging evidence and state clear predictions about the anatomical sources, magnitude and direction (increases vs. decreases) of allele- and task-specific brain activity associations. To begin to develop a framework for shaping our imaging genetic hypotheses, we focus on previous results and the wider imaging genetic literature. Particular emphasis is placed on converging evidence that links system-level and biochemical studies with models of synaptic function. In shaping our own imaging genetic hypotheses on the development of Attention Networks, we review relevant literature on core models of synaptic physiology and development in the anterior cingulate cortex.
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Affiliation(s)
- John Fossella
- Department of Psychiatry, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, United States.
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328
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Piazzon N, Rage F, Schlotter F, Moine H, Branlant C, Massenet S. In vitro and in cellulo evidences for association of the survival of motor neuron complex with the fragile X mental retardation protein. J Biol Chem 2007; 283:5598-610. [PMID: 18093976 DOI: 10.1074/jbc.m707304200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by reduced levels of the survival of motor neuron (SMN) protein. Although the SMN complex is essential for assembly of spliceosomal U small nuclear RNPs, it is still not understood why reduced levels of the SMN protein specifically cause motor neuron degeneration. SMN was recently proposed to have specific functions in mRNA transport and translation regulation in neuronal processes. The defective protein in Fragile X mental retardation syndrome (FMRP) also plays a role in transport of mRNPs and in their translation. Therefore, we examined possible relationships of SMN with FMRP. We observed granules containing both transiently expressed red fluorescent protein(RFP)-tagged SMN and green fluorescent protein(GFP)-tagged FMRP in cell bodies and processes of rat primary neurons of hypothalamus in culture. By immunoprecipitation experiments, we detected an association of FMRP with the SMN complex in human neuroblastoma SH-SY5Y cells and in murine motor neuron MN-1 cells. Then, by in vitro experiments, we demonstrated that the SMN protein is essential for this association. We showed that the COOH-terminal region of FMRP, as well as the conserved YG box and the region encoded by exon 7 of SMN, are required for the interaction. Our findings suggest a link between the SMN complex and FMRP in neuronal cells.
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Affiliation(s)
- Nathalie Piazzon
- Laboratoire de Maturation des ARN et Enzymologie Moléculaire, UMR 7567 CNRS-UHP Nancy I, Faculté des Sciences, BP 239, 54506 Vandoeuvre-les-Nancy Cedex
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329
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Fiore R, Schratt G. MicroRNAs in synapse development: tiny molecules to remember. Expert Opin Biol Ther 2007; 7:1823-31. [PMID: 18034648 DOI: 10.1517/14712598.7.12.1823] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
MicroRNAs are a recently discovered class of small non-coding RNAs that play a key role in post-transcriptional gene regulation during development and disease. MicroRNAs are abundant in the nervous system and have already been shown to have an important function during neuronal patterning and cell specification. It is now becoming increasingly evident that they are also essential for synaptic development and that they might contribute to the etiology of neuronal diseases characterized by synaptic dysfunction. This review focuses on the recent examples that describe a function of microRNAs in synapse formation and plasticity, and discusses how the microRNA pathway might be exploited to treat neurologic diseases.
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Affiliation(s)
- Roberto Fiore
- University of Heidelberg, Interdisciplinary Centre for Neurosciences (IZN), SFB488 Junior Group, and University Hospital of Heidelberg, Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany
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330
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Drosophila fragile X mental retardation protein and metabotropic glutamate receptor A convergently regulate the synaptic ratio of ionotropic glutamate receptor subclasses. J Neurosci 2007; 27:12378-89. [PMID: 17989302 DOI: 10.1523/jneurosci.2970-07.2007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A current hypothesis proposes that fragile X mental retardation protein (FMRP), an RNA-binding translational regulator, acts downstream of glutamatergic transmission, via metabotropic glutamate receptor (mGluR) G(q)-dependent signaling, to modulate protein synthesis critical for trafficking ionotropic glutamate receptors (iGluRs) at synapses. However, direct evidence linking FMRP and mGluR function with iGluR synaptic expression is limited. In this study, we use the Drosophila fragile X model to test this hypothesis at the well characterized glutamatergic neuromuscular junction (NMJ). Two iGluR classes reside at this synapse, each containing common GluRIIC (III), IID and IIE subunits, and variable GluRIIA (A-class) or GluRIIB (B-class) subunits. In Drosophila fragile X mental retardation 1 (dfmr1) null mutants, A-class GluRs accumulate and B-class GluRs are lost, whereas total GluR levels do not change, resulting in a striking change in GluR subclass ratio at individual synapses. The sole Drosophila mGluR, DmGluRA, is also expressed at the NMJ. In dmGluRA null mutants, both iGluR classes increase, resulting in an increase in total synaptic GluR content at individual synapses. Targeted postsynaptic dmGluRA overexpression causes the exact opposite GluR phenotype to the dfmr1 null, confirming postsynaptic GluR subtype-specific regulation. In dfmr1; dmGluRA double null mutants, there is an additive increase in A-class GluRs, and a similar additive impact on B-class GluRs, toward normal levels in the double mutants. These results show that both dFMRP and DmGluRA differentially regulate the abundance of different GluR subclasses in a convergent mechanism within individual postsynaptic domains.
