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Fragile X AND neuron

Jeremy Veenstra-VanderWeele, Edwin H Cook, Bryan H King, Peter Zarevics, Maryann Cherubini, Karen Walton-Bowen, Mark F Bear, Paul P Wang, Randall L Carpenter
Several lines of emerging data point to an imbalance between neuronal excitation and inhibition in at least a subgroup of individuals with autism spectrum disorder (ASD), including in those with fragile X syndrome (FXS), one of the most common genetic syndromes within ASD. In animal models of FXS and of ASD, GABA-B agonists have improved both brain and behavioral phenotypes, including social behavior. A phase 2 randomized, placebo-controlled, crossover trial found that the GABA-B agonist arbaclofen improved social avoidance symptoms in FXS...
October 17, 2016: Neuropsychopharmacology: Official Publication of the American College of Neuropsychopharmacology
Ping Lu, Xiaolong Chen, Yun Feng, Qiao Zeng, Cizhong Jiang, Xianmin Zhu, Guoping Fan, Zhigang Xue
Fragile X syndrome (FXS) patients carry the expansion of over 200 CGG repeats at the promoter of fragile X mental retardation 1 (FMR1), leading to decreased or absent expression of its encoded fragile X mental retardation protein (FMRP). However, the global transcriptional alteration by FMRP deficiency has not been well characterized at single nucleotide resolution, i.e., RNA-seq. Here, we performed in-vitro neuronal differentiation of human induced pluripotent stem (iPS) cells that were derived from fibroblasts of a FXS patient (FXS-iPSC)...
October 11, 2016: Science China. Life Sciences
Yifan Zhou, Daman Kumari, Nicholas Sciascia, Karen Usdin
BACKGROUND: Fragile X syndrome (FXS), a common cause of intellectual disability and autism, results from the expansion of a CGG-repeat tract in the 5' untranslated region of the FMR1 gene to >200 repeats. Such expanded alleles, known as full mutation (FM) alleles, are epigenetically silenced in differentiated cells thus resulting in the loss of FMRP, a protein important for learning and memory. The timing of repeat expansion and FMR1 gene silencing is controversial. METHODS: We monitored the repeat size and methylation status of FMR1 alleles with expanded CGG repeats in patient-derived induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs) that were grown for extended period of time either as stem cells or differentiated into neurons...
2016: Molecular Autism
Hagar Mor-Shaked, Rachel Eiges
Fragile X syndrome (FXS) is the most common heritable form of cognitive impairment. It results from a loss-of-function mutation by a CGG repeat expansion at the 5' untranslated region of the X-linked fragile X mental retardation 1 (FMR1) gene. Expansion of the CGG repeats beyond 200 copies results in protein deficiency by leading to aberrant methylation of the FMR1 promoter and the switch from active to repressive histone modifications. Additionally, the CGGs become increasingly unstable, resulting in high degree of variation in expansion size between and within tissues of affected individuals...
2016: Genes
Randall Michael Golovin, Kendal Broadie
Evidence accumulating over the past 15 years refutes the dogma that the Drosophila nervous system is hardwired. The preponderance of studies reveals activity-dependent neural circuit refinement driving the optimization of behavioral outputs. Here, we describe developmental, sensory input-dependent plasticity in the brain olfactory antennal lobe that we term long-term central adaption (LTCA). LTCA is evoked by prolonged exposure to an odorant during the first week of post-eclosion life, resulting in a persistent decreased response to aversive odors and enhanced response to attractive odors...
September 28, 2016: Journal of Neurophysiology
Olfa Khalfallah, Marielle Jarjat, Laetitia Davidovic, Nicolas Nottet, Sandrine Cestèle, Massimo Mantegazza, Barbara Bardoni
Fragile X syndrome (FXS) is the most common form of inherited intellectual disability (ID) and a leading cause of autism. FXS is due to the silencing of the Fragile X Mental Retardation Protein (FMRP), an RNA binding protein mainly involved in translational control, dendritic spine morphology and synaptic plasticity. Despite extensive studies, there is currently no cure for FXS. With the purpose to decipher the initial molecular events leading to this pathology, we developed a stem-cell-based disease model by knocking-down the expression of Fmr1 in mouse embryonic stem cells (ESCs)...
