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Kojak N, Kuno J, Fittipaldi KE, Khan A, Wenger D, Glasser M, Donnianni RA, Tang Y, Zhang J, Huling K, Ally R, Mujica AO, Turner T, Magardino G, Huang PY, Kerk SY, Droguett G, Prissette M, Rojas J, Gomez T, Gagliardi A, Hunt C, Rabinowitz JS, Gong G, Poueymirou W, Chiao E, Zambrowicz B, Siao CJ, Kajimura D. Somatic and intergenerational G4C2 hexanucleotide repeat instability in a human C9orf72 knock-in mouse model. Nucleic Acids Res 2024; 52:5732-5755. [PMID: 38597682 PMCID: PMC11162798 DOI: 10.1093/nar/gkae250] [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: 06/12/2023] [Revised: 03/19/2024] [Accepted: 03/28/2024] [Indexed: 04/11/2024] Open
Abstract
Expansion of a G4C2 repeat in the C9orf72 gene is associated with familial Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). To investigate the underlying mechanisms of repeat instability, which occurs both somatically and intergenerationally, we created a novel mouse model of familial ALS/FTD that harbors 96 copies of G4C2 repeats at a humanized C9orf72 locus. In mouse embryonic stem cells, we observed two modes of repeat expansion. First, we noted minor increases in repeat length per expansion event, which was dependent on a mismatch repair pathway protein Msh2. Second, we found major increases in repeat length per event when a DNA double- or single-strand break (DSB/SSB) was artificially introduced proximal to the repeats, and which was dependent on the homology-directed repair (HDR) pathway. In mice, the first mode primarily drove somatic repeat expansion. Major changes in repeat length, including expansion, were observed when SSB was introduced in one-cell embryos, or intergenerationally without DSB/SSB introduction if G4C2 repeats exceeded 400 copies, although spontaneous HDR-mediated expansion has yet to be identified. These findings provide a novel strategy to model repeat expansion in a non-human genome and offer insights into the mechanism behind C9orf72 G4C2 repeat instability.
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Affiliation(s)
- Nada Kojak
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Junko Kuno
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | - David Wenger
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | - Yajun Tang
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Jade Zhang
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Katie Huling
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Roxanne Ally
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | | | - Pei Yi Huang
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Sze Yen Kerk
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | - Jose Rojas
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | | | | | - Guochun Gong
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | - Eric Chiao
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
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Mirceta M, Shum N, Schmidt MHM, Pearson CE. Fragile sites, chromosomal lesions, tandem repeats, and disease. Front Genet 2022; 13:985975. [PMID: 36468036 PMCID: PMC9714581 DOI: 10.3389/fgene.2022.985975] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 09/02/2022] [Indexed: 09/16/2023] Open
Abstract
Expanded tandem repeat DNAs are associated with various unusual chromosomal lesions, despiralizations, multi-branched inter-chromosomal associations, and fragile sites. Fragile sites cytogenetically manifest as localized gaps or discontinuities in chromosome structure and are an important genetic, biological, and health-related phenomena. Common fragile sites (∼230), present in most individuals, are induced by aphidicolin and can be associated with cancer; of the 27 molecularly-mapped common sites, none are associated with a particular DNA sequence motif. Rare fragile sites ( ≳ 40 known), ≤ 5% of the population (may be as few as a single individual), can be associated with neurodevelopmental disease. All 10 molecularly-mapped folate-sensitive fragile sites, the largest category of rare fragile sites, are caused by gene-specific CGG/CCG tandem repeat expansions that are aberrantly CpG methylated and include FRAXA, FRAXE, FRAXF, FRA2A, FRA7A, FRA10A, FRA11A, FRA11B, FRA12A, and FRA16A. The minisatellite-associated rare fragile sites, FRA10B, FRA16B, can be induced by AT-rich DNA-ligands or nucleotide analogs. Despiralized lesions and multi-branched inter-chromosomal associations at the heterochromatic satellite repeats of chromosomes 1, 9, 16 are inducible by de-methylating agents like 5-azadeoxycytidine and can spontaneously arise in patients with ICF syndrome (Immunodeficiency Centromeric instability and Facial anomalies) with mutations in genes regulating DNA methylation. ICF individuals have hypomethylated satellites I-III, alpha-satellites, and subtelomeric repeats. Ribosomal repeats and subtelomeric D4Z4 megasatellites/macrosatellites, are associated with chromosome location, fragility, and disease. Telomere repeats can also assume fragile sites. Dietary deficiencies of folate or vitamin B12, or drug insults are associated with megaloblastic and/or pernicious anemia, that display chromosomes with fragile sites. The recent discovery of many new tandem repeat expansion loci, with varied repeat motifs, where motif lengths can range from mono-nucleotides to megabase units, could be the molecular cause of new fragile sites, or other chromosomal lesions. This review focuses on repeat-associated fragility, covering their induction, cytogenetics, epigenetics, cell type specificity, genetic instability (repeat instability, micronuclei, deletions/rearrangements, and sister chromatid exchange), unusual heritability, disease association, and penetrance. Understanding tandem repeat-associated chromosomal fragile sites provides insight to chromosome structure, genome packaging, genetic instability, and disease.
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Affiliation(s)
- Mila Mirceta
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Natalie Shum
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Monika H. M. Schmidt
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Christopher E. Pearson
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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3
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Baud A, Derbis M, Tutak K, Sobczak K. Partners in crime: Proteins implicated in
RNA
repeat expansion diseases. WIRES RNA 2022; 13:e1709. [PMID: 35229468 PMCID: PMC9539487 DOI: 10.1002/wrna.1709] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 12/07/2021] [Accepted: 12/08/2021] [Indexed: 11/06/2022]
Affiliation(s)
- Anna Baud
- Department of Gene Expression Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University Poznan Poland
| | - Magdalena Derbis
- Department of Gene Expression Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University Poznan Poland
| | - Katarzyna Tutak
- Department of Gene Expression Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University Poznan Poland
| | - Krzysztof Sobczak
- Department of Gene Expression Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University Poznan Poland
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Schröder C, Horsthemke B, Depienne C. GC-rich repeat expansions: associated disorders and mechanisms. MED GENET-BERLIN 2021; 33:325-335. [PMID: 38835438 PMCID: PMC11006399 DOI: 10.1515/medgen-2021-2099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 11/12/2021] [Indexed: 06/06/2024]
Abstract
Noncoding repeat expansions are a well-known cause of genetic disorders mainly affecting the central nervous system. Missed by most standard technologies used in routine diagnosis, pathogenic noncoding repeat expansions have to be searched for using specific techniques such as repeat-primed PCR or specific bioinformatics tools applied to genome data, such as ExpansionHunter. In this review, we focus on GC-rich repeat expansions, which represent at least one third of all noncoding repeat expansions described so far. GC-rich expansions are mainly located in regulatory regions (promoter, 5' untranslated region, first intron) of genes and can lead to either a toxic gain-of-function mediated by RNA toxicity and/or repeat-associated non-AUG (RAN) translation, or a loss-of-function of the associated gene, depending on their size and their methylation status. We herein review the clinical and molecular characteristics of disorders associated with these difficult-to-detect expansions.
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Affiliation(s)
- Christopher Schröder
- Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Bernhard Horsthemke
- Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Christel Depienne
- Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
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5
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Park E, Lau AG, Arendt KL, Chen L. FMRP Interacts with RARα in Synaptic Retinoic Acid Signaling and Homeostatic Synaptic Plasticity. Int J Mol Sci 2021; 22:ijms22126579. [PMID: 34205274 PMCID: PMC8235556 DOI: 10.3390/ijms22126579] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/16/2021] [Accepted: 06/17/2021] [Indexed: 01/08/2023] Open
Abstract
The fragile X syndrome (FXS) is an X-chromosome-linked neurodevelopmental disorder with severe intellectual disability caused by inactivation of the fragile X mental retardation 1 (FMR1) gene and subsequent loss of the fragile X mental retardation protein (FMRP). Among the various types of abnormal synaptic function and synaptic plasticity phenotypes reported in FXS animal models, defective synaptic retinoic acid (RA) signaling and subsequent defective homeostatic plasticity have emerged as a major synaptic dysfunction. However, the mechanism underlying the defective synaptic RA signaling in the absence of FMRP is unknown. Here, we show that RARα, the RA receptor critically involved in synaptic RA signaling, directly interacts with FMRP. This interaction is enhanced in the presence of RA. Blocking the interaction between FMRP and RARα with a small peptide corresponding to the critical binding site in RARα abolishes RA-induced increases in excitatory synaptic transmission, recapitulating the phenotype seen in the Fmr1 knockout mouse. Taken together, these data suggest that not only are functional FMRP and RARα necessary for RA-dependent homeostatic synaptic plasticity, but that the interaction between these two proteins is essential for proper transcription-independent RA signaling. Our results may provide further mechanistic understanding into FXS synaptic pathophysiology.
