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Jiraanont P, Zafarullah M, Sulaiman N, Espinal GM, Randol JL, Durbin-Johnson B, Schneider A, Hagerman RJ, Hagerman PJ, Tassone F. FMR1 Protein Expression Correlates with Intelligence Quotient in Both Peripheral Blood Mononuclear Cells and Fibroblasts from Individuals with an FMR1 Mutation. J Mol Diagn 2024; 26:498-509. [PMID: 38522837 DOI: 10.1016/j.jmoldx.2024.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 02/15/2024] [Accepted: 02/23/2024] [Indexed: 03/26/2024] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable form of intellectual disability and is caused by CGG repeat expansions exceeding 200 (full mutation). Such expansions lead to hypermethylation and transcriptional silencing of the fragile X messenger ribonucleoprotein 1 (FMR1) gene. As a consequence, little or no FMR1 protein (FMRP) is produced; absence of the protein, which normally is responsible for neuronal development and maintenance, causes the syndrome. Previous studies have demonstrated the causal relationship between FMRP levels and cognitive abilities in peripheral blood mononuclear cells (PBMCs) and dermal fibroblast cell lines of patients with FXS. However, it is arguable whether PBMCs or fibroblasts would be the preferred surrogate for measuring molecular markers, particularly FMRP, to represent the cognitive impairment, a core symptom of FXS. To address this concern, CGG repeats, methylation status, FMR1 mRNA, and FMRP levels were measured in both PBMCs and fibroblasts derived from 66 individuals. The findings indicated a strong association between FMR1 mRNA expression levels and CGG repeat numbers in PBMCs of premutation males after correcting for methylation status. Moreover, FMRP expression levels from both PBMCs and fibroblasts of male participants with a hypermethylated full mutation and with mosaicism demonstrated significant association between the intelligence quotient levels and FMRP levels, suggesting that PBMCs may be preferable for FXS clinical studies, because of their greater accessibility.
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Affiliation(s)
- Poonnada Jiraanont
- Division of Molecular and Cellular Medicine, Faculty of Medicine, King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand
| | - Marwa Zafarullah
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Noor Sulaiman
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Glenda M Espinal
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Jamie L Randol
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Blythe Durbin-Johnson
- Division of Biostatistics, University of California, Davis, School of Medicine, Davis, California
| | - Andrea Schneider
- Department of Pediatrics, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California
| | - Randi J Hagerman
- Department of Pediatrics, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California
| | - Paul J Hagerman
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California.
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Hnoonual A, Plong-On O, Worachotekamjorn J, Charalsawadi C, Limprasert P. Clinical and molecular characteristics of FMR1 microdeletion in patient with fragile X syndrome and review of the literature. Clin Chim Acta 2024; 553:117728. [PMID: 38142803 DOI: 10.1016/j.cca.2023.117728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/09/2023] [Accepted: 12/16/2023] [Indexed: 12/26/2023]
Abstract
BACKGROUND Fragile X syndrome (FXS) is mainly caused by FMR1 CGG repeat expansions. Other types of mutations, particularly deletions, are also responsible for FXS phenotypes, however these mutations are often missed by routine clinical testing. MATERIALS AND METHODS Molecular diagnosis in cases of suspected FXS was a combination of PCR and Southern blot. Measurement of the FMRP protein level was useful for detecting potentially deleterious impact. RESULTS PCR analysis and Southern blot revealed a case with premutation and suspected deletion alleles. Sanger sequencing showed that the deletion involved 313 bp upstream of repeats and some parts of CGG repeat tract, leaving transcription start site. FMRP was detected in 5.5 % of blood lymphocytes. CONCLUSION According to our review of case reports, most patients carrying microdeletion and full mutation had typical features of FXS. To our knowledge, our case is the first to describe mosaicism of a premutation and microdeletion in the FMR1 gene. The patient was probably protected from the effects of the deletion by mosaicism with premutation allele, leading to milder phenotype. It is thus important to consider appropriate techniques for detecting FMR1 variants other than repeat expansions which cannot be detected by routine FXS diagnosis.
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Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Oradawan Plong-On
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | | | - Chariyawan Charalsawadi
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
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Edwards N, Combrinck C, McCaughey-Chapman A, Connor B. Directly reprogrammed fragile X syndrome dorsal forebrain precursor cells generate cortical neurons exhibiting impaired neuronal maturation. Front Cell Neurosci 2023; 17:1254412. [PMID: 37810261 PMCID: PMC10552551 DOI: 10.3389/fncel.2023.1254412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 09/01/2023] [Indexed: 10/10/2023] Open
Abstract
Introduction The neurodevelopmental disorder fragile X syndrome (FXS) is the most common monogenic cause of intellectual disability associated with autism spectrum disorder. Inaccessibility to developing human brain cells is a major barrier to studying FXS. Direct-to-neural precursor reprogramming provides a unique platform to investigate the developmental profile of FXS-associated phenotypes throughout neural precursor and neuron generation, at a temporal resolution not afforded by post-mortem tissue and in a patient-specific context not represented in rodent models. Direct reprogramming also circumvents the protracted culture times and low efficiency of current induced pluripotent stem cell strategies. Methods We have developed a chemically modified mRNA (cmRNA) -based direct reprogramming protocol to generate dorsal forebrain precursors (hiDFPs) from FXS patient-derived fibroblasts, with subsequent differentiation to glutamatergic cortical neurons and astrocytes. Results We observed differential expression of mature neuronal markers suggesting impaired neuronal development and maturation in FXS- hiDFP-derived neurons compared to controls. FXS- hiDFP-derived cortical neurons exhibited dendritic growth and arborization deficits characterized by reduced neurite length and branching consistent with impaired neuronal maturation. Furthermore, FXS- hiDFP-derived neurons exhibited a significant decrease in the density of pre- and post- synaptic proteins and reduced glutamate-induced calcium activity, suggesting impaired excitatory synapse development and functional maturation. We also observed a reduced yield of FXS- hiDFP-derived neurons with a significant increase in FXS-affected astrocytes. Discussion This study represents the first reported derivation of FXS-affected cortical neurons following direct reprogramming of patient fibroblasts to dorsal forebrain precursors and subsequently neurons that recapitulate the key molecular hallmarks of FXS as it occurs in human tissue. We propose that direct to hiDFP reprogramming provides a unique platform for further study into the pathogenesis of FXS as well as the identification and screening of new drug targets for the treatment of FXS.
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Affiliation(s)
| | | | | | - Bronwen Connor
- Department of Pharmacology and Clinical Pharmacology, Centre for Brain Research, School of Medical Science, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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Lee HG, Imaichi S, Kraeutler E, Aguilar R, Lee YW, Sheridan SD, Lee JT. Site-specific R-loops induce CGG repeat contraction and fragile X gene reactivation. Cell 2023; 186:2593-2609.e18. [PMID: 37209683 DOI: 10.1016/j.cell.2023.04.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 01/15/2023] [Accepted: 04/26/2023] [Indexed: 05/22/2023]
Abstract
Here, we describe an approach to correct the genetic defect in fragile X syndrome (FXS) via recruitment of endogenous repair mechanisms. A leading cause of autism spectrum disorders, FXS results from epigenetic silencing of FMR1 due to a congenital trinucleotide (CGG) repeat expansion. By investigating conditions favorable to FMR1 reactivation, we find MEK and BRAF inhibitors that induce a strong repeat contraction and full FMR1 reactivation in cellular models. We trace the mechanism to DNA demethylation and site-specific R-loops, which are necessary and sufficient for repeat contraction. A positive feedback cycle comprising demethylation, de novo FMR1 transcription, and R-loop formation results in the recruitment of endogenous DNA repair mechanisms that then drive excision of the long CGG repeat. Repeat contraction is specific to FMR1 and restores the production of FMRP protein. Our study therefore identifies a potential method of treating FXS in the future.
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Affiliation(s)
- Hun-Goo Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Sachiko Imaichi
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Elizabeth Kraeutler
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Rodrigo Aguilar
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Yong-Woo Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Steven D Sheridan
- Center for Quantitative Health Center for Genomic Medicine and Department of Psychiatry, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Psychiatry, Harvard Medical School, Boston, MA 02114, USA
| | - Jeannie T Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA.
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Aishworiya R, Hwang YH, Santos E, Hayward B, Usdin K, Durbin-Johnson B, Hagerman R, Tassone F. Clinical implications of somatic allele expansion in female FMR1 premutation carriers. Sci Rep 2023; 13:7050. [PMID: 37120588 PMCID: PMC10148869 DOI: 10.1038/s41598-023-33528-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 04/14/2023] [Indexed: 05/01/2023] Open
Abstract
Carriers of a premutation allele (PM) in the FMR1 gene are at risk of developing a number of Fragile X premutation asssociated disorders (FXPAC), including Fragile X-associated Tremor/Ataxia Syndrome (FXTAS), Fragile X-associated Primary Ovarian Insufficiency (FXPOI), and Fragile X-associated neuropsychiatric disorders (FXAND). We have recently reported somatic CGG allele expansion in female PM; however, its clinical significance remains unclear. The aim of this study was to examine the potential clinical association between somatic FMR1 allele instability and PM associated disorders. Participants comprised of 424 female PM carriers age 0.3- 90 years. FMR1 molecular measures and clinical information on the presence of medical conditions, were determined for all subjects for primary analysis. Two sub-groups of participants (age ≥ 25, N = 377 and age ≥ 50, N = 134) were used in the analysis related to presence of FXPOI and FXTAS, respectively. Among all participants (N = 424), the degree of instability (expansion) was significantly higher (median 2.5 vs 2.0, P = 0.026) in participants with a diagnosis of attention deficit hyperactivity disorder (ADHD) compared to those without. FMR1 mRNA expression was significantly higher in subjects with any psychiatric disorder diagnosis (P = 0.0017); specifically, in those with ADHD (P = 0.009), and with depression (P = 0.025). Somatic FMR1 expansion was associated with the presence of ADHD in female PM and FMR1 mRNA levels were associated with the presence of mental health disorders. The findings of our research are innovative as they suggest a potential role of the CGG expansion in the clinical phenotype of PM and may potentially guide clinical prognosis and management.
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Affiliation(s)
- Ramkumar Aishworiya
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, 2825 50Th Street, Sacramento, CA, 95817, USA
- Khoo Teck Puat-National University Children's Medical Institute, National University Health System, 5 Lower Kent Ridge Road, Singapore, 119074, Singapore
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Drive, Singapore, 117597, Singapore
| | - Ye Hyun Hwang
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, 4610 X St, Sacramento, CA, 95817, USA
| | - Ellery Santos
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, 2825 50Th Street, Sacramento, CA, 95817, USA
- Department of Pediatrics, University of California Davis, School of Medicine, 4610 X St, Sacramento, CA, 95817, USA
| | - Bruce Hayward
- Laboratory of Cell and Molecular Biology, Digestive and Kidney Diseases, National Institute of Diabetes, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Karen Usdin
- Laboratory of Cell and Molecular Biology, Digestive and Kidney Diseases, National Institute of Diabetes, 9000 Rockville Pike, Bethesda, MD, 20892, USA
| | - Blythe Durbin-Johnson
- Department of Public Health Sciences, University of California, Davis, School of Medicine, 4610 X St, Sacramento, CA, 95817, USA
| | - Randi Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, 2825 50Th Street, Sacramento, CA, 95817, USA
- Department of Pediatrics, University of California Davis, School of Medicine, 4610 X St, Sacramento, CA, 95817, USA
| | - Flora Tassone
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, 2825 50Th Street, Sacramento, CA, 95817, USA.
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, 4610 X St, Sacramento, CA, 95817, USA.
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Abstract
The histories of targeted treatment trials in fragile X syndrome (FXS) are reviewed in animal studies and human trials. Advances in understanding the neurobiology of FXS have identified a number of pathways that are dysregulated in the absence of FMRP and are therefore pathways that can be targeted with new medication. The utilization of quantitative outcome measures to assess efficacy in multiple studies has improved the quality of more recent trials. Current treatment trials including the use of cannabidiol (CBD) topically and metformin orally have positive preliminary data, and both of these medications are available clinically. The use of the phosphodiesterase inhibitor (PDE4D), BPN1440, which raised the level of cAMP that is low in FXS has very promising results for improving cognition in adult males who underwent a controlled trial. There are many more targeted treatments that will undergo trials in FXS, so the future looks bright for new treatments.