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331
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el Bekay R, Romero-Zerbo Y, Decara J, Sanchez-Salido L, Del Arco-Herrera I, Rodríguez-de Fonseca F, de Diego-Otero Y. Enhanced markers of oxidative stress, altered antioxidants and NADPH-oxidase activation in brains from Fragile X mental retardation 1-deficient mice, a pathological model for Fragile X syndrome. Eur J Neurosci 2007; 26:3169-80. [PMID: 18005058 DOI: 10.1111/j.1460-9568.2007.05939.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Fragile X syndrome is the most common form of inherited mental retardation in humans. It originates from the loss of expression of the Fragile X mental retardation 1 (FMR1) gene, which results in the absence of the Fragile X mental retardation protein. However, the biochemical mechanisms involved in the pathological phenotype are mostly unknown. The availability of the FMR1-knockout mouse model offers an excellent model system in which to study the biochemical alterations related to brain abnormalities in the syndrome. We show for the first time that brains from Fmr1-knockout mice, a validated model for the syndrome, display higher levels of reactive oxygen species, nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase activation, lipid peroxidation and protein oxidation than brains from wild-type mice. Furthermore, the antioxidant system is deficient in Fmr1-knockout mice, as shown by altered levels of components of the glutathione system. FMR1-knockout mice lacking Fragile X mental retardation protein were compared with congenic FVB129 wild-type controls. Our results support the hypothesis that the lack of Fragile X mental retardation protein function leads to a moderate increase of the oxidative stress status in the brain that may contribute to the pathophysiology of the Fragile X syndrome.
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Affiliation(s)
- Rajaa el Bekay
- Research Laboratory, Fundación IMABIS-Hospital Carlos Haya, Hospital Civil, Pabellón 5 Sótano, E-29009 Málaga, Spain
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332
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Multiple Gq-coupled receptors converge on a common protein synthesis-dependent long-term depression that is affected in fragile X syndrome mental retardation. J Neurosci 2007; 27:11624-34. [PMID: 17959805 DOI: 10.1523/jneurosci.2266-07.2007] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Gq-coupled, M1 muscarinic acetylcholine receptors (mAChRs) facilitate hippocampal learning, memory, and synaptic plasticity. M1 mAChRs induce long-term synaptic depression (LTD), but little is known about the underlying mechanisms of mAChR-dependent LTD and its link to cognitive function. Here, we demonstrate that chemical activation of M1 mAChRs induces LTD in hippocampal area CA1, which relies on rapid protein synthesis, as well as the extracellular signal-regulated kinase and mammalian target of rapamycin translational activation pathways. Synaptic stimulation of M1 mAChRs, alone, or together with the Gq-coupled glutamate receptors (mGluRs), also results in protein synthesis-dependent LTD. New proteins maintain mAChR-dependent LTD through a persistent decrease in surface AMPA receptors. mAChRs stimulate translation of the RNA-binding protein, Fragile X mental retardation protein (FMRP) and FMRP target mRNAs. In mice without FMRP (Fmr1 knock-out), a model for human Fragile X syndrome mental retardation (FXS), both mGluR- and mAChR-dependent protein synthesis and LTD are affected. Our results reveal that multiple Gq-coupled receptors converge on a common protein synthesis-dependent LTD mechanism, which is aberrant in FXS. These findings suggest novel therapeutic strategies for FXS in the form of mAChR antagonists.
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333
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Wang H, Dictenberg JB, Ku L, Li W, Bassell GJ, Feng Y. Dynamic association of the fragile X mental retardation protein as a messenger ribonucleoprotein between microtubules and polyribosomes. Mol Biol Cell 2007; 19:105-14. [PMID: 17978095 DOI: 10.1091/mbc.e07-06-0583] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The fragile X mental retardation protein (FMRP) is a selective RNA-binding protein that regulates translation and plays essential roles in synaptic function. FMRP is bound to specific mRNA ligands, actively transported into neuronal processes in a microtubule-dependent manner, and associated with polyribosomes engaged in translation elongation. However, the biochemical relationship between FMRP-microtubule association and FMRP-polyribosome association remains elusive. Here, we report that although the majority of FMRP is incorporated into elongating polyribosomes in the soluble cytoplasm, microtubule-associated FMRP is predominantly retained in translationally dormant, polyribosome-free messenger ribonucleoprotein (mRNP) complexes. Interestingly, FMRP-microtubule association is increased when mRNPs are dynamically released from polyribosomes as a result of inhibiting translation initiation. Furthermore, the I304N mutant FMRP that fails to be incorporated into polyribosomes is associated with microtubules in mRNP particles and transported into neuronal dendrites in a microtubule-dependent, 3,5-dihydroxyphenylglycine-stimulated manner with similar kinetics to that of wild-type FMRP. Hence, polyribosome-free FMRP-mRNP complexes travel on microtubules and wait for activity-dependent translational derepression at the site of function. The dual participation of FMRP in dormant mRNPs and polyribosomes suggests distinct roles of FMRP in dendritic transport and translational regulation, two distinct phases that control local protein production to accommodate synaptic plasticity.