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Laboratory testing for fragile X, 2021 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG). Genet Med 2021; 23:799-812. [PMID: 33795824 DOI: 10.1038/s41436-021-01115-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 11/08/2022] Open
Abstract
Molecular genetic testing of the FMR1 gene is commonly performed in clinical laboratories. Pathogenic variants in the FMR1 gene are associated with fragile X syndrome, fragile X-associated tremor ataxia syndrome (FXTAS), and fragile X-associated primary ovarian insufficiency (FXPOI). This document provides updated information regarding FMR1 pathogenic variants, including prevalence, genotype-phenotype correlations, and variant nomenclature. Methodological considerations are provided for Southern blot analysis and polymerase chain reaction (PCR) amplification of FMR1, including triplet repeat-primed and methylation-specific PCR.The American College of Medical Genetics and Genomics (ACMG) Laboratory Quality Assurance Committee has the mission of maintaining high technical standards for the performance and interpretation of genetic tests. In part, this is accomplished by the publication of the document ACMG Technical Standards for Clinical Genetics Laboratories, which is now maintained online ( http://www.acmg.net ). This subcommittee also reviews the outcome of national proficiency testing in the genetics area and may choose to focus on specific diseases or methodologies in response to those results. Accordingly, the subcommittee selected fragile X syndrome to be the first topic in a series of supplemental sections, recognizing that it is one of the most frequently ordered genetic tests and that it has many alternative methods with different strengths and weaknesses. This document is the fourth update to the original standards and guidelines for fragile X testing that were published in 2001, with revisions in 2005 and 2013, respectively.This versionClarifies the clinical features associated with different FMRI variants (Section 2.3)Discusses important reporting considerations (Section 3.3.1.3)Provides updates on technology (Section 4.1).
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Khampang S, Parnpai R, Mahikul W, Easley CA, Cho IK, Chan AWS. CAG repeat instability in embryonic stem cells and derivative spermatogenic cells of transgenic Huntington's disease monkey. J Assist Reprod Genet 2021; 38:1215-1229. [PMID: 33611676 DOI: 10.1007/s10815-021-02106-3] [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: 12/07/2020] [Accepted: 02/08/2021] [Indexed: 12/16/2022] Open
Abstract
PURPOSE The expansion of CAG (glutamine; Q) trinucleotide repeats (TNRs) predominantly occurs through male lineage in Huntington's disease (HD). As a result, offspring will have larger CAG repeats compared to their fathers, which causes an earlier onset of the disease called genetic anticipation. This study aims to develop a novel in vitro model to replicate CAG repeat instability in early spermatogenesis and demonstrate the biological process of genetic anticipation by using the HD stem cell model for the first time. METHODS HD rhesus monkey embryonic stem cells (rESCs) were cultured in vitro for an extended period. Male rESCs were used to derive spermatogenic cells in vitro with a 10-day differentiation. The assessment of CAG repeat instability was performed by GeneScan and curve fit analysis. RESULTS Spermatogenic cells derived from rESCs exhibit progressive expansion of CAG repeats with high daily expansion rates compared to the extended culture of rESCs. The expansion of CAG repeats is cell type-specific and size-dependent. CONCLUSIONS Here, we report a novel stem cell model that replicates genome instability and CAG repeat expansion in in vitro derived HD monkey spermatogenic cells. The in vitro spermatogenic cell model opens a new opportunity for studying TNR instability and the underlying mechanism of genetic anticipation, not only in HD but also in other TNR diseases.
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Affiliation(s)
- Sujittra Khampang
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA.,Embryo Technology and Stem Cell Research Center, School of Biotechnology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Rangsun Parnpai
- Embryo Technology and Stem Cell Research Center, School of Biotechnology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Wiriya Mahikul
- Faculty of Medicine and Public Health, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok, Thailand
| | - Charles A Easley
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA.,Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA, USA.,Regenerative Bioscience Center, University of Georgia, Athens, GA, USA
| | - In Ki Cho
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA. .,Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
| | - Anthony W S Chan
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA. .,Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
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8
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Zhang SF, Gao J, Liu CM. The Role of Non-Coding RNAs in Neurodevelopmental Disorders. Front Genet 2019; 10:1033. [PMID: 31824553 PMCID: PMC6882276 DOI: 10.3389/fgene.2019.01033] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 09/25/2019] [Indexed: 12/24/2022] Open
Abstract
Non-coding RNAs, a group of ribonucleic acids that are ubiquitous in the body and do not encode proteins, emerge as important regulatory factors in almost all biological processes in the brain. Extensive studies have suggested the involvement of non-coding RNAs in brain development and neurodevelopmental disorders, and dysregulation of non-coding RNAs is associated with abnormal brain development and the etiology of neurodevelopmental disorders. Here we provide an overview of the roles and working mechanisms of non-coding RNAs, and discuss potential clinical applications of non-coding RNAs as diagnostic and prognostic markers and as therapeutic targets in neurodevelopmental disorders.
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Affiliation(s)
- Shuang-Feng Zhang
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Jun Gao
- Department of Neurosurgery, Peking Union Medical College Hospital, Chinese Academy of Medicine Sciences & Peking Union Medical College, Beijing, China
| | - Chang-Mei Liu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
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9
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Verma V, Paul A, Amrapali Vishwanath A, Vaidya B, Clement JP. Understanding intellectual disability and autism spectrum disorders from common mouse models: synapses to behaviour. Open Biol 2019; 9:180265. [PMID: 31185809 PMCID: PMC6597757 DOI: 10.1098/rsob.180265] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Normal brain development is highly dependent on the timely coordinated actions of genetic and environmental processes, and an aberration can lead to neurodevelopmental disorders (NDDs). Intellectual disability (ID) and autism spectrum disorders (ASDs) are a group of co-occurring NDDs that affect between 3% and 5% of the world population, thus presenting a great challenge to society. This problem calls for the need to understand the pathobiology of these disorders and to design new therapeutic strategies. One approach towards this has been the development of multiple analogous mouse models. This review discusses studies conducted in the mouse models of five major monogenic causes of ID and ASDs: Fmr1, Syngap1, Mecp2, Shank2/3 and Neuroligins/Neurnexins. These studies reveal that, despite having a diverse molecular origin, the effects of these mutations converge onto similar or related aetiological pathways, consequently giving rise to the typical phenotype of cognitive, social and emotional deficits that are characteristic of ID and ASDs. This convergence, therefore, highlights common pathological nodes that can be targeted for therapy. Other than conventional therapeutic strategies such as non-pharmacological corrective methods and symptomatic alleviation, multiple studies in mouse models have successfully proved the possibility of pharmacological and genetic therapy enabling functional recovery.
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Affiliation(s)
- Vijaya Verma
- Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bengaluru 560 064, Karnataka, India
| | - Abhik Paul
- Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bengaluru 560 064, Karnataka, India
| | - Anjali Amrapali Vishwanath
- Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bengaluru 560 064, Karnataka, India
| | - Bhupesh Vaidya
- Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bengaluru 560 064, Karnataka, India
| | - James P Clement
- Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur, Bengaluru 560 064, Karnataka, India
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10
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Zhang Z, Marro SG, Zhang Y, Arendt KL, Patzke C, Zhou B, Fair T, Yang N, Südhof TC, Wernig M, Chen L. The fragile X mutation impairs homeostatic plasticity in human neurons by blocking synaptic retinoic acid signaling. Sci Transl Med 2018; 10:eaar4338. [PMID: 30068571 PMCID: PMC6317709 DOI: 10.1126/scitranslmed.aar4338] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 07/12/2018] [Indexed: 11/02/2022]
Abstract
Fragile X syndrome (FXS) is an X chromosome-linked disease leading to severe intellectual disabilities. FXS is caused by inactivation of the fragile X mental retardation 1 (FMR1) gene, but how FMR1 inactivation induces FXS remains unclear. Using human neurons generated from control and FXS patient-derived induced pluripotent stem (iPS) cells or from embryonic stem cells carrying conditional FMR1 mutations, we show here that loss of FMR1 function specifically abolished homeostatic synaptic plasticity without affecting basal synaptic transmission. We demonstrated that, in human neurons, homeostatic plasticity induced by synaptic silencing was mediated by retinoic acid, which regulated both excitatory and inhibitory synaptic strength. FMR1 inactivation impaired homeostatic plasticity by blocking retinoic acid-mediated regulation of synaptic strength. Repairing the genetic mutation in the FMR1 gene in an FXS patient cell line restored fragile X mental retardation protein (FMRP) expression and fully rescued synaptic retinoic acid signaling. Thus, our study reveals a robust functional impairment caused by FMR1 mutations that might contribute to neuronal dysfunction in FXS. In addition, our results suggest that FXS patient iPS cell-derived neurons might be useful for studying the mechanisms mediating functional abnormalities in FXS.
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Affiliation(s)
- Zhenjie Zhang
- Departments of Neurosurgery, and Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305-5453, USA
| | - Samuele G Marro
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Yingsha Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Kristin L Arendt
- Departments of Neurosurgery, and Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305-5453, USA
| | - Christopher Patzke
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Bo Zhou
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Tyler Fair
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Nan Yang
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA.
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Marius Wernig
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5453, USA.
- Institute of Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305-5453, USA
| | - Lu Chen
- Departments of Neurosurgery, and Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 265 Campus Drive, Stanford, CA 94305-5453, USA.