September 24, 2016: Stem Cells
Kirsty Sawicka, Alexander Pyronneau, Miranda Chao, Michael V L Bennett, R Suzanne Zukin
Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and a leading genetic form of autism. The Fmr1 KO mouse, a model of FXS, exhibits elevated translation in the hippocampus and the cortex. ERK (extracellular signal-regulated kinase) and mTOR (mechanistic target of rapamycin) signaling regulate protein synthesis by activating downstream targets critical to translation initiation and elongation and are known to contribute to hippocampal defects in fragile X. Here we show that the effect of loss of fragile X mental retardation protein (FMRP) on these pathways is brain region specific...
October 11, 2016: Proceedings of the National Academy of Sciences of the United States of America
Stephanie E Zimmer, Steven G Doll, A Denise R Garcia, Michael R Akins
The autism-related protein Fragile X mental retardation protein (FMRP) is an RNA binding protein that plays important roles during both nervous system development and experience dependent plasticity. Alternative splicing of the Fmr1 locus gives rise to 12 different FMRP splice forms that differ in the functional and regulatory domains they contain as well as in their expression profile among brain regions and across development. Complete loss of FMRP leads to morphological and functional changes in neurons, including an increase in the size and complexity of the axonal arbor...
September 19, 2016: Developmental Neurobiology
Sarah Wahlstrom-Helgren, Vitaly A Klyachko
Feed-forward inhibitory (FFI) circuits are important for many information-processing functions. FFI circuit operations critically depend on the balance and timing between the excitatory and inhibitory components, which undergo rapid dynamic changes during neural activity due to short-term plasticity (STP) of both components. How dynamic changes in excitation/inhibition (E/I) balance during spike trains influence FFI circuit operations remains poorly understood. Here we examined the role of STP in the FFI circuit functions in the mouse hippocampus...
September 7, 2016: Journal of Neurophysiology
Jason Arsenault, Shervin Gholizadeh, Yosuke Niibori, Laura K Pacey, Sebok K Halder, Enea Koxhioni, Ayumu Konno, Hirokazu Hirai, David R Hampson
Fragile X mental retardation protein (FMRP) is absent or highly reduced in Fragile X Syndrome, a genetic disorder causing cognitive impairment and autistic behaviors. Previous proof-of-principle studies have demonstrated that restoring FMRP in the brain using viral vectors can improve pathological abnormalities in mouse models of fragile X. However, unlike small molecule drugs where the dose can readily be adjusted during treatment, viral vector-based biological therapeutic drugs present challenges in terms of achieving optimal dosing and expression levels...
September 7, 2016: Human Gene Therapy
Rustam Esanov, Nadja S Andrade, Sarah Bennison, Claes Wahlestedt, Zane Zeier
Fragile X syndrome (FXS) results from a repeat expansion mutation near the FMR1 gene promoter and is the most common form of heritable intellectual disability and autism. Full mutations larger than 200 CGG repeats trigger FMR1 heterochromatinization and loss of gene expression, which is primarily responsible for the pathological features of FXS . In contrast, smaller pre-mutations of 55-200 CGG are associated with FMR1 overexpression and Fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset neurodegenerative condition...
September 5, 2016: Human Molecular Genetics
Ricardos Tabet, Nicolas Vitale, Hervé Moine
Fragile X syndrome (FXS) is the most common cause of inherited intellectual disability and autism. FXS results from the absence of FMRP, an RNA binding protein associated to ribosomes that influences the translation of specific mRNAs in post-synaptic compartments of neurons. The main molecular consequence of the absence of FMRP is an excessive translation of neuronal protein in several areas of the brain. This local protein synthesis deregulation is proposed to underlie the defect in synaptic plasticity responsible for FXS...
September 3, 2016: Biochimie
Owen D Jones
Synapses undergo significant structural and functional reorganization in response to varying patterns of stimulation. These forms of plasticity are considered fundamental to cognition and neuronal homeostasis. An increasing number of reports highlight the importance of activity-dependent synaptic strengthening (long term potentiation: LTP) for learning. However, the functional significance of activity-dependent weakening of synapses (long term depression: LTD) remains relatively poorly understood. One form of synaptic weakening, induced by group I metabotropic glutamate receptors (mGluRs), has received significant attention from a mechanistic point of view and because of its augmentation in a murine model of Fragile X Syndrome...
August 18, 2016: Neurobiology of Learning and Memory
Diego A R Zorio, Christine M Jackson, Yong Liu, Edwin W Rubel, Yuan Wang
The fragile X mental retardation protein (FMRP) plays an important role in normal brain development. Absence of FMRP results in abnormal neuronal morphologies in a selected manner throughout the brain, leading to intellectual deficits and sensory dysfunction in the fragile X syndrome (FXS). Despite FMRP importance for proper brain function, its overall expression pattern in the mammalian brain at the resolution of individual neuronal cell groups is not known. In this study we used FMR1 knockout and isogenic wildtype mice to systematically map the distribution of FMRP expression in the entire mouse brain...