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Affiliation(s)
- Houping Wang
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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334
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Westmark CJ, Malter JS. FMRP mediates mGluR5-dependent translation of amyloid precursor protein. PLoS Biol 2007; 5:e52. [PMID: 17298186 PMCID: PMC1808499 DOI: 10.1371/journal.pbio.0050052] [Citation(s) in RCA: 222] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 12/18/2006] [Indexed: 01/31/2023] Open
Abstract
Amyloid precursor protein (APP) facilitates synapse formation in the developing brain, while beta-amyloid (Aβ) accumulation, which is associated with Alzheimer disease, results in synaptic loss and impaired neurotransmission. Fragile X mental retardation protein (FMRP) is a cytoplasmic mRNA binding protein whose expression is lost in fragile X syndrome. Here we show that FMRP binds to the coding region of APP mRNA at a guanine-rich, G-quartet–like sequence. Stimulation of cortical synaptoneurosomes or primary neuronal cells with the metabotropic glutamate receptor agonist DHPG increased APP translation in wild-type but not fmr-1 knockout samples. APP mRNA coimmunoprecipitated with FMRP in resting synaptoneurosomes, but the interaction was lost shortly after DHPG treatment. Soluble Aβ40 or Aβ42 levels were significantly higher in multiple strains of fmr-1 knockout mice compared to wild-type controls. Our data indicate that postsynaptic FMRP binds to and regulates the translation of APP mRNA through metabotropic glutamate receptor activation and suggests a possible link between Alzheimer disease and fragile X syndrome. Alzheimer disease (AD) and fragile X syndrome (FXS) are devastating neurological disorders associated with synaptic dysfunction resulting in cognitive impairment and behavioral deficits. Despite these similar endpoints, the pathobiology of AD and FXS have not previously been linked. We have established that translation of amyloid precursor protein (APP), which is cleaved to generate neurotoxic βamyloid, is normally repressed by the fragile X mental retardation protein (FMRP) in the dendritic processes of neurons. Activation of a particular subtype of glutamate receptor (mGluR5) rapidly increases translation of APP in neurons by displacing FMRP from a guanidine-rich sequence in the coding region of APP mRNA. In the absence of FMRP, APP synthesis is constitutively increased and nonresponsive to mGluR-mediated signaling. Excess APP is proteolytically cleaved to generate significantly elevated βamyloid in multiple mutant mouse strains lacking FMRP compared to wild type. Our data support a growing consensus that FMRP binds to guanine-rich domains of some dendritic mRNAs, suppressing their translation and suggest that AD (neurodegenerative disorder) and FXS (neurodevelopmental disorder) may share a common molecular pathway leading to the overproduction of APP and its protein-cleaving derivatives. FMRP, the cytoplasmic mRNA-binding protein lost in fragile X syndrome, regulates the translation of amyloid precursor protein in neurons.
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Affiliation(s)
- Cara J Westmark
- Department of Pathology and Laboratory Medicine, Waisman Center for Developmental Disabilities, University of Wisconsin, Madison, Wisconsin, United States of America.
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335
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Abstract
Many cellular functions require the synthesis of a specific protein or functional cohort of proteins at a specific time and place in the cell. Local protein synthesis in neuronal dendrites is essential for understanding how neural activity patterns are transduced into persistent changes in synaptic connectivity during cortical development, memory storage and other long-term adaptive brain responses. Regional and temporal changes in protein levels are commonly coordinated by an asymmetric distribution of mRNAs. This Review attempts to integrate current knowledge of dendritic mRNA transport, storage and translation, placing particular emphasis on the coordination of regulation and function during activity-dependent synaptic plasticity in the adult mammalian brain.
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Affiliation(s)
- Clive R Bramham
- Department of Biomedicine and Bergen Mental Health Research Center, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway.
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336
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Kelley DJ, Davidson RJ, Elliott JL, Lahvis GP, Yin JCP, Bhattacharyya A. The cyclic AMP cascade is altered in the fragile X nervous system. PLoS One 2007; 2:e931. [PMID: 17895972 PMCID: PMC1976557 DOI: 10.1371/journal.pone.0000931] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 09/04/2007] [Indexed: 01/31/2023] Open
Abstract
Fragile X syndrome (FX), the most common heritable cause of mental retardation and autism, is a developmental disorder characterized by physical, cognitive, and behavioral deficits. FX results from a trinucleotide expansion mutation in the fmr1 gene that reduces levels of fragile X mental retardation protein (FMRP). Although research efforts have focused on FMRP's impact on mGluR signaling, how the loss of FMRP leads to the individual symptoms of FX is not known. Previous studies on human FX blood cells revealed alterations in the cyclic adenosine 3', 5'-monophosphate (cAMP) cascade. We tested the hypothesis that cAMP signaling is altered in the FX nervous system using three different model systems. Induced levels of cAMP in platelets and in brains of fmr1 knockout mice are substantially reduced. Cyclic AMP induction is also significantly reduced in human FX neural cells. Furthermore, cAMP production is decreased in the heads of FX Drosophila and this defect can be rescued by reintroduction of the dfmr gene. Our results indicate that a robust defect in cAMP production in FX is conserved across species and suggest that cAMP metabolism may serve as a useful biomarker in the human disease population. Reduced cAMP induction has implications for the underlying causes of FX and autism spectrum disorders. Pharmacological agents known to modulate the cAMP cascade may be therapeutic in FX patients and can be tested in these models, thus supplementing current efforts centered on mGluR signaling.
