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Stephen T Warren - One of the best experts on this subject based on the ideXlab platform.
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reactivation of FMR1 by crispr cas9 mediated deletion of the expanded cgg repeat of the fragile x chromosome
PLOS ONE, 2016Co-Authors: He Gong, Joshua A Suhl, Pankaj Chopra, Tao Wang, Stephen T WarrenAbstract:Fragile X syndrome (FXS) is a common cause of intellectual disability that is most often due to a CGG-repeat expansion mutation in the FMR1 gene that triggers epigenetic gene silencing. Epigenetic modifying drugs can only transiently and modestly induce FMR1 reactivation in the presence of the elongated CGG repeat. As a proof-of-principle, we excised the expanded CGG-repeat in both somatic cell hybrids containing the human fragile X chromosome and human FXS iPS cells using the CRISPR/Cas9 genome editing. We observed transcriptional reactivation in approximately 67% of the CRISPR cut hybrid colonies and in 20% of isolated human FXS iPSC colonies. The reactivated cells produced FMRP and exhibited a decline in DNA methylation at the FMR1 locus. These data demonstrate the excision of the expanded CGG-repeat from the fragile X chromosome can result in FMR1 reactivation.
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a 3 untranslated region variant in FMR1 eliminates neuronal activity dependent translation of fmrp by disrupting binding of the rna binding protein hur
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Joshua A Suhl, Gary J Bassell, Jeannie Visootsak, Ravi S Muddashetty, Marius F. Ifrim, Bart R Anderson, Stephen T WarrenAbstract:Fragile X syndrome is a common cause of intellectual disability and autism spectrum disorder. The gene underlying the disorder, fragile X mental retardation 1 (FMR1), is silenced in most cases by a CGG-repeat expansion mutation in the 5′ untranslated region (UTR). Recently, we identified a variant located in the 3′UTR of FMR1 enriched among developmentally delayed males with normal repeat lengths. A patient-derived cell line revealed reduced levels of endogenous fragile X mental retardation protein (FMRP), and a reporter containing a patient 3′UTR caused a decrease in expression. A control reporter expressed in cultured mouse cortical neurons showed an expected increase following synaptic stimulation that was absent when expressing the patient reporter, suggesting an impaired response to neuronal activity. Mobility-shift assays using a control RNA detected an RNA–protein interaction that is lost with the patient RNA, and HuR was subsequently identified as an associated protein. Cross-linking immunoprecipitation experiments identified the locus as an in vivo target of HuR, supporting our in vitro findings. These data suggest that the disrupted interaction of HuR impairs activity-dependent translation of FMRP, which may hinder synaptic plasticity in a clinically significant fashion.
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human fmrp contains an integral tandem agenet tudor and kh motif in the amino terminal domain
Human Molecular Genetics, 2015Co-Authors: Leila K Myrick, Hideharu Hashimoto, Xiaodong Cheng, Stephen T WarrenAbstract:Fragile X syndrome, a common cause of intellectual disability and autism, is due to mutational silencing of the FMR1 gene leading to the absence of its gene product, fragile X mental retardation protein (FMRP). FMRP is a selective RNA binding protein owing to two central K-homology domains and a C-terminal arginine-glycine-glycine (RGG) box. However, several properties of the FMRP amino terminus are unresolved. It has been documented for over a decade that the amino terminus has the ability to bind RNA despite having no recognizable functional motifs. Moreover, the amino terminus has recently been shown to bind chromatin and influence the DNA damage response as well as function in the presynaptic space, modulating action potential duration.Wereportheretheaminoterminalcrystalstructuresofwild-typeFMRP,andamutant (R138Q)thatdisruptstheamino terminus function, containing an integral tandem Agenet and discover a novel KH motif.
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independent role for presynaptic fmrp revealed by an FMR1 missense mutation associated with intellectual disability and seizures
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Leila K Myrick, Pan Yue Deng, Hideharu Hashimoto, Young Mi Oh, Mickael Poidevin, Joshua A Suhl, Jeannie Visootsak, Valeria Cavalli, Xiaodong Cheng, Stephen T WarrenAbstract:Fragile X syndrome (FXS) results in intellectual disability (ID) most often caused by silencing of the fragile X mental retardation 1 (FMR1) gene. The resulting absence of fragile X mental retardation protein 1 (FMRP) leads to both pre- and postsynaptic defects, yet whether the pre- and postsynaptic functions of FMRP are independent and have distinct roles in FXS neuropathology remain poorly understood. Here, we demonstrate an independent presynaptic function for FMRP through the study of an ID patient with an FMR1 missense mutation. This mutation, c.413G > A (R138Q), preserves FMRP’s canonical functions in RNA binding and translational regulation, which are traditionally associated with postsynaptic compartments. However, neuronally driven expression of the mutant FMRP is unable to rescue structural defects at the neuromuscular junction in fragile x mental retardation 1 (dFMR1)-deficient Drosophila, suggesting a presynaptic-specific impairment. Furthermore, mutant FMRP loses the ability to rescue presynaptic action potential (AP) broadening in FMR1 KO mice. The R138Q mutation also disrupts FMRP’s interaction with the large-conductance calcium-activated potassium (BK) channels that modulate AP width. These results reveal a presynaptic- and translation-independent function of FMRP that is linked to a specific subset of FXS phenotypes.