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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: 85] [Impact Index Per Article: 12.1] [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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β-glucuronidase use as a single internal control gene may confound analysis in FMR1 mRNA toxicity studies. PLoS One 2018; 13:e0192151. [PMID: 29474364 PMCID: PMC5825026 DOI: 10.1371/journal.pone.0192151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 01/17/2018] [Indexed: 12/02/2022] Open
Abstract
Relationships between Fragile X Mental Retardation 1 (FMR1) mRNA levels in blood and intragenic FMR1 CGG triplet expansions support the pathogenic role of RNA gain of function toxicity in premutation (PM: 55–199 CGGs) related disorders. Real-time PCR (RT-PCR) studies reporting these findings normalised FMR1 mRNA level to a single internal control gene called β-glucuronidase (GUS). This study evaluated FMR1 mRNA-CGG correlations in 33 PM and 33 age- and IQ-matched control females using three normalisation strategies in peripheral blood mononuclear cells (PBMCs): (i) GUS as a single internal control; (ii) the mean of GUS, Eukaryotic Translation Initiation Factor 4A2 (EIF4A2) and succinate dehydrogenase complex flavoprotein subunit A (SDHA); and (iii) the mean of EIF4A2 and SDHA (with no contribution from GUS). GUS mRNA levels normalised to the mean of EIF4A2 and SDHA mRNA levels and EIF4A2/SDHA ratio were also evaluated. FMR1mRNA level normalised to the mean of EIF4A2 and SDHA mRNA levels, with no contribution from GUS, showed the most significant correlation with CGG size and the greatest difference between PM and control groups (p = 10−11). Only 15% of FMR1 mRNA PM results exceeded the maximum control value when normalised to GUS, compared with over 42% when normalised to the mean of EIF4A2 and SDHA mRNA levels. Neither GUS mRNA level normalised to the mean RNA levels of EIF4A2 and SDHA, nor to the EIF4A2/SDHA ratio were correlated with CGG size. However, greater variability in GUS mRNA levels were observed for both PM and control females across the full range of CGG repeat as compared to the EIF4A2/SDHA ratio. In conclusion, normalisation with multiple control genes, excluding GUS, can improve assessment of the biological significance of FMR1 mRNA-CGG size relationships.
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Tang J, Yu Y, Yang W. Long noncoding RNA and its contribution to autism spectrum disorders. CNS Neurosci Ther 2017; 23:645-656. [PMID: 28635106 PMCID: PMC6492731 DOI: 10.1111/cns.12710] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 05/15/2017] [Accepted: 05/17/2017] [Indexed: 12/13/2022] Open
Abstract
Recent studies have indicated that long noncoding RNAs (lncRNAs) play important roles in multiple processes, such as epigenetic regulation, gene expression regulation, development, nutrition-related and other diseases, toxic response, and response to drugs. Although the functional roles and mechanisms of several lncRNAs have been discovered, a better understanding of the vast majority of lncRNAs remains elusive. To understand the functional roles and mechanisms of lncRNAs is critical because these transcripts represent the majority of the transcriptional output of the mammalian genome. Recent studies have also suggested that lncRNAs are more abundant in the human brain and are involved in neurodevelopment and neurodevelopmental disorders, including autism spectrum disorders (ASDs). In this study, we review several known functions of lncRNAs and the potential contribution of lncRNAs to ASDs and to other genetic syndromes that have a similar clinical presentation to ASDs, such as fragile X syndrome and Rett syndrome.
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Affiliation(s)
- Jie Tang
- The First Affiliated Hospital of Guangzhou Medical UniversityGuangzhouChina
- Department of Preventive MedicineSchool of Public HealthGuangzhou Medical UniversityXinzaoPanyu DistrictGuangzhouChina
| | - Yizhen Yu
- Department of Child and Women Health CareSchool of Public HealthTongji Medical CollegeHuazhong University of Science and TechnologyWuhanChina
| | - Wei Yang
- Department of Nutrition and Food HygieneHubei Key Laboratory of Food Nutrition and SafetyTongji Medical CollegeHuazhong University of Science and TechnologyWuhanChina
- Department of Nutrition and Food HygieneMOE Key Lab of Environment and HealthSchool of Public HealthTongji Medical CollegeHuazhong University of Science and TechnologyWuhanChina
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Mor-Shaked H, Eiges R. Modeling Fragile X Syndrome Using Human Pluripotent Stem Cells. Genes (Basel) 2016; 7:genes7100077. [PMID: 27690107 PMCID: PMC5083916 DOI: 10.3390/genes7100077] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/02/2016] [Accepted: 09/12/2016] [Indexed: 02/06/2023] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable form of cognitive impairment. It results from a loss-of-function mutation by a CGG repeat expansion at the 5′ untranslated region of the X-linked fragile X mental retardation 1 (FMR1) gene. Expansion of the CGG repeats beyond 200 copies results in protein deficiency by leading to aberrant methylation of the FMR1 promoter and the switch from active to repressive histone modifications. Additionally, the CGGs become increasingly unstable, resulting in high degree of variation in expansion size between and within tissues of affected individuals. It is still unclear how the FMR1 protein (FMRP) deficiency leads to disease pathology in neurons. Nor do we know the mechanisms by which the CGG expansion results in aberrant DNA methylation, or becomes unstable in somatic cells of patients, at least in part due to the lack of appropriate animal or cellular models. This review summarizes the current contribution of pluripotent stem cells, mutant human embryonic stem cells, and patient-derived induced pluripotent stem cells to disease modeling of FXS for basic and applied research, including the development of new therapeutic approaches.
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Affiliation(s)
- Hagar Mor-Shaked
- Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center Affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
| | - Rachel Eiges
- Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center Affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
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15
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Family Communication and Cascade Testing for Fragile X Syndrome. J Genet Couns 2016; 25:1075-84. [DOI: 10.1007/s10897-016-9940-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 02/18/2016] [Indexed: 10/22/2022]
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16
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Suhl JA, Warren ST. Single-Nucleotide Mutations in FMR1 Reveal Novel Functions and Regulatory Mechanisms of the Fragile X Syndrome Protein FMRP. J Exp Neurosci 2015; 9:35-41. [PMID: 26819560 PMCID: PMC4720182 DOI: 10.4137/jen.s25524] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 11/04/2015] [Accepted: 11/08/2015] [Indexed: 11/05/2022] Open
Abstract
Fragile X syndrome is a monogenic disorder and a common cause of intellectual disability. Despite nearly 25 years of research on FMR1, the gene underlying the syndrome, very few pathological mutations other than the typical CGG-repeat expansion have been reported. This is in contrast to other X-linked, monogenic, intellectual disability disorders, such as Rett syndrome, where many point mutations have been validated as causative of the disorder. As technology has improved and significantly driven down the cost of sequencing, allowing for whole genes to be sequenced with relative ease, in-depth sequencing studies on FMR1 have recently been performed. These studies have led to the identification of novel variants in FMR1, where some of which have been functionally evaluated and are likely pathogenic. In this review, we discuss recently identified FMR1 variants, the ways these novel variants cause dysfunction, and how they reveal new regulatory mechanisms and functionalities of the gene.
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Affiliation(s)
- Joshua A Suhl
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - Stephen T Warren
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.; Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA.; Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
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17
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Biancalana V, Glaeser D, McQuaid S, Steinbach P. EMQN best practice guidelines for the molecular genetic testing and reporting of fragile X syndrome and other fragile X-associated disorders. Eur J Hum Genet 2014; 23:417-25. [PMID: 25227148 PMCID: PMC4666582 DOI: 10.1038/ejhg.2014.185] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 07/09/2014] [Accepted: 07/10/2014] [Indexed: 01/25/2023] Open
Abstract
Different mutations occurring in the unstable CGG repeat in 5' untranslated region of FMR1 gene are responsible for three fragile X-associated disorders. An expansion of over ∼200 CGG repeats when associated with abnormal methylation and inactivation of the promoter is the mutation termed ‘full mutation' and is responsible for fragile X syndrome (FXS), a neurodevelopmental disorder described as the most common cause of inherited intellectual impairment. The term ‘abnormal methylation' is used here to distinguish the DNA methylation induced by the expanded repeat from the ‘normal methylation' occurring on the inactive X chromosomes in females with normal, premutation, and full mutation alleles. All male and roughly half of the female full mutation carriers have FXS. Another anomaly termed ‘premutation' is characterized by the presence of 55 to ∼200 CGGs without abnormal methylation, and is the cause of two other diseases with incomplete penetrance. One is fragile X-associated primary ovarian insufficiency (FXPOI), which is characterized by a large spectrum of ovarian dysfunction phenotypes and possible early menopause as the end stage. The other is fragile X-associated tremor/ataxia syndrome (FXTAS), which is a late onset neurodegenerative disorder affecting males and females. Because of the particular pattern and transmission of the CGG repeat, appropriate molecular testing and reporting is very important for the optimal genetic counselling in the three fragile X-associated disorders. Here, we describe best practice guidelines for genetic analysis and reporting in FXS, FXPOI, and FXTAS, including carrier and prenatal testing.
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Affiliation(s)
- Valérie Biancalana
- Laboratoire Diagnostic Génétique, Faculté de Médecine-CHRU, Strasbourg, France
| | | | - Shirley McQuaid
- National Centre for Medical Genetics, Our Lady's Children's Hospital, Crumlin, Dublin, Ireland
| | - Peter Steinbach
- Institute of Human Genetics, University Hospital of Ulm, Ulm, Germany
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18
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Usdin K, Hayward BE, Kumari D, Lokanga RA, Sciascia N, Zhao XN. Repeat-mediated genetic and epigenetic changes at the FMR1 locus in the Fragile X-related disorders. Front Genet 2014; 5:226. [PMID: 25101111 PMCID: PMC4101883 DOI: 10.3389/fgene.2014.00226] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 06/29/2014] [Indexed: 01/01/2023] Open
Abstract
The Fragile X-related disorders are a group of genetic conditions that include the neurodegenerative disorder, Fragile X-associated tremor/ataxia syndrome (FXTAS), the fertility disorder, Fragile X-associated primary ovarian insufficiency (FXPOI) and the intellectual disability, Fragile X syndrome (FXS). The pathology in all these diseases is related to the number of CGG/CCG-repeats in the 5′ UTR of the Fragile X mental retardation 1 (FMR1) gene. The repeats are prone to continuous expansion and the increase in repeat number has paradoxical effects on gene expression increasing transcription on mid-sized alleles and decreasing it on longer ones. In some cases the repeats can simultaneously both increase FMR1 mRNA production and decrease the levels of the FMR1 gene product, Fragile X mental retardation 1 protein (FMRP). Since FXTAS and FXPOI result from the deleterious consequences of the expression of elevated levels of FMR1 mRNA and FXS is caused by an FMRP deficiency, the clinical picture is turning out to be more complex than once appreciated. Added complications result from the fact that increasing repeat numbers make the alleles somatically unstable. Thus many individuals have a complex mixture of different sized alleles in different cells. Furthermore, it has become apparent that the eponymous fragile site, once thought to be no more than a useful diagnostic criterion, may have clinical consequences for females who inherit chromosomes that express this site. This review will cover what is currently known about the mechanisms responsible for repeat instability, for the repeat-mediated epigenetic changes that affect expression of the FMR1 gene, and for chromosome fragility. It will also touch on what current and future options are for ameliorating some of these effects.
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Affiliation(s)
- Karen Usdin
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda MD, USA
| | - Bruce E Hayward
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda MD, USA
| | - Daman Kumari
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda MD, USA
| | - Rachel A Lokanga
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda MD, USA
| | - Nicholas Sciascia
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda MD, USA
| | - Xiao-Nan Zhao
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda MD, USA
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19
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Inaba Y, Schwartz CE, Bui QM, Li X, Skinner C, Field M, Wotton T, Hagerman RJ, Francis D, Amor DJ, Hopper JL, Loesch DZ, Bretherton L, Slater HR, Godler DE. Early Detection of Fragile X Syndrome: Applications of a Novel Approach for Improved Quantitative Methylation Analysis in Venous Blood and Newborn Blood Spots. Clin Chem 2014; 60:963-73. [DOI: 10.1373/clinchem.2013.217331] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Abstract
BACKGROUND
Standard fragile X syndrome (FXS) diagnostic tests that target methylation of the fragile X mental retardation 1 (FMR1) CpG island 5′ of the CGG expansion can be used to predict severity of the disease in males from birth, but not in females.
METHODS
We describe methylation specific–quantitative melt analysis (MS-QMA) that targets 10 CpG sites, with 9 within FMR1 intron 1, to screen for FXS from birth in both sexes. The novel method combines the qualitative strengths of high-resolution melt and the high-throughput, quantitative real-time PCR standard curve to provide accurate quantification of DNA methylation in a single assay. Its performance was assessed in 312 control (CGG <40), 143 premutation (PM) (CGG 56–170), 197 full mutation (FM) (CGG 200–2000), and 33 CGG size and methylation mosaic samples.
RESULTS
In male and female newborn blood spots, MS-QMA differentiated FM from control alleles, with sensitivity, specificity, and positive and negative predictive values between 92% and 100%. In venous blood of FM females between 6 and 35 years of age, MS-QMA correlated most strongly with verbal IQ impairment (P = 0.002). In the larger cohort of males and females, MS-QMA correlated with reference methods Southern blot and MALDI-TOF mass spectrometry (P < 0.05), but was not significantly correlated with age. Unmethylated alleles in high-functioning FM and PM males determined by both reference methods were also unmethylated by MS-QMA.
CONCLUSIONS
MS-QMA has an immediate application in FXS diagnostics, with a potential use of its quantitative methylation output for prognosis in both sexes.
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Affiliation(s)
- Yoshimi Inaba
- Cyto-molecular Diagnostic Research Laboratory, Victorian Clinical Genetics Services and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Charles E Schwartz
- Center for Molecular Studies, J.C. Self Research Institute of Human Genetics, Greenwood Genetic Center, Greenwood, SC
| | - Quang M Bui
- Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, University of Melbourne, Carlton, Victoria, Australia
| | - Xin Li
- Cyto-molecular Diagnostic Research Laboratory, Victorian Clinical Genetics Services and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Cindy Skinner
- Center for Molecular Studies, J.C. Self Research Institute of Human Genetics, Greenwood Genetic Center, Greenwood, SC
| | - Michael Field
- Genetics of Learning Disability Service, New South Wales, Australia
| | - Tiffany Wotton
- New South Wales Newborn Screening Program, Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Randi J Hagerman
- The MIND Institute, University of California, Davis Medical Center, Sacramento, CA
- Department of Pediatrics, University of California, Davis School of Medicine, Sacramento, CA
| | - David Francis
- Cyto-molecular Diagnostic Research Laboratory, Victorian Clinical Genetics Services and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - David J Amor
- Cyto-molecular Diagnostic Research Laboratory, Victorian Clinical Genetics Services and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Melbourne Victoria, Australia
| | - John L Hopper
- Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, University of Melbourne, Carlton, Victoria, Australia
| | - Danuta Z Loesch
- School of Psychological Science, La Trobe University, Melbourne, Victoria, Australia
| | - Lesley Bretherton
- Department of Paediatrics, University of Melbourne, Melbourne Victoria, Australia
- Melbourne School of Psychological Sciences, University of Melbourne; Melbourne Victoria, Australia
- Department of Clinical Psychology, The Royal Children's Hospital, Melbourne; Victoria, Australia
| | - Howard R Slater
- Cyto-molecular Diagnostic Research Laboratory, Victorian Clinical Genetics Services and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
- Department of Paediatrics, University of Melbourne, Melbourne Victoria, Australia
| | - David E Godler
- Cyto-molecular Diagnostic Research Laboratory, Victorian Clinical Genetics Services and Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
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20
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Alfaro MP, Cohen M, Vnencak-Jones CL. Maternal FMR1 premutation allele expansion and contraction in fraternal twins. Am J Med Genet A 2013; 161A:2620-5. [PMID: 23949867 DOI: 10.1002/ajmg.a.36123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/10/2013] [Indexed: 11/11/2022]
Abstract
Fragile X syndrome results from an expansion of the CGG trinucleotide repeat in the 5' untranslated region of the Fragile X Mental Retardation 1 (FMR1) gene. Expansion of a maternal premutation allele is the mechanism by which a full mutation allele arises; contraction of a maternal premutation allele is rare. Here we report on both an expansion and contraction of a maternal FMR1 premutation allele in fraternal twins. The propositus was the product of a 29-week gestation twin pregnancy and was referred for FMR1 testing due to developmental delay. A FMR1 full mutation with complete methylation was observed on Southern blot analysis. Evaluation of the maternal FMR1 gene by PCR revealed a normal and premutation allele with CGG repeat numbers of 30 and 93, respectively. Subsequent FMR1 testing on the twin sister of the propositus detected CGG repeat numbers of 30 and 54. The FMR1 CGG repeat number of the reproductive partner was 30. The FMR1 CGG repeat 30 allele in the twin sister was determined to be of paternal origin and the FMR1 allele with a CGG repeat number of 54 was of maternal origin. This observation is particularly interesting not only because of the concomitant donation of a FMR1 expanded and contracted premutation allele in a twin pregnancy but also because of the significant degree of contraction (39 repeats) of the maternal premutation allele.
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Affiliation(s)
- Maria P Alfaro
- Department of Pathology, Microbiology and Immunology, Nashville, Tennessee
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21
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Monaghan KG, Lyon E, Spector EB. ACMG Standards and Guidelines for fragile X testing: a revision to the disease-specific supplements to the Standards and Guidelines for Clinical Genetics Laboratories of the American College of Medical Genetics and Genomics. Genet Med 2013; 15:575-86. [PMID: 23765048 DOI: 10.1038/gim.2013.61] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 04/04/2013] [Indexed: 12/29/2022] Open
Abstract
Molecular genetic testing of the FMR1 gene is commonly performed in clinical laboratories. Mutations in the FMR1 gene are associated with fragile X syndrome, fragile X tremor ataxia syndrome, and premature ovarian insufficiency. This document provides updated information regarding FMR1 gene mutations, including prevalence, genotype-phenotype correlation, and mutation nomenclature. Methodological considerations are provided for Southern blot analysis and polymerase chain reaction amplification of the FMR1 gene, including triplet repeat-primed and methylation-specific polymerase chain reaction. In addition to report elements, examples of laboratory reports for various genotypes are also included.