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Affiliation(s)
- Devon Johnson
- MIND Institute, University of California Davis Health, Sacramento, CA, USA
| | - Courtney Clark
- MIND Institute, University of California Davis Health, Sacramento, CA, USA
| | - Randi Hagerman
- MIND Institute, University of California Davis Health, Sacramento, CA, USA
- Department of Pediatrics, University of California Davis Health, Sacramento, CA, USA
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Wu YY, Yang C, Yan HJ, Lu P, Zhang L, Feng WC, Long YS. Lysine acetylome profiling in mouse hippocampus and its alterations upon FMRP deficiency linked to abnormal energy metabolism. J Proteomics 2022; 269:104720. [PMID: 36089189 DOI: 10.1016/j.jprot.2022.104720] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/07/2022] [Accepted: 09/02/2022] [Indexed: 10/14/2022]
Abstract
Loss of fragile X retardation protein (FMRP) leads to fragile X syndrome (FXS), a common cause of inherited intellectual disability. Protein lysine acetylation (K-ac), a reversible post-translational modification of proteins, is associated with the regulation of brain development and neuropathies. However, a comprehensive hippocampal K-ac protein profile in response to FMRP deficiency has not been reported until now. Using LC-MS/MS to analyze the enriched K-ac peptides, this study identified 1629 K-ac hits across 717 proteins in the mouse hippocampus, and these proteins were enriched in several metabolic processes. Of them, 51 K-ac hits across 45 proteins were significantly changed upon loss of FMRP. These altered K-ac proteins were enriched in energy metabolic processes including carboxylic acid metabolism process, aerobic respiration and citrate cycle, linking with several neurological disorders such as lactic acidosis, Lewy body disease, Leigh disease and encephalopathies. In the mouse hippocampus and the hippocampal HT-22 cells, FMRP deficiency could induce altered K-ac modification of several key enzymes, decrease in ATP and increase in lactate. Thus, this study identified a global hippocampal lysine acetylome and an altered K-ac protein profile upon loss of FMRP linked to abnormal energy metabolism, implicating in the pathogenesis of FXS. SIGNIFICANCE: Fragile X syndrome (FXS) is a common inherited neurodevelopment disorder characterized by intellectual disability and an increased risk for autism spectrum disorder. FXS is resulted from silencing of the FMR1 gene, which induces loss of its encoding protein FMRP. Molecular and metabolic changes of Fmr1-null animal models of FXS have been identified to potentially contribute to the pathogenesis of FXS. Here, we used a TMT-labeled quantitative proteomic analysis of the peptides enriched by anti-K-ac antibodies and identified a global K-ac protein profile in the mouse hippocampus with a total of 1629 K-ac peptides on 717 proteins. Of them, 51 K-ac peptides regarding 45 proteins altered in response to loss of FMRP, which were enriched in energy metabolic processes and were implicated in several neurological disorders. Thus this study for the first time provides a global hippocampal lysine acetylome upon FMRP deficiency linked to abnormal metabolic pathways, which may contribute to pathogenic mechanism of FXS.
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Affiliation(s)
- Yue-Ying Wu
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Cui Yang
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Hua-Juan Yan
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Ping Lu
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Li Zhang
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Weng-Cai Feng
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China
| | - Yue-Sheng Long
- Department of Neurology, Institute of Neuroscience, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou 510260, China.
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Saldarriaga W, González-Teshima LY, Forero-Forero JV, Tang HT, Tassone F. Mosaicism in Fragile X syndrome: A family case series. JOURNAL OF INTELLECTUAL DISABILITIES : JOID 2022; 26:800-807. [PMID: 33998336 DOI: 10.1177/1744629521995346] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Fragile X syndrome (FXS) has a classic phenotype, however its expression can be variable among full mutation males. This is secondary to variable methylation mosaicisms and the number of CGG triplet repeats in the non-coding region of the Fragile X Mental Retardation 1 (FMR1) gene, producing a variable expression of the Fragile X Mental Retardation Protein (FMRP). Here we report a family with several individuals affected by FXS: a boy with a hypermethylated FMR1 mutation and a classic phenotype; a man with an FMR1 gene mosaicism in the range of premutation (PM) and full mutation (FM), who has a mild phenotype due to which FXS was initially disregarded; and the cases of four women with a FM and mosaicism. This report highlights the importance of DNA molecular testing for the diagnosis of FXS in patients with developmental delay, intellectual disability and/or autism due to the variable phenotype that occurs in individuals with FMR1 mosaicisms.
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Aishworiya R, Protic D, Hagerman R. Autism spectrum disorder in the fragile X premutation state: possible mechanisms and implications. J Neurol 2022; 269:4676-4683. [PMID: 35723724 DOI: 10.1007/s00415-022-11209-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 05/26/2022] [Accepted: 05/27/2022] [Indexed: 12/23/2022]
Abstract
There is increasing recognition of the heterogeneity of origin of cases of autism spectrum disorder (ASD) with multiple forms of ASD having been identified over the decades. Among these, a genetic etiology can be identified in 20-40% of cases when a full genetic work-up is completed. The Fragile X premutation state (characterized by the presence of 55-200 CGG repeats in the FMR1 gene) is a relatively newly identified disease state that has since been associated with several disorders including fragile X-associated tremor ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI) and most recently, fragile X-associated neurodevelopmental disorders (FXAND) which commonly includes anxiety and depression. In addition to these associated disorders, extant literature and clinical observations have suggested an association between the premutation state and ASD. In this paper, we review the literature pertinent to this and discuss possible molecular mechanisms that may explain this association. This includes lowered levels of the FMR1 Protein (FMRP), GABA deficits, mitochondrial dysfunction and secondary genetic abnormalities that is seen in premutation carriers as well as their increased vulnerability to environmental stressors. Understanding these mechanisms can facilitate development of targeted treatment for specific sub-groups of ASD and premutation disorders in future.
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Affiliation(s)
- Ramkumar Aishworiya
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, 2825 50th Street, Sacramento, CA, 95817, USA. .,Khoo Teck Puat-National University Children's Medical Institute, National University Health System, 5 Lower Kent Ridge Road, Singapore, 119074, Singapore. .,Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Drive, Singapore, 117597, Singapore.
| | - Dragana Protic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Randi Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California Davis, 2825 50th Street, Sacramento, CA, 95817, USA.,Department of Pediatrics, University of California Davis School of Medicine, 4610 X St, Sacramento, CA, 95817, USA
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Neurodegenerative diseases associated with non-coding CGG tandem repeat expansions. Nat Rev Neurol 2022; 18:145-157. [PMID: 35022573 DOI: 10.1038/s41582-021-00612-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2021] [Indexed: 02/07/2023]
Abstract
Non-coding CGG repeat expansions cause multiple neurodegenerative disorders, including fragile X-associated tremor/ataxia syndrome, neuronal intranuclear inclusion disease, oculopharyngeal myopathy with leukodystrophy, and oculopharyngodistal myopathy. The underlying genetic causes of several of these diseases have been identified only in the past 2-3 years. These expansion disorders have substantial overlapping clinical, neuroimaging and histopathological features. The shared features suggest common mechanisms that could have implications for the development of therapies for this group of diseases - similar therapeutic strategies or drugs may be effective for various neurodegenerative disorders induced by non-coding CGG expansions. In this Review, we provide an overview of clinical and pathological features of these CGG repeat expansion diseases and consider the likely pathological mechanisms, including RNA toxicity, CGG repeat-associated non-AUG-initiated translation, protein aggregation and mitochondrial impairment. We then discuss future research needed to improve the identification and diagnosis of CGG repeat expansion diseases, to improve modelling of these diseases and to understand their pathogenesis. We also consider possible therapeutic strategies. Finally, we propose that CGG repeat expansion diseases may represent manifestations of a single underlying neuromyodegenerative syndrome in which different organs are affected to different extents depending on the gene location of the repeat expansion.
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FMRP Levels in Human Peripheral Blood Leukocytes Correlates with Intellectual Disability. Diagnostics (Basel) 2021; 11:diagnostics11101780. [PMID: 34679478 PMCID: PMC8534530 DOI: 10.3390/diagnostics11101780] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 11/17/2022] Open
Abstract
Fragile X syndrome (FXS) is the most common form of inherited intellectual disability. FXS is an X-linked, neurodevelopmental disorder caused by a CGG trinucleotide repeat expansion in the 5′ untranslated region (UTR) of the Fragile X Mental Retardation gene, FMR1. Greater than 200 CGG repeats results in epigenetic silencing of the gene leading to the deficiency or absence of Fragile X mental retardation protein (FMRP). The loss of FMRP is considered the root cause of FXS. The relationship between neurological function and FMRP expression in peripheral blood mononuclear cells (PBMCs) has not been well established. Assays to detect and measure FMR1 and FMRP have been described; however, none are sufficiently sensitive, precise, or quantitative to properly characterize the relationships between cognitive ability and CGG repeat number, FMR1 mRNA expression, or FMRP expression measured in PBMCs. To address these limitations, two novel immunoassays were developed and optimized, an electro-chemiluminescence immunoassay and a multiparameter flow cytometry assay. Both assays were performed on PMBCs isolated from 27 study participants with FMR1 CGG repeats ranging from normal to full mutation. After correcting for methylation, a significant positive correlation between CGG repeat number and FMR1 mRNA expression levels and a significant negative correlation between FMRP levels and CGG repeat expansion was observed. Importantly, a high positive correlation was observed between intellectual quotient (IQ) and FMRP expression measured in PBMCs.
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Ordemann GJ, Apgar CJ, Chitwood RA, Brager DH. Altered A-Type Potassium Channel Function Impairs Dendritic Spike Initiation and Temporoammonic Long-Term Potentiation in Fragile X Syndrome. J Neurosci 2021; 41:5947-5962. [PMID: 34083256 PMCID: PMC8265803 DOI: 10.1523/jneurosci.0082-21.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 04/19/2021] [Accepted: 04/26/2021] [Indexed: 01/14/2023] Open
Abstract
Fragile X syndrome (FXS) is the leading monogenetic cause of cognitive impairment and autism spectrum disorder. Area CA1 of the hippocampus receives current information about the external world from the entorhinal cortex via the temporoammonic (TA) pathway. Given its role in learning and memory, it is surprising that little is known about TA long-term potentiation (TA-LTP) in FXS. We found that TA-LTP was impaired in male fmr1 KO mice. Although there were no significant differences in basal synaptic transmission, synaptically evoked dendritic calcium signals were smaller in KO neurons. Using dendritic recording, we found no difference in complex spikes or pharmacologically isolated Ca2+ spikes; however, the threshold for fast, Na+-dependent dendritic spikes was depolarized in fmr1 KO mice. Cell-attached patch-clamp recordings found no difference in Na+ channels between wild-type and fmr1 KO CA1 dendrites. Dendritic spike threshold and TA-LTP were restored by blocking A-type K+ channels with either 150 µm Ba2+ or the more specific toxin AmmTx3. The impairment of TA-LTP shown here, coupled with previously described enhanced Schaffer collateral LTP, may contribute to spatial memory alterations in FXS. Furthermore, as both of these LTP phenotypes are attributed to changes in A-type K+ channels in FXS, our findings provide a potential therapeutic target to treat cognitive impairments in FXS.SIGNIFICANCE STATEMENT Alterations in synaptic function and plasticity are likely contributors to learning and memory impairments in many neurologic disorders. Fragile X syndrome is marked by dysfunctional learning and memory and changes in synaptic structure and function. This study shows a lack of LTP at temporoammonic synapses in CA1 neurons associated with biophysical differences in A-type K+ channels in fmr1 KO CA1 neurons. Our results, along with previous findings on A-type K+ channel effects on Schaffer collateral LTP, reveal differential effects of a single ion channelopathy on LTP at the two major excitatory pathways of CA1 pyramidal neurons. These findings expand our understanding of memory deficits in FXS and provide a potential therapeutic target for the treatment of memory dysfunction in FXS.
