1
|
Rajan-Babu IS, Dolzhenko E, Eberle MA, Friedman JM. Sequence composition changes in short tandem repeats: heterogeneity, detection, mechanisms and clinical implications. Nat Rev Genet 2024; 25:476-499. [PMID: 38467784 DOI: 10.1038/s41576-024-00696-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2024] [Indexed: 03/13/2024]
Abstract
Short tandem repeats (STRs) are a class of repetitive elements, composed of tandem arrays of 1-6 base pair sequence motifs, that comprise a substantial fraction of the human genome. STR expansions can cause a wide range of neurological and neuromuscular conditions, known as repeat expansion disorders, whose age of onset, severity, penetrance and/or clinical phenotype are influenced by the length of the repeats and their sequence composition. The presence of non-canonical motifs, depending on the type, frequency and position within the repeat tract, can alter clinical outcomes by modifying somatic and intergenerational repeat stability, gene expression and mutant transcript-mediated and/or protein-mediated toxicities. Here, we review the diverse structural conformations of repeat expansions, technological advances for the characterization of changes in sequence composition, their clinical correlations and the impact on disease mechanisms.
Collapse
Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada.
| | | | | | - Jan M Friedman
- Department of Medical Genetics, The University of British Columbia, and Children's & Women's Hospital, Vancouver, British Columbia, Canada
- BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada
| |
Collapse
|
2
|
Rodrigues B, Sousa V, Yrigollen CM, Tassone F, Villate O, Allen EG, Glicksman A, Tortora N, Nolin SL, Nogueira AJA, Jorge P. FMR1 allelic complexity in premutation carriers provides no evidence for a correlation with age at amenorrhea. Reprod Biol Endocrinol 2024; 22:71. [PMID: 38907244 PMCID: PMC11191145 DOI: 10.1186/s12958-024-01227-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 05/09/2024] [Indexed: 06/23/2024] Open
Abstract
BACKGROUND Premutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene, defined as between 55 and 200 CGGs, have been implicated in fragile X-associated primary ovarian insufficiency (FXPOI). Only 20% of female premutation carriers develop early ovulatory dysfunction, the reason for this incomplete penetrance is unknown. This study validated the mathematical model in premutation alleles, after assigning each allele a score representing allelic complexity. Subsequently, allelic scores were used to investigate the impact of allele complexity on age at amenorrhea for 58 premutation cases (116 alleles) previously published. METHODS The allelic score was determined using a formula previously described by our group. The impact of each allelic score on age at amenorrhea was analyzed using Pearson's test and a contour plot generated to visualize the effect. RESULTS Correlation of allelic score revealed two distinct complexity behaviors in premutation alleles. No significant correlation was observed between the allelic score of premutation alleles and age at amenorrhea. The same lack of significant correlation was observed regarding normal-sized alleles, despite a nearly significant trend. CONCLUSIONS Our results suggest that the use of allelic scores combination have the potential to explain female infertility, namely the development of FXPOI, or ovarian dysfunction, despite the lack of correlation with age at amenorrhea. Such a finding is of great clinical significance for early identification of females at risk of ovulatory dysfunction, enhancement of fertility preservation techniques, and increasing the probability for a successful pregnancy in females with premutations. Additional investigation is necessary to validate this hypothesis.
Collapse
Affiliation(s)
- Bárbara Rodrigues
- Molecular Genetics Laboratory, Laboratory Genetics Service, Genetics and Pathology Clinic, Unidade Local de Saúde de Santo António (ULSSA), Porto, Portugal
- UMIB - Unit for Multidisciplinary Research in Biomedicine, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal
| | - Vanessa Sousa
- Molecular Genetics Laboratory, Laboratory Genetics Service, Genetics and Pathology Clinic, Unidade Local de Saúde de Santo António (ULSSA), Porto, Portugal
- UMIB - Unit for Multidisciplinary Research in Biomedicine, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal
- Cytogenetics Laboratory, Department of Microscopy, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal
| | - Carolyn M Yrigollen
- Raymond G. Perelman Center for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Stockton Blvd, USA
- MIND Institute, School of Medicine, University of California, Davis, CA, USA
| | - Olatz Villate
- Pediatric Oncology Group, Biocruces Bizkaia Health Research Institute, Barakaldo, Biscay, Basque Country, Spain
| | - Emily G Allen
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
| | - Anne Glicksman
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY, USA
| | - Nicole Tortora
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY, USA
| | - Sarah L Nolin
- New York State Institute for Basic Research in Developmental Disabilities, New York, NY, USA
| | - António J A Nogueira
- CESAM - Center for Environmental and Marine Studies, Department of Biology, University of Aveiro, Aveiro, Portugal
| | - Paula Jorge
- Molecular Genetics Laboratory, Laboratory Genetics Service, Genetics and Pathology Clinic, Unidade Local de Saúde de Santo António (ULSSA), Porto, Portugal.