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Affiliation(s)
- Daniel J. Kelley
- Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
- Neuroscience Training Program, University of Wisconsin School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
- Medical Scientist Training Program, University of Wisconsin School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Richard J. Davidson
- Waisman Laboratory for Brain Imaging and Behavior, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Jamie L. Elliott
- Medical Scientist Training Program, University of Wisconsin School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Garet P. Lahvis
- Department of Surgery, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Jerry C. P. Yin
- Department of Genetics, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Anita Bhattacharyya
- Stem Cells and Developmental Disorders Laboratory, Waisman Center, University of Wisconsin, Madison, Wisconsin, United States of America
- * To whom correspondence should be addressed. E-mail:
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337
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Synaptic localization of seizure-induced matrix metalloproteinase-9 mRNA. Neuroscience 2007; 150:31-9. [PMID: 17928157 DOI: 10.1016/j.neuroscience.2007.08.026] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2007] [Revised: 06/25/2007] [Accepted: 08/28/2007] [Indexed: 11/20/2022]
Abstract
The phenomenon of dendritic transport and local translation of mRNA is considered to be one of the most fundamental mechanisms underlying long-term synaptic plasticity. Matrix metalloproteinase 9 (gelatinase B) (MMP-9) is a matrix metalloproteinase implicated in synaptic long-term potentiation and hippocampus-dependent memory. It was recently shown to be prominently up-regulated in the hippocampal dentate gyrus (DG) upon kainate-mediated seizures. Here, using a high resolution nonradioactive in situ hybridization at the light- and electron-microscopic levels, as well as subcellular fractionation, we provide evidence that in the rat hippocampus, MMP-9 mRNA is associated with dendrites and dendritic spines bearing asymmetric (excitatory) synapses. Moreover we observe that after kainate treatment the number of dendrites and synapses containing MMP-9 mRNA increases markedly. Our results indicate that we are observing the phenomenon of dendritic transport of seizure-induced MMP-9 mRNA.
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338
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Perkins DO, Jeffries CD, Jarskog LF, Thomson JM, Woods K, Newman MA, Parker JS, Jin J, Hammond SM. microRNA expression in the prefrontal cortex of individuals with schizophrenia and schizoaffective disorder. Genome Biol 2007; 8:R27. [PMID: 17326821 PMCID: PMC1852419 DOI: 10.1186/gb-2007-8-2-r27] [Citation(s) in RCA: 415] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Revised: 01/25/2007] [Accepted: 02/27/2007] [Indexed: 12/21/2022] Open
Abstract
Transcriptional profiling reveals a possible association between schizophrenia and altered miRNA expression Background microRNAs (miRNAs) are small, noncoding RNA molecules that are now thought to regulate the expression of many mRNAs. They have been implicated in the etiology of a variety of complex diseases, including Tourette's syndrome, Fragile × syndrome, and several types of cancer. Results We hypothesized that schizophrenia might be associated with altered miRNA profiles. To investigate this possibility we compared the expression of 264 human miRNAs from postmortem prefrontal cortex tissue of individuals with schizophrenia (n = 13) or schizoaffective disorder (n = 2) to tissue of 21 psychiatrically unaffected individuals using a custom miRNA microarray. Allowing a 5% false discovery rate, we found that 16 miRNAs were differentially expressed in prefrontal cortex of patient subjects, with 15 expressed at lower levels (fold change 0.63 to 0.89) and 1 at a higher level (fold change 1.77) than in the psychiatrically unaffected comparison subjects. The expression levels of 12 selected miRNAs were also determined by quantitative RT-PCR in our lab. For the eight miRNAs distinguished by being expressed at lower microarray levels in schizophrenia samples versus comparison samples, seven were also expressed at lower levels with quantitative RT-PCR. Conclusion This study is the first to find altered miRNA profiles in postmortem prefrontal cortex from schizophrenia patients.