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Affiliation(s)
- Gregory J Ordemann
- Department of Neuroscience, Institute for Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712
| | - Christopher J Apgar
- Department of Neuroscience, Institute for Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712
| | - Raymond A Chitwood
- Department of Neuroscience, Institute for Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712
| | - Darrin H Brager
- Department of Neuroscience, Institute for Neuroscience, Center for Learning and Memory, University of Texas at Austin, Austin, Texas 78712
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Johnson D, Santos E, Kim K, Ponzini MD, McLennan YA, Schneider A, Tassone F, Hagerman RJ. Increased Pain Symptomatology Among Females vs. Males With Fragile X-Associated Tremor/Ataxia Syndrome. Front Psychiatry 2021; 12:762915. [PMID: 35126193 PMCID: PMC8811376 DOI: 10.3389/fpsyt.2021.762915] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 12/27/2021] [Indexed: 12/12/2022] Open
Abstract
Individuals with the fragile X premutation report symptoms of chronic pain from multiple systems, have increased incidence of comorbid conditions where pain is a prominent feature, and pathophysiology that supports disrupted pain regulation, inflammation, and energy imbalance. Less is known about how pain manifests for the subpopulation of carriers that develop the motor and cognitive changes of fragile X-associated tremor and ataxia syndrome (FXTAS), and how pain may differ between men and women. We gathered data collected from 104 males and females with FXTAS related to chronic pain, comorbid conditions related to pain, and medications used for pain control to further explore the types of pain experienced and to better characterize how individuals with the fragile X premutation experience pain sensation across genders. We found that women experience significantly more pain symptoms than men, particularly allodynia (20 vs. 2.0%, p = 0.008), peripheral neuropathy pain (43.9 vs. 25.4%, p = 0.0488), migraine (43.9 vs. 14.5%, p = 0.0008), fibromyalgia (26.8 vs. 0%, p = 0.0071) and back pain (48.5 vs. 23.4%, p = 0.008). We found onset of peripheral neuropathy predicts the onset of ataxia (β = 0.63 ± 0.25, p = 0.019) and tremor (β = 0.56 ± 0.17, p = 0.004) across gender. Women also report significantly more anxiety (82.9 vs. 39.7%, p < 0.001), which has implications for ideal pain treatment. These pain symptoms need to be recognized in the medical history and treated appropriately, with consideration for overlapping comorbidities.
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Affiliation(s)
- Devon Johnson
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Ellery Santos
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Kyoungmi Kim
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States.,Division of Biostatistics, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Matthew D Ponzini
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States.,Division of Biostatistics, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Yingratana A McLennan
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Andrea Schneider
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States.,Department of Pediatrics, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Flora Tassone
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States.,Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Randi J Hagerman
- Medical Investigation of Neurodevelopmental Disorders Institute, School of Medicine, University of California, Davis, Davis, CA, United States.,Department of Pediatrics, School of Medicine, University of California, Davis, Davis, CA, United States
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14
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Marsillo A, David L, Gerges B, Kerr D, Sadek R, Lasiychuk V, Salame D, Soliman Y, Menkes S, Chatterjee A, Mancuso A, Banerjee P. PKC epsilon as a neonatal target to correct FXS-linked AMPA receptor translocation in the hippocampus, boost PVN oxytocin expression, and normalize adult behavior in Fmr1 knockout mice. Biochim Biophys Acta Mol Basis Dis 2020; 1867:166048. [PMID: 33359697 DOI: 10.1016/j.bbadis.2020.166048] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/19/2020] [Accepted: 12/14/2020] [Indexed: 12/29/2022]
Abstract
Fragile X Syndrome (FXS) is an inherited developmental disorder caused by the non-expression of the Fmr1 gene. FXS is associated with abnormal social and anxiety behavior that is more prominent among males. Given that oxytocin (OXT) regulates both social and anxiety behavior, we studied the effect of FXS in the hypothalamic paraventricular nucleus (PVN), the major central source of OXT. We observed a significant suppression of protein kinase C epsilon (PKCε) (34%) in the ventral hippocampal CA1 region of postnatal day-18 (P18) male Fmr1 knockout (KO) mice, which displayed social behavior deficits and hyper-anxiety in adulthood. These mice also displayed a 39% increase in cell surface α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR) at P18 (measured by the surface level of the AMPAR subunit GluR2), thereby indicating excitation of the CA1 neurons. It is known that neuronal activation at CA1 is linked to an inhibition of the PVN neurons. As expected, these mice also displayed a 25% suppression of oxytocin+ (OXT+) cells in the PVN at P20. Stimulating PKCε during postnatal days 6-,14 (P6-14) mice using a selective activator, dicyclopropyl-linoleic acid (DCP-LA), corrected AMPAR externalization in CA1 and suppression of OXT+ cell number in PVN in a PKCε dependent manner. Most notably, neonatal DCP-LA treatment rescued social behavior deficits and hyper-anxiety, displayed by adult (≥P60) male but not female KO mice. Thus, neonatal stimulation of PKCε could be a strategy to correct endophenotypic anomalies during brain development and aberrant adult behavior of the FXS males to the wild-type levels.
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Affiliation(s)
- Alexandra Marsillo
- CUNY Doctoral Programs in Biology, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Lovena David
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Bishoy Gerges
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Daniel Kerr
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Rodina Sadek
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Vitaliy Lasiychuk
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - David Salame
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Youstina Soliman
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Silvia Menkes
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Aheli Chatterjee
- Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Andrew Mancuso
- CUNY Doctoral Programs in Biochemistry, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America
| | - Probal Banerjee
- CUNY Doctoral Programs in Biology, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America; Department of Chemistry, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America; Center for Developmental Neuroscience, The College of Staten Island (CUNY), Staten Island, NY 10314-6609, United States of America.
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15
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Elevated FMR1-mRNA and lowered FMRP - A double-hit mechanism for psychiatric features in men with FMR1 premutations. Transl Psychiatry 2020; 10:205. [PMID: 32576818 PMCID: PMC7311546 DOI: 10.1038/s41398-020-00863-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 05/19/2020] [Accepted: 05/22/2020] [Indexed: 01/07/2023] Open
Abstract
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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16
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Suardi GAM, Haddad LA. FMRP ribonucleoprotein complexes and RNA homeostasis. ADVANCES IN GENETICS 2020; 105:95-136. [PMID: 32560791 DOI: 10.1016/bs.adgen.2020.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The Fragile Mental Retardation 1 gene (FMR1), at Xq27.3, encodes the fragile mental retardation protein (FMRP), and displays in its 5'-untranslated region a series of polymorphic CGG triplet repeats that may undergo dynamic mutation. Fragile X syndrome (FXS) is the leading cause of inherited intellectual disability among men, and is most frequently due to FMR1 full mutation and consequent transcription repression. FMR1 premutations may associate with at least two other clinical conditions, named fragile X-associated primary ovarian insufficiency (FXPOI) and tremor and ataxia syndrome (FXTAS). While FXPOI and FXTAS appear to be mediated by FMR1 mRNA accumulation, relative reduction of FMRP, and triplet repeat translation, FXS is due to the lack of the RNA-binding protein FMRP. Besides its function as mRNA translation repressor in neuronal and stem/progenitor cells, RNA editing roles have been assigned to FMRP. In this review, we provide a brief description of FMR1 transcribed microsatellite and associated clinical disorders, and discuss FMRP molecular roles in ribonucleoprotein complex assembly and trafficking, as well as aspects of RNA homeostasis affected in FXS cells.
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Affiliation(s)
- Gabriela Aparecida Marcondes Suardi
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Luciana Amaral Haddad
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
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17
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Kim K, Hessl D, Randol JL, Espinal GM, Schneider A, Protic D, Aydin EY, Hagerman RJ, Hagerman PJ. Association between IQ and FMR1 protein (FMRP) across the spectrum of CGG repeat expansions. PLoS One 2019; 14:e0226811. [PMID: 31891607 PMCID: PMC6938341 DOI: 10.1371/journal.pone.0226811] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 12/05/2019] [Indexed: 12/20/2022] Open
Abstract
Fragile X syndrome, the leading heritable form of intellectual disability, is caused by hypermethylation and transcriptional silencing of large (CGG) repeat expansions (> 200 repeats) in the 5′ untranslated region of the fragile X mental retardation 1 (FMR1) gene. As a consequence of FMR1 gene silencing, there is little or no production of FMR1 protein (FMRP), an important element in normal synaptic function. Although the absence of FMRP has long been known to be responsible for the cognitive impairment in fragile X syndrome, the relationship between FMRP level and cognitive ability (IQ) is only imprecisely understood. To address this issue, a high-throughput, fluorescence resonance energy transfer (FRET) assay has been used to quantify FMRP levels in dermal fibroblasts, and the relationship between FMRP and IQ measures was assessed by statistical analysis in a cohort of 184 individuals with CGG-repeat lengths spanning normal (< 45 CGGs) to full mutation (> 200 CGGs) repeat ranges in fibroblasts. The principal findings of the current study are twofold: i) For those with normal CGG repeats, IQ is no longer sensitive to further increases in FMRP above an FMRP threshold of ~70% of the mean FMRP level; below this threshold, IQ decreases steeply with further decreases in FMRP; and ii) For the current cohort, a mean IQ of 85 (lower bound for the normal IQ range) is attained for FMRP levels that are only ~35% of the mean FMRP level among normal CGG-repeat controls. The current results should help guide expectations for efforts to induce FMR1 gene activity and for the levels of cognitive function expected for a given range of FMRP levels.
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Affiliation(s)
- Kyoungmi Kim
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Davis, California, United States of America
| | - David Hessl
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
- Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, California, United States of America
| | - Jamie L. Randol
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California, United States of America
| | - Glenda M. Espinal
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California, United States of America
| | - Andrea Schneider
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
- Department of Pediatrics, University of California, Davis, School of Medicine, Sacramento, California, United States of America
| | - Dragana Protic
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
| | - Elber Yuksel Aydin
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
| | - Randi J. Hagerman
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
- Department of Pediatrics, University of California, Davis, School of Medicine, Sacramento, California, United States of America
| | - Paul J. Hagerman
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, United States of America
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California, United States of America
- * E-mail:
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18
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The Application of Adeno-Associated Viral Vector Gene Therapy to the Treatment of Fragile X Syndrome. Brain Sci 2019; 9:brainsci9020032. [PMID: 30717399 PMCID: PMC6406794 DOI: 10.3390/brainsci9020032] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/30/2019] [Accepted: 01/31/2019] [Indexed: 01/18/2023] Open
Abstract
Viral vector-mediated gene therapy has grown by leaps and bounds over the past several years. Although the reasons for this progress are varied, a deeper understanding of the basic biology of the viruses, the identification of new and improved versions of viral vectors, and simply the vast experience gained by extensive testing in both animal models of disease and in clinical trials, have been key factors. Several studies have investigated the efficacy of adeno-associated viral (AAV) vectors in the mouse model of fragile X syndrome where AAVs have been used to express fragile X mental retardation protein (FMRP), which is missing or highly reduced in the disorder. These studies have demonstrated a range of efficacies in different tests from full correction, to partial rescue, to no effect. Here we provide a backdrop of recent advances in AAV gene therapy as applied to central nervous system disorders, outline the salient features of the fragile X studies, and discuss several key issues for moving forward. Collectively, the findings to date from the mouse studies on fragile X syndrome, and data from clinical trials testing AAVs in other neurological conditions, indicate that AAV-mediated gene therapy could be a viable strategy for treating fragile X syndrome.
