1
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Kargar M, Hagerman RJ, Martínez-Cerdeño V. Neurodegeneration of White and Gray Matter in the Hippocampus with FXTAS. Int J Mol Sci 2023; 24:17266. [PMID: 38139097 PMCID: PMC10743470 DOI: 10.3390/ijms242417266] [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: 09/27/2023] [Revised: 11/07/2023] [Accepted: 12/05/2023] [Indexed: 12/24/2023] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder that affects older premutation carriers (55-200 CGG repeats) of the fragile X gene. Despite the high prevalence of the FXTAS disorder, neuropathology studies of individuals affected by FXTAS are limited. We performed hematoxylin and eosin (H&E) staining in the hippocampus of 26 FXTAS cases and analyzed the tissue microscopically. The major neuropathological characteristics were white matter disease, intranuclear inclusions in neurons and astrocytes, and neuron loss. Astrocytes contained more and larger inclusions than neurons. There was a negative correlation between age of death and CGG repeat length in cases over the age of 60. The number of astroglial inclusions (CA3 and dentate gyrus) and the number of CA3 neuronal inclusions increased with elevated CGG repeat length. In the two cases with a CGG repeat size less than 65, FXTAS intranuclear inclusions were not present in the hippocampus, while in the two cases with less than 70 (65-70) CGG repeat expansion, neurons and astrocytes with inclusions were occasionally identified in the CA1 sub-region. These findings add hippocampus neuropathology to the previously reported changes in other areas of the brain in FXTAS patients, with implications for understanding FXTAS pathogenesis.
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Affiliation(s)
- Maryam Kargar
- Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA 95817, USA
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA
| | - Randi J. Hagerman
- MIND Institute, UC Davis School of Medicine, Sacramento, CA 95817, USA;
| | - Verónica Martínez-Cerdeño
- Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children, Sacramento, CA 95817, USA
- Department of Pathology and Laboratory Medicine, UC Davis School of Medicine, Sacramento, CA 95817, USA
- MIND Institute, UC Davis School of Medicine, Sacramento, CA 95817, USA;
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2
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Zhang S, Pei G, Li B, Li P, Lin Y. Abnormal phase separation of biomacromolecules in human diseases. Acta Biochim Biophys Sin (Shanghai) 2023; 55:1133-1152. [PMID: 37475546 PMCID: PMC10423695 DOI: 10.3724/abbs.2023139] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 07/07/2023] [Indexed: 07/22/2023] Open
Abstract
Membrane-less organelles (MLOs) formed through liquid-liquid phase separation (LLPS) are associated with numerous important biological functions, but the abnormal phase separation will also dysregulate the physiological processes. Emerging evidence points to the importance of LLPS in human health and diseases. Nevertheless, despite recent advancements, our knowledge of the molecular relationship between LLPS and diseases is frequently incomplete. In this review, we outline our current understanding about how aberrant LLPS affects developmental disorders, tandem repeat disorders, cancers and viral infection. We also examine disease mechanisms driven by aberrant condensates, and highlight potential treatment approaches. This study seeks to expand our understanding of LLPS by providing a valuable new paradigm for understanding phase separation and human disorders, as well as to further translate our current knowledge regarding LLPS into therapeutic discoveries.
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Affiliation(s)
- Songhao Zhang
- State Key Laboratory of Membrane BiologyTsinghua University-Peking University Joint Centre for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing100084China
- IDG/McGovern Institute for Brain Research at Tsinghua UniversityBeijing100084China
| | - Gaofeng Pei
- State Key Laboratory of Membrane BiologyTsinghua University-Peking University Joint Centre for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing100084China
- Frontier Research Center for Biological StructureTsinghua UniversityBeijing100084China
| | - Boya Li
- State Key Laboratory of Membrane BiologyTsinghua University-Peking University Joint Centre for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing100084China
- IDG/McGovern Institute for Brain Research at Tsinghua UniversityBeijing100084China
| | - Pilong Li
- State Key Laboratory of Membrane BiologyTsinghua University-Peking University Joint Centre for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing100084China
- Frontier Research Center for Biological StructureTsinghua UniversityBeijing100084China
| | - Yi Lin
- State Key Laboratory of Membrane BiologyTsinghua University-Peking University Joint Centre for Life SciencesSchool of Life SciencesTsinghua UniversityBeijing100084China
- IDG/McGovern Institute for Brain Research at Tsinghua UniversityBeijing100084China
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3
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Abbasi DA, Nguyen TTA, Hall DA, Robertson-Dick E, Berry-Kravis E, Cologna SM. Characterization of the Cerebrospinal Fluid Proteome in Patients with Fragile X-Associated Tremor/Ataxia Syndrome. THE CEREBELLUM 2021; 21:86-98. [PMID: 34046842 DOI: 10.1007/s12311-021-01262-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/16/2021] [Indexed: 01/11/2023]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS), first described in 2001, is a neurodegenerative and movement disorder, caused by a premutation in the fragile X mental retardation 1 (FMR1) gene. To date, the biological mechanisms causing this condition are still not well understood, as not all premutation carriers develop FXTAS. To further understand this syndrome, we quantitatively compared the cerebrospinal fluid (CSF) proteome of FXTAS patients with age-matched controls using mass spectrometry. We identified 415 proteins of which 97 were altered in FXTAS patients. These proteins suggest changes in acute phase response signaling, liver X receptor/ retinoid X receptor (LXR/RXR) activation, and farnesoid X receptor (FXR)/RXR activation, which are the main pathways found to be affected. Additionally, we detected changes in many other proteins including amyloid-like protein 2, contactin-1, afamin, cell adhesion molecule 4, NPC intracellular cholesterol transporter 2, and cathepsin B, that had been previously noted to hold important roles in other movement disorders. Specific to RXR pathways, several apolipoproteins (APOA1, APOA2, APOA4, APOC2, and APOD) showed significant changes in the CSF of FXTAS patients. Lastly, CSF parameters were analyzed to investigate abnormalities in blood brain barrier function. Correlations were observed between patient albumin quotient values, a measure of permeability, and CGG repeat length as well as FXTAS rating scale scores.
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Affiliation(s)
- Diana A Abbasi
- Department of Pediatrics and Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
| | - Thu T A Nguyen
- Department of Chemistry, University of Illinois At Chicago, Chicago, IL, USA
| | - Deborah A Hall
- Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
| | - Erin Robertson-Dick
- Department of Communication Sciences and Disorders, Northwestern University, Chicago, IL, USA
| | - Elizabeth Berry-Kravis
- Department of Pediatrics and Neurological Sciences, Rush University Medical Center, Chicago, IL, USA
| | - Stephanie M Cologna
- Department of Chemistry, University of Illinois At Chicago, Chicago, IL, USA.
- Laboratory of Integrated Neuroscience, University of Illinois At Chicago, 845 W Taylor Street, Room 4500, Chicago, IL, 60607, USA.
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4
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The emerging molecular mechanisms for mitochondrial dysfunctions in FXTAS. Biochim Biophys Acta Mol Basis Dis 2020; 1866:165918. [PMID: 32800941 DOI: 10.1016/j.bbadis.2020.165918] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 12/16/2022]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is an inherited neurodegenerative disorder caused by an expansion of 55-200 CGG repeats at 5UTR of FMR1 gene, known as premutation. The main clinical and neuropathological features of FXTAS include progressive intention tremor, gait ataxia, neuronal cell loss and presence of ubiquitin-positive intranuclear inclusions in neurons and astrocytes. Various mitochondrial dysfunctions are reported in in vitro/vivo models of FXTAS; however, the molecular mechanisms underlying such mitochondrial dysfunctions are unclear. CGG expansions are pathogenic through distinct mechanisms involving RNA gain of function, impaired DNA damage repair and FMRpolyG toxicity. Here, we have systematically reviewed the reports of mitochondrial dysfunctions under premutation condition. We have also focused on potential emerging mechanisms to understand mitochondrial associated pathology in FXTAS. This review highlights the important role of mitochondria in FXTAS and other related disorders; and suggests focus of future studies on mitochondrial dysfunction along with other prevailing mechanisms to alleviate neurodegeneration.
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5
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Haify SN, Botta-Orfila T, Hukema RK, Tartaglia GG. In silico, in vitro, and in vivo Approaches to Identify Molecular Players in Fragile X Tremor and Ataxia Syndrome. Front Mol Biosci 2020; 7:31. [PMID: 32219099 PMCID: PMC7078329 DOI: 10.3389/fmolb.2020.00031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 02/11/2020] [Indexed: 12/22/2022] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative monogenetic disorder affecting carriers of premutation (PM) forms of the FMR1 gene, resulting in a progressive development of tremors, ataxia, and neuropsychological problems. This highly disabling disease is quite common in the general population with an estimation of about 20 million PM carriers worldwide. The chances of developing FXTAS increase dramatically with age, with about 45% of male carriers over the age of 50 being affected. Both the gene and pathogenic trigger, a mutant expansion of CGG RNA, causing FXTAS are known. This makes it an interesting disease to develop targeted therapeutic interventions for. Yet, no such interventions are available at this moment. Here we discuss in silico, in vitro, and in vivo approaches and how they have been used to identify the molecular determinants of FXTAS pathology. These approaches have yielded substantial information about FXTAS pathology and, consequently, many markers have emerged to play a key role in understanding the disease mechanism. Integration of the different approaches is expected to provide crucial information about the value of these markers as either therapeutic target or biomarker, essential to monitor therapeutic interventions in the future.
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Affiliation(s)
- Saif N Haify
- Department of Clinical Genetics, Erasmus MC, Rotterdam, Netherlands
| | - Teresa Botta-Orfila
- Biological Fluids Bank of the Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Renate K Hukema
- Department of Clinical Genetics, Erasmus MC, Rotterdam, Netherlands
| | - Gian Gaetano Tartaglia
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.,Department of Biology 'Charles Darwin', Sapienza University of Rome, Rome, Italy.,Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa, Italy.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
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6
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Gabis LV, Shefer S, Raas-Rothschild A. Ethical Dilemmas Linked to Fragile X Testing of Minors—a Preliminary Survey Among Professionals. J Mol Neurosci 2020; 70:254-259. [DOI: 10.1007/s12031-019-01445-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 11/13/2019] [Indexed: 11/29/2022]
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7
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Cid-Samper F, Gelabert-Baldrich M, Lang B, Lorenzo-Gotor N, Ponti RD, Severijnen LAWFM, Bolognesi B, Gelpi E, Hukema RK, Botta-Orfila T, Tartaglia GG. An Integrative Study of Protein-RNA Condensates Identifies Scaffolding RNAs and Reveals Players in Fragile X-Associated Tremor/Ataxia Syndrome. Cell Rep 2019; 25:3422-3434.e7. [PMID: 30566867 PMCID: PMC6315285 DOI: 10.1016/j.celrep.2018.11.076] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/26/2018] [Accepted: 11/19/2018] [Indexed: 12/21/2022] Open
Abstract
Recent evidence indicates that specific RNAs promote the formation of ribonucleoprotein condensates by acting as scaffolds for RNA-binding proteins (RBPs). We systematically investigated RNA-RBP interaction networks to understand ribonucleoprotein assembly. We found that highly contacted RNAs are structured, have long UTRs, and contain nucleotide repeat expansions. Among the RNAs with such properties, we identified the FMR1 3' UTR that harbors CGG expansions implicated in fragile X-associated tremor/ataxia syndrome (FXTAS). We studied FMR1 binding partners in silico and in vitro and prioritized the splicing regulator TRA2A for further characterization. In a FXTAS cellular model, we validated the TRA2A-FMR1 interaction and investigated implications of its sequestration at both transcriptomic and post-transcriptomic levels. We found that TRA2A co-aggregates with FMR1 in a FXTAS mouse model and in post-mortem human samples. Our integrative study identifies key components of ribonucleoprotein aggregates, providing links to neurodegenerative disease and allowing the discovery of therapeutic targets.
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Affiliation(s)
- Fernando Cid-Samper
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Mariona Gelabert-Baldrich
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Benjamin Lang
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Nieves Lorenzo-Gotor
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Riccardo Delli Ponti
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | | | - Benedetta Bolognesi
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Ellen Gelpi
- Neurological Tissue Biobank of the Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Carrer del Rosselló, 149, 08036, Barcelona, Spain; Institute of Neurology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | - Renate K Hukema
- Department of Clinical Genetics, Erasmus MC, 3000 CA Rotterdam, the Netherlands
| | - Teresa Botta-Orfila
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain.
| | - Gian Gaetano Tartaglia
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain; Department of Biology 'Charles Darwin', Sapienza University of Rome, P.le A. Moro 5, Rome 00185, Italy; Institució Catalana de Recerca i Estudis Avançats (ICREA), 23 Passeig Lluís Companys, 08010 Barcelona, Spain.
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8
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Ma L, Herren AW, Espinal G, Randol J, McLaughlin B, Martinez-Cerdeño V, Pessah IN, Hagerman RJ, Hagerman PJ. Composition of the Intranuclear Inclusions of Fragile X-associated Tremor/Ataxia Syndrome. Acta Neuropathol Commun 2019; 7:143. [PMID: 31481131 PMCID: PMC6720097 DOI: 10.1186/s40478-019-0796-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 08/24/2019] [Indexed: 12/11/2022] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder associated with a premutation repeat expansion (55-200 CGG repeats) in the 5' noncoding region of the FMR1 gene. Solitary intranuclear inclusions within FXTAS neurons and astrocytes constitute a hallmark of the disorder, yet our understanding of how and why these bodies form is limited. Here, we have discovered that FXTAS inclusions emit a distinct autofluorescence spectrum, which forms the basis of a novel, unbiased method for isolating FXTAS inclusions by preparative fluorescence-activated cell sorting (FACS). Using a combination of autofluorescence-based FACS and liquid chromatography/tandem mass spectrometry (LC-MS/MS)-based proteomics, we have identified more than two hundred proteins that are enriched within the inclusions relative to FXTAS whole nuclei. Whereas no single protein species dominates inclusion composition, highly enriched levels of conjugated small ubiquitin-related modifier 2 (SUMO 2) protein and p62/sequestosome-1 (p62/SQSTM1) protein were found within the inclusions. Many additional proteins involved with RNA binding, protein turnover, and DNA damage repair were enriched within inclusions relative to total nuclear protein. The current analysis has also allowed the first direct detection, through peptide sequencing, of endogenous FMRpolyG peptide, the product of repeat-associated non-ATG (RAN) translation of the FMR1 mRNA. However, this peptide was found only at extremely low levels and not within whole FXTAS nuclear preparations, raising the question whether endogenous RAN products exist at quantities sufficient to contribute to FXTAS pathogenesis. The abundance of the inclusion-associated ubiquitin- and SUMO-based modifiers supports a model for inclusion formation as the result of increased protein loads and elevated oxidative stress leading to maladaptive autophagy. These results highlight the need to further investigate FXTAS pathogenesis in the context of endogenous systems.
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Affiliation(s)
- Lisa Ma
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, One Shields Ave, Davis, CA, USA
| | - Anthony W Herren
- Genome Center, University of California Davis, Davis, California, USA
| | - Glenda Espinal
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, One Shields Ave, Davis, CA, USA
| | - Jamie Randol
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, One Shields Ave, Davis, CA, USA
| | - Bridget McLaughlin
- Department of Pathology and Laboratory Medicine, University of California Davis, School of Medicine, Sacramento, California, USA
| | - Veronica Martinez-Cerdeño
- Department of Pathology and Laboratory Medicine, University of California Davis, School of Medicine, Sacramento, California, USA
- Institute for Pediatric Regenerative Medicine, Shriners Hospital of Northern California, University of California Davis, School of Medicine, Sacramento, California, USA
- MIND Institute, University of California Davis Health, Sacramento, California, USA
| | - Isaac N Pessah
- MIND Institute, University of California Davis Health, Sacramento, California, USA
- Department of Molecular Biosciences, University of California Davis, School of Veterinary Medicine, Davis, California, USA
| | - Randi J Hagerman
- MIND Institute, University of California Davis Health, Sacramento, California, USA
- Department of Pediatrics, University of California Davis, School of Medicine, Sacramento, California, USA
| | - Paul J Hagerman
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, One Shields Ave, Davis, CA, USA.
- MIND Institute, University of California Davis Health, Sacramento, California, USA.
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9
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Gelpi E, Botta-Orfila T, Bodi L, Marti S, Kovacs G, Grau-Rivera O, Lozano M, Sánchez-Valle R, Muñoz E, Valldeoriola F, Pagonabarraga J, Tartaglia GG, Milà M. Neuronal intranuclear (hyaline) inclusion disease and fragile X-associated tremor/ataxia syndrome: a morphological and molecular dilemma. Brain 2019; 140:e51. [PMID: 28899011 DOI: 10.1093/brain/awx156] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Ellen Gelpi
- Neurological Tissue Bank of the Biobanc-Hospital Clinic-IDIBAPS, Barcelona, Spain
| | - Teresa Botta-Orfila
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Laia Bodi
- Department of Genetics, Hospital Clinic de Barcelona, Barcelona, Spain
| | - Stefanie Marti
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Gabor Kovacs
- Institute of Neurology, Medical University of Vienna, Austria
| | - Oriol Grau-Rivera
- Neurological Tissue Bank of the Biobanc-Hospital Clinic-IDIBAPS, Barcelona, Spain.,Neurology Department, Alzheimer's disease and other Cognitive Disorders Unit, Hospital Clinic de Barcelona, Barcelona, Spain
| | - Manuel Lozano
- Neurology Department, Hospital Germans Trias I Pujol, Badalona, Spain
| | - Raquel Sánchez-Valle
- Neurology Department, Alzheimer's disease and other Cognitive Disorders Unit, Hospital Clinic de Barcelona, Barcelona, Spain
| | - Esteban Muñoz
- Neurology Department, Movement Disorders Unit, Hospital Clinic de Barcelona, Barcelona, Spain
| | - Francesc Valldeoriola
- Neurology Department, Movement Disorders Unit, Hospital Clinic de Barcelona, Barcelona, Spain
| | | | - Gian-Gaetano Tartaglia
- Centre for Genomic Regulation (CRG), The Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Montserrat Milà
- Department of Genetics, Hospital Clinic de Barcelona, Barcelona, Spain
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10
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Fragile X syndrome and fragile X-associated tremor ataxia syndrome. HANDBOOK OF CLINICAL NEUROLOGY 2018; 147:377-391. [PMID: 29325626 DOI: 10.1016/b978-0-444-63233-3.00025-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Fragile X-associated disorders encompass several conditions, which are caused by expansion mutations in the fragile X mental retardation 1 (FMR1) gene. Fragile X syndrome is the most common inherited etiology of intellectual disability and results from a full mutation or >200 CGG repeats in FMR1. It is associated with developmental delay, autism spectrum disorder, and seizures. Fragile X-associated tremor/ataxia syndrome is a progressive neurodegenerative disease that occurs in premutation carriers of 55-200 CGG repeats in FMR1 and is characterized by kinetic tremor, gait ataxia, parkinsonism, executive dysfunction, and neuropathy. Fragile X-associated primary ovarian insufficiency also occurs in premutation carrier women and manifests with infertility and early menopause. The diseases constituting fragile X-associated disorders differ mechanistically, due to the distinct molecular properties of premutation versus full mutations. Fragile X syndrome occurs when there is a lack of fragile X mental retardation protein (FMRP) due to FMR1 methylation and silencing. In fragile X-associated tremor ataxia syndrome, a toxic gain of function is postulated with the production of excess CGG repeat-containing FMR1 mRNA, abnormal translation of the repeat sequence leading to production of polyglycine, polyalanine, and other polypeptides and to outright deficits in translation leading to reduced FMRP at larger premutation sizes. The changes in underlying brain chemistry due to FMR1 mutations have led to therapeutic studies in these disorders, with some progress being made in fragile X syndrome. This paper also summarizes indications for testing, genetic counseling issues, and what the future holds for these disorders.