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mosaic FMR1 deletion causes fragile x syndrome and can lead to molecular misdiagnosis a case report and review of the literature
American Journal of Medical Genetics Part A, 2008Co-Authors: Bradford Coffee, Morna Ikeda, Dejan B Budimirovic, Lawrence N Hjelm, Walter E Kaufmann, Stephen T WarrenAbstract:The most common cause of fragile X syndrome is expansion of a CGG trinucleotide repeat in the 5′UTR of FMR1. This expansion leads to transcriptional silencing of the gene. However, other mutational mechanisms, such as deletions of FMR1, also cause fragile X syndrome. The result is the same for both the expansion mediated silencing and deletion, absence of the gene product, FMRP. We report here on an 11-year-old boy with a cognitive and behavioral profile with features compatible with, but not specific to, fragile X syndrome. A mosaic deletion of 1,013,395 bp was found using high-density X chromosome microarray analysis followed by sequencing of the deletion breakpoints. We review the literature of FMR1 deletions and present this case in the context of other FMR1 deletions having mental retardation that may or may not have the classic fragile X phenotype. © 2008 Wiley-Liss, Inc.
Rob Willemsen - One of the best experts on this subject based on the ideXlab platform.
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Paradoxical effect of baclofen on social behavior in the fragile X syndrome mouse model
Brain and behavior, 2018Co-Authors: Shimriet Zeidler, Israa A. Jaafar, Helen De Boer, Ronald A.m. Buijsen, Celine De Esch, Ingeborg Nieuwenhuizen-bakker, Renate K. Hukema, Rob WillemsenAbstract:textabstractIntroduction: Fragile X syndrome (FXS) is a common monogenetic cause of intellectual disability, autism spectrum features, and a broad range of other psychiatric and medical problems. FXS is caused by the lack of the fragile X mental retardation protein (FMRP), a translational regulator of specific mRNAs at the postsynaptic compartment. The absence of FMRP leads to aberrant synaptic plasticity, which is believed to be caused by an imbalance in excitatory and inhibitory network functioning of the synapse. Evidence from studies in mice demonstrates that GABA, the major inhibitory neurotransmitter in the brain, and its receptors, is involved in the pathogenesis of FXS. Moreover, several FXS phenotypes, including social behavior deficits, could be corrected in FMR1 KO mice after acute treatment with GABAB agonists. Methods: As FXS would probably require a lifelong treatment, we investigated the effect of chronic treatment with the GABAB agonist baclofen on social behavior in FMR1 KO mice on two behavioral paradigms for social behavior: the automated tube test and the three-chamber sociability test. Results: Unexpectedly, chronic baclofen treatment resulted in worsening of the FXS phenotypes in these behavior tests. Strikingly, baclofen treatment also affected wild-type animals in both behavioral tests, inducing a phenotype similar to that of untreated FMR1 KO mice. Conclusion: Altogether, the disappointing results of recent clinical trials with the R-baclofen enantiomer arbaclofen and our current results indicate that baclofen should be reconsidered and further evaluated before its application in targeted treatment for FXS.
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Synaptic vesicle dynamic changes in a model of fragile X
Molecular Autism, 2016Co-Authors: Jantine A. C. Broek, Rob Willemsen, Chris I De Zeeuw, H. Martijn De Gruiter, Heleen Van ‘t Spijker, Elize D. Haasdijk, Sureyya Ozcan, Gert W. A. Van Cappellen, Adriaan B. Houtsmuller, Sabine BahnAbstract:Background Fragile X syndrome (FXS) is a single-gene disorder that is the most common heritable cause of intellectual disability and the most frequent monogenic cause of autism spectrum disorders (ASD). FXS is caused by an expansion of trinucleotide repeats in the promoter region of the fragile X mental retardation gene ( FMR1 ). This leads to a lack of fragile X mental retardation protein (FMRP), which regulates translation of a wide range of messenger RNAs (mRNAs). The extent of expression level alterations of synaptic proteins affected by FMRP loss and their consequences on synaptic dynamics in FXS has not been fully investigated. Methods Here, we used an FMR1 knockout (KO) mouse model to investigate the molecular mechanisms underlying FXS by monitoring protein expression changes using shotgun label-free liquid-chromatography mass spectrometry (LC-MS^E) in brain tissue and synaptosome fractions. FXS-associated candidate proteins were validated using selected reaction monitoring (SRM) in synaptosome fractions for targeted protein quantification. Furthermore, functional alterations in synaptic release and dynamics were evaluated using live-cell imaging, and interpretation of synaptic dynamics differences was investigated using electron microscopy. Results Key findings relate to altered levels of proteins involved in GABA-signalling, especially in the cerebellum. Further exploration using microscopy studies found reduced synaptic vesicle unloading of hippocampal neurons and increased vesicle unloading in cerebellar neurons, which suggests a general decrease of synaptic transmission. Conclusions Our findings suggest that FMRP is a regulator of synaptic vesicle dynamics, which supports the role of FMRP in presynaptic functions. Taken together, these studies provide novel insights into the molecular changes associated with FXS.