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Affiliation(s)
- Kristin G Monaghan
- Department of Medical Genetics, Henry Ford Health System, Detroit, Michigan, USA.
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22
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Barasoain M, Barrenetxea G, Ortiz-Lastra E, González J, Huerta I, Télez M, Ramírez JM, Domínguez A, Gurtubay P, Criado B, Arrieta I. Single nucleotide polymorphism and FMR1 CGG repeat instability in two Basque valleys. Ann Hum Genet 2012; 76:110-20. [PMID: 22211843 DOI: 10.1111/j.1469-1809.2011.00696.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fragile X Syndrome (FXS, MIM 309550) is mainly due to the expansion of a CGG trinucleotide repeat sequence, found in the 5' untranslated region of the FMR1 gene. Some studies suggest that stable markers, such as single nucleotide polymorphisms (SNPs) and the study of populations with genetic identity, could provide a distinct advance to investigate the origin of CGG repeat instability. In this study, seven SNPs (WEX28 rs17312728:G>T, WEX70 rs45631657:C>T, WEX1 rs10521868:A>C, ATL1 rs4949:A>G, FMRb rs25707:A>G, WEX17 rs12010481:C>T and WEX10 ss71651741:C>T) have been analyzed in two Basque valleys (Markina and Arratia). We examined the association between these SNPs and the CGG repeat size, the AGG interruption pattern and two microsatellite markers (FRAXAC1 and DXS548). The results suggest that in both valleys WEX28-T, WEX70-C, WEX1-C, ATL1-G, and WEX10-C are preferably associated with cis-acting sequences directly influencing instability. But comparison of the two valleys reveals also important differences with respect to: (1) frequency and structure of "susceptible" alleles and (2) association between "susceptible" alleles and STR and SNP haplotypes. These results may indicate that, in Arratia, SNP status does not identify a pool of susceptible alleles, as it does in Markina. In Arratia valley, the SNP haplotype association reveals also a potential new "protective" factor.
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Affiliation(s)
- Maitane Barasoain
- Department of Genetics, Physical Anthropology and Animal physiology, Faculty of Science and Technology, University of the Basque Country, Bilbao, Spain
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23
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Loesch D, Hagerman R. Unstable Mutations in the FMR1 Gene and the Phenotypes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 769:78-114. [DOI: 10.1007/978-1-4614-5434-2_6] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
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24
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Coffee RL, Williamson AJ, Adkins CM, Gray MC, Page TL, Broadie K. In vivo neuronal function of the fragile X mental retardation protein is regulated by phosphorylation. Hum Mol Genet 2011; 21:900-15. [PMID: 22080836 DOI: 10.1093/hmg/ddr527] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Fragile X syndrome (FXS), caused by loss of the Fragile X Mental Retardation 1 (FMR1) gene product (FMRP), is the most common heritable cause of intellectual disability and autism spectrum disorders. It has been long hypothesized that the phosphorylation of serine 500 (S500) in human FMRP controls its function as an RNA-binding translational repressor. To test this hypothesis in vivo, we employed neuronally targeted expression of three human FMR1 transgenes, including wild-type (hFMR1), dephosphomimetic (S500A-hFMR1) and phosphomimetic (S500D-hFMR1), in the Drosophila FXS disease model to investigate phosphorylation requirements. At the molecular level, dfmr1 null mutants exhibit elevated brain protein levels due to loss of translational repressor activity. This defect is rescued for an individual target protein and across the population of brain proteins by the phosphomimetic, whereas the dephosphomimetic phenocopies the null condition. At the cellular level, dfmr1 null synapse architecture exhibits increased area, branching and bouton number. The phosphomimetic fully rescues these synaptogenesis defects, whereas the dephosphomimetic provides no rescue. The presence of Futsch-positive (microtubule-associated protein 1B) supernumerary microtubule loops is elevated in dfmr1 null synapses. The human phosphomimetic restores normal Futsch loops, whereas the dephosphomimetic provides no activity. At the behavioral level, dfmr1 null mutants exhibit strongly impaired olfactory associative learning. The human phosphomimetic targeted only to the brain-learning center restores normal learning ability, whereas the dephosphomimetic provides absolutely no rescue. We conclude that human FMRP S500 phosphorylation is necessary for its in vivo function as a neuronal translational repressor and regulator of synaptic architecture, and for the manifestation of FMRP-dependent learning behavior.
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Affiliation(s)
- R Lane Coffee
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37232, USA
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25
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Clinical utility gene card for: fragile X mental retardation syndrome, fragile X-associated tremor/ataxia syndrome and fragile X-associated primary ovarian insufficiency. Eur J Hum Genet 2011; 19:ejhg201155. [PMID: 21540884 DOI: 10.1038/ejhg.2011.55] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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26
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Coffee RL, Tessier CR, Woodruff EA, Broadie K. Fragile X mental retardation protein has a unique, evolutionarily conserved neuronal function not shared with FXR1P or FXR2P. Dis Model Mech 2010; 3:471-85. [PMID: 20442204 DOI: 10.1242/dmm.004598] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Fragile X syndrome (FXS), resulting solely from the loss of function of the human fragile X mental retardation 1 (hFMR1) gene, is the most common heritable cause of mental retardation and autism disorders, with syndromic defects also in non-neuronal tissues. In addition, the human genome encodes two closely related hFMR1 paralogs: hFXR1 and hFXR2. The Drosophila genome, by contrast, encodes a single dFMR1 gene with close sequence homology to all three human genes. Drosophila that lack the dFMR1 gene (dfmr1 null mutants) recapitulate FXS-associated molecular, cellular and behavioral phenotypes, suggesting that FMR1 function has been conserved, albeit with specific functions possibly sub-served by the expanded human gene family. To test evolutionary conservation, we used tissue-targeted transgenic expression of all three human genes in the Drosophila disease model to investigate function at (1) molecular, (2) neuronal and (3) non-neuronal levels. In neurons, dfmr1 null mutants exhibit elevated protein levels that alter the central brain and neuromuscular junction (NMJ) synaptic architecture, including an increase in synapse area, branching and bouton numbers. Importantly, hFMR1 can, comparably to dFMR1, fully rescue both the molecular and cellular defects in neurons, whereas hFXR1 and hFXR2 provide absolutely no rescue. For non-neuronal requirements, we assayed male fecundity and testes function. dfmr1 null mutants are effectively sterile owing to disruption of the 9+2 microtubule organization in the sperm tail. Importantly, all three human genes fully and equally rescue mutant fecundity and spermatogenesis defects. These results indicate that FMR1 gene function is evolutionarily conserved in neural mechanisms and cannot be compensated by either FXR1 or FXR2, but that all three proteins can substitute for each other in non-neuronal requirements. We conclude that FMR1 has a neural-specific function that is distinct from its paralogs, and that the unique FMR1 function is responsible for regulating neuronal protein expression and synaptic connectivity.
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Affiliation(s)
- R Lane Coffee
- Department of Biological Sciences, Vanderbilt Brain Institute, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235-1634, USA
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27
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Galloway JN, Nelson DL. Evidence for RNA-mediated toxicity in the fragile X-associated tremor/ataxia syndrome. FUTURE NEUROLOGY 2009; 4:785. [PMID: 20161676 DOI: 10.2217/fnl.09.44] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Fragile X premutation carriers are at risk for developing a late-onset, progressive neurodegenerative disorder termed fragile X-associated tremor/ataxia syndrome (FXTAS). A growing body of evidence suggests the characteristic excess CGG repeat containing FMR1 mRNA observed in premutation carriers is pathogenic and leads to clinical features of FXTAS. The current model suggests premutation mRNA transcripts can induce the formation of intranuclear inclusions by the sequestration of RNA-binding proteins and other proteins. The sequestered proteins are prevented from performing their normal functions, which is thought to lead to the neuropathology-observed FXTAS. This paper discusses the existing evidence that microsatellite expansions at the level of RNA play a role in the disease pathogenesis of FXTAS and some of the approaches that may uncover downstream effects of expanded riboCGG expression.