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19
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Hagerman RJ, Protic D, Rajaratnam A, Salcedo-Arellano MJ, Aydin EY, Schneider A. Fragile X-Associated Neuropsychiatric Disorders (FXAND). Front Psychiatry 2018; 9:564. [PMID: 30483160 PMCID: PMC6243096 DOI: 10.3389/fpsyt.2018.00564] [Citation(s) in RCA: 125] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 10/18/2018] [Indexed: 12/12/2022] Open
Abstract
Fragile X syndrome (FXS) is caused by the full mutation (>200 CGG repeats) in the Fragile X Mental Retardation 1 (FMR1) gene. It is the most common inherited cause of intellectual disability (ID) and autism. This review focuses on neuropsychiatric disorders frequently experienced by premutation carriers with 55 to 200 CGG repeats and the pathophysiology involves elevated FMR1 mRNA levels, which is different from the absence or deficiency of fragile X mental retardation protein (FMRP) seen in FXS. Neuropsychiatric disorders are the most common problems associated with the premutation, and they affect approximately 50% of individuals with 55 to 200 CGG repeats in the FMR1 gene. Neuropsychiatric disorders in children with the premutation include anxiety, ADHD, social deficits, or autism spectrum disorders (ASD). In adults with the premutation, anxiety and depression are the most common problems, although obsessive compulsive disorder, ADHD, and substance abuse are also common. These problems are often exacerbated by chronic fatigue, chronic pain, fibromyalgia, autoimmune disorders and sleep problems, which are also associated with the premutation. Here we review the clinical studies, neuropathology and molecular underpinnings of RNA toxicity associated with the premutation. We also propose the name Fragile X-associated Neuropsychiatric Disorders (FXAND) in an effort to promote research and the use of fragile X DNA testing to enhance recognition and treatment for these disorders.
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Affiliation(s)
- Randi J. Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Davis, Sacramento, CA, United States
- Department of Pediatrics, University of California Davis School of Medicine, Sacramento, CA, United States
| | - Dragana Protic
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Davis, Sacramento, CA, United States
- Department of Pharmacology, Clinical Pharmacology and Toxicology, School of Medicine, University of Belgrade, Belgrade, Serbia
| | - Akash Rajaratnam
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Davis, Sacramento, CA, United States
- Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Maria J. Salcedo-Arellano
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Davis, Sacramento, CA, United States
- Department of Pediatrics, University of California Davis School of Medicine, Sacramento, CA, United States
| | - Elber Yuksel Aydin
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Davis, Sacramento, CA, United States
- Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
| | - Andrea Schneider
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, University of California, Davis, Sacramento, CA, United States
- Department of Pediatrics, University of California Davis School of Medicine, Sacramento, CA, United States
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20
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Shen X, Yeung HT, Lai KO. Application of Human-Induced Pluripotent Stem Cells (hiPSCs) to Study Synaptopathy of Neurodevelopmental Disorders. Dev Neurobiol 2018; 79:20-35. [PMID: 30304570 DOI: 10.1002/dneu.22644] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 09/27/2018] [Accepted: 10/04/2018] [Indexed: 12/15/2022]
Abstract
Synapses are the basic structural and functional units for information processing and storage in the brain. Their diverse properties and functions ultimately underlie the complexity of human behavior. Proper development and maintenance of synapses are essential for normal functioning of the nervous system. Disruption in synaptogenesis and the consequent alteration in synaptic function have been strongly implicated to cause neurodevelopmental disorders such as autism spectrum disorders (ASDs) and schizophrenia (SCZ). The introduction of human-induced pluripotent stem cells (hiPSCs) provides a new path to elucidate disease mechanisms and potential therapies. In this review, we will discuss the advantages and limitations of using hiPSC-derived neurons to study synaptic disorders. Many mutations in genes encoding for proteins that regulate synaptogenesis have been identified in patients with ASDs and SCZ. We use Methyl-CpG binding protein 2 (MECP2), SH3 and multiple ankyrin repeat domains 3 (SHANK3) and Disrupted in schizophrenia 1 (DISC1) as examples to illustrate the promise of using hiPSCs as cellular models to elucidate the mechanisms underlying disease-related synaptopathy.
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Affiliation(s)
- Xuting Shen
- Faculty of Medicine, School of Biomedical Sciences, The University of Hong Kong, 21 Sassoon Road, Hong Kong, China
| | - Hoi Ting Yeung
- Faculty of Medicine, School of Biomedical Sciences, The University of Hong Kong, 21 Sassoon Road, Hong Kong, China
| | - Kwok-On Lai
- Faculty of Medicine, School of Biomedical Sciences, The University of Hong Kong, 21 Sassoon Road, Hong Kong, China.,State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, 21 Sassoon Road, Hong Kong, China
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21
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Jiraanont P, Kumar M, Tang HT, Espinal G, Hagerman PJ, Hagerman RJ, Chutabhakdikul N, Tassone F. Size and methylation mosaicism in males with Fragile X syndrome. Expert Rev Mol Diagn 2018; 17:1023-1032. [PMID: 28929824 DOI: 10.1080/14737159.2017.1377612] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Size and methylation mosaicism are a common phenomenon in Fragile X syndrome (FXS). Here, the authors report a study on twelve fragile X males with atypical mosaicism, seven of whom presented with autism spectrum disorder. METHODS A combination of Southern Blot and PCR analysis was used for CGG allele sizing and methylation. FMR1 mRNA and FMRP expression were measured by qRT-PCR and by Homogeneous Time Resolved Fluorescence methodology, respectively. RESULTS DNA analysis showed atypical size- or methylation-mosaicism with both, full mutation and smaller (normal to premutation) alleles, as well as a combination of methylated and unmethylated alleles. Four individuals carried a deletion of the CGG repeat and portions of the flanking regions. The extent of methylation among the participants was reflected in the lower FMR1 mRNA and FMRP expression levels detected in these subjects. CONCLUSION Decreased gene expression is likely the main contributor to the cognitive impairment observed in these subjects; although the presence of a normal allele did not appear to compensate for the presence of the full mutation, it correlated with better cognitive function in some but not all of the reported cases emphasizing the complexity of the molecular and clinical profile in FXS.
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Affiliation(s)
- Poonnada Jiraanont
- a Department of Biochemistry and Molecular Medicine , University of California, School of Medicine , Davis , CA , USA.,b Research Center for Neuroscience, Institute of Molecular Biosciences , Mahidol University , Nakornpathom , Thailand
| | - Madhur Kumar
- a Department of Biochemistry and Molecular Medicine , University of California, School of Medicine , Davis , CA , USA
| | - Hiu-Tung Tang
- a Department of Biochemistry and Molecular Medicine , University of California, School of Medicine , Davis , CA , USA
| | - Glenda Espinal
- a Department of Biochemistry and Molecular Medicine , University of California, School of Medicine , Davis , CA , USA
| | - Paul J Hagerman
- a Department of Biochemistry and Molecular Medicine , University of California, School of Medicine , Davis , CA , USA.,c M.I.N.D. Institute , University of California Davis Medical Center , Sacramento , CA , USA
| | - Randi J Hagerman
- c M.I.N.D. Institute , University of California Davis Medical Center , Sacramento , CA , USA.,d Department of Pediatrics , University of California, Davis Medical Center , Sacramento , CA , USA
| | - Nuanchan Chutabhakdikul
- b Research Center for Neuroscience, Institute of Molecular Biosciences , Mahidol University , Nakornpathom , Thailand
| | - Flora Tassone
- a Department of Biochemistry and Molecular Medicine , University of California, School of Medicine , Davis , CA , USA.,c M.I.N.D. Institute , University of California Davis Medical Center , Sacramento , CA , USA
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22
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FMR1 allele size distribution in 35,000 males and females: a comparison of developmental delay and general population cohorts. Genet Med 2018; 20:1627-1634. [DOI: 10.1038/gim.2018.52] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 02/20/2018] [Indexed: 01/01/2023] Open
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23
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Dahlhaus R. Of Men and Mice: Modeling the Fragile X Syndrome. Front Mol Neurosci 2018; 11:41. [PMID: 29599705 PMCID: PMC5862809 DOI: 10.3389/fnmol.2018.00041] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 01/31/2018] [Indexed: 12/26/2022] Open
Abstract
The Fragile X Syndrome (FXS) is one of the most common forms of inherited intellectual disability in all human societies. Caused by the transcriptional silencing of a single gene, the fragile x mental retardation gene FMR1, FXS is characterized by a variety of symptoms, which range from mental disabilities to autism and epilepsy. More than 20 years ago, a first animal model was described, the Fmr1 knock-out mouse. Several other models have been developed since then, including conditional knock-out mice, knock-out rats, a zebrafish and a drosophila model. Using these model systems, various targets for potential pharmaceutical treatments have been identified and many treatments have been shown to be efficient in preclinical studies. However, all attempts to turn these findings into a therapy for patients have failed thus far. In this review, I will discuss underlying difficulties and address potential alternatives for our future research.
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Affiliation(s)
- Regina Dahlhaus
- Institute for Biochemistry, Emil-Fischer Centre, University of Erlangen-Nürnberg, Erlangen, Germany
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Muslimov IA, Eom T, Iacoangeli A, Chuang SC, Hukema RK, Willemsen R, Stefanov DG, Wong RKS, Tiedge H. BC RNA Mislocalization in the Fragile X Premutation. eNeuro 2018; 5:ENEURO.0091-18.2018. [PMID: 29766042 PMCID: PMC5952321 DOI: 10.1523/eneuro.0091-18.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 03/20/2018] [Accepted: 03/27/2018] [Indexed: 12/27/2022] Open
Abstract
Fragile X premutation disorder is caused by CGG triplet repeat expansions in the 5' untranslated region of FMR1 mRNA. The question of how expanded CGG repeats cause disease is a subject of continuing debate. Our work indicates that CGG-repeat structures compete with regulatory BC1 RNA for access to RNA transport factor hnRNP A2. As a result, BC1 RNA is mislocalized in vivo, as its synapto-dendritic presence is severely diminished in brains of CGG-repeat knock-in animals (a premutation mouse model). Lack of BC1 RNA is known to cause seizure activity and cognitive dysfunction. Our working hypothesis thus predicted that absence, or significantly reduced presence, of BC1 RNA in synapto-dendritic domains of premutation animal neurons would engender cognate phenotypic alterations. Testing this prediction, we established epileptogenic susceptibility and cognitive impairments as major phenotypic abnormalities of CGG premutation mice. In CA3 hippocampal neurons of such animals, synaptic release of glutamate elicits neuronal hyperexcitability in the form of group I metabotropic glutamate receptor-dependent prolonged epileptiform discharges. CGG-repeat knock-in animals are susceptible to sound-induced seizures and are cognitively impaired as revealed in the Attentional Set Shift Task. These phenotypic disturbances occur in young-adult premutation animals, indicating that a neurodevelopmental deficit is an early-initial manifestation of the disorder. The data are consistent with the notion that RNA mislocalization can contribute to pathogenesis.
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Affiliation(s)
- Ilham A. Muslimov
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Taesun Eom
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Anna Iacoangeli
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Shih-Chieh Chuang
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Renate K. Hukema
- Department of Clinical Genetics, Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Rob Willemsen
- Department of Clinical Genetics, Erasmus Medical Center, 3000 CA Rotterdam, The Netherlands
| | - Dimitre G. Stefanov
- Statistical Design and Analysis, Research Division, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Robert K. S. Wong
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Neurology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Henri Tiedge
- The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Physiology and Pharmacology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
- Department of Neurology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
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Xu B, Zhang Y, Zhan S, Wang X, Zhang H, Meng X, Ge W. Proteomic Profiling of Brain and Testis Reveals the Diverse Changes in Ribosomal Proteins in fmr1 Knockout Mice. Neuroscience 2017; 371:469-483. [PMID: 29292077 DOI: 10.1016/j.neuroscience.2017.12.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 12/15/2017] [Accepted: 12/18/2017] [Indexed: 01/01/2023]
Abstract
Fragile X syndrome (FXS), the leading cause of inherited forms of mental retardation and autism, is caused by the transcriptional silencing of fmr1 encoding the fragile X mental retardation protein (FMRP). FMRP is an RNA-binding protein that is a widely expressed, but primarily in the brain and testis, and associated approximately 4% of transcripts. Macro-orchidism is a common symptom associated with FXS both in humans and mice. Thus, we analyze the pooled samples of cerebral cortex, hippocampus and testis from both the fmr1-KO and wild-type mice by a LC-MS/MS proteomic study. Among the identified proteins, most of those showing significant changes in expression were up- or downregulated in the absence of FMRP. Proteins (FMRP, RPS8, RPL23a and ATPIF1, RPL6, GAP43, MTCH2 and MPZ in brain, and FMRP, CAH3, AKR1B7 and C9 in testis) identified by MS/MS were also verified by Western blotting. The Gene Ontology and WikiPathways analysis revealed that the differentially expressed proteins were clustered in the polyribosome and RNA-binding protein categories in both cerebral cortex and hippocampus, but not in testis. Although this study was limited by the little number of samples, our results provide detailed insights into the ribosomal protein profiles of cerebral cortex, hippocampus and testis in the absence of FMRP. Our studies also provide a better understanding of protein profile changes and the underlying dysregulated pathways arising from fmr1 silencing in FXS.
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Affiliation(s)
- Benhong Xu
- Affiliated Hospital of Hebei University, No. 212, Yu Hua East Road, Nan Shi District, Baoding, Hebei 071000, China; State Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, No. 5 Dongdansantiao, Dongcheng District, Beijing 100005, China; Key Laboratory of Modern Toxicology of Shenzhen, Institute of Toxicology, Shenzhen Center for Disease Control and Prevention, Shenzhen 518055, China
| | - Yusheng Zhang
- State Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, No. 5 Dongdansantiao, Dongcheng District, Beijing 100005, China
| | - Shaohua Zhan
- State Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, No. 5 Dongdansantiao, Dongcheng District, Beijing 100005, China
| | - Xia Wang
- State Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, No. 5 Dongdansantiao, Dongcheng District, Beijing 100005, China
| | - Haisong Zhang
- Affiliated Hospital of Hebei University, No. 212, Yu Hua East Road, Nan Shi District, Baoding, Hebei 071000, China
| | - Xianbin Meng
- MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Wei Ge
- Affiliated Hospital of Hebei University, No. 212, Yu Hua East Road, Nan Shi District, Baoding, Hebei 071000, China; State Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, No. 5 Dongdansantiao, Dongcheng District, Beijing 100005, China.
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Rajaratnam A, Shergill J, Salcedo-Arellano M, Saldarriaga W, Duan X, Hagerman R. Fragile X syndrome and fragile X-associated disorders. F1000Res 2017; 6:2112. [PMID: 29259781 PMCID: PMC5728189 DOI: 10.12688/f1000research.11885.1] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/20/2017] [Indexed: 12/26/2022] Open
Abstract
Fragile X syndrome (FXS) is caused by a full mutation on the
FMR1 gene and a subsequent lack of FMRP, the protein product of
FMR1. FMRP plays a key role in regulating the translation of many proteins involved in maintaining neuronal synaptic connections; its deficiency may result in a range of intellectual disabilities, social deficits, psychiatric problems, and dysmorphic physical features. A range of clinical involvement is also associated with the
FMR1 premutation, including fragile X-associated tremor ataxia syndrome, fragile X-associated primary ovarian insufficiency, psychiatric problems, hypertension, migraines, and autoimmune problems. Over the past few years, there have been a number of advances in our knowledge of FXS and fragile X-associated disorders, and each of these advances offers significant clinical implications. Among these developments are a better understanding of the clinical impact of the phenomenon known as mosaicism, the revelation that various types of mutations can cause FXS, and improvements in treatment for FXS.
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Affiliation(s)
| | | | | | - Wilmar Saldarriaga
- MIND Institute, UC Davis Health, Sacramento, CA, USA.,Department of Morphology and Obstetrics & Gynecology, Universidad del Valle, School of Medicine, Cali, Valle del Cauca, Colombia
| | - Xianlai Duan
- MIND Institute, UC Davis Health, Sacramento, CA, USA.,Department of Neurology, The Third Hospital of Changsha, Hunan Sheng, China
| | - Randi Hagerman
- MIND Institute, UC Davis Health, Sacramento, CA, USA.,Department of Pediatrics, University of California, Davis, School of Medicine, Sacramento, CA, USA
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Boivin M, Willemsen R, Hukema RK, Sellier C. Potential pathogenic mechanisms underlying Fragile X Tremor Ataxia Syndrome: RAN translation and/or RNA gain-of-function? Eur J Med Genet 2017; 61:674-679. [PMID: 29223504 DOI: 10.1016/j.ejmg.2017.11.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 09/19/2017] [Accepted: 11/08/2017] [Indexed: 10/18/2022]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is an inherited neurodegenerative disease caused by an expansion of 55-200 CGG repeats located in the FMR1 gene. The main clinical and neuropathological features of FXTAS are progressive intention tremor and gait ataxia associated with brain atrophy, neuronal cell loss and presence of ubiquitin-positive intranuclear inclusions in both neurons and astrocytes. At the molecular level, FXTAS is characterized by increased expression of FMR1 sense and antisense RNA containing expanded CGG or GGC repeats, respectively. Here, we discuss the putative molecular mechanisms underlying FXTAS and notably recent reports that expanded CGG and GGC repeats may be pathogenic through RAN translation into toxic proteins.
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Affiliation(s)
- Manon Boivin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, University of Strasbourg, 67400 Illkirch, France
| | - Rob Willemsen
- Department of Clinical Genetics, Erasmus MC, 3015 CN Rotterdam, The Netherlands
| | - Renate K Hukema
- Department of Clinical Genetics, Erasmus MC, 3015 CN Rotterdam, The Netherlands
| | - Chantal Sellier
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR7104, University of Strasbourg, 67400 Illkirch, France.
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Wheeler A, Raspa M, Hagerman R, Mailick M, Riley C. Implications of the FMR1 Premutation for Children, Adolescents, Adults, and Their Families. Pediatrics 2017; 139:S172-S182. [PMID: 28814538 PMCID: PMC5621635 DOI: 10.1542/peds.2016-1159d] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/24/2017] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND OBJECTIVES Given the nature of FMR1 gene expansions, most biological mothers, and often multiple other family members of children with fragile X syndrome (FXS), will have a premutation, which may increase individual and family vulnerabilities. This article summarizes important gaps in knowledge and notes potential implications for pediatric providers with regard to developmental and medical risks for children and adolescents with an FMR1 premutation, including possible implications into adulthood. METHODS A structured electronic literature search was conducted on FMR1 pre- and full mutations, yielding a total of 306 articles examined. Of these, 116 focused primarily on the premutation and are included in this review. RESULTS Based on the literature review, 5 topic areas are discussed: genetics and epidemiology; phenotypic characteristics of individuals with the premutation; implications for carrier parents of children with FXS; implications for the extended family; and implications for pediatricians. CONCLUSIONS Although the premutation phenotype is typically less severe in clinical presentation than in FXS, premutation carriers are much more common and are therefore more likely to be seen in a typical pediatric practice. In addition, there is a wide range of medical, cognitive/developmental, and psychiatric associated features that individuals with a premutation are at increased risk for having, which underscores the importance of awareness on the part of pediatricians in identifying and monitoring premutation carriers and recognizing the impact this identification may have on family members.
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Affiliation(s)
- Anne Wheeler
- RTI International, Research Triangle Park, North Carolina;
| | - Melissa Raspa
- RTI International, Research Triangle Park, North Carolina
| | - Randi Hagerman
- MIND Institute, University of California at Davis, Sacramento, California
| | - Marsha Mailick
- Waisman Center, University of Wisconsin-Madison, Madison, Wisconsin; and
| | - Catharine Riley
- National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia
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Detection and Quantification of the Fragile X Mental Retardation Protein 1 (FMRP). Genes (Basel) 2016; 7:genes7120121. [PMID: 27941672 PMCID: PMC5192497 DOI: 10.3390/genes7120121] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 01/11/2023] Open
Abstract
The final product of FMR1 gene transcription, Fragile X Mental Retardation Protein 1 (FMRP), is an RNA binding protein that acts as a repressor of translation. FMRP is expressed in several tissues and plays important roles in neurogenesis, synaptic plasticity, and ovarian functions and has been implicated in a number of neuropsychological disorders. The loss of FMRP causes Fragile X Syndrome (FXS). In most cases, FXS is due to large expansions of a CGG repeat in FMR1—normally containing 6–54 repeats—to over 200 CGGs and identified as full mutation (FM). Hypermethylation of the repeat induces FMR1 silencing and lack of FMRP expression in FM male. Mosaic FM males express low levels of FMRP and present a less severe phenotype that inversely correlates with FMRP levels. Carriers of pre-mutations (55–200 CGG) show increased mRNA, and normal to reduced FMRP levels. Alternative splicing of FMR1 mRNA results in 24 FMRP predicted isoforms whose expression are tissues and developmentally regulated. Here, we summarize the approaches used by several laboratories including our own to (a) detect and estimate the amount of FMRP in different tissues, developmental stages and various pathologies; and (b) to accurately quantifying FMRP for a direct diagnosis of FXS in adults and newborns.
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30
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Wheeler AC, Sideris J, Hagerman R, Berry-Kravis E, Tassone F, Bailey DB. Developmental profiles of infants with an FMR1 premutation. J Neurodev Disord 2016; 8:40. [PMID: 27822316 PMCID: PMC5095966 DOI: 10.1186/s11689-016-9171-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 10/16/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Emerging evidence suggests that a subset of FMR1 premutation carriers is at an increased risk for cognitive, emotional, and medical conditions. However, because the premutation is rarely diagnosed at birth, the early developmental trajectories of children with a premutation are not known. METHODS This exploratory study examined the cognitive, communication, and social-behavioral profiles of 26 infants with a premutation who were identified through participation in a newborn screening for fragile X syndrome pilot study. In this study, families whose newborn screened positive for an FMR1 premutation were invited to participate in a longitudinal study of early development. Twenty-six infants with the premutation and 21 matched, screen-negative comparison babies were assessed using validated standardized measures at 6-month intervals starting as young as 3 months of age. The babies were assessed up to seven times over a 4-year period. RESULTS The premutation group was not statistically different from the comparison group on measures of cognitive development, adaptive behavior, temperament, or overall communication. However, the babies with the premutation had a significantly different developmental trajectory on measures of nonverbal communication and hyperresponsivity to sensory experiences. They also were significantly more hyporesponsive at all ages than the comparison group. Cytosine-guanine-guanine repeat length was linearly associated with overall cognitive development. CONCLUSIONS These results suggest that infants with a premutation may present with subtle developmental differences as young as 12 months of age that may be early markers of later anxiety, social deficits, or other challenges thought to be experienced by a subset of carriers.
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Affiliation(s)
- Anne C Wheeler
- RTI International, 3040 E. Cornwallis Road, P.O. Box 12194, Research Triangle Park, NC 27709 USA
| | - John Sideris
- University of North Carolina at Chapel Hill, Chapel Hill, NC USA
| | - Randi Hagerman
- Davis MIND (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California at Davis, Davis, CA USA ; Department of Pediatrics, University of California at Davis, Davis, CA USA
| | | | - Flora Tassone
- Davis MIND (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California at Davis, Davis, CA USA
| | - Donald B Bailey
- RTI International, 3040 E. Cornwallis Road, P.O. Box 12194, Research Triangle Park, NC 27709 USA
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Foote M, Arque G, Berman RF, Santos M. Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS) Motor Dysfunction Modeled in Mice. CEREBELLUM (LONDON, ENGLAND) 2016; 15:611-22. [PMID: 27255703 PMCID: PMC5014696 DOI: 10.1007/s12311-016-0797-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that affects some carriers of the fragile X premutation (PM). In PM carriers, there is a moderate expansion of a CGG trinucleotide sequence (55-200 repeats) in the fragile X gene (FMR1) leading to increased FMR1 mRNA and small to moderate decreases in the fragile X mental retardation protein (FMRP) expression. The key symptoms of FXTAS include cerebellar gait ataxia, kinetic tremor, sensorimotor deficits, neuropsychiatric changes, and dementia. While the specific trigger(s) that causes PM carriers to progress to FXTAS pathogenesis remains elusive, the use of animal models has shed light on the underlying neurobiology of the altered pathways involved in disease development. In this review, we examine the current use of mouse models to study PM and FXTAS, focusing on recent advances in the field. Specifically, we will discuss the construct, face, and predictive validities of these PM mouse models, the insights into the underlying disease mechanisms, and potential treatments.
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Affiliation(s)
- Molly Foote
- Department of Neurological Surgery, University of California, Davis, CA, USA.
| | - Gloria Arque
- Department of Molecular Neuroscience, Medical University of Vienna, Vienna, Austria
| | - Robert F Berman
- Department of Neurological Surgery, University of California, Davis, CA, USA
| | - Mónica Santos
- Institute of Biology, Otto-von-Guericke University, Magdeburg, Germany
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Molecular Inconsistencies in a Fragile X Male with Early Onset Ataxia. Genes (Basel) 2016; 7:genes7090068. [PMID: 27657133 PMCID: PMC5042398 DOI: 10.3390/genes7090068] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 08/22/2016] [Accepted: 09/13/2016] [Indexed: 12/20/2022] Open
Abstract
Mosaicism for FMR1 premutation (PM: 55–199 CGG)/full mutation (FM: >200 CGG) alleles or the presence of unmethylated FM (UFM) have been associated with a less severe fragile X syndrome (FXS) phenotype and fragile X associated tremor/ataxia syndrome (FXTAS)—a late onset neurodegenerative disorder. We describe a 38 year old male carrying a 100% methylated FM detected with Southern blot (SB), which is consistent with complete silencing of FMR1 and a diagnosis of fragile X syndrome. However, his formal cognitive scores were not at the most severe end of the FXS phenotype and he displayed tremor and ataxic gait. With the association of UFM with FXTAS, we speculated that his ataxia might be related to an undetected proportion of UFM alleles. Such UFM alleles were confirmed by more sensitive PCR based methylation testing showing FM methylation between 60% and 70% in blood, buccal, and saliva samples and real-time PCR analysis showing incomplete silencing of FMR1. While he did not meet diagnostic criteria for FXTAS based on MRI findings, the underlying cause of his ataxia may be related to UFM alleles not detected by SB, and follow-up clinical and molecular assessment are justified if his symptoms worsen.
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Sensory hypo-excitability in a rat model of fetal development in Fragile X Syndrome. Sci Rep 2016; 6:30769. [PMID: 27465362 PMCID: PMC4964352 DOI: 10.1038/srep30769] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 07/07/2016] [Indexed: 12/19/2022] Open
Abstract
Fragile X syndrome (FXS) is characterized by sensory hyper-sensitivity, and animal models suggest that neuronal hyper-excitability contributes to this phenotype. To understand how sensory dysfunction develops in FXS, we used the rat model (FMR-KO) to quantify the maturation of cortical visual responses from the onset of responsiveness prior to eye-opening, through age equivalents of human juveniles. Rather than hyper-excitability, visual responses before eye-opening had reduced spike rates and an absence of early gamma oscillations, a marker for normal thalamic function at this age. Despite early hypo-excitability, the developmental trajectory of visual responses in FMR-KO rats was normal, and showed the expected loss of visually evoked bursting at the same age as wild-type, two days before eye-opening. At later ages, during the third and fourth post-natal weeks, signs of mild hyper-excitability emerged. These included an increase in the visually-evoked firing of regular spiking, presumptive excitatory, neurons, and a reduced firing of fast-spiking, presumptive inhibitory, neurons. Our results show that early network changes in the FMR-KO rat arise at ages equivalent to fetal humans and have consequences for excitability that are opposite those found in adults. This suggests identification and treatment should begin early, and be tailored in an age-appropriate manner.
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Foote MM, Careaga M, Berman RF. What has been learned from mouse models of the Fragile X Premutation and Fragile X-associated tremor/ataxia syndrome? Clin Neuropsychol 2016; 30:960-72. [PMID: 27355912 DOI: 10.1080/13854046.2016.1158254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE To describe in this review how research using mouse models developed to study the Fragile X premutation (PM) and Fragile X-associated tremor/ataxia syndrome (FXTAS) have contributed to understanding these disorders. PM carriers bear an expanded CGG trinucleotide repeat on the Fragile X Mental Retardation 1 (FMR1) gene, and are at risk for developing the late onset neurodegenerative disorder FXTAS. CONCLUSIONS Much has been learned about these genetic disorders from the development and study of mouse models. This includes new insights into the early cellular and molecular events that occur in PM carriers and in FXTAS, the presence of multiorgan pathology beyond the CNS, immunological dysregulation, unexpected synthesis of a potentially toxic peptide in FXTAS (i.e., FMRpolyG), and evidence that the disease process may be halted or reversed by appropriate molecular therapies given early in the course of disease.
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Affiliation(s)
- Molly M Foote
- a Department of Neurological Surgery , University of California Davis , Davis , CA , USA
| | - Milo Careaga
- b Department of Psychiatry and UC Davis M.I.N.D. Institute , University of California Davis , Davis , CA , USA
| | - Robert F Berman
- c Department of Neurological Surgery and the UC Davis M.I.N.D. Institute , University of California Davis , Davis , CA , USA
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Molecular Pathophysiology of Fragile X-Associated Tremor/Ataxia Syndrome and Perspectives for Drug Development. THE CEREBELLUM 2016; 15:599-610. [DOI: 10.1007/s12311-016-0800-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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36
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Napoli E, Ross-Inta C, Song G, Wong S, Hagerman R, Gane LW, Smilowitz JT, Tassone F, Giulivi C. Premutation in the Fragile X Mental Retardation 1 (FMR1) Gene Affects Maternal Zn-milk and Perinatal Brain Bioenergetics and Scaffolding. Front Neurosci 2016; 10:159. [PMID: 27147951 PMCID: PMC4835505 DOI: 10.3389/fnins.2016.00159] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 03/29/2016] [Indexed: 12/12/2022] Open
Abstract
Fragile X premutation alleles have 55–200 CGG repeats in the 5′ UTR of the FMR1 gene. Altered zinc (Zn) homeostasis has been reported in fibroblasts from >60 years old premutation carriers, in which Zn supplementation significantly restored Zn-dependent mitochondrial protein import/processing and function. Given that mitochondria play a critical role in synaptic transmission, brain function, and cognition, we tested FMRP protein expression, brain bioenergetics, and expression of the Zn-dependent synaptic scaffolding protein SH3 and multiple ankyrin repeat domains 3 (Shank3) in a knock-in (KI) premutation mouse model with 180 CGG repeats. Mitochondrial outcomes correlated with FMRP protein expression (but not FMR1 gene expression) in KI mice and human fibroblasts from carriers of the pre- and full-mutation. Significant deficits in brain bioenergetics, Zn levels, and Shank3 protein expression were observed in the Zn-rich regions KI hippocampus and cerebellum at PND21, with some of these effects lasting into adulthood (PND210). A strong genotype × age interaction was observed for most of the outcomes tested in hippocampus and cerebellum, whereas in cortex, age played a major role. Given that the most significant effects were observed at the end of the lactation period, we hypothesized that KI milk might have a role at compounding the deleterious effects on the FMR1 genetic background. A higher gene expression of ZnT4 and ZnT6, Zn transporters abundant in brain and lactating mammary glands, was observed in the latter tissue of KI dams. A cross-fostering experiment allowed improving cortex bioenergetics in KI pups nursing on WT milk. Conversely, WT pups nursing on KI milk showed deficits in hippocampus and cerebellum bioenergetics. A highly significant milk type × genotype interaction was observed for all three-brain regions, being cortex the most influenced. Finally, lower milk-Zn levels were recorded in milk from lactating women carrying the premutation as well as other Zn-related outcomes (Zn-dependent alkaline phosphatase activity and lactose biosynthesis—whose limiting step is the Zn-dependent β-1,4-galactosyltransferase). In premutation carriers, altered Zn homeostasis, brain bioenergetics and Shank3 levels could be compounded by Zn-deficient milk, increasing the risk of developing emotional and neurological/cognitive problems and/or FXTAS later in life.
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Affiliation(s)
- Eleonora Napoli
- Department of Molecular Biosciences, School of Veterinary Medicine Davis, CA, USA
| | - Catherine Ross-Inta
- Department of Molecular Biosciences, School of Veterinary Medicine Davis, CA, USA
| | - Gyu Song
- Department of Molecular Biosciences, School of Veterinary Medicine Davis, CA, USA
| | - Sarah Wong
- Department of Molecular Biosciences, School of Veterinary Medicine Davis, CA, USA
| | - Randi Hagerman
- Medical Investigations of Neurodevelopmental Disorders Institute, University of California, DavisDavis, CA, USA; Department of Pediatrics, University of California Davis Medical CenterSacramento, CA, USA
| | - Louise W Gane
- Medical Investigations of Neurodevelopmental Disorders Institute, University of California, Davis Davis, CA, USA
| | - Jennifer T Smilowitz
- Department of Food Science and Technology and Foods for Health Institute, University of California, Davis Davis, CA, USA
| | - Flora Tassone
- Medical Investigations of Neurodevelopmental Disorders Institute, University of California, DavisDavis, CA, USA; Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, DavisDavis, CA, USA
| | - Cecilia Giulivi
- Department of Molecular Biosciences, School of Veterinary MedicineDavis, CA, USA; Medical Investigations of Neurodevelopmental Disorders Institute, University of California, DavisDavis, CA, USA
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Bhattacharyya A, Zhao X. Human pluripotent stem cell models of Fragile X syndrome. Mol Cell Neurosci 2015; 73:43-51. [PMID: 26640241 DOI: 10.1016/j.mcn.2015.11.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 11/03/2015] [Accepted: 11/25/2015] [Indexed: 01/18/2023] Open
Abstract
Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and autism. The causal mutation in FXS is a trinucleotide CGG repeat expansion in the FMR1 gene that leads to human specific epigenetic silencing and loss of Fragile X Mental Retardation Protein (FMRP) expression. Human pluripotent stem cells (PSCs), including human embryonic stem cells (ESCs) and particularly induced PSCs (iPSCs), offer a model system to reveal cellular and molecular events underlying human neuronal development and function in FXS. Human FXS PSCs have been established and have provided insight into the epigenetic silencing of the FMR1 gene as well as aspects of neuronal development.
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Affiliation(s)
- Anita Bhattacharyya
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, United States.
| | - Xinyu Zhao
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, United States.
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Abstract
Autism spectrum disorder (ASD) is a complex behavioral condition with onset during early childhood and a lifelong course in the vast majority of cases. To date, no behavioral, genetic, brain imaging, or electrophysiological test can specifically validate a clinical diagnosis of ASD. However, these medical procedures are often implemented in order to screen for syndromic forms of the disorder (i.e., autism comorbid with known medical conditions). In the last 25 years a good deal of information has been accumulated on the main components of the "endocannabinoid (eCB) system", a rather complex ensemble of lipid signals ("endocannabinoids"), their target receptors, purported transporters, and metabolic enzymes. It has been clearly documented that eCB signaling plays a key role in many human health and disease conditions of the central nervous system, thus opening the avenue to the therapeutic exploitation of eCB-oriented drugs for the treatment of psychiatric, neurodegenerative, and neuroinflammatory disorders. Here we present a modern view of the eCB system, and alterations of its main components in human patients and animal models relevant to ASD. This review will thus provide a critical perspective necessary to explore the potential exploitation of distinct elements of eCB system as targets of innovative therapeutics against ASD.
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Affiliation(s)
- Bhismadev Chakrabarti
- Centre for Integrative Neuroscience and Neurodynamics, School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK
| | - Antonio Persico
- Center of Integrated Research and School of Medicine, Campus Bio-Medico University of Rome, Via Alvaro del Portillo 21, 00128, Rome, Italy
- Mafalda Luce Center for Pervasive Developmental Disorders, Milan, Italy
| | - Natalia Battista
- Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Teramo, Italy
| | - Mauro Maccarrone
- Center of Integrated Research and School of Medicine, Campus Bio-Medico University of Rome, Via Alvaro del Portillo 21, 00128, Rome, Italy.
- European Center for Brain Research (CERC)/Santa Lucia Foundation, Rome, Italy.