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Affiliation(s)
- Diana O Perkins
- Department of Psychiatry, University of North Carolina at Chapel Hill, CB 7160, Chapel Hill, NC 27599, USA
| | - Clark D Jeffries
- School of Pharmacy, University of North Carolina at Chapel Hill, CB 7360, Chapel Hill, NC 27599, USA
- Renaissance Computing Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - L Fredrik Jarskog
- Department of Psychiatry, University of North Carolina at Chapel Hill, CB 7160, Chapel Hill, NC 27599, USA
| | - J Michael Thomson
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, CB 7090, Chapel Hill, NC 27599, USA
| | - Keith Woods
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, CB 7090, Chapel Hill, NC 27599, USA
| | - Martin A Newman
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, CB 7090, Chapel Hill, NC 27599, USA
| | - Joel S Parker
- Constella Group, LLC, Meridian Parkway, Durham, NC 27713, USA
| | - Jianping Jin
- Department of Molecular Biology, University of North Carolina at Chapel Hill, CB 7104, Chapel Hill, NC 27599, USA
| | - Scott M Hammond
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, CB 7090, Chapel Hill, NC 27599, USA
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339
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McEvoy M, Cao G, Llopis PM, Kundel M, Jones K, Hofler C, Shin C, Wells DG. Cytoplasmic polyadenylation element binding protein 1-mediated mRNA translation in Purkinje neurons is required for cerebellar long-term depression and motor coordination. J Neurosci 2007; 27:6400-11. [PMID: 17567800 PMCID: PMC6672430 DOI: 10.1523/jneurosci.5211-06.2007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The ability of neurons to modify synaptic connections is critical for proper brain development and function in the adult. It is now clear that changes in synaptic strength are often accompanied by changes in synaptic morphology. This synaptic plasticity can be maintained for varying lengths of time depending on the type of neuronal activity that first induced the changes. Long-term synaptic plasticity requires the synthesis of new proteins, and one mechanism for the regulation of experience-induced protein synthesis in neurons involves cytoplasmic polyadenylation element binding protein (CPEB1). CPEB1 can bidirectionally regulate mRNA translation, first repressing translation, and then activating translation after the phosphorylation of two critical residues (T171 and S177). To determine the full extent of CPEB1-mediated protein synthesis in synaptic function, we engineered a line of mice expressing CPEB1 with these phosphorylation sites mutated to alanines (mCPEB1-AA) exclusively in cerebellar Purkinje neurons (PNs). Thus, mRNAs bound by mCPEB1-AA would be held in a translationally dormant state. We show that mCPEB1-AA localizes to synapses in cerebellum and resulted in a loss of protein synthesis-dependent phase of parallel fiber-PN long-term depression. This was accompanied by a change in spine number and spine length that are likely attributable in part to the dysregulation of IRSp53, a protein known to play a role in synaptic structure. Finally, mCPEB1-AA mice displayed a significant impairment of motor coordination and a motor learning delay.
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Affiliation(s)
- Michael McEvoy
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Guan Cao
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Paula Montero Llopis
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Mitchell Kundel
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Kendrick Jones
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Catherine Hofler
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - Chan Shin
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | - David G. Wells
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
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340
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Abstract
The past decade has seen tremendous advances in our understanding of the molecular and genetic basis of many neuropsychiatric disorders. Although the genetic aberrations that lead to these syndromes have been identified in many cases, not much is known about specific gene products and their function. This article reviews the molecular basis of well-known neurogenetic disorders. The syndromes discussed here follow a Mendelian pattern of inheritance and are predominantly single-gene disorders; however, most childhood and adolescent psychiatric disorders are polygenic in nature. This genetic complexity and heterogeneity has made it difficult to identify the genes involved in their etiology. Identification of genetic and environmental risk factors involved in the etiology of complex disorders, such as autism, will help in the discovery of medications that can ameliorate the symptoms.
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341
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Abstract
Fragile X syndrome (FraX) is the most common known cause of inherited mental impairment. FMR1 gene mutations, the cause of FraX, lead to reduced expression of FMR1 protein and an increased risk for a particular profile of cognitive, behavioral, and emotional dysfunction. The study of individuals with FraX provides a unique window of understanding into important disorders such as autism, social phobia, cognitive disability, and depression. This review highlights the typical phenotypic features of individuals with FraX, discussing the apparent strengths and weaknesses in intellectual functioning, as evidenced from longitudinal follow-up studies. It also discusses recent neuroanatomic findings that may pave the way for more focused disease-specific pharmacologic and behavioral interventions. This article describes the results of recent medication trials designed to target symptoms associated with FraX. It also describes some recent behavioral interventions that were conducted in our laboratory.
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Affiliation(s)
- Allan L Reiss
- Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305-5975, USA
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342
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Vickers CA, Wyllie DJA. Late-phase, protein synthesis-dependent long-term potentiation in hippocampal CA1 pyramidal neurones with destabilized microtubule networks. Br J Pharmacol 2007; 151:1071-7. [PMID: 17549044 PMCID: PMC2042922 DOI: 10.1038/sj.bjp.0707314] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Protein synthesis-dependent late-long term potentiation (L-LTP) is an enduring form of synaptic plasticity that has been shown to rely on, at least partly, protein synthesis at synaptic and/or dendritic sites. Evidence suggests that somatic transcription of new mRNAs may provide a significant contribution to the availability of mRNAs at synaptic sites where they are made available for dendritic translation. Transport of mRNAs from somatic to dendritic sites might be expected to involve movement along a microtubule network. In this study we examined whether it was possible to maintain L-LTP in hippocampal slices with destabilized microtubule networks. EXPERIMENTAL APPROACH Extracellular field excitatory postsynaptic potentials (fEPSPs) were recorded from rat hippocampal slices and following a period of baseline recording, stimuli were given that induced LTP. LTP was monitored for 5 h in both control slices and slices treated with vincristine to depolymerize tubulin. KEY RESULTS L-LTP was induced and maintained in vincristine-treated slices. Four hours after tetanic stimulation fEPSPs were 196+/-19% of baseline values. The magnitude of potentiation was similar to that seen in untreated slices (175+/-15%). L-LTP in vincristine-treated slices was, however, not maintained in the presence of the protein synthesis inhibitor, rapamycin. Immunohistochemistry and confocal microscopy of vincristine-treated slices verified that the microtubule network had been destabilized. CONCLUSIONS AND IMPLICATIONS Communication between somatic and synaptic sites through protein and/or mRNA trafficking via an intact microtubule network is not required for protein synthesis dependent L-LTP.
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Affiliation(s)
- C A Vickers
- Centre for Neuroscience Research, University of Edinburgh Edinburgh, UK
| | - D J A Wyllie
- Centre for Neuroscience Research, University of Edinburgh Edinburgh, UK
- Author for correspondence:
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343
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Muddashetty RS, Kelić S, Gross C, Xu M, Bassell GJ. Dysregulated metabotropic glutamate receptor-dependent translation of AMPA receptor and postsynaptic density-95 mRNAs at synapses in a mouse model of fragile X syndrome. J Neurosci 2007; 27:5338-48. [PMID: 17507556 PMCID: PMC6672337 DOI: 10.1523/jneurosci.0937-07.2007] [Citation(s) in RCA: 336] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Fragile X syndrome, a common form of inherited mental retardation, is caused by the loss of fragile X mental retardation protein (FMRP), an mRNA binding protein that is hypothesized to regulate local mRNA translation in dendrites downstream of gp1 metabotropic glutamate receptors (mGluRs). However, specific FMRP-associated mRNAs that localize to dendrites in vivo and show altered mGluR-dependent translation at synapses of Fmr1 knock-out mice are unknown so far. Using fluorescence in situ hybridization, we discovered that GluR1/2 and postsynaptic density-95 (PSD-95) mRNAs are localized to dendrites of cortical and hippocampal neurons in vivo. Quantitative analyses of their dendritic mRNA levels in cultured neurons and synaptoneurosomes did not detect differences between wild-type and Fmr1 knock-out (KO) mice. In contrast, PSD-95, GluR1/2, and calcium/calmodulin-dependent kinase IIalpha (CaMKIIalpha) mRNA levels in actively translating polyribosomes were dysregulated in synaptoneurosomes from Fmr1 knock-out mice in response to mGluR activation. [35S]methionine incorporation into newly synthesized proteins similarly revealed impaired stimulus-induced protein synthesis of CaMKIIalpha and PSD-95 in synaptoneurosomes from Fmr1 KO mice. Quantitative analysis of mRNA levels in FMRP-specific immunoprecipitations from synaptoneurosomes demonstrated the association of FMRP with CaMKIIalpha, PSD-95, and GluR1/2 mRNAs. These findings suggest a novel mechanism whereby FMRP regulates the local synthesis AMPA receptor (AMPAR) subunits, PSD-95, and CaMKIIalpha downstream of mGluR-activation. Dysregulation of local translation of AMPAR and associated factors at synapses may impair control of the molecular composition of the postsynaptic density and consequently alter synaptic transmission, causing impairments of neuronal plasticity observed in Fmr1 knock-out mice and fragile X syndrome.
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Affiliation(s)
| | - Sofija Kelić
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | | | - Mei Xu
- Neurology, Emory University, Atlanta, Georgia 30322, and
| | - Gary J. Bassell
- Departments of Cell Biology and
- Neurology, Emory University, Atlanta, Georgia 30322, and
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344
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Nishimura Y, Martin CL, Vazquez-Lopez A, Spence SJ, Alvarez-Retuerto AI, Sigman M, Steindler C, Pellegrini S, Schanen NC, Warren ST, Geschwind DH. Genome-wide expression profiling of lymphoblastoid cell lines distinguishes different forms of autism and reveals shared pathways. Hum Mol Genet 2007; 16:1682-98. [PMID: 17519220 DOI: 10.1093/hmg/ddm116] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Autism is a heterogeneous condition that is likely to result from the combined effects of multiple genetic factors interacting with environmental factors. Given its complexity, the study of autism associated with Mendelian single gene disorders or known chromosomal etiologies provides an important perspective. We used microarray analysis to compare the mRNA expression profile in lymphoblastoid cells from males with autism due to a fragile X mutation (FMR1-FM), or a 15q11-q13 duplication (dup(15q)), and non-autistic controls. Gene expression profiles clearly distinguished autism from controls and separated individuals with autism based on their genetic etiology. We identified 68 genes that were dysregulated in common between autism with FMR1-FM and dup(15q). We also identified a potential molecular link between FMR1-FM and dup(15q), the cytoplasmic FMR1 interacting protein 1 (CYFIP1), which was up-regulated in dup(15q) patients. We were able to confirm this link in vitro by showing common regulation of two other dysregulated genes, JAKMIP1 and GPR155, downstream of FMR1 or CYFIP1. We also confirmed the reduction of the Jakmip1 protein in Fmr1 knock-out mice, demonstrating in vivo relevance. Finally, we showed independent confirmation of roles for JAKMIP1 and GPR155 in autism spectrum disorders (ASDs) by showing their differential expression in male sib pairs discordant for idiopathic ASD. These results provide evidence that blood derived lymphoblastoid cells gene expression is likely to be useful for identifying etiological subsets of autism and exploring its pathophysiology.
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Affiliation(s)
- Yuhei Nishimura
- Center for Autism Research and Treatment, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA
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345
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Meredith RM, Holmgren CD, Weidum M, Burnashev N, Mansvelder HD. Increased Threshold for Spike-Timing-Dependent Plasticity Is Caused by Unreliable Calcium Signaling in Mice Lacking Fragile X Gene Fmr1. Neuron 2007; 54:627-38. [PMID: 17521574 DOI: 10.1016/j.neuron.2007.04.028] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Revised: 02/15/2007] [Accepted: 04/26/2007] [Indexed: 11/23/2022]
Abstract
Fragile X syndrome, caused by a mutation in the Fmr1 gene, is characterized by mental retardation. Several studies reported the absence of long-term potentiation (LTP) at neocortical synapses in Fmr1 knockout (FMR1-KO) mice, but underlying cellular mechanisms are unknown. We find that in the prefrontal cortex (PFC) of FMR1-KO mice, spike-timing-dependent LTP (tLTP) is not so much absent, but rather, the threshold for tLTP induction is increased. Calcium signaling in dendrites and spines is compromised. First, dendrites and spines more often fail to show calcium transients. Second, the activity of L-type calcium channels is absent in spines. tLTP could be restored by improving reliability and amplitude of calcium signaling by increasing neuronal activity. In FMR1-KO mice that were raised in enriched environments, tLTP was restored to WT levels. Our results show that mechanisms for synaptic plasticity are in place in the FMR1-KO mouse PFC, but require stronger neuronal activity to be triggered.
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Affiliation(s)
- Rhiannon M Meredith
- Department of Experimental Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
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346
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Pfeiffer BE, Huber KM. Fragile X mental retardation protein induces synapse loss through acute postsynaptic translational regulation. J Neurosci 2007; 27:3120-30. [PMID: 17376973 PMCID: PMC6672463 DOI: 10.1523/jneurosci.0054-07.2007] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Fragile X syndrome, as well as other forms of mental retardation and autism, is associated with altered dendritic spine number and structure. Fragile X syndrome is caused by loss-of-function mutations in Fragile X mental retardation protein (FMRP), an RNA-binding protein that regulates protein synthesis in vivo. It is unknown whether FMRP plays a direct, cell-autonomous role in regulation of synapse number, function, or maturation. Here, we report that acute postsynaptic expression of FMRP in Fmr1 knock-out (KO) neurons results in a decrease in the number of functional and structural synapses without an effect on their synaptic strength or maturational state. Similarly, neurons endogenously expressing FMRP (wild-type) have fewer synapses than neighboring Fmr1 KO neurons. An intact K homology domain 2 (KH2) RNA-binding domain and dephosphorylation of FMRP at S500 were required for the effects of FMRP on synapse number, indicating that FMRP interaction with RNA and translating polyribosomes leads to synapse loss.
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Affiliation(s)
- Brad E Pfeiffer
- Center for Basic Neuroscience, Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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347
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Zalfa F, Eleuteri B, Dickson KS, Mercaldo V, De Rubeis S, di Penta A, Tabolacci E, Chiurazzi P, Neri G, Grant SG, Bagni C. A new function for the fragile X mental retardation protein in regulation of PSD-95 mRNA stability. Nat Neurosci 2007; 10:578-87. [PMID: 17417632 PMCID: PMC2804293 DOI: 10.1038/nn1893] [Citation(s) in RCA: 292] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 03/14/2007] [Indexed: 11/09/2022]
Abstract
Fragile X syndrome (FXS) results from the loss of the fragile X mental retardation protein (FMRP), an RNA-binding protein that regulates a variety of cytoplasmic mRNAs. FMRP regulates mRNA translation and may be important in mRNA localization to dendrites. We report a third cytoplasmic regulatory function for FMRP: control of mRNA stability. In mice, we found that FMRP binds, in vivo, the mRNA encoding PSD-95, a key molecule that regulates neuronal synaptic signaling and learning. This interaction occurs through the 3' untranslated region of the PSD-95 (also known as Dlg4) mRNA, increasing message stability. Moreover, stabilization is further increased by mGluR activation. Although we also found that the PSD-95 mRNA is synaptically localized in vivo, localization occurs independently of FMRP. Through our functional analysis of this FMRP target we provide evidence that dysregulation of mRNA stability may contribute to the cognitive impairments in individuals with FXS.
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Affiliation(s)
- Francesca Zalfa
- Dipartimento di Biologia, Università “Tor Vergata”, Via della Ricerca Scientifica 1. 00133 Rome, Italy
- Istituto di Neuroscienze Sperimentali, Fondazione Santa Lucia, Via del Fosso di Fiorano 63, 00143 Rome, Italy
| | - Boris Eleuteri
- Dipartimento di Biologia, Università “Tor Vergata”, Via della Ricerca Scientifica 1. 00133 Rome, Italy
- Istituto di Neuroscienze Sperimentali, Fondazione Santa Lucia, Via del Fosso di Fiorano 63, 00143 Rome, Italy
| | - Kirsten S. Dickson
- Div. of Neuroscience, University of Edinburgh, George Sq, Edinburgh, UK EH8 9JZ
- Correspondence should be addressed to either Claudia Bagni () or Kirsten S. Dickson ()
| | - Valentina Mercaldo
- Dipartimento di Biologia, Università “Tor Vergata”, Via della Ricerca Scientifica 1. 00133 Rome, Italy
- Istituto di Neuroscienze Sperimentali, Fondazione Santa Lucia, Via del Fosso di Fiorano 63, 00143 Rome, Italy
| | - Silvia De Rubeis
- Dipartimento di Biologia, Università “Tor Vergata”, Via della Ricerca Scientifica 1. 00133 Rome, Italy
- Istituto di Neuroscienze Sperimentali, Fondazione Santa Lucia, Via del Fosso di Fiorano 63, 00143 Rome, Italy
| | - Alessandra di Penta
- Istituto di Neuroscienze Sperimentali, Fondazione Santa Lucia, Via del Fosso di Fiorano 63, 00143 Rome, Italy
| | - Elisabetta Tabolacci
- Istituto di Genetica Medica, Università Cattolica, Largo F. Vito, 1. 00168 Rome, Italy
| | - Pietro Chiurazzi
- Istituto di Genetica Medica, Università Cattolica, Largo F. Vito, 1. 00168 Rome, Italy
| | - Giovanni Neri
- Istituto di Genetica Medica, Università Cattolica, Largo F. Vito, 1. 00168 Rome, Italy
| | - Seth G.N. Grant
- Div. of Neuroscience, University of Edinburgh, George Sq, Edinburgh, UK EH8 9JZ
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK CB10 1SA
| | - Claudia Bagni
- Dipartimento di Biologia, Università “Tor Vergata”, Via della Ricerca Scientifica 1. 00133 Rome, Italy
- Istituto di Neuroscienze Sperimentali, Fondazione Santa Lucia, Via del Fosso di Fiorano 63, 00143 Rome, Italy
- Correspondence should be addressed to either Claudia Bagni () or Kirsten S. Dickson ()
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348
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Abstract
Varieties of neuropathological disorders are caused by a perturbation of normal developmental processes, resulting from insults by heterogeneous etiologic factors. These factors trigger the sequence of molecular, biochemical, and morphologic alterations of the brain, resulting morphologically and/or functionally abnormal brain. The resulting brain contains basic components of the normal brain but is assembled in an abnormal way. The developmental stage when the insults occur appears to largely dictate the outcome of the pathological processes. Depending on the developmental stage involved, the morphology of the brain may be grossly abnormal or is apparently normal but functionally abnormal. The brain development progresses in an orderly fashion and can be divided into several major developmental stages; the neurulation (neural tube formation), ventral induction (formation of prosencephalon), neuroepithelial cell proliferation and migration, neuroglial differentiation and establishment of neuronal circuits. The perturbation of these developmental stages results in uniquely specific pathological outcome, regardless of the etiologic factors/agents. In this review, I will briefly discuss the normal pattern of brain development and neuropathology of the representative disorders resulting from the deviation of normal developmental processes in the individual developmental stage.
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Affiliation(s)
- Kinuko Suzuki
- Department of Pathology and Laboratory Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27278, USA.
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349
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Faulkner RL, Low LK, Cheng HJ. Axon pruning in the developing vertebrate hippocampus. Dev Neurosci 2007; 29:6-13. [PMID: 17148945 DOI: 10.1159/000096207] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Accepted: 03/23/2006] [Indexed: 11/19/2022] Open
Abstract
During early development of the central nervous system (CNS), there is an exuberant outgrowth of projections which later need to be refined to achieve precise connectivity. One widely used strategy for this refinement is axon pruning. Axon pruning has also been suggested to be involved in creating more diverse connection patterns between different species. An understanding of the mechanism of pruning, however, has been elusive in the CNS. Recent studies have focused on a stereotyped pruning event that occurs within the mossy fibers of the developing vertebrate hippocampus. In the following discussion, we will review the cellular and molecular factors that are known to regulate pruning in the hippocampus and highlight some advantages this system presents for future studies on pruning in the developing CNS.
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Affiliation(s)
- Regina L Faulkner
- Center for Neuroscience, University of California, Davis, CA 95616, USA
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350
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Abstract
The localisation of specific RNAs is a widely employed mechanism to generate asymmetry in various biological systems, e.g. during embryonic development and cellular differentiation. Here, we highlight the importance of RNA localisation in mature neurons. Specific examples of mRNAs localised in neurons are those encoding Arc, beta-actin, CaMKIIalpha and MAP2. Moreover, non-coding RNAs, such as BC1/BC200 and microRNAs (miRNAs), which play important roles in the translational regulation of localised mRNAs, receive increasing attention. The process of RNA localisation, including RNP biogenesis, transport, anchoring and translational control, and the importance of RNA localisation for the function of the nervous system are discussed.
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Affiliation(s)
- Ralf Dahm
- Medical University of Vienna, Center for Brain Research, Division of Neuronal Cell Biology, Spitalgasse 4, A-1090 Vienna, Austria
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