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Affiliation(s)
- Jocelyn N Galloway
- Baylor College of Medicine, Interdepartmental Program in Cell & Molecular Biology, One Baylor Plaza, Room 904E, Houston, TX 77030, USA, Tel.: +1 713 798 7898, Fax.: +1 713 798 1116
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28
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Godler DE, Loesch DZ, Huggins R, Gordon L, Slater HR, Gehling F, Burgess T, Choo KHA. Improved methodology for assessment of mRNA levels in blood of patients with FMR1 related disorders. BMC Clin Pathol 2009; 9:5. [PMID: 19505339 PMCID: PMC2708186 DOI: 10.1186/1472-6890-9-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 06/09/2009] [Indexed: 11/16/2022] Open
Abstract
Background Elevated levels of FMR1 mRNA in blood have been implicated in RNA toxicity associated with a number of clinical conditions. Due to the extensive inter-sample variation in the time lapse between the blood collection and RNA extraction in clinical practice, the resulting variation in mRNA quality significantly confounds mRNA analysis by real-time PCR. Methods Here, we developed an improved method to normalize for mRNA degradation in a sample set with large variation in rRNA quality, without sample omission. Initially, RNA samples were artificially degraded, and analyzed using capillary electrophoresis and real-time PCR standard curve method, with the aim of defining the best predictors of total RNA and mRNA degradation. Results We found that: (i) the 28S:18S ratio and RNA quality indicator (RQI) were good predictors of severe total RNA degradation, however, the greatest changes in the quantity of different mRNAs (FMR1, DNMT1, GUS, B2M and GAPDH) occurred during the early to moderate stages of degradation; (ii) chromatographic features for the 18S, 28S and the inter-peak region were the most reliable predictors of total RNA degradation, however their use for target gene normalization was inferior to internal control genes, of which GUS was the most appropriate. Using GUS for normalization, we examined in the whole blood the relationship between the FMR1 mRNA and CGG expansion in a non-coding portion of this gene, in a sample set (n = 30) with the large variation in rRNA quality. By combining FMR1 3' and 5' mRNA analyses the confounding impact of mRNA degradation on the correlation between FMR1 expression and CGG size was minimized, and the biological significance increased from p = 0.046 for the 5' FMR1 assay, to p = 0.018 for the combined FMR1 3' and 5' mRNA analysis. Conclusion Our observations demonstrate that, through the use of an appropriate internal control and the direct analysis of multiple sites of target mRNA, samples that do not conform to the conventional rRNA criteria can still be utilized to obtain biologically/clinically relevant data. Although, this strategy clearly has application for improved assessment of FMR1 mRNA toxicity in blood, it may also have more general implications for gene expression studies in fresh and archival tissues.
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Affiliation(s)
- David E Godler
- Chromosome and Chromatin Research, Murdoch Childrens Research Institute, Royal Children's Hospital, Melbourne, Australia.
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Gharehbaghi-Schneli EB, Finsterei J, Korschineck I, Mamoli B, Binder BR. Genotype -phenotype correlation in myotonic dystrophy. Clin Genet 2008. [DOI: 10.1111/j.1399-0004.1998.tb02576.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Zuñiga A, Juan J, Mila M, Guerrero A. Expansion of an intermediate allele of the FMR1 gene in only two generations. Clin Genet 2005; 68:471-3. [PMID: 16207218 DOI: 10.1111/j.1399-0004.2005.00514.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Mitchell RJ, Holden JJA, Zhang C, Curlis Y, Slater HR, Burgess T, Kirkby KC, Carmichael A, Heading KD, Loesch DZ. FMR1 alleles in Tasmania: a screening study of the special educational needs population. Clin Genet 2005; 67:38-46. [PMID: 15617547 DOI: 10.1111/j.1399-0004.2004.00344.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The distribution of fragile X mental retardation-1 (FMR1) allele categories, classified by the number of CGG repeats, in the population of Tasmania was investigated in 1253 males with special educational needs (SEN). The frequencies of these FMR1 categories were compared with those seen in controls as represented by 578 consecutive male births. The initial screening was based on polymerase chain reaction analysis of dried blood spots. Inconclusive results were verified by Southern analysis of a venous blood sample. The frequencies of common FMR1 alleles in both samples, and of grey zone alleles in the controls, were similar to those in other Caucasian populations. Consistent with earlier reports, we found some (although insignificant) increase of grey zone alleles in SEN subjects compared with controls. The frequencies of predisposing flanking haplotypes among grey zone males FMR1 alleles were similar to those seen in other Caucasian SEN samples. Contrary to expectation, given the normal frequency of grey zone alleles, no premutation (PM) or full mutation (FM) allele was detected in either sample, with only 15 fragile X families diagnosed through routine clinical admissions registered in Tasmania up to 2002. An explanation of this discrepancy could be that the C19th founders of Tasmania carried few PM or FM alleles. The eight to ten generations since white settlement of Tasmania has been insufficient time for susceptible grey zone alleles to evolve into the larger expansions.
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Affiliation(s)
- R J Mitchell
- Department of Genetics and Human Variation, School of Molecular Sciences, La Trobe University, Melbourne, Australia.
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Napierala M, Michalowski D, de Mezer M, Krzyzosiak WJ. Facile FMR1 mRNA structure regulation by interruptions in CGG repeats. Nucleic Acids Res 2005; 33:451-63. [PMID: 15659577 PMCID: PMC548340 DOI: 10.1093/nar/gki186] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
RNA metabolism is a major contributor to the pathogenesis of clinical disorders associated with premutation size alleles of the fragile X mental retardation (FMR1) gene. Herein, we determined the structural properties of numerous FMR1 transcripts harboring different numbers of both CGG repeats and AGG interruptions. The stability of hairpins formed by uninterrupted repeat-containing transcripts increased with the lengthening of the repeat tract. Even a single AGG interruption in the repeated sequence dramatically changed the folding of the 5'UTR fragments, typically resulting in branched hairpin structures. Transcripts containing different lengths of CGG repeats, but sharing a common AGG pattern, adopted similar types of secondary structures. We postulate that interruption-dependent structure variants of the FMR1 mRNA contribute to the phenotype diversity, observed in premutation carriers.
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Gambarini GHR, Della-Rosa VA, Machado de Moraes AMS. Comparative Cytogenetic and PCR Studies in Fragile X Syndrome. CYTOLOGIA 2005. [DOI: 10.1508/cytologia.70.233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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34
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Arrieta I, Peñagarikano O, Télez M, Ortega B, Flores P, Criado B, Veiga I, Peixoto AL, Lostao CM. The FMR1 CGG repeat and linked microsatellite markers in two Basque valleys. Heredity (Edinb) 2003; 90:206-11. [PMID: 12634803 DOI: 10.1038/sj.hdy.6800218] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Fragile X syndrome is associated with an unstable CGG repeat sequence in the 5' untranslated region of the first exon of the FMR1 gene. The present study involved the evaluation of factors implicated in CGG repeat stability in a normal sample from two Basque valleys (Markina and Arratia), to discover whether the Basque population shows allelic diversity and to identify factors involved, by using the data in conjunction with previous findings. The study was based on a sample of 204 and 58 X chromosomes from the Markina and Arratia valleys, respectively. The CGG repeat, the AGG interspersion and two flanking microsatellite markers, FRAXAC1 and DXS548, were examined. In the Markina valley, gray zone alleles (> or =35 CGG repeats) were associated with anchoring AGGs, with the longest 3' pure CGG repeats of the valley (=15), with the 5' instability structure 9+n and with one principal fragile X FRAXAC1-DXS548 haplotype 42-50. In the Arratia valley, gray zone alleles (> or =35 CGG repeats) showed the highest frequency among the Basque samples analyzed, and were associated with anchoring AGGs, with the longest 3' pure repeats (> or =20), with the 5' instability structure 9+n and with one "normal" FRAXAC1-DXS548 haplotype 38-40 (these data from Arratia suggest the existence of a "protective" haplotype). The results showed, on the one hand, differences between Markina and Arratia in factors implicated in CGG repeat instability and, on the other hand, a great similarity between the general Basque sample from Biscay and the Markina valley.
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Affiliation(s)
- I Arrieta
- Dipartamento Biología Animal y Genética, Facultad de Ciencias, Universidad del País Vasco, Apdo 644, Bilbao 48080, Spain.
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Steyaert J, Legius E, Borghgraef M, Fryns JP. A distinct neurocognitive phenotype in female fragile-X premutation carriers assessed with visual attention tasks. Am J Med Genet A 2003; 116A:44-51. [PMID: 12476450 DOI: 10.1002/ajmg.a.10821] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Premature ovarian failure (POF) and underlying hormonal changes are recognized as a distinct phenotype in female fragile-X premutation carriers. Neurocognitive deficits, in particular mental retardation, are associated with the full mutation in males and females. In female full mutation carriers this neurocognitive phenotype is expressed more mildly than in males. Research on whether the fragile-X premutation is associated with a particular neurocognitive phenotype or not has been equivocal. By means of the Sonneville Visual Attentions Tasks (SVAT) computer-based battery of neurocognitive tasks, we assessed reaction time on different tasks in three groups of subjects: female premutation carriers, female full mutation carriers, and female control subjects. The results show that a fraction of the female premutation carriers perform poorly on several selective attention tasks, but not on other tasks. Their neurocognitive profile is different from that of control subjects and of the majority of female premutation carriers. It may also be different from the phenotype of female full mutation carriers, though in that respect this study remains inconclusive. These findings support earlier findings that the fragile-X premutation may affect neurocognitive functioning, in particular aspects of attention.