August 19, 2016: Journal of Comparative Neurology
V N Perfilova, I N Tyurenkov
The data on the structure, location and functions of the metabotropic glutamate receptor is shown. The family consists of 8 mGluRs subtypes and is divided into three groups: I group--mGluRs1/mGluRs5, II group--mGluRs2/mGluRs3, III group--mGluRs4/mGluRs6/mGluRs7/mGluRs8. They are associated with G-protein; signaling in the cells is carried out by IP3 or adenylate cyclase signaling pathways, in the result of which, mGluRs modify glial and neuronal excitability. Receptors are localized in the CNS and periphery in non-neuronal tissues: bone, heart, kidney, pancreas pod and platelets, the gastrointestinal tract, immune system...
April 2016: Uspekhi Fiziologicheskikh Nauk
Clive R Bramham, Kirk B Jensen, Christopher G Proud
The eukaryotic translation initiation factor (eIF) 4E, which binds to the 5'-cap of mRNA, undergoes phosphorylation on a single conserved serine, executed by the mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs). However, the functional consequences and physiological roles of MNK signalling have remained obscure. Now, new pharmacological and genetic tools have provided unprecedented insights into the function of MNKs and eIF4E phosphorylation. The studies suggest that MNKs control the translation of specific mRNAs in cancer metastasis and neuronal synaptic plasticity by a novel mechanism involving the regulation of the translational repressor, cytoplasmic fragile-X protein-interacting protein 1 (CYFIP1)...
October 2016: Trends in Biochemical Sciences
Pritha Majumder, Jen-Fei Chu, Biswanath Chatterjee, Krishna B S Swamy, Che-Kun James Shen
For proper mammalian brain development and functioning, the translation of many neuronal mRNAs needs to be repressed without neuronal activity stimulations. We have discovered that the expression of a subclass of neuronal proteins essential for neurodevelopment and neuron plasticity is co-regulated at the translational level by TDP-43 and the Fragile X Syndrome protein FMRP. Using molecular, cellular and imaging approaches, we show that these two RNA-binding proteins (RBP) co-repress the translation initiation of Rac1, Map1b and GluR1 mRNAs, and consequently the hippocampal spinogenesis...
August 12, 2016: Acta Neuropathologica
Lu Wang, Yan Wang, Shimeng Zhou, Liukun Yang, Qixin Shi, Yujiao Li, Kun Zhang, Le Yang, Minggao Zhao, Qi Yang
Fragile X syndrome (FXS) is a form of inherited mental retardation that results from the absence of the fragile X mental retardation protein (FMRP), the product of the Fmr1 gene. Numerous studies have shown that FMRP expression in astrocytes is important in the development of FXS. Although astrocytes affect neuronal dendrite development in Fmr1 knockout (KO) mice, the factors released by astrocytes are still unclear. We cultured wild type (WT) cortical neurons in astrocyte-conditioned medium (ACM) from WT or Fmr1 KO mice...
2016: Genes
Felipe J Bodaleo, Christian Gonzalez-Billault
The capacity of the nervous system to generate neuronal networks relies on the establishment and maintenance of synaptic contacts. Synapses are composed of functionally different presynaptic and postsynaptic compartments. An appropriate synaptic architecture is required to provide the structural basis that supports synaptic transmission, a process involving changes in cytoskeletal dynamics. Actin microfilaments are the main cytoskeletal components present at both presynaptic and postsynaptic terminals in glutamatergic synapses...
2016: Frontiers in Molecular Neuroscience
Torrey L S Truszkowski, Eric J James, Mashfiq Hasan, Tyler J Wishard, Zhenyu Liu, Kara G Pratt, Hollis T Cline, Carlos D Aizenman
BACKGROUND: Fragile X Syndrome is the leading monogenetic cause of autism and most common form of intellectual disability. Previous studies have implicated changes in dendritic spine architecture as the primary result of loss of Fragile X Mental Retardation Protein (FMRP), but recent work has shown that neural proliferation is decreased and cell death is increased with either loss of FMRP or overexpression of FMRP. The purpose of this study was to investigate the effects of loss of FMRP on behavior and cellular activity...
August 8, 2016: Neural Development
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