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rescue of dendritic spine phenotype in FMR1 ko mice with the mglur5 antagonist afq056 mavoglurant
Psychopharmacology, 2014Co-Authors: Josien Levenga, Ronald A.m. Buijsen, Celine De Esch, Ben A Oostra, Ingeborg M Nieuwenhuizen, Fabrizio Gasparini, Tracy Li, Aaron Isaacs, Rob WillemsenAbstract:Fragile X syndrome (FXS) is the leading monogenic cause of intellectual disability and autism. The disease is a result of lack of expression of the fragile X mental retardation protein. Brain tissues of patients with FXS and mice with FMRP deficiency have shown an abnormal dendritic spine phenotype. We investigated the dendritic spine length and density of hippocampal CA1 pyramidal neurons in 2-, 10-, and 25-week-old FMR1 knockout (KO). Next, we studied the effects of long-term treatment with an mGluR5 antagonist, AFQ056/Mavoglurant, on the spine phenotype in adult FMR1 KO mice. We observed alterations in the spine phenotype during development, with a decreased spine length in 2-week-old FMR1 KO mice compared with age-match wild-type littermates, but with increased spine length in FMR1 KO mice compared with 10- and 25-week-old wild-type controls. No difference was found in spine density at any age. We report a rescue of the abnormal spine length in adult FMR1 KO mice after a long-term treatment with AFQ056/Mavoglurant. This finding suggests that long-term treatment at later stage is sufficient to reverse the structural spine abnormalities and represents a starting point for future studies aimed at improving treatments for FXS.
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chronic administration of afq056 mavoglurant restores social behaviour in FMR1 knockout mice
Behavioural Brain Research, 2013Co-Authors: Ilse Gantois, Ronald A.m. Buijsen, Celine De Esch, Ben A Oostra, Tine Pooters, Baltazar Gomezmancilla, Fabrizio Gasparini, Rudi Dhooge, Rob WillemsenAbstract:Fragile X syndrome is caused by lack of FMR1 protein (FMRP) leading to severe symptoms, including intellectual disability, hyperactivity and autistic-like behaviour. FMRP is an RNA binding protein involved in the regulation of translation of specific target mRNAs upon stimulation of metabotropic glutamate receptor 5 (mGluR5) at the synapse. The absence of FMRP leads to enhanced activity of mGluR5 signal transduction pathways. Many conflicting results have been reported regarding social behaviour deficits in FMR1 knockout mice, and little is known about the involvement of mGluR5 pathways on social behaviour.In this study, a three-chambered task was used to determine sociability and preference for social novelty in FMR1 knockout mice. Disruption of FMR1 functioning resulted in enhanced interaction with stranger mouse during sociability while no significant changes were observed during preference for social novelty assay. Chronic administration of a specific mGluR5 antagonist, AFQ056/Mavoglurant, was able to restore sociability behaviour of FMR1 knockout mice to levels of wild type littermates.These results support the importance of mGluR5 signalling pathways on social interaction behaviour and that AFQ056/Mavoglurant might be useful as potential therapeutic intervention to rescue various behavioural aspects of the fragile X phenotype. © 2012 .
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rescue of behavioral phenotype and neuronal protrusion morphology in FMR1 ko mice
Neurobiology of Disease, 2008Co-Authors: Femke M S De Vrij, Ben A Oostra, David L Nelson, Josien Levenga, Herma C Van Der Linde, S K E Koekkoek, Chris I De Zeeuw, Rob WillemsenAbstract: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.
Flora Tassone - One of the best experts on this subject based on the ideXlab platform.
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Elevated FMR1-mRNA and lowered FMRP – A double-hit mechanism for psychiatric features in men with FMR1 premutations
Translational Psychiatry, 2020Co-Authors: Andrea Schneider, Flora Tassone, Paul J Hagerman, Louise W Gane, Tri Indah Winarni, Ana María Cabal-herrera, Susan Bacalman, Randi J HagermanAbstract:Fragile X syndrome (FXS) is caused by a full mutation of the FMR1 gene (>200 CGG repeats and subsequent methylation), such that there is little or no FMR1 protein (FMRP) produced, leading to intellectual disability (ID). Individuals with the premutation allele (55–200 CGG repeats, generally unmethylated) have elevated FMR1 mRNA levels, a consequence of enhanced transcription, resulting in neuronal toxicity and a spectrum of premutation-associated disorders, including the neurodegenerative disorder fragile X-associated tremor/ataxia syndrome (FXTAS). Here we described 14 patients who had both lowered FMRP and elevated FMR1 mRNA levels, representing dual mechanisms of clinical involvement, which may combine features of both FXS and FXTAS. In addition, the majority of these cases show psychiatric symptoms, including bipolar disorder, and/or psychotic features, which are rarely seen in those with just FXS.
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reduced vagal tone in women with the FMR1 premutation is associated with FMR1 mrna but not depression or anxiety
Journal of Neurodevelopmental Disorders, 2017Co-Authors: Jessica Klusek, Ted W Brown, Flora Tassone, Giuseppe Lafauci, Tatyana Adayev, Jane E RobertsAbstract:Autonomic dysfunction is implicated in a range of psychological conditions, including depression and anxiety. The fragile X mental retardation-1 (FMR1) premutation is a common genetic mutation that affects ~1:150 women and is associated with psychological vulnerability. This study examined cardiac indicators of autonomic function among women with the FMR1 premutation and control women as potential biomarkers for psychological risk that may be linked to FMR1. Baseline inter-beat interval and respiratory sinus arrhythmia (a measure of parasympathetic vagal tone) were measured in 35 women with the FMR1 premutation and 28 controls. The women completed anxiety and depression questionnaires. FMR1 genetic indices (i.e., CGG repeat, quantitative FMRP, FMR1 mRNA, activation ratio) were obtained for the premutation group. Respiratory sinus arrhythmia was reduced in the FMR1 premutation group relative to controls. While depression symptoms were associated with reduced respiratory sinus arrhythmia among control women, these variables were unrelated in the FMR1 premutation. Elevated FMR1 mRNA was associated with higher respiratory sinus arrhythmia. Women with the FMR1 premutation demonstrated autonomic dysregulation characterized by reduced vagal tone. Unlike patterns observed in the general population and in study controls, vagal activity and depression symptoms were decoupled in women with the FMR1 premutation, suggesting independence between autonomic regulation and psychopathological symptoms that is atypical and potentially specific to the FMR1 premutation. The association between vagal tone and mRNA suggests that molecular variation associated with FMR1 plays a role in autonomic regulation.
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clinical and molecular implications of mosaicism in FMR1 full mutations
Frontiers in Genetics, 2014Co-Authors: Dalyir I Pretto, Randi J Hagerman, Paul J Hagerman, Carolyn M Yrigollen, Hiu Tung Tang, John Williamson, Glenda M Espinal, Chris K Iwahashi, Blythe Durbinjohnson, Flora TassoneAbstract:Expansions of more than 200 CGG repeats (full mutation) in the FMR1 gene give rise to fragile X syndrome (FXS) through a process that generally involves hypermethylation of the FMR1 promoter region and gene silencing, resulting in absence of expression of the encoded protein, FMRP. However, mosaicism with alleles differing in size and extent of methylation often exist within or between tissues of individuals with FXS. In the current work, CGG-repeat lengths and methylation status were assessed for eighteen individuals with FXS, including 13 mosaics, for which peripheral blood cells (PBMCs) and primary fibroblast cells were available. Our results show that for both PBMCs and fibroblasts, FMR1 mRNA and FMRP expression are directly correlated with the percent of methylation of the FMR1 allele. In addition, Full Scale IQ scores were inversely correlated with the percent methylation and positively correlated with higher FMRP expression. These latter results point toward a positive impact on cognition for full mutation mosaics with lower methylation compared to individuals with fully methylated, full mutation alleles. However, we did not observe a significant reduction in the number of seizures, nor in the severity of hyperactivity or autism spectrum disorder, among individuals with mosaic genotypes in the presentation of FXS. These observations suggest that low, but non-zero expression of FMRP may be sufficient to positively impact cognitive function in individuals with FXS, with methylation mosaicism (lowered methylation fraction) contributing to a more positive clinical outcome.
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methylation of novel markers of fragile x alleles is inversely correlated with fmrp expression and FMR1 activation ratio
Human Molecular Genetics, 2010Co-Authors: David E Godler, Flora Tassone, Randi J Hagerman, Annette K Taylor, Danuta Z Loesch, Freya Gehling, Trent Burgess, Devika Ganesamoorthy, Debbie HennerichAbstract:The fragile X syndrome (FXS) is caused by silencing of the fragile X mental retardation gene (FMR1) and the absence of its product, fragile X mental retardation protein (FMRP), resulting from CpG island methylation associated with large CGG repeat expansions (more than 200) termed full mutation (FM). We have identified a number of novel epigenetic markers for FXS using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), naming the most informative fragile X-related epigenetic element 1 (FREE1) and 2 (FREE2). Methylation of both regions was correlated with that of the FMR1 CpG island detected using Southern blot (FREE1 R = 0.97; P < 0.00001, n = 23 and FREE2 R = 0.93; P < 0.00001, n = 23) and negatively correlated with lymphocyte expression of FMRP (FREE1 R = −0.62; P = 0.01, n = 15 and FREE2 R = −0.55; P = 0.03, n = 15) in blood of partially methylated ‘high functioning’ FM males. In blood of FM carrier females, methylation of both markers was inversely correlated with the FMR1 activation ratio (FREE1 R = −0.93; P < 0.0001, n = 12 and FREE2 R = −0.95; P < 0.0001, n = 9). In a sample set of 49 controls, 18 grey zone (GZ 40–54 repeats), 22 premutation (PM 55–170 repeats) and 22 (affected) FXS subjects, the FREE1 methylation pattern was consistent between blood and chorionic villi as a marker of methylated FM alleles and could be used to differentiate FXS males and females from controls, as well as from carriers of GZ/PM alleles, but not between GZ and PM alleles and controls. Considering its high-throughput and specificity for pathogenic FM alleles, low cost and minimal DNA requirements, FREE MALDI-TOF MS offers a unique tool in FXS diagnostics and newborn population screening.
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abnormal elevation of FMR1 mrna is associated with psychological symptoms in individuals with the fragile x premutation
American Journal of Medical Genetics, 2005Co-Authors: David R Hessl, Flora Tassone, Louise W Gane, Danuta Z Loesch, Elizabeth Berrykravis, Maureen A Leehey, Ingrid Barbato, Cathlin Rice, Emma Gould, Deborah A HallAbstract:Until recently, individuals with premutation alleles (55–200 CGG repeats) of the fragile X mental retardation 1 (FMR1) gene were believed to be psychologically unaffected. However, the recent documentation of abnormal elevation of FMR1 mRNA, discovery of fragile X-associated tremor/ataxia syndrome (FXTAS), and reports of psychiatric disorders in children and adults with the premutation have suggested a pathogenic gene–brain–behavior mechanism. In a large collaborative study, 68 men and 144 women with the FMR1 premutation completed a psychological symptoms checklist and FMR1 genetic testing, including determination of CGG repeat size, percentage of FMR1 protein (FMRP)-positive lymphocytes, and FMR1 mRNA levels. Relative to published norms, men and women with FXTAS symptoms reported higher levels of several types of psychological symptoms. In addition, men and women with the premutation and no overt evidence of FXTAS reported higher levels of obsessive-compulsive symptoms. Elevated FMR1 mRNA, but not CGG repeat size or reduced FMRP (as measured by immunocytochemistry), was significantly associated with increased psychological symptoms, predominantly obsessive-compulsive symptoms and psychoticism, in premutation men with and without FXTAS symptoms. There was no relationship between CGG repeat size, FMR1 mRNA or FMRP and psychological symptoms in premutation women unless the sample was restricted to those with skewed X-activation ratio toward >50% active premutation alleles. The results of this study support the hypothesis that FMR1 function is associated with psychological difficulties in individuals with the premutation, and provide evidence concordant with an RNA toxic gain-of-function model in a neuropsychiatric phenotype. © 2005 Wiley-Liss, Inc.
Paul J Hagerman - One of the best experts on this subject based on the ideXlab platform.
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Elevated FMR1-mRNA and lowered FMRP – A double-hit mechanism for psychiatric features in men with FMR1 premutations
Translational Psychiatry, 2020Co-Authors: Andrea Schneider, Flora Tassone, Paul J Hagerman, Louise W Gane, Tri Indah Winarni, Ana María Cabal-herrera, Susan Bacalman, Randi J HagermanAbstract:Fragile X syndrome (FXS) is caused by a full mutation of the FMR1 gene (>200 CGG repeats and subsequent methylation), such that there is little or no FMR1 protein (FMRP) produced, leading to intellectual disability (ID). Individuals with the premutation allele (55–200 CGG repeats, generally unmethylated) have elevated FMR1 mRNA levels, a consequence of enhanced transcription, resulting in neuronal toxicity and a spectrum of premutation-associated disorders, including the neurodegenerative disorder fragile X-associated tremor/ataxia syndrome (FXTAS). Here we described 14 patients who had both lowered FMRP and elevated FMR1 mRNA levels, representing dual mechanisms of clinical involvement, which may combine features of both FXS and FXTAS. In addition, the majority of these cases show psychiatric symptoms, including bipolar disorder, and/or psychotic features, which are rarely seen in those with just FXS.
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clinical and molecular implications of mosaicism in FMR1 full mutations
Frontiers in Genetics, 2014Co-Authors: Dalyir I Pretto, Randi J Hagerman, Paul J Hagerman, Carolyn M Yrigollen, Hiu Tung Tang, John Williamson, Glenda M Espinal, Chris K Iwahashi, Blythe Durbinjohnson, Flora TassoneAbstract:Expansions of more than 200 CGG repeats (full mutation) in the FMR1 gene give rise to fragile X syndrome (FXS) through a process that generally involves hypermethylation of the FMR1 promoter region and gene silencing, resulting in absence of expression of the encoded protein, FMRP. However, mosaicism with alleles differing in size and extent of methylation often exist within or between tissues of individuals with FXS. In the current work, CGG-repeat lengths and methylation status were assessed for eighteen individuals with FXS, including 13 mosaics, for which peripheral blood cells (PBMCs) and primary fibroblast cells were available. Our results show that for both PBMCs and fibroblasts, FMR1 mRNA and FMRP expression are directly correlated with the percent of methylation of the FMR1 allele. In addition, Full Scale IQ scores were inversely correlated with the percent methylation and positively correlated with higher FMRP expression. These latter results point toward a positive impact on cognition for full mutation mosaics with lower methylation compared to individuals with fully methylated, full mutation alleles. However, we did not observe a significant reduction in the number of seizures, nor in the severity of hyperactivity or autism spectrum disorder, among individuals with mosaic genotypes in the presentation of FXS. These observations suggest that low, but non-zero expression of FMRP may be sufficient to positively impact cognitive function in individuals with FXS, with methylation mosaicism (lowered methylation fraction) contributing to a more positive clinical outcome.
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Influence of the fragile X mental retardation (FMR1) gene on the brain and working memory in men with normal FMR1 alleles.
NeuroImage, 2012Co-Authors: Jun Yi Wang, Randi J Hagerman, Paul J Hagerman, David R Hessl, Christine Iwahashi, Katherine Cheung, Andrea Schneider, Susan M. RiveraAbstract:Abstract The fragile X mental retardation 1 (FMR1) gene plays an important role in the development and maintenance of neuronal circuits that are essential for cognitive functioning. We explored the functional linkage(s) among lymphocytic FMR1 gene expression, brain structure, and working memory in healthy adult males. We acquired T1-weighted and diffusion tensor imaging from 37 males (18–80 years, mean ± SD = 40.7 ± 17.3 years) with normal FMR1 alleles and performed genetic and working memory assessments. Brain measurements were obtained from fiber tracts important for working memory (i.e. the arcuate fasciculus, anterior cingulum bundle, inferior longitudinal fasciculus, and the genu and anterior body of the corpus callosum), individual voxels, and whole brain. Both FMR1 mRNA and protein (FMRP) levels exhibited significant associations with brain measurements, with FMRP correlating positively with gray matter volume and white matter structural organization, and FMR1 mRNA negatively with white matter structural organization. The correlation was widespread, impacting rostral white matter and 2 working-memory fiber tracts for FMRP, and all cerebral white matter areas except the fornix and cerebellar peduncles and all 4 fiber tracts for FMR1 mRNA. In addition, the levels of FMR1 mRNA as well as the fiber tracts demonstrated a significant correlation with working memory performance. While FMR1 mRNA exhibited a negative correlation with working memory, fiber tract structural organization showed a positive correlation. These findings suggest that the FMR1 gene is a genetic factor common for both working memory and brain structure, and has implications for our understanding of the transmission of intelligence and brain structure.
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the cgg n repeat element within the 5 untranslated region of the FMR1 message provides both positive and negative cis effects on in vivo translation of a downstream reporter
Human Molecular Genetics, 2003Co-Authors: Li Sheng Chen, Flora Tassone, Parminder Sahota, Paul J HagermanAbstract:The human fragile X mental retardation 1 (FMR1) gene contains a polymorphic (CGG) trinucleotide repeat element in its 5' untranslated region. Expansion of the (CGG) n element beyond 200 repeats (full mutation range) generally leads to transcriptional silencing; consequent loss of the FMR1 protein (FMRP) results in fragile X syndrome, the most frequent form of inherited mental impairment. For carriers of smaller expansions (55 ≤ n ≤ 200; premutation range), FMRP levels are gradually reduced with increasing repeat number, despite elevated FMR1 mRNA levels, suggesting that translation is impeded within the premutation range. To examine in more detail the influence of the CGG repeat on translation, CMV immediate-early promoter constructs, containing the FMR1 5'-UTR with various (CGG) n repeat lengths (0≤n≤99) and a downstream (luciferase) reporter, were transfected into two human cell lines, a neural cell-derived line (SK) and a fetal kidney cell-derived line (293). For both cell types, the CGG element exerts distinct effects on reporter expression, depending on the length of the repeat. For n ≥ 30, luciferase expression decreases with increasing repeat length, consistent with earlier observations of decreased FMRP expression in peripheral blood leucocytes over the same repeat range, despite a slight increase in mRNA level for the larger repeats. Surprisingly, for smaller alleles (0 ≤ n ≤ 30), reporter expression actually increases by nearly two-fold with increasing repeat length in the absence of any change in mRNA level. These results suggest that the CGG repeat element can exert both positive (n 30) effects on translation. Interestingly, optimal translation appears to occur near the modal repeat number within the general human population.