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11
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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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12
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Shin JW, Lee JM. The prospects of CRISPR-based genome engineering in the treatment of neurodegenerative disorders. Ther Adv Neurol Disord 2017; 11:1756285617741837. [PMID: 29399048 PMCID: PMC5784517 DOI: 10.1177/1756285617741837] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/16/2017] [Indexed: 12/11/2022] Open
Abstract
Over the past few decades, as gene discovery methods and sequencing technologies have evolved, many genetic variations that significantly increase the risk of or cause neurodegenerative diseases have been identified. However, knowledge of those pathogenic mutations and subsequent mechanism-focused studies has rarely yielded effective treatments, warranting alternative strategies for refining rational therapeutic targets. Nevertheless, with the evolution of gene targeting methods, it has been increasingly recognized that the disease-causing gene itself is the best therapeutic target even when we do not have a full understanding of its biological functions. Considering this, CRISPR/Cas gene editing technology offers the promise of permanently silencing or correcting the disease-causing mutations, potentially overcoming key limitations of RNA-targeting approaches. The versatile CRISPR/Cas-based strategies have the potential to become treatment options for challenging disorders such as neurodegenerative diseases. Here, we summarize recent reports of preclinical applications of CRISPR/Cas in models of neurodegenerative disorders to provide perspectives on therapeutic gene editing for diseases of the nervous system.
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Affiliation(s)
- Jun Wan Shin
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA; Department of Neurology, Harvard Medical School, Boston, MA 02115, USA; Medical and Population Genetics Program, The Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA Department of Neurology, Harvard Medical School, Boston, MA, USA
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13
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Shelton AL, Cornish KM, Godler D, Bui QM, Kolbe S, Fielding J. White matter microstructure, cognition, and molecular markers in fragile X premutation females. Neurology 2017; 88:2080-2088. [DOI: 10.1212/wnl.0000000000003979] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 02/14/2017] [Indexed: 01/06/2023] Open
Abstract
Objective:To examine the interrelationships between fragile X mental retardation 1 (FMR1) mRNA and the FMR1 exon 1/intron 1 boundary methylation, white matter microstructure, and executive function, in women with a FMR1 premutation expansion (PM; 55–199 CGG repeats) and controls (CGG < 44).Methods:Twenty women with PM without fragile X-associated tremor/ataxia syndrome (FXTAS) and 20 control women between 22 and 54 years of age completed this study. FMR1 mRNA and methylation levels for 9 CpG sites within the FMR1 exon 1/intron 1 boundary from peripheral blood samples were analyzed. To measure white matter microstructure, diffusion-weighted imaging was used, from which fractional anisotropy (FA) and mean diffusivity (MD) values from anatomic regions within the corpus callosum and cerebellar peduncles were extracted. Executive function was assessed across a range of tasks.Results:No differences were revealed in white matter microstructure between women with PM and controls. However, we reveal that for women with PM (but not controls), higher FMR1 mRNA correlated with lower MD values within the middle cerebellar peduncle and Paced Auditory Serial Addition Test scores, higher methylation of the FMR1 exon 1/intron 1 boundary correlated with lower MD within the inferior and middle cerebellar peduncles and longer prosaccade latencies, and higher FA values within the corpus callosum and cerebellar peduncle regions corresponded to superior executive function.Conclusions:We provide evidence linking white matter microstructure to executive dysfunction and elevated FMR1 mRNA and FMR1 exon 1/intron 1 boundary methylation in women with PM without FXTAS. This suggests that the FXTAS phenotype may not be distinct but may form part of a spectrum of PM involvement.
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