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Affiliation(s)
- Jean Steyaert
- Department of Clinical Genetics, University of Maastricht, The Netherlands
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36
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Abstract
Fragile X syndrome is one of the most common forms of inherited mental retardation. In most cases the disease is caused by the methylation-induced transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene that occurs as a result of the expansion of a CGG repeat in the gene's 5'UTR and leads to the loss of protein product fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that associates with translating polyribosomes as part of a large messenger ribonucleoprotein (mRNP) and modulates the translation of its RNA ligands. Pathological studies from the brains of patients and from Fmr1 knockout mice show abnormal dendritic spines implicating FMRP in synapse formation and function. Evidence from both in vitro and in vivo neuronal studies indicates that FMRP is located at the synapse and the loss of FMRP alters synaptic plasticity. As synaptic plasticity has been implicated in learning and memory, analysis of synapse abnormalities in patients and Fmr1 knockout mice should prove useful in studying the pathogenesis of fragile X syndrome and understanding learning and cognition in general. If an appreciable portion of the total variance (in IQ) is due to sex linked genes, it is of more importance that a boy should have a clever mother than a clever father. Hogben 1932 (quoted in Lehrke 1974)
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Affiliation(s)
- William T O'Donnell
- Howard Hughes Medical Institute and Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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37
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Abstract
Fragile X syndrome results from the massive expansion of a CGG repeat in the 5' untranslated region of the gene FMR1. Data suggest that the hyperexpansion properties of FMR1 CGG repeats may depend on flanking cis-acting elements. We have therefore used homologous recombination in yeast to introduce an in situ CGG expansion corresponding to a premutation-sized allele into a human YAC carrying the FMR1 locus. Several transgenic lines were generated that carried repeats of varying lengths and amounts of flanking sequence. Length-dependent instability in the form of small expansions and contractions was observed in both male and female transmissions over five generations. No parent-of-origin effect or somatic instability was observed. Alterations in tract length were found to occur exclusively in the 3' uninterrupted CGG tract. Large expansion events indicative of a transition from a premutation to a full mutation were not observed. Overall, our results indicate both similarities and differences between the behavior of a premutation-sized repeat in mouse and that in human.
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Affiliation(s)
- Andrea M Peier
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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38
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Mingroni-Netto RC, Angeli CB, Auricchio MTBM, Leal-Mesquita ER, Ribeiro-dos-Santos AKC, Ferrari I, Hutz MH, Salzano FM, Hill K, Hurtado AM, Vianna-Morgante AM. Distribution of CGG repeats and FRAXAC1/DXS548 alleles in South American populations. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 111:243-52. [PMID: 12210320 DOI: 10.1002/ajmg.10572] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In order to assess the molecular variability related to fragile X (FMR1 locus), we investigated the distribution of CGG repeats and DXS548/FRAXAC1 haplotypes in normal South American populations of different ethnic backgrounds. Special attention was given to Amerindian Wai-Wai (Northern Brazil) and Ache (Paraguay), as well as to Brazilian isolated communities of African ancestry, the remnants of quilombos. Comparison of samples from quilombos, Amerindians, and the ethnically mixed, but mainly European-derived population of São Paulo revealed that the 30-copy allele of the fragile X gene is the most frequent in all groups. A second peak at 20 repeats was present in the population of São Paulo only, confirming this as a European peculiarity. The distribution of DXS548 and FRAXAC1 alleles led to a high expected heterozygosity in African Brazilians, followed by that observed in the population of São Paulo. Amerindians showed the lowest diversity in CGG repeats and DXS548/FRAXAC1 haplotypes. Some rare alleles, for example, the 148-bp (FRAXAC1) or 200-bp (DXS548) variants, which seem to be almost absent in Europe, occurred in higher frequencies among African Brazilians. This suggests a general trend for higher genetic diversity among Africans; these rarer alleles could be African in origin and would have been lost or possibly were not present in the groups that gave rise to the Europeans.
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39
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Tassone F, Hagerman RJ, Chamberlain WD, Hagerman PJ. Transcription of the FMR1 gene in individuals with fragile X syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 97:195-203. [PMID: 11449488 DOI: 10.1002/1096-8628(200023)97:3<195::aid-ajmg1037>3.0.co;2-r] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Fragile X syndrome generally arises as a consequence of a large expansion of a CGG trinucleotide repeat element that is located in the GC-rich promoter region of the fragile X mental retardation gene (FMR1). In the conventional model for fragile X, clinical involvement arises as a consequence of silencing of the FMR1 gene, with the attendant loss of FMR1 protein (FMRP). However, it has recently been demonstrated that most males with large premutation alleles (100-200 repeats), or with unmethylated full mutation alleles, have FMR1 mRNA levels that are higher than normal, despite reduced levels of FMRP. In the current work, we extend and confirm these observations using quantitative (fluorescent) reverse transcription polymerase chain reaction on larger sample populations, establishing that even for smaller premutation alleles (55-100 repeats) the mRNA levels are significantly elevated (mean 2.1-fold elevation; P = 3.9 x 10(-3)), relative to normal controls. Thus, an abnormal molecular phenotype is established close to the upper end of the normal range. We also demonstrate that the levels of FMR1 mRNA are elevated in females with premutation alleles; however, the mRNA levels are more varied than in the males, and are attenuated in a manner that is consistent with the fraction of normal alleles that are active in any given individual. Finally, we demonstrate that in lymphoblastoid cells derived from a patient with a severe form of fragile X caused by a point mutation in the second KH domain of the gene, but with a normal CGG element (25 repeats), the FMR1 mRNA level is normal. Thus, although models in which FMRP level (or level of function) modulates transcriptional activity remain viable, other explanations for the elevated message levels, including direct (cis) effects of the CGG element on transcription, must also be considered.
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Affiliation(s)
- F Tassone
- Department of Biochemistry and Molecular Genetics B-121, University of Colorado School of Medicine, 4200 East 9th Avenue, Denver, CO 80262, USA.
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40
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Abstract
Fragile X syndrome is almost always caused by the absence or deficit of the FMR1 protein (FMRP). Diagnostic methods include polymerase chain reaction and Southern blotting, which are performed on DNA isolated from peripheral leukocytes. Recently, different immunocytochemical tests have been described to identify patients with fragile X syndrome, based on the detection of FMRP in cells by a monoclonal antibody. This review aims to provide an update on the different antibody methods for prenatal and postnatal diagnosis of the fragile X syndrome.
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Affiliation(s)
- R Willemsen
- Department of Clinical Genetics, Erasmus University, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
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41
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Affiliation(s)
- R J Hagerman
- M.I.N.D. Institute and Department of Pediatrics, University of California at Davis Medical Center, Sacramento, California 95817, USA.
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42
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Wöhrle D, Salat U, Hameister H, Vogel W, Steinbach P. Demethylation, reactivation, and destabilization of human fragile X full-mutation alleles in mouse embryocarcinoma cells. Am J Hum Genet 2001; 69:504-15. [PMID: 11462172 PMCID: PMC1235481 DOI: 10.1086/322739] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2001] [Accepted: 06/19/2001] [Indexed: 12/14/2022] Open
Abstract
The major causes of fragile X syndrome are mutational expansion of the CGG repeat in the FMR1 gene, hypermethylation, and transcriptional silencing. Most fragile X embryos develop somatic mosaicism of disease-causing "full" expansions of different lengths. Homogeneity of the mosaic patterns among multiple tissues in the same individual indicates that these previously unstable expansions acquire mitotic stability early in fetal life. Since mitotic stability is found strictly associated with hypermethylation in adult tissues, current theory has fixed the time of instability to developmental stages when fully expanded CGG repeats exist in an unmethylated state. We used murine embryocarcinoma (EC) cells (PC13) as a model system of pluripotent embryonic cells. Hypermethylated and unmethylated full expansions on human fragile X chromosomes were transferred from murine A9 hybrids into EC cells, by means of microcell fusion. As demonstrated in the present study for the first time, even full expansion alleles that were fully methylated and stable in the donors' fibroblasts and in A9 became demethylated, reactivated, and destabilized in undifferentiated EC hybrids. When destabilized expansions were reintroduced from EC cells into A9, instability was reversed to stability. Our results strongly support the idea that fully expanded alleles are initially unstable and unmethylated in the human embryo and gain stability upon genetic or epigenetic change of the embryonic cells.
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Affiliation(s)
- D Wöhrle
- Department of Human Genetics, University Hospital of Ulm, 89073 Ulm, Germany
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44
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Tzountzouris J, Kennedy D, Skuterud M, Connolly-Wilson M, Holden JJ, Lin CC, Mak-Tam E, Somerville MJ, Summers AM, Allingham-Hawkins DJ. Apparently unstable normal FMR1 alleles in nine developmentally delayed patients: implications for molecular diagnosis of the fragile X syndrome. GENETIC TESTING 2001; 4:235-9. [PMID: 11142752 DOI: 10.1089/10906570050501434] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The Fragile X syndrome is a common form of X-linked mental retardation, affecting approximately 1 in 4,000 males. Since the discovery of the FMR1 gene responsible for the syndrome, molecular, rather than cytogenetic, diagnosis of Fragile X syndrome has become the gold standard. Numerous molecular diagnostic centers worldwide use PCR and Southern blotting to characterize the size of the CGG repeats within the gene, expansion of which has been shown to be associated with the vast majority of cases of Fragile X syndrome. Instability of this repeat through successive generations has been demonstrated in many patients and has been associated with numerous factors, including repeat length and molecular structure of the repeat. Nine males with normal-size alleles that exhibit repeat length instability by the presence of a second normal length distinct band by repeated PCR analysis from peripheral lymphocytes are reported. Many hypotheses addressing the reason for this apparent instability were tested without elucidating the underlying molecular causes, including cytogenetic analysis, sequence analysis of the repeat locus, and analysis of flanking dinucleotide repeat loci. All patients exhibited a normal complement of sex chromosomes by cytogenetic and molecular analysis. These results from the widely used PCR analysis illustrate an interesting molecular phenomenon and raise many questions relating to the factors and mechanisms involved in trinucleotide instability as well as having implications for the diagnostic testing of the Fragile X syndrome.
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Affiliation(s)
- J Tzountzouris
- Department of Genetics, North York General Hosptial, Toronto, Ontario, Canada
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Durán Domínguez M, Molina Carrillo M, Fernández Toral J, Martínez Merino T, López Arístegui M, Álvarez Retuerto A, Onaindía Urquijo M, Tejada Mínguez M. Diagnóstico molecular por reacción en cadena de la polimerasa del síndrome X frágil: aplicación de un protocolo diagnóstico en 50 familias del norte de España. An Pediatr (Barc) 2001. [DOI: 10.1016/s1695-4033(01)77539-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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46
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Salat U, Bardoni B, Wöhrle D, Steinbach P. Increase of FMRP expression, raised levels of FMR1 mRNA, and clonal selection in proliferating cells with unmethylated fragile X repeat expansions: a clue to the sex bias in the transmission of full mutations? J Med Genet 2000; 37:842-50. [PMID: 11073538 PMCID: PMC1734474 DOI: 10.1136/jmg.37.11.842] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Fragile X syndrome is a triplet repeat disorder caused by expansions of a CGG repeat in the fragile X mental retardation gene (FMR1) to more than 220 triplets (full mutation) that usually coincide with hypermethylation and transcriptional silencing. The disease phenotype results from deficiency or loss of FMR1 protein (FMRP) and occurs in both sexes. The underlying full mutations arise exclusively on transmission from a mother who carries a premutation allele (60-200 CGGs). While the absolute requirement of female transmission could result from different mechanisms, current evidence favours selection or contraction processes acting at gametogenesis of pre- and full mutation males. To address these questions experimentally, we used a model system of cultured fibroblasts from a male who presented heterogeneous unmethylated expansions in the pre- and full mutation size range. On continual cell proliferation to 30 doublings we re-examined the behaviour of the expanded repeats on Southern blots and also determined the expression of the FMR1 gene by FMRP immunocytochemistry, western analysis, and RT-PCR. With increasing population doublings, expansion patterns changed and showed accumulation of shorter alleles. The FMRP levels were below normal but increased continuously while the cells that were immunoreactive for FMRP accumulated. The level of FMR1 mRNA was raised with even higher levels of mRNA measured at higher passages. Current results support the theory of a selection advantage of FMRP positive over FMRP deficient cells. During extensive proliferation of spermatogonia in fragile X males, this selection mechanism would eventually replace all full mutations by shorter alleles allowing more efficient FMRP translation. At the proliferation of oogonia of carrier females, the same mechanism would, in theory, favour transmission of any expanded FMR1 allele on inactive X chromosomes.
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Affiliation(s)
- U Salat
- Department of Human Genetics, University Hospital, 89070 Ulm, Germany.
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Tassone F, Hagerman RJ, Loesch DZ, Lachiewicz A, Taylor AK, Hagerman PJ. Fragile X males with unmethylated, full mutation trinucleotide repeat expansions have elevated levels of FMR1 messenger RNA. AMERICAN JOURNAL OF MEDICAL GENETICS 2000; 94:232-6. [PMID: 10995510 DOI: 10.1002/1096-8628(20000918)94:3<232::aid-ajmg9>3.0.co;2-h] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Fragile X syndrome normally arises as a consequence of large expansions (n >200) of a (CGG)(n) trinucleotide repeat in the promoter region of the FMR1 gene. The clinical phenotype is thought to result from hypermethylation of the repeat and adjacent upstream elements, with consequent down-regulation of transcription (transcriptional silencing). However, the relationship between repeat expansion and transcription has not been defined in the full mutation range. Using the method of quantitative (fluorescence) reverse transcriptase polymerase chain reaction, we demonstrated previously that FMR1 mRNA levels are substantially elevated in premutation (55 </= n < 200) male carriers. In the current work, we report that in fragile X males with unmethylated alleles in the full mutation range (n > 200), FMR1 mRNA levels remain significantly elevated (mean 3.5-fold elevation; P = 6.7 x 10(-3)) relative to normal controls, even for alleles exceeding 300 repeats. This conclusion is independent of any assumption regarding the transcriptional activity of methylated alleles. However, if it were assumed that all methylated alleles were transcriptionally silent, the FMR1 mRNA levels for cells with unmethylated alleles would be even higher (mean 4.5-fold elevation; P = 2.1 x 10(-4)). These observations show that the full-mutation CGG expansion per se is not a strong impediment to transcription and that the apparent up-regulation of the FMR1 locus remains active in at least some cells with full-mutation alleles.
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Affiliation(s)
- F Tassone
- Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Crawford DC, Schwartz CE, Meadows KL, Newman JL, Taft LF, Gunter C, Brown WT, Carpenter NJ, Howard-Peebles PN, Monaghan KG, Nolin SL, Reiss AL, Feldman GL, Rohlfs EM, Warren ST, Sherman SL. Survey of the fragile X syndrome CGG repeat and the short-tandem-repeat and single-nucleotide-polymorphism haplotypes in an African American population. Am J Hum Genet 2000; 66:480-93. [PMID: 10677308 PMCID: PMC1288101 DOI: 10.1086/302762] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Previous studies have shown that specific short-tandem-repeat (STR) and single-nucleotide-polymorphism (SNP)-based haplotypes within and among unaffected and fragile X white populations are found to be associated with specific CGG-repeat patterns. It has been hypothesized that these associations result from different mutational mechanisms, possibly influenced by the CGG structure and/or cis-acting factors. Alternatively, haplotype associations may result from the long mutational history of increasing instability. To understand the basis of the mutational process, we examined the CGG-repeat size, three flanking STR markers (DXS548-FRAXAC1-FRAXAC2), and one SNP (ATL1) spanning 150 kb around the CGG repeat in unaffected (n=637) and fragile X (n=63) African American populations and compared them with unaffected (n=721) and fragile X (n=102) white populations. Several important differences were found between the two ethnic groups. First, in contrast to that seen in the white population, no associations were observed among the African American intermediate or "predisposed" alleles (41-60 repeats). Second, two previously undescribed haplotypes accounted for the majority of the African American fragile X population. Third, a putative "protective" haplotype was not found among African Americans, whereas it was found among whites. Fourth, in contrast to that seen in whites, the SNP ATL1 was in linkage equilibrium among African Americans, and it did not add new information to the STR haplotypes. These data indicate that the STR- and SNP-based haplotype associations identified in whites probably reflect the mutational history of the expansion, rather than a mutational mechanism or pathway.
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Affiliation(s)
- Dana C. Crawford
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Charles E. Schwartz
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Kellen L. Meadows
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - James L. Newman
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Lisa F. Taft
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Chris Gunter
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - W. Ted Brown
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Nancy J. Carpenter
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Patricia N. Howard-Peebles
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Kristin G. Monaghan
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Sarah L. Nolin
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Allan L. Reiss
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Gerald L. Feldman
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Elizabeth M. Rohlfs
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Stephen T. Warren
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
| | - Stephanie L. Sherman
- Departments of Genetics and Biochemistry, Emory University School of Medicine, and Howard Hughes Medical Institute, Atlanta; Greenwood Genetic Center, Greenwood, South Carolina; Genetics & IVF Institute, Fairfax, Virginia; Medical College of Virginia, Richmond; Department of Human Genetics, New York Staten Institute for Basic Research in Developmental Disabilities, Staten Island; Division of Child and Adolescent Psychiatry and Child Development, Departments of Psychiatry and Pediatrics, Stanford University School of Medicine, Stanford; Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill; Department of Medical Genetics, Henry Ford Hospital, Detroit; H. A. Chapman Institute of Medical Genetics, Tulsa
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Sermon K, Seneca S, Vanderfaeillie A, Lissens W, Joris H, Vandervorst M, Van Steirteghem A, Liebaers I. Preimplantation diagnosis for fragile X syndrome based on the detection of the non-expanded paternal and maternal CGG. Prenat Diagn 1999. [DOI: 10.1002/(sici)1097-0223(199912)19:13<1223::aid-pd724>3.0.co;2-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Nolin SL, Houck GE, Gargano AD, Blumstein H, Dobkin CS, Brown WT. FMR1 CGG-repeat instability in single sperm and lymphocytes of fragile-X premutation males. Am J Hum Genet 1999; 65:680-8. [PMID: 10441574 PMCID: PMC1377974 DOI: 10.1086/302543] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
To determine the meiotic instability of the CGG-triplet repeat in the fragile-X gene, FMR1, we examined the size of the repeat in single sperm from four premutation males. The males had CGG-repeat sizes of 68, 75, 78, and 100, as determined in peripheral blood samples. All samples showed a broad range of variations, with expansions more common than contractions. Examination of single lymphocytes indicated that somatic cells were relatively more stable than sperm. Surprisingly, the repeats in sperm from the 75- and 78-repeat males had very different size ranges and distribution patterns despite the similarity of the repeat size and AGG interruption in their somatic cells. These results suggest that cis or trans factors may have a role in male germline repeat instability.
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Affiliation(s)
- S L Nolin
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY 10314, USA.
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