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reduced FMR1 mrna translation efficiency in fragile x patients with premutations
RNA, 2002Co-Authors: Beatrice Primerano, Flora Tassone, Randi J Hagerman, Paul J Hagerman, Francesco Amaldi, Claudia BagniAbstract:The Fragile X mental retardation gene (FMR1) contains a polymorphic trinucleotide CGG repeat in the 59 untranslated region (UTR) of the FMR1 messenger. We have characterized three lymphoblastoid cell lines derived from unrelated male carriers of a premutation that overexpress FMR1 mRNA and show reduced FMRP level compared to normal cells. The analysis of polysomes/mRNPs distribution of mRNA in the cell lines with a premutation shows that the polysomal association of FMR1 mRNA, which is high in normal cells, becomes progressively lower with increasing CGG repeat expansion. In addition, we could detect a very low level of FMR1 mRNA in a lymphoblastoid cell line from a patient with a full mutation. In this case, FMR1 mRNA is not at all associated with polysomes, in agreement with the complete absence of FMRP. The impairment of FMR1 mRNA translation in patients with the Fragile X syndrome with FMR1 premutation is the cause of the lower FMRP levels that leads to the clinical involvement.
Randi J Hagerman - One of the best experts on this subject based on the ideXlab platform.
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Elevated FMR1-mRNA and lowered FMRP – A double-hit mechanism for psychiatric features in men with FMR1 premutations
Translational Psychiatry, 2020Co-Authors: Andrea Schneider, Flora Tassone, Paul J Hagerman, Louise W Gane, Tri Indah Winarni, Ana María Cabal-herrera, Susan Bacalman, Randi J HagermanAbstract:Fragile X syndrome (FXS) is caused by a full mutation of the FMR1 gene (>200 CGG repeats and subsequent methylation), such that there is little or no FMR1 protein (FMRP) produced, leading to intellectual disability (ID). Individuals with the premutation allele (55–200 CGG repeats, generally unmethylated) have elevated FMR1 mRNA levels, a consequence of enhanced transcription, resulting in neuronal toxicity and a spectrum of premutation-associated disorders, including the neurodegenerative disorder fragile X-associated tremor/ataxia syndrome (FXTAS). Here we described 14 patients who had both lowered FMRP and elevated FMR1 mRNA levels, representing dual mechanisms of clinical involvement, which may combine features of both FXS and FXTAS. In addition, the majority of these cases show psychiatric symptoms, including bipolar disorder, and/or psychotic features, which are rarely seen in those with just FXS.
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genetics white matter and cognition the effects of methylation on FMR1
Neurology, 2017Co-Authors: Paul A Nyquist, Randi J HagermanAbstract:The fragile X-associated tremor/ataxia syndrome (FXTAS) is an X-linked genetic disorder in which the premutation (55–200 CGG repeats) in fragile X mental retardation 1 ( FMR1 ) causes elevated levels of FMR1 mRNA, which in turn causes RNA toxicity through sequestration of critical proteins, dysregulated DNA repair processes, and production of FMRpolyG, a toxic protein produced from repeat-associated non-AUG (RAN) translation.1,2 FXTAS is associated with tremor and ataxia, and it presents in aging carriers of the premutation. However, there is evidence that the premutation causes changes in the brain far earlier than the onset of tremor and ataxia.3,4 The premutation is unmethylated, whereas those with fragile X syndrome have a full mutation (>200 CGG repeats), and the full mutation is methylated, leading to a lack of mRNA and a lack of fragile X mental retardation protein (FMRP).