- UMIB - Unit for Multidisciplinary Research in Biomedicine, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal.
- ITR - Laboratory for Integrative and Translational Research in Population Health, Porto, Portugal.
- Cytogenetics Laboratory, Department of Microscopy, ICBAS - School of Medicine and Biomedical Sciences, UPorto - University of Porto, Porto, Portugal.
| |
Collapse
|
3
|
Pengo M, Squitieri F. Beyond CAG Repeats: The Multifaceted Role of Genetics in Huntington Disease. Genes (Basel) 2024; 15:807. [PMID: 38927742 PMCID: PMC11203031 DOI: 10.3390/genes15060807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 06/11/2024] [Accepted: 06/18/2024] [Indexed: 06/28/2024] Open
Abstract
Huntington disease (HD) is a dominantly inherited neurodegenerative disorder caused by a CAG expansion on the huntingtin (HTT) gene and is characterized by progressive motor, cognitive, and neuropsychiatric decline. Recently, new genetic factors besides CAG repeats have been implicated in the disease pathogenesis. Most genetic modifiers are involved in DNA repair pathways and, as the cause of the loss of CAA interruption in the HTT gene, they exert their main influence through somatic expansion. However, this mechanism might not be the only driver of HD pathogenesis, and future studies are warranted in this field. The aim of the present review is to dissect the many faces of genetics in HD pathogenesis, from cis- and trans-acting genetic modifiers to RNA toxicity, mitochondrial DNA mutations, and epigenetics factors. Exploring genetic modifiers of HD onset and progression appears crucial to elucidate not only disease pathogenesis, but also to improve disease prediction and prevention, develop biomarkers of disease progression and response to therapies, and recognize new therapeutic opportunities. Since the same genetic mechanisms are also described in other repeat expansion diseases, their implications might encompass the whole spectrum of these disorders.
Collapse
Affiliation(s)
- Marta Pengo
- Department of Molecular and Translational Medicine, University of Brescia, 25121 Brescia, Italy;
| | - Ferdinando Squitieri
- Centre for Neurological Rare Diseases (CMNR), Fondazione Lega Italiana Ricerca Huntington (LIRH), 00161 Rome, Italy
- Huntington and Rare Diseases Unit, IRCCS Casa Sollievo della Sofferenza, 71013 San Giovanni Rotondo, Italy
| |
Collapse
|
4
|
Currò R, Dominik N, Facchini S, Vegezzi E, Sullivan R, Galassi Deforie V, Fernández-Eulate G, Traschütz A, Rossi S, Garibaldi M, Kwarciany M, Taroni F, Brusco A, Good JM, Cavalcanti F, Hammans S, Ravenscroft G, Roxburgh RH, Parolin Schnekenberg R, Rugginini B, Abati E, Manini A, Quartesan I, Ghia A, Lòpez de Munaìn A, Manganelli F, Kennerson M, Santorelli FM, Infante J, Marques W, Jokela M, Murphy SM, Mandich P, Fabrizi GM, Briani C, Gosal D, Pareyson D, Ferrari A, Prados F, Yousry T, Khurana V, Kuo SH, Miller J, Troakes C, Jaunmuktane Z, Giunti P, Hartmann A, Basak N, Synofzik M, Stojkovic T, Hadjivassiliou M, Reilly MM, Houlden H, Cortese A. Role of the repeat expansion size in predicting age of onset and severity in RFC1 disease. Brain 2024; 147:1887-1898. [PMID: 38193360 PMCID: PMC11068103 DOI: 10.1093/brain/awad436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 12/04/2023] [Accepted: 12/10/2023] [Indexed: 01/10/2024] Open
Abstract
RFC1 disease, caused by biallelic repeat expansion in RFC1, is clinically heterogeneous in terms of age of onset, disease progression and phenotype. We investigated the role of the repeat size in influencing clinical variables in RFC1 disease. We also assessed the presence and role of meiotic and somatic instability of the repeat. In this study, we identified 553 patients carrying biallelic RFC1 expansions and measured the repeat expansion size in 392 cases. Pearson's coefficient was calculated to assess the correlation between the repeat size and age at disease onset. A Cox model with robust cluster standard errors was adopted to describe the effect of repeat size on age at disease onset, on age at onset of each individual symptoms, and on disease progression. A quasi-Poisson regression model was used to analyse the relationship between phenotype and repeat size. We performed multivariate linear regression to assess the association of the repeat size with the degree of cerebellar atrophy. Meiotic stability was assessed by Southern blotting on first-degree relatives of 27 probands. Finally, somatic instability was investigated by optical genome mapping on cerebellar and frontal cortex and unaffected peripheral tissue from four post-mortem cases. A larger repeat size of both smaller and larger allele was associated with an earlier age at neurological onset [smaller allele hazard ratio (HR) = 2.06, P < 0.001; larger allele HR = 1.53, P < 0.001] and with a higher hazard of developing disabling symptoms, such as dysarthria or dysphagia (smaller allele HR = 3.40, P < 0.001; larger allele HR = 1.71, P = 0.002) or loss of independent walking (smaller allele HR = 2.78, P < 0.001; larger allele HR = 1.60; P < 0.001) earlier in disease course. Patients with more complex phenotypes carried larger expansions [smaller allele: complex neuropathy rate ratio (RR) = 1.30, P = 0.003; cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) RR = 1.34, P < 0.001; larger allele: complex neuropathy RR = 1.33, P = 0.008; CANVAS RR = 1.31, P = 0.009]. Furthermore, larger repeat expansions in the smaller allele were associated with more pronounced cerebellar vermis atrophy (lobules I-V β = -1.06, P < 0.001; lobules VI-VII β = -0.34, P = 0.005). The repeat did not show significant instability during vertical transmission and across different tissues and brain regions. RFC1 repeat size, particularly of the smaller allele, is one of the determinants of variability in RFC1 disease and represents a key prognostic factor to predict disease onset, phenotype and severity. Assessing the repeat size is warranted as part of the diagnostic test for RFC1 expansion.
Collapse
Affiliation(s)
- Riccardo Currò
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| | - Natalia Dominik
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Stefano Facchini
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| | | | - Roisin Sullivan
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | | | - Gorka Fernández-Eulate
- Nord/Est/Ile-de-France Neuromuscular Reference Center, Institute of Myology, Pitié-Salpêtrière Hospital, APHP, 75013 Paris, France
| | - Andreas Traschütz
- Research Division ‘Translational Genomics of Neurodegenerative Diseases’, Hertie-Institute for Clinical Brain Research and Center of Neurology, University of Tübingen, 72076 Tübingen, Germany
- German Center for Neurodegenerative Diseases (DZNE), University of Tübingen, 72076 Tübingen, Germany
| | - Salvatore Rossi
- Dipartimento di Scienze dell'Invecchiamento, Neurologiche, Ortopediche e della Testa-Collo, UOC Neurologia, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168 Rome, Italy
- Facoltà di Medicina e Chirurgia, Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Matteo Garibaldi
- Neuromuscular and Rare Disease Center, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sant'Andrea Hospital, Sapienza University of Rome, 00189 Rome, Italy
| | - Mariusz Kwarciany
- Department of Adult Neurology, Medical University of Gdańsk, 80-952 Gdańsk, Poland
| | - Franco Taroni
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20133, Italy
| | - Alfredo Brusco
- Department of Medical Sciences, University of Torino, 10124 Turin, Italy
| | - Jean-Marc Good
- Division of Genetic Medicine, Lausanne University Hospital (CHUV), 1011 Lausanne, Switzerland
| | - Francesca Cavalcanti
- Institute for Biomedical Research and Innovation (IRIB), Italian National Research Council (CNR), 87050 Mangone, Italy
| | - Simon Hammans
- Wessex Neurological Centre, Southampton General Hospital, Southampton, SO16 6YD, UK
| | - Gianina Ravenscroft
- Neurogenetic Diseases Group, Centre for Medical Research, QEII Medical Centre, University of Western Australia, Nedland, WA 6009, Australia
| | - Richard H Roxburgh
- Neurology Department, Auckland City Hospital, New Zealand and the Centre for Brain Research, University of Auckland, Auckland 1142, New Zealand
| | | | - Bianca Rugginini
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| | - Elena Abati
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
- Department of Pathophysiology and Transplantation, University of Milan, 20122 Milan, Italy
| | - Arianna Manini
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
- Department of Pathophysiology and Transplantation, University of Milan, 20122 Milan, Italy
| | - Ilaria Quartesan
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| | - Arianna Ghia
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| | - Adolfo Lòpez de Munaìn
- Neurology Department, Donostia University Hospital, University of the Basque Country-Osakidetza-CIBERNED-Biodonostia, 20014 Donostia-San Sebastián, Spain
| | - Fiore Manganelli
- Department of Neuroscience and Reproductive and Odontostomatological Sciences, University of Naples Federico II, 80131 Naples, Italy
| | - Marina Kennerson
- Sydney Medical School, Faculty of Medicine and Health, University of Sydney, Sydney, NSW 2050, Australia
| | - Filippo Maria Santorelli
- IRCCS Stella Maris Foundation, Molecular Medicine for Neurodegenerative and Neuromuscular Disease Unit, 56128 Pisa, Italy
| | - Jon Infante
- University Hospital Marquès de Valdecilla-IDIVAL, University of Cantabria, 39008 Santander, Spain
| | - Wilson Marques
- Department of Neurology, School of Medicine of Ribeirão Preto, University of São Paulo, 2650 Ribeirão Preto, Brazil
| | - Manu Jokela
- Neuromuscular Research Center, Department of Neurology, Tampere University and University Hospital, 33520 Tampere, Finland
- Neurocenter, Department of Neurology, Clinical Neurosciences, Turku University Hospital and University of Turku, 20014 Turku, Finland
| | - Sinéad M Murphy
- Department of Neurology, Tallaght University Hospital, D24 NR0A Dublin, Ireland
- Academic Unit of Neurology, Trinity College Dublin, D02 R590 Dublin, Ireland
| | - Paola Mandich
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, 16132 Genoa, Italy
- IRCCS Ospedale Policlinico San Martino-UOC Genetica Medica, 16132 Genova, Italy
| | - Gian Maria Fabrizi
- Department of Neurosciences, Biomedicine, and Movement Sciences, University of Verona, 37134 Verona, Italy
| | - Chiara Briani
- Department of Neurosciences, ERN Neuromuscular Unit, University of Padova, 35100 Padova, Italy
| | - David Gosal
- Manchester Centre for Clinical Neurosciences, Salford Royal Hospital, Northern Care Alliance NHS Foundation Trust, Greater Manchester, M6 8HD, UK
| | - Davide Pareyson
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan 20133, Italy
| | | | - Ferran Prados
- Centre for Medical Image Computing (CMIC), Department of Medical Physics and Biomedical Engineering, University College London, London, WC1V 6LJ, UK
- NMR Research Unit, Institute of Neurology, University College London (UCL), London, WC1N 3BG, UK
- e-Health Centre, Universitat Oberta de Catalunya, 08018 Barcelona, Spain
| | - Tarek Yousry
- Neuroradiological Academic Unit, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Vikram Khurana
- Division of Movement Disorders and Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Sheng-Han Kuo
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - James Miller
- Department of Neurology, Royal Victoria Hospitals, The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle, NE1 4LP, UK
| | - Claire Troakes
- London Neurodegenerative Diseases Brain Bank, Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, SE21 8EA, UK
| | - Zane Jaunmuktane
- Department of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Paola Giunti
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Annette Hartmann
- Division of General Psychiatry, Medical University of Vienna, 1090 Vienna, Austria
| | - Nazli Basak
- Koç University, School of Medicine, Suna and İnan Kıraç Foundation, Neurodegeneration Research Laboratory (NDAL), Research Center for Translational Medicine, 34010 Istanbul, Turkey
| | - Matthis Synofzik
- Research Division ‘Translational Genomics of Neurodegenerative Diseases’, Hertie-Institute for Clinical Brain Research and Center of Neurology, University of Tübingen, 72076 Tübingen, Germany
- German Center for Neurodegenerative Diseases (DZNE), University of Tübingen, 72076 Tübingen, Germany
| | - Tanya Stojkovic
- Nord/Est/Ile-de-France Neuromuscular Reference Center, Institute of Myology, Pitié-Salpêtrière Hospital, APHP, 75013 Paris, France
| | - Marios Hadjivassiliou
- Academic Department of Neurosciences, Sheffield Teaching Hospitals NHS Trust and University of Sheffield, Sheffield, S10 2JF, UK
| | - Mary M Reilly
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Henry Houlden
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Andrea Cortese
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy
| |
Collapse
|
5
|
Randol JL, Kim K, Ponzini MD, Tassone F, Falcon AK, Hagerman RJ, Hagerman PJ. Variation of FMRP Expression in Peripheral Blood Mononuclear Cells from Individuals with Fragile X Syndrome. Genes (Basel) 2024; 15:356. [PMID: 38540415 PMCID: PMC10969917 DOI: 10.3390/genes15030356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/02/2024] [Accepted: 03/08/2024] [Indexed: 04/07/2024] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and autism spectrum disorder. The syndrome is often caused by greatly reduced or absent protein expression from the fragile X messenger ribonucleoprotein 1 (FMR1) gene due to expansion of a 5'-non-coding trinucleotide (CGG) element beyond 200 repeats (full mutation). To better understand the complex relationships among FMR1 allelotype, methylation status, mRNA expression, and FMR1 protein (FMRP) levels, FMRP was quantified in peripheral blood mononuclear cells for a large cohort of FXS (n = 154) and control (n = 139) individuals using time-resolved fluorescence resonance energy transfer. Considerable size and methylation mosaicism were observed among individuals with FXS, with FMRP detected only in the presence of such mosaicism. No sample with a minimum allele size greater than 273 CGG repeats had significant levels of FMRP. Additionally, an association was observed between FMR1 mRNA and FMRP levels in FXS samples, predominantly driven by those with the lowest FMRP values. This study underscores the complexity of FMR1 allelotypes and FMRP expression and prompts a reevaluation of FXS therapies aimed at reactivating large full mutation alleles that are likely not capable of producing sufficient FMRP to improve cognitive function.
Collapse
Affiliation(s)
- Jamie L. Randol
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Kyoungmi Kim
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Matthew D. Ponzini
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
| | - Alexandria K. Falcon
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Randi J. Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Pediatrics, School of Medicine, University of California, Davis, Sacramento, CA 95817, USA
| | - Paul J. Hagerman
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
| |
Collapse
|
6
|
Hnoonual A, Plong-On O, Worachotekamjorn J, Charalsawadi C, Limprasert P. Clinical and molecular characteristics of FMR1 microdeletion in patient with fragile X syndrome and review of the literature. Clin Chim Acta 2024; 553:117728. [PMID: 38142803 DOI: 10.1016/j.cca.2023.117728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/09/2023] [Accepted: 12/16/2023] [Indexed: 12/26/2023]
Abstract
BACKGROUND Fragile X syndrome (FXS) is mainly caused by FMR1 CGG repeat expansions. Other types of mutations, particularly deletions, are also responsible for FXS phenotypes, however these mutations are often missed by routine clinical testing. MATERIALS AND METHODS Molecular diagnosis in cases of suspected FXS was a combination of PCR and Southern blot. Measurement of the FMRP protein level was useful for detecting potentially deleterious impact. RESULTS PCR analysis and Southern blot revealed a case with premutation and suspected deletion alleles. Sanger sequencing showed that the deletion involved 313 bp upstream of repeats and some parts of CGG repeat tract, leaving transcription start site. FMRP was detected in 5.5 % of blood lymphocytes. CONCLUSION According to our review of case reports, most patients carrying microdeletion and full mutation had typical features of FXS. To our knowledge, our case is the first to describe mosaicism of a premutation and microdeletion in the FMR1 gene. The patient was probably protected from the effects of the deletion by mosaicism with premutation allele, leading to milder phenotype. It is thus important to consider appropriate techniques for detecting FMR1 variants other than repeat expansions which cannot be detected by routine FXS diagnosis.
Collapse
Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Oradawan Plong-On
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | | | - Chariyawan Charalsawadi
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
| |
Collapse
|
7
|
Méreaux JL, Davoine CS, Pellerin D, Coarelli G, Coutelier M, Ewenczyk C, Monin ML, Anheim M, Le Ber I, Thobois S, Gobert F, Guillot-Noël L, Forlani S, Jornea L, Heinzmann A, Sangare A, Gaymard B, Guyant-Maréchal L, Charles P, Marelli C, Honnorat J, Degos B, Tison F, Sangla S, Simonetta-Moreau M, Salachas F, Tchikviladzé M, Castelnovo G, Mochel F, Klebe S, Castrioto A, Fenu S, Méneret A, Bourdain F, Wandzel M, Roth V, Bonnet C, Riant F, Stevanin G, Noël S, Fauret-Amsellem AL, Bahlo M, Lockhart PJ, Brais B, Renaud M, Brice A, Durr A. Clinical and genetic keys to cerebellar ataxia due to FGF14 GAA expansions. EBioMedicine 2024; 99:104931. [PMID: 38150853 PMCID: PMC10784672 DOI: 10.1016/j.ebiom.2023.104931] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/26/2023] [Accepted: 12/06/2023] [Indexed: 12/29/2023] Open
Abstract
BACKGROUND SCA27B caused by FGF14 intronic heterozygous GAA expansions with at least 250 repeats accounts for 10-60% of cases with unresolved cerebellar ataxia. We aimed to assess the size and frequency of FGF14 expanded alleles in individuals with cerebellar ataxia as compared with controls and to characterize genetic and clinical variability. METHODS We sized this repeat in 1876 individuals from France sampled for research purposes in this cross-sectional study: 845 index cases with cerebellar ataxia and 324 affected relatives, 475 controls, as well as 119 cases with spastic paraplegia, and 113 with familial essential tremor. FINDINGS A higher frequency of expanded allele carriers in index cases with ataxia was significant only above 300 GAA repeats (10.1%, n = 85) compared with controls (1.1%, n = 5) (p < 0.0001) whereas GAA250-299 alleles were detected in 1.7% of both groups. Eight of 14 index cases with GAA250-299 repeats had other causal pathogenic variants (4/14) and/or discordance of co-segregation (5/14), arguing against GAA causality. We compared the clinical signs in 127 GAA≥300 carriers to cases with non-expanded GAA ataxia resulting in defining a key phenotype triad: onset after 45 years, downbeat nystagmus, episodic ataxic features including diplopia; and a frequent absence of dysarthria. All maternally transmitted alleles above 100 GAA were unstable with a median expansion of +18 repeats per generation (r2 = 0.44; p < 0.0001). In comparison, paternally transmitted alleles above 100 GAA mostly decreased in size (-15 GAA (r2 = 0.63; p < 0.0001)), resulting in the transmission bias observed in SCA27B pedigrees. INTERPRETATION SCA27B diagnosis must consider both the phenotype and GAA expansion size. In carriers of GAA250-299 repeats, the absence of documented familial transmission and a presentation deviating from the key SCA27B phenotype, should prompt the search for an alternative cause. Affected fathers have a reduced risk of having affected children, which has potential implications for genetic counseling. FUNDING This work was supported by the Fondation pour la Recherche Médicale, grant number 13338 to JLM, the Association Connaître les Syndrome Cérébelleux - France (to GS) and by the European Union's Horizon 2020 research and innovation program under grant agreement No 779257 ("SOLVE-RD" to GS). DP holds a Fellowship award from the Canadian Institutes of Health Research (CIHR). SK received a grant (01GM1905C) from the Federal Ministry of Education and Research, Germany, through the TreatHSP network. This work was supported by the Australian Government National Health and Medical Research Council grants (GNT2001513 and MRFF2007677) to MB and PJL.
Collapse
Affiliation(s)
- Jean-Loup Méreaux
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Claire-Sophie Davoine
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - David Pellerin
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, QC, Canada; Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and the National Hospital for Neurology and Neurosurgery, University College London, London, United Kingdom
| | - Giulia Coarelli
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Unité de Génétique Clinique, AP-HP, Hôpital Pitié-Salpêtrière, Paris, France
| | - Marie Coutelier
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Claire Ewenczyk
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Unité de Génétique Clinique, AP-HP, Hôpital Pitié-Salpêtrière, Paris, France
| | - Marie-Lorraine Monin
- Centre de Reference Maladies Rares « Neurogénétique », Service de Génétique Médicale, Bordeaux University Hospital (CHU Bordeaux), 33000, Bordeaux, France
| | - Mathieu Anheim
- Department of Neurology, Strasbourg University Hospital, 67098, Strasbourg, France; Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), INSERM-U964, CNRS-UMR7104, University of Strasbourg, 67400, Illkirch-Graffenstaden, France
| | - Isabelle Le Ber
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Stéphane Thobois
- Department of Neurology C, Expert Parkinson Centre NS-Park/F-CRIN, Hospices Civils de Lyon, Pierre Wertheimer Neurological Hospital, 69677, Bron, France; Marc Jeannerod Cognitive Neuroscience Institute, CNRS, UMR 5229, Bron, France; Faculté de Médecine Et de Maïeutique Lyon Sud Charles Mérieux, Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France
| | - Florent Gobