scholarly journals Impaired GABA Neural Circuits Are Critical for Fragile X Syndrome

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Fei Gao ◽  
Lijun Qi ◽  
Zhongzhen Yang ◽  
Tao Yang ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Gaba Receptors ◽  
Neural Circuits ◽  
Neural Circuit ◽  
Fragile X ◽  
Gamma Aminobutyric Acid ◽  
Severe Intellectual Disability ◽  
Sleep Rhythms ◽  
Mental Retardation Protein ◽  
Gaba Receptor Subunits

Fragile X syndrome (FXS) is an inheritable neuropsychological disease caused by silence of the fmr1 gene and the deficiency of Fragile X mental retardation protein (FMRP). Patients present neuronal alterations that lead to severe intellectual disability and altered sleep rhythms. However, the neural circuit mechanisms underlying FXS remain unclear. Previous studies have suggested that metabolic glutamate and gamma-aminobutyric acid (GABA) receptors/circuits are two counter-balanced factors involved in FXS pathophysiology. More and more studies demonstrated that attenuated GABAergic circuits in the absence of FMRP are critical for abnormal progression of FXS. Here, we reviewed the changes of GABA neural circuits that were attributed to intellectual-deficient FXS, from several aspects including deregulated GABA metabolism, decreased expressions of GABA receptor subunits, and impaired GABAergic neural circuits. Furthermore, the activities of GABA neural circuits are modulated by circadian rhythm of FMRP metabolism and reviewed the abnormal condition of FXS mice or patients.

scholarly journals Heart Activity and Autistic Behavior in Infants and Toddlers With Fragile X Syndrome

2012 ◽  
Vol 117 (2) ◽  
pp. 90-102 ◽  
Author(s):  
Jane E. Roberts ◽  
Bridgette Tonnsen ◽  
Ashley Robinson ◽  
Svetlana V. Shinkareva
Keyword(s):  
Fragile X Syndrome ◽  
Fragile X ◽  
Physiological Arousal ◽  
First Year ◽  
Typically Developing ◽  
Infants And Toddlers ◽  
Autistic Behavior ◽  
Endogenous Factors ◽  
Linear Effect ◽  
Mental Retardation Protein

Abstract The present study contrasted physiological arousal in infants and toddlers with fragile X syndrome to typically developing control participants and examined physiological predictors early in development to autism severity later in development in fragile X syndrome. Thirty-one males with fragile X syndrome (ages 8–40 months) and 25 age-matched control participants were included. The group with fragile X syndrome showed shorter interbeat intervals (IBIs), lower vagal tone (VT), and less modulation of IBI. Data suggested a nonlinear effect with IBI and autistic behavior; however, a linear effect with VT and autistic behavior emerged. These findings suggest that atypical physiological arousal emerges within the first year and predicts severity of autistic behavior in fragile X syndrome. These relationships are complex and dynamic, likely reflecting endogenous factors assumed to reflect atypical brain function secondary to reduced fragile X mental retardation protein. This research has important implications for the early identification and treatment of autistic behaviors in young children with fragile X syndrome.

scholarly journals Genetic removal of p70 S6K1 corrects coding sequence length-dependent alterations in mRNA translation in fragile X syndrome mice

2020 ◽  
Author(s):  
Sameer Aryal ◽  
Francesco Longo ◽  
Eric Klann
Keyword(s):  
Protein Synthesis ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
Mrna Translation ◽  
Ribosome Profiling ◽  
Sequence Length ◽  
Rna Seq ◽  
Double Knockout ◽  
Coding Sequence ◽  
Mental Retardation Protein

AbstractLoss of the fragile X mental retardation protein (FMRP) causes fragile X syndrome (FXS). FMRP is widely thought to repress protein synthesis, but its translational targets and modes of control remain in dispute. We previously showed that genetic removal of p70 S6 kinase 1 (S6K1) corrects altered protein synthesis as well as synaptic and behavioral phenotypes in FXS mice. In this study, we examined the gene-specificity of altered mRNA translation in FXS and the mechanism of rescue with genetic reduction of S6K1 by carrying out ribosome profiling and RNA-Seq on cortical lysates from wild-type, FXS, S6K1 knockout, and double knockout mice. We observed reduced ribosome footprint abundance in the majority of differentially translated genes in the cortices of FXS mice. We used molecular assays to discover evidence that the reduction in ribosome footprint abundance reflects an increased rate of ribosome translocation, which is captured as a decrease in the number of translating ribosomes at steady state, and is normalized by inhibition of S6K1. We also found that genetic removal of S6K1 prevented a positive-to-negative gradation of alterations in translation efficiencies (RF/mRNA) with coding sequence length across mRNAs in FXS mouse cortices. Our findings reveal the identities of dysregulated mRNAs and a molecular mechanism by which reduction of S6K1 prevents altered translation in FXS.

scholarly journals Role of microRNA Pathway in Mental Retardation

2007 ◽  
Vol 7 ◽  
pp. 146-154 ◽  
Author(s):  
Abrar Qurashi ◽  
Shuang Chang ◽  
Peng Jin
Keyword(s):  
Mental Retardation ◽  
Fragile X Syndrome ◽  
Genetic Basis ◽  
Fragile X ◽  
Biological Pathways ◽  
Fragile X Mental Retardation ◽  
Mental Retardation Protein ◽  
Mirna Pathway ◽  
Microrna Pathway

Deficits in cognitive functions lead to mental retardation (MR). Understanding the genetic basis of inherited MR has provided insights into the pathogenesis of MR. Fragile X syndrome is one of the most common forms of inherited MR, caused by the loss of functional Fragile X Mental Retardation Protein (FMRP).MicroRNAs (miRNAs) are endogenous, single-stranded RNAs between 18 and 25 nucleotides in length, which have been implicated in diversified biological pathways. Recent studies have linked the miRNA pathway to fragile X syndrome. Here we review the role of the miRNA pathway in fragile X syndrome and discuss its implication in MR in general.

Metformin for Treatment of Fragile X Syndrome and Other Neurological Disorders

2019 ◽  
Vol 70 (1) ◽  
pp. 167-181 ◽  
Author(s):  
Ilse Gantois ◽  
Jelena Popic ◽  
Arkady Khoutorsky ◽  
Nahum Sonenberg
Keyword(s):  
Fragile X Syndrome ◽  
Cognitive Deficits ◽  
Neurological Disorders ◽  
Fragile X ◽  
Autism Spectrum ◽  
Cellular Models ◽  
The Us ◽  
Mental Retardation Protein ◽  
Drug Treatments ◽  
Core Symptoms

Fragile X syndrome (FXS) is the most frequent inherited form of intellectual disability and autism spectrum disorder. Loss of the fragile X mental retardation protein, FMRP, engenders molecular, behavioral, and cognitive deficits in FXS patients. Experiments using different animal models advanced our knowledge of the pathophysiology of FXS and led to the discovery of many targets for drug treatments. In this review, we discuss the potential of metformin, an antidiabetic drug approved by the US Food and Drug Administration, to correct core symptoms of FXS and other neurological disorders in humans. We summarize its mechanisms of action in different animal and cellular models and human diseases.

scholarly journals The Fragile X Mental Retardation Protein: A Valuable Partner in the Battle against Epileptogenesis

2009 ◽  
Vol 9 (4) ◽  
pp. 116-118 ◽  
Author(s):  
Lisa R. Merlin
Keyword(s):  
Mental Retardation ◽  
Fragile X Syndrome ◽  
Metabotropic Glutamate Receptor ◽  
Mossy Fiber ◽  
Fragile X ◽  
Critical Role ◽  
Fmr1 Gene ◽  
Metabotropic Glutamate ◽  
Fragile X Mental Retardation ◽  
Mental Retardation Protein

Correction of Fragile X Syndrome in Mice. Dölen G, Osterweil E, Rao BSS, Smith GB, Auerbach BD, Chattarji S, Bear MF. Neuron 2007;56:955–962. Fragile X syndrome (FXS) is the most common form of heritable mental retardation and the leading identified cause of autism. FXS is caused by transcriptional silencing of the FMR1 gene that encodes the fragile X mental retardation protein (FMRP), but the pathogenesis of the disease is unknown. According to one proposal, many psychiatric and neurological symptoms of FXS result from unchecked activation of mGluR5, a metabotropic glutamate receptor. To test this idea we generated Fmr1 mutant mice with a 50% reduction in mGluR5 expression and studied a range of phenotypes with relevance to the human disorder. Our results demonstrate that mGluR5 contributes significantly to the pathogenesis of the disease, a finding that has significant therapeutic implications for fragile X and related developmental disorders. Limbic Epileptogenesis in a Mouse Model of Fragile X Syndrome. Qiu LF, Lu TJ, Hu XL, Yi YH, Liao WP, Xiong ZQ. Cereb Cortex 2009 in press. (doi:10.1093/cercor/bhn163) Fragile X syndrome (FXS), caused by silencing of the Fmr1 gene, is the most common form of inherited mental retardation. Epilepsy is reported to occur in 20–25% of individuals with FXS. However, no overall increased excitability has been reported in Fmr1 knockout (KO) mice, except for increased sensitivity to auditory stimulation. Here, we report that kindling increased the expressions of Fmr1 mRNA and protein in the forebrain of wild-type (WT) mice. Kindling development was dramatically accelerated in Fmr1 KO mice, and Fmr1 KO mice also displayed prolonged electrographic seizures during kindling and more severe mossy fiber sprouting after kindling. The accelerated rate of kindling was partially repressed by inhibiting N-methyl-D-aspartic acid receptor (NMDAR) with MK-801 or mGluR5 receptor with 2-methyl-6-(phenylethynyl)-pyridine (MPEP). The rate of kindling development in WT was not effected by MPEP, however, suggesting that FMRP normally suppresses epileptogenic signaling downstream of metabotropic glutamate receptors. Our findings reveal that FMRP plays a critical role in suppressing limbic epileptogenesis and predict that the enhanced susceptibility of patients with FXS to epilepsy is a direct consequence of the loss of an important homeostatic factor that mitigates vulnerability to excessive neuronal excitation.

scholarly journals The Contribution of Pluripotent Stem Cell (PSC)-Based Models to the Study of Fragile X Syndrome (FXS)

2019 ◽  
Vol 9 (2) ◽  
pp. 42 ◽  
Author(s):  
Manar Abu Diab ◽  
Rachel Eiges
Keyword(s):  
Stem Cells ◽  
Gene Silencing ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
Embryonic Stem ◽  
Cgg Repeat ◽  
Molecular Features ◽  
Epigenetic Gene Silencing ◽  
Mental Retardation Protein ◽  
Induced Pluripotent

Fragile X syndrome (FXS) is the most common heritable form of cognitive impairment. It results from a deficiency in the fragile X mental retardation protein (FMRP) due to a CGG repeat expansion in the 5′-UTR of the X-linked FMR1 gene. When CGGs expand beyond 200 copies, they lead to epigenetic gene silencing of the gene. In addition, the greater the allele size, the more likely it will become unstable and exhibit mosaicism for expansion size between and within tissues in affected individuals. The timing and mechanisms of FMR1 epigenetic gene silencing and repeat instability are far from being understood given the lack of appropriate cellular and animal models that can fully recapitulate the molecular features characteristic of the disease pathogenesis in humans. This review summarizes the data collected to date from mutant human embryonic stem cells, induced pluripotent stem cells, and hybrid fusions, and discusses their contribution to the investigation of FXS, their key limitations, and future prospects.

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