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clinical and molecular implications of mosaicism in FMR1 full mutations
Frontiers in Genetics, 2014Co-Authors: Dalyir I Pretto, Randi J Hagerman, Paul J Hagerman, Carolyn M Yrigollen, Hiu Tung Tang, John Williamson, Glenda M Espinal, Chris K Iwahashi, Blythe Durbinjohnson, Flora TassoneAbstract:Expansions of more than 200 CGG repeats (full mutation) in the FMR1 gene give rise to fragile X syndrome (FXS) through a process that generally involves hypermethylation of the FMR1 promoter region and gene silencing, resulting in absence of expression of the encoded protein, FMRP. However, mosaicism with alleles differing in size and extent of methylation often exist within or between tissues of individuals with FXS. In the current work, CGG-repeat lengths and methylation status were assessed for eighteen individuals with FXS, including 13 mosaics, for which peripheral blood cells (PBMCs) and primary fibroblast cells were available. Our results show that for both PBMCs and fibroblasts, FMR1 mRNA and FMRP expression are directly correlated with the percent of methylation of the FMR1 allele. In addition, Full Scale IQ scores were inversely correlated with the percent methylation and positively correlated with higher FMRP expression. These latter results point toward a positive impact on cognition for full mutation mosaics with lower methylation compared to individuals with fully methylated, full mutation alleles. However, we did not observe a significant reduction in the number of seizures, nor in the severity of hyperactivity or autism spectrum disorder, among individuals with mosaic genotypes in the presentation of FXS. These observations suggest that low, but non-zero expression of FMRP may be sufficient to positively impact cognitive function in individuals with FXS, with methylation mosaicism (lowered methylation fraction) contributing to a more positive clinical outcome.
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Influence of the fragile X mental retardation (FMR1) gene on the brain and working memory in men with normal FMR1 alleles.
NeuroImage, 2012Co-Authors: Jun Yi Wang, Randi J Hagerman, Paul J Hagerman, David R Hessl, Christine Iwahashi, Katherine Cheung, Andrea Schneider, Susan M. RiveraAbstract:Abstract The fragile X mental retardation 1 (FMR1) gene plays an important role in the development and maintenance of neuronal circuits that are essential for cognitive functioning. We explored the functional linkage(s) among lymphocytic FMR1 gene expression, brain structure, and working memory in healthy adult males. We acquired T1-weighted and diffusion tensor imaging from 37 males (18–80 years, mean ± SD = 40.7 ± 17.3 years) with normal FMR1 alleles and performed genetic and working memory assessments. Brain measurements were obtained from fiber tracts important for working memory (i.e. the arcuate fasciculus, anterior cingulum bundle, inferior longitudinal fasciculus, and the genu and anterior body of the corpus callosum), individual voxels, and whole brain. Both FMR1 mRNA and protein (FMRP) levels exhibited significant associations with brain measurements, with FMRP correlating positively with gray matter volume and white matter structural organization, and FMR1 mRNA negatively with white matter structural organization. The correlation was widespread, impacting rostral white matter and 2 working-memory fiber tracts for FMRP, and all cerebral white matter areas except the fornix and cerebellar peduncles and all 4 fiber tracts for FMR1 mRNA. In addition, the levels of FMR1 mRNA as well as the fiber tracts demonstrated a significant correlation with working memory performance. While FMR1 mRNA exhibited a negative correlation with working memory, fiber tract structural organization showed a positive correlation. These findings suggest that the FMR1 gene is a genetic factor common for both working memory and brain structure, and has implications for our understanding of the transmission of intelligence and brain structure.
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methylation of novel markers of fragile x alleles is inversely correlated with fmrp expression and FMR1 activation ratio
Human Molecular Genetics, 2010Co-Authors: David E Godler, Flora Tassone, Randi J Hagerman, Annette K Taylor, Danuta Z Loesch, Freya Gehling, Trent Burgess, Devika Ganesamoorthy, Debbie HennerichAbstract:The fragile X syndrome (FXS) is caused by silencing of the fragile X mental retardation gene (FMR1) and the absence of its product, fragile X mental retardation protein (FMRP), resulting from CpG island methylation associated with large CGG repeat expansions (more than 200) termed full mutation (FM). We have identified a number of novel epigenetic markers for FXS using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), naming the most informative fragile X-related epigenetic element 1 (FREE1) and 2 (FREE2). Methylation of both regions was correlated with that of the FMR1 CpG island detected using Southern blot (FREE1 R = 0.97; P < 0.00001, n = 23 and FREE2 R = 0.93; P < 0.00001, n = 23) and negatively correlated with lymphocyte expression of FMRP (FREE1 R = −0.62; P = 0.01, n = 15 and FREE2 R = −0.55; P = 0.03, n = 15) in blood of partially methylated ‘high functioning’ FM males. In blood of FM carrier females, methylation of both markers was inversely correlated with the FMR1 activation ratio (FREE1 R = −0.93; P < 0.0001, n = 12 and FREE2 R = −0.95; P < 0.0001, n = 9). In a sample set of 49 controls, 18 grey zone (GZ 40–54 repeats), 22 premutation (PM 55–170 repeats) and 22 (affected) FXS subjects, the FREE1 methylation pattern was consistent between blood and chorionic villi as a marker of methylated FM alleles and could be used to differentiate FXS males and females from controls, as well as from carriers of GZ/PM alleles, but not between GZ and PM alleles and controls. Considering its high-throughput and specificity for pathogenic FM alleles, low cost and minimal DNA requirements, FREE MALDI-TOF MS offers a unique tool in FXS diagnostics and newborn population screening.