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Birch RC, Hocking DR, Cornish KM, Menant JC, Georgiou-Karistianis N, Godler DE, Wen W, Hackett A, Rogers C, Trollor JN. Preliminary evidence of an effect of cerebellar volume on postural sway in FMR1 premutation males. GENES BRAIN AND BEHAVIOR 2015; 14:251-9. [PMID: 25689687 DOI: 10.1111/gbb.12204] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/27/2015] [Accepted: 01/28/2015] [Indexed: 11/29/2022]
Abstract
Recent evidence suggests that early changes in postural control may be discernible among females with premutation expansions (55-200 CGG repeats) of the fragile X mental retardation 1 (FMR1) gene at risk of developing fragile X-associated tremor ataxia syndrome (FXTAS). Cerebellar dysfunction is well described in males and females with FXTAS, yet the interrelationships between cerebellar volume, CGG repeat length, FMR1 messenger RNA (mRNA) levels and changes in postural control remain unknown. This study examined postural sway during standing in a cohort of 22 males with the FMR1 premutation (ages 26-80) and 24 matched controls (ages 26-77). The influence of cerebellar volume, CGG repeat length and FMR1 mRNA levels on postural sway was explored using multiple linear regression. The results provide preliminary evidence that increasing CGG repeat length and decreasing cerebellar volume were associated with greater postural sway among premutation males. The relationship between CGG repeat length and postural sway was mediated by a negative association between CGG repeat size and cerebellar volume. While FMR1 mRNA levels were significantly elevated in the premutation group and correlated with CGG repeat length, FMR1 mRNA levels were not significantly associated with postural sway scores. These findings show for the first time that greater postural sway among males with the FMR1 premutation may reflect CGG repeat-mediated disruption in vulnerable cerebellar circuits implicated in postural control. However, longitudinal studies in larger samples are required to confirm whether the relationships between cerebellar volume, CGG repeat length and postural sway indicate greater risk for neurological decline.
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Affiliation(s)
- R C Birch
- Department of Developmental Disability Neuropsychiatry, School of Psychiatry, University of New South Wales, Sydney
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Cornish KM, Kraan CM, Bui QM, Bellgrove MA, Metcalfe SA, Trollor JN, Hocking DR, Slater HR, Inaba Y, Li X, Archibald AD, Turbitt E, Cohen J, Godler DE. Novel methylation markers of the dysexecutive-psychiatric phenotype in FMR1 premutation women. Neurology 2015; 84:1631-8. [PMID: 25809302 DOI: 10.1212/wnl.0000000000001496] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 12/08/2014] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE To examine the epigenetic basis of psychiatric symptoms and dysexecutive impairments in FMR1 premutation (PM: 55 to 199 CGG repeats) women. METHODS A total of 35 FMR1 PM women aged between 22 and 55 years and 35 age- and IQ-matched women controls (CGG <45) participated in this study. All participants completed a range of executive function tests and self-reported symptoms of psychiatric disorders. The molecular measures included DNA methylation of the FMR1 CpG island in blood, presented as FMR1 activation ratio (AR), and 9 CpG sites located at the FMR1 exon1/intron 1 boundary, CGG size, and FMR1 mRNA levels. RESULTS We show that FMR1 intron 1 methylation levels could be used to dichotomize PM women into greater and lower risk categories (p = 0.006 to 0.037; odds ratio = 14-24.8), with only FMR1 intron 1 methylation, and to a lesser extent AR, being significantly correlated with the likelihood of probable dysexecutive or psychiatric symptoms (p < 0.05). Furthermore, the significant relationships between methylation and social anxiety were found to be mediated by executive function performance, but only in PM women. FMR1 exon 1 methylation, CGG size, and FMR1 mRNA could not predict probable dysexecutive/psychiatric disorders in PM women. CONCLUSIONS This is the first study supporting presence of specific epigenetic etiology associated with increased risk of developing comorbid dysexecutive and social anxiety symptoms in PM women. These findings could have implications for early intervention and risk estimate recommendations aimed at improving the outcomes for PM women and their families.
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Affiliation(s)
- Kim M Cornish
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia.
| | - Claudine M Kraan
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Quang Minh Bui
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Mark A Bellgrove
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Sylvia A Metcalfe
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Julian N Trollor
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Darren R Hocking
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Howard R Slater
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Yoshimi Inaba
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Xin Li
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Alison D Archibald
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Erin Turbitt
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - Jonathan Cohen
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
| | - David E Godler
- From the School of Psychological Sciences, Faculty of Medicine, Nursing and Health Sciences (K.M.C., C.M.K., M.A.B.), and the Centre for Developmental Disability Health Victoria (J.C.), Monash University, Clayton; the Centre for Epidemiology and Biostatistics (Q.M.B.), Melbourne School of Population and Global Health, University of Melbourne; Genetics Education and Health Research (S.A.M., A.D.A., E.T.), the Cytomolecular Diagnostic Research Laboratory (H.R.S., Y.I., X.L., D.E.G.) and Victorian Clinical Genetics Services (A.D.A.), Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Melbourne; the Department of Paediatrics, Faculty of Medicine, Dentistry and Health Sciences (S.A.M., A.D.A., E.T.), The University of Melbourne, Parkville; the Department of Developmental Disability Neuropsychiatry and Centre for Healthy Brain Ageing (J.N.T.), UNSW Australia, Sydney; Olga Tennison Autism Research Centre (D.R.H.), School of Psychological Science, La Trobe, Bundoora; and Fragile X Alliance Inc. (Clinic) (J.C.), North Caufield, Australia
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Hagerman PJ, Hagerman RJ. Fragile X-associated tremor/ataxia syndrome. Ann N Y Acad Sci 2015; 1338:58-70. [PMID: 25622649 PMCID: PMC4363162 DOI: 10.1111/nyas.12693] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 12/04/2014] [Accepted: 12/18/2014] [Indexed: 12/20/2022]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that affects some but not all carriers of small, noncoding CGG-repeat expansions (55-200 repeats; premutation) within the fragile X gene (FMR1). Principal features of FXTAS include intention tremor, cerebellar ataxia, Parkinsonism, memory and executive function deficits, autonomic dysfunction, brain atrophy with white matter disease, and cognitive decline. Although FXTAS was originally considered to be confined to the premutation range, rare individuals with a gray zone (45-54 repeats) or an unmethylated full mutation (>200 repeats) allele have now been described, the constant feature of the disorder remaining the requirement for FMR1 expression, in contradistinction to the gene silencing mechanism of fragile X syndrome. Although transcriptional activity is required for FXTAS pathogenesis, the specific trigger(s) for FXTAS pathogenesis remains elusive, highlighting the need for more research in this area. This need is underscored by recent neuroimaging findings of changes in the central nervous system that consistently appear well before the onset of clinical symptoms, thus creating an opportunity to delay or prevent the appearance of FXTAS.
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Affiliation(s)
- Paul J Hagerman
- Department of Biochemistry and Molecular Medicine, University of California , Davis , School of Medicine, Davis, California; The MIND Institute, University of California , Davis , Health System, Sacramento, California
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Reduced phenotypic severity following adeno-associated virus-mediated Fmr1 gene delivery in fragile X mice. Neuropsychopharmacology 2014; 39:3100-11. [PMID: 24998620 PMCID: PMC4229583 DOI: 10.1038/npp.2014.167] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/06/2014] [Accepted: 06/24/2014] [Indexed: 12/21/2022]
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a trinucleotide repeat expansion in the FMR1 gene that codes for fragile X mental retardation protein (FMRP). To determine if FMRP expression in the central nervous system could reverse phenotypic deficits in the Fmr1 knockout (KO) mouse model of FXS, we used a single-stranded adeno-associated viral (AAV) vector with viral capsids from serotype 9 that contained a major isoform of FMRP. FMRP transgene expression was driven by the neuron-selective synapsin-1 promoter. The vector was delivered to the brain via a single bilateral intracerebroventricular injection into neonatal Fmr1 KO mice and transgene expression and behavioral assessments were conducted 22-26 or 50-56 days post injection. Western blotting and immunocytochemical analyses of AAV-FMRP-injected mice revealed FMRP expression in the striatum, hippocampus, retrosplenial cortex, and cingulate cortex. Cellular expression was selective for neurons and reached ∼ 50% of wild-type levels in the hippocampus and cortex at 56 days post injection. The pathologically elevated repetitive behavior and the deficit in social dominance behavior seen in phosphate-buffered saline-injected Fmr1 KO mice were reversed in AAV-FMRP-injected mice. These results provide the first proof of principle that gene therapy can correct specific behavioral abnormalities in the mouse model of FXS.
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Lozano R, Rosero CA, Hagerman RJ. Fragile X spectrum disorders. Intractable Rare Dis Res 2014; 3:134-46. [PMID: 25606363 PMCID: PMC4298643 DOI: 10.5582/irdr.2014.01022] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 11/28/2014] [Indexed: 12/13/2022] Open
Abstract
The fragile X mental retardation 1 gene (FMR1), which codes for the fragile X mental retardation 1 protein (FMRP), is located at Xp27.3. The normal allele of the FMR1 gene typically has 5 to 40 CGG repeats in the 5' untranslated region; abnormal alleles of dynamic mutations include the full mutation (> 200 CGG repeats), premutation (55-200 CGG repeats) and the gray zone mutation (45-54 CGG repeats). Premutation carriers are common in the general population with approximately 1 in 130-250 females and 1 in 250-810 males, whereas the full mutation and Fragile X syndrome (FXS) occur in approximately 1 in 4000 to 1 in 7000. FMR1 mutations account for a variety of phenotypes including the most common monogenetic cause of inherited intellectual disability (ID) and autism (FXS), the most common genetic form of ovarian failure, the fragile X-associated primary ovarian insufficiency (FXPOI, premutation); and fragile X-associated tremor/ataxia syndrome (FXTAS, premutation). The premutation can also cause developmental problems including ASD and ADHD especially in boys and psychopathology including anxiety and depression in children and adults. Some premutation carriers can have a deficit of FMRP and some unmethylated full mutation individuals can have elevated FMR1 mRNA that is considered a premutation problem. Therefore the term "Fragile X Spectrum Disorder" (FXSD) should be used to include the wide range of overlapping phenotypes observed in affected individuals with FMR1 mutations. In this review we focus on the phenotypes and genotypes of children with FXSD.
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Affiliation(s)
- Reymundo Lozano
- UC Davis MIND Institute and Department of Pediatrics, UC Davis Medical Center, Sacramento, CA, USA
- Address correspondence to: Dr. Reymundo Lozano, UC Davis MIND Institute and Department of Pediatrics, UC Davis Medical Center, Sacramento, CA, USA. E-mail:
| | - Carolina Alba Rosero
- Instituto Colombiano del Sistema Nervioso, Clínica Montserrat, Bogotá D.C, Colombia
| | - Randi J Hagerman
- UC Davis MIND Institute and Department of Pediatrics, UC Davis Medical Center, Sacramento, CA, USA
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Muzar Z, Lozano R. Current research, diagnosis, and treatment of fragile X-associated tremor/ataxia syndrome. Intractable Rare Dis Res 2014; 3:101-9. [PMID: 25606360 PMCID: PMC4298640 DOI: 10.5582/irdr.2014.01029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 11/30/2014] [Indexed: 12/13/2022] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is caused by a premutation CGG-repeat expansion in the 5'UTR of the fragile X mental retardation 1 (FMR1) gene. The classical clinical manifestations include tremor, cerebellar ataxia, cognitive decline and psychiatric disorders. Other less frequent features are peripheral neuropathy and autonomic dysfunction. Cognitive decline, a form of frontal subcortical dementia, memory loss and executive function deficits are also characteristics of this disorder. In this review, we present an expansion of recommendations for genetic testing for adults with suspected premutation disorders and provide an update of the clinical, radiological and molecular research of FXTAS, as well as the current research in the treatment for this intractable complex neurodegenerative genetic disorder.
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Affiliation(s)
- Zukhrofi Muzar
- UC Davis MIND Institute and Department of Pediatrics, UC Davis Medical Center, Sacramento, CA, USA
| | - Reymundo Lozano
- UC Davis MIND Institute and Department of Pediatrics, UC Davis Medical Center, Sacramento, CA, USA
- Address correspondence to: Dr. Reymundo Lozano, UC Davis MIND Institute and Department of Pediatrics, UC Davis Medical Center, Sacramento, CA, USA. E-mail:
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Renoux AJ, Carducci NM, Ahmady AA, Todd PK. Fragile X mental retardation protein expression in Alzheimer's disease. Front Genet 2014; 5:360. [PMID: 25452762 PMCID: PMC4233940 DOI: 10.3389/fgene.2014.00360] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 09/27/2014] [Indexed: 12/31/2022] Open
Abstract
The FMR1 protein product, FMRP, is an mRNA binding protein associated with translational inhibition of target transcripts. One FMRP target is the amyloid precursor protein (APP) mRNA, and APP levels are elevated in Fmr1 KO mice. Given that elevated APP protein expression can elicit Alzheimer's disease (AD) in patients and model systems, we evaluated whether FMRP expression might be altered in Alzheimer's autopsy brain samples and mouse models compared to controls. In a double transgenic mouse model of AD (APP/PS1), we found no difference in FMRP expression in aged AD model mice compared to littermate controls. FMRP expression was also similar in AD and control patient frontal cortex and cerebellum samples. Fragile X-associated tremor/ataxia syndrome (FXTAS) is an age-related neurodegenerative disorder caused by expanded CGG repeats in the 5' untranslated region of the FMR1 gene. Patients experience cognitive impairment and dementia in addition to motor symptoms. In parallel studies, we measured FMRP expression in cortex and cerebellum from three FXTAS patients and found reduced expression compared to both controls and Alzheimer's patient brains, consistent with animal models. We also find increased APP levels in cerebellar, but not cortical, samples of FXTAS patients compared to controls. Taken together, these data suggest that a decrease in FMRP expression is unlikely to be a primary contributor to Alzheimer's disease pathogenesis.
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Affiliation(s)
- Abigail J Renoux
- Department of Molecular and Integrative Physiology, University of Michigan , Ann Arbor, MI, USA ; Department of Neurology, University of Michigan , Ann Arbor, MI, USA
| | | | - Arya A Ahmady
- Department of Neurology, University of Michigan , Ann Arbor, MI, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan , Ann Arbor, MI, USA
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Qin M, Huang T, Liu Z, Kader M, Burlin T, Xia Z, Zeidler Z, Hukema RK, Smith CB. Cerebral protein synthesis in a knockin mouse model of the fragile X premutation. ASN Neuro 2014; 6:6/5/1759091414551957. [PMID: 25290064 PMCID: PMC4187003 DOI: 10.1177/1759091414551957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The (CGG)n-repeat in the 5′-untranslated region of the fragile X mental retardation gene (FMR1) gene is polymorphic and may become unstable on transmission to the next generation. In fragile X syndrome, CGG repeat lengths exceed 200, resulting in silencing of FMR1 and absence of its protein product, fragile X mental retardation protein (FMRP). CGG repeat lengths between 55 and 200 occur in fragile X premutation (FXPM) carriers and have a high risk of expansion to a full mutation on maternal transmission. FXPM carriers have an increased risk for developing progressive neurodegenerative syndromes and neuropsychological symptoms. FMR1 mRNA levels are elevated in FXPM, and it is thought that clinical symptoms might be caused by a toxic gain of function due to elevated FMR1 mRNA. Paradoxically, FMRP levels decrease moderately with increasing CGG repeat length in FXPM. Lowered FMRP levels may also contribute to the appearance of clinical problems. We previously reported increases in regional rates of cerebral protein synthesis (rCPS) in the absence of FMRP in an Fmr1 knockout mouse model and in a FXPM knockin (KI) mouse model with 120 to 140 CGG repeats in which FMRP levels are profoundly reduced (80%–90%). To explore whether the concentration of FMRP contributes to the rCPS changes, we measured rCPS in another FXPM KI model with a similar CGG repeat length and a 50% reduction in FMRP. In all 24 brain regions examined, rCPS were unaffected. These results suggest that even with 50% reductions in FMRP, normal protein synthesis rates are maintained.
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Affiliation(s)
- Mei Qin
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Tianjian Huang
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Zhonghua Liu
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Michael Kader
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Thomas Burlin
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Zengyan Xia
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Zachary Zeidler
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
| | - Renate K Hukema
- Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
| | - Carolyn B Smith
- Section on Neuroadaptation and Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA
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Pretto D, Yrigollen CM, Tang HT, Williamson J, Espinal G, Iwahashi CK, Durbin-Johnson B, Hagerman RJ, Hagerman PJ, Tassone F. Clinical and molecular implications of mosaicism in FMR1 full mutations. Front Genet 2014; 5:318. [PMID: 25278957 PMCID: PMC4166380 DOI: 10.3389/fgene.2014.00318] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/25/2014] [Indexed: 12/27/2022] Open
Abstract
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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Affiliation(s)
- Dalyir Pretto
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA
| | - Carolyn M Yrigollen
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA
| | - Hiu-Tung Tang
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA
| | - John Williamson
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA
| | - Glenda Espinal
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA
| | - Chris K Iwahashi
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA
| | - Blythe Durbin-Johnson
- Department of Public Health Sciences, School of Medicine, University of California at Davis Davis, CA, USA
| | - Randi J Hagerman
- Department of Pediatrics, School of Medicine, University of California at Davis Davis, CA, USA ; MIND Institute, UC Davis Medical Center Sacramento, CA, USA
| | - Paul J Hagerman
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA ; Department of Pediatrics, School of Medicine, University of California at Davis Davis, CA, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California at Davis Davis, CA, USA ; Department of Pediatrics, School of Medicine, University of California at Davis Davis, CA, USA
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Berman RF, Buijsen RA, Usdin K, Pintado E, Kooy F, Pretto D, Pessah IN, Nelson DL, Zalewski Z, Charlet-Bergeurand N, Willemsen R, Hukema RK. Mouse models of the fragile X premutation and fragile X-associated tremor/ataxia syndrome. J Neurodev Disord 2014; 6:25. [PMID: 25136376 PMCID: PMC4135345 DOI: 10.1186/1866-1955-6-25] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 01/29/2014] [Indexed: 11/10/2022] Open
Abstract
Carriers of the fragile X premutation (FPM) have CGG trinucleotide repeat expansions of between 55 and 200 in the 5'-UTR of FMR1, compared to a CGG repeat length of between 5 and 54 for the general population. Carriers were once thought to be without symptoms, but it is now recognized that they can develop a variety of early neurological symptoms as well as being at risk for developing the late onset neurodegenerative disorder fragile X-associated tremor/ataxia syndrome (FXTAS). Several mouse models have contributed to our understanding of FPM and FXTAS, and findings from studies using these models are summarized here. This review also discusses how this information is improving our understanding of the molecular and cellular abnormalities that contribute to neurobehavioral features seen in some FPM carriers and in patients with FXTAS. Mouse models show much of the pathology seen in FPM carriers and in individuals with FXTAS, including the presence of elevated levels of Fmr1 mRNA, decreased levels of fragile X mental retardation protein, and ubiquitin-positive intranuclear inclusions. Abnormalities in dendritic spine morphology in several brain regions are associated with neurocognitive deficits in spatial and temporal memory processes, impaired motor performance, and altered anxiety. In vitro studies have identified altered dendritic and synaptic architecture associated with abnormal Ca(2+) dynamics and electrical network activity. FPM mice have been particularly useful in understanding the roles of Fmr1 mRNA, fragile X mental retardation protein, and translation of a potentially toxic polyglycine peptide in pathology. Finally, the potential for using these and emerging mouse models for preclinical development of therapies to improve neurological function in FXTAS is considered.
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Affiliation(s)
- Robert F Berman
- Department of Neurological Surgery, Room 502C, UC Davis, 1515 Newton Court, Davis, CA 95618, USA
| | | | - Karen Usdin
- NIDDK, National Institutes of Health, Bethesda, MD, USA
| | | | - Frank Kooy
- Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
| | | | - Isaac N Pessah
- Department Molecular Biosciences, UC Davis, Davis, CA, USA
| | - David L Nelson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Zachary Zalewski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | | | - Rob Willemsen
- Department Clinical Genetics, Erasmus MC, Rotterdam, Netherlands
| | - Renate K Hukema
- Department Clinical Genetics, Erasmus MC, Rotterdam, Netherlands
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Lozano R, Summers S, Lozano C, Mu Y, Hessl D, Nguyen D, Tassone F, Hagerman R. Association between macroorchidism and intelligence in FMR1 premutation carriers. Am J Med Genet A 2014; 164A:2206-11. [PMID: 24903624 DOI: 10.1002/ajmg.a.36624] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 05/01/2014] [Indexed: 11/08/2022]
Abstract
Characteristics of fragile X syndrome include macroorchidism and intellectual disability, which are associated with decreased FMRP levels. FMRP is highly expressed in many tissues, but primarily in the brain and testis. The relationship between these two characteristics has not previously been studied in the premutation or carrier state. To examine this among premutation carriers and a possible association with IQ, we evaluated macroorchidism status among 213 males including 142 premutation carriers and 71 controls. The prevalence of macroorchidism among premutation carriers was 32.4% (46 out of 142), and 5.6% among controls (4 out of 71, P < 0.0001). Among premutation carriers, the age-adjusted odds ratio (OR) of macroorchidism was significantly increased with increasing FMR1 mRNA (OR 1.84, 95% confidence interval [CI] 1.04-3.25; P = 0.035). With respect to the association between macroorchidism and IQ, after adjustment for number of CGG repeats and age, premutation carriers with macroorchidism had lower verbal IQ (104.67 ± 15.86, P = 0.0152) and full scale IQ (102.98 ± 15.78, P = 0.0227) than premutation carriers without macroorchidism (verbal IQ 112.38 ± 14.14, full scale IQ 110.24 ± 14.21). Similar associations were observed for both verbal IQ (P = 0.034) and full scale IQ (P = 0.039) after being adjusted for age and FMR1 mRNA. These preliminary data support a correlation between macroorchidism and lower verbal and full scale IQ in a relevant proportion of premutation carrier males. Whether this is due to higher levels of FMR1 mRNA or to lower FMRP levels it remains to be established.
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Affiliation(s)
- Reymundo Lozano
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Medical Center, Sacramento, California; Departments of Pediatrics, UC Davis Medical Center, Sacramento, California
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Juang BT, Ludwig AL, Benedetti KL, Gu C, Collins K, Morales C, Asundi A, Wittmann T, L'Etoile N, Hagerman PJ. Expression of an expanded CGG-repeat RNA in a single pair of primary sensory neurons impairs olfactory adaptation in Caenorhabditis elegans. Hum Mol Genet 2014; 23:4945-59. [PMID: 24821701 PMCID: PMC4140470 DOI: 10.1093/hmg/ddu210] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a severe neurodegenerative disorder that affects carriers of premutation CGG-repeat expansion alleles of the fragile X mental retardation 1 (FMR1) gene; current evidence supports a causal role of the expanded CGG repeat within the FMR1 mRNA in the pathogenesis of FXTAS. Though the mRNA has been observed to induce cellular toxicity in FXTAS, the mechanisms are unclear. One common neurophysiological characteristic of FXTAS patients is their inability to properly attenuate their response to an auditory stimulus upon receipt of a small pre-stimulus. Therefore, to gain genetic and cell biological insight into FXTAS, we examined the effect of expanded CGG repeats on the plasticity of the olfactory response of the genetically tractable nematode, Caenorhabditis elegans (C. elegans). While C. elegans is innately attracted to odors, this response can be downregulated if the odor is paired with starvation. We found that expressing expanded CGG repeats in olfactory neurons interfered with this plasticity without affecting either the innate odor-seeking response or the olfactory neuronal morphology. Interrogation of three RNA regulatory pathways indicated that the expanded CGG repeats act via the C. elegans microRNA (miRNA)-specific Argonaute ALG-2 to diminish olfactory plasticity. This observation suggests that the miRNA-Argonaute pathway may play a pathogenic role in subverting neuronal function in FXTAS.
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Affiliation(s)
- Bi-Tzen Juang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 300, Taiwan
| | - Anna L Ludwig
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, CA 95616, USA
| | - Kelli L Benedetti
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Chen Gu
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Kimberly Collins
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Christopher Morales
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Aarati Asundi
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Torsten Wittmann
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Noelle L'Etoile
- Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Paul J Hagerman
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, CA 95616, USA, MIND Institute, University of California, Davis, Health System, Sacramento, CA 95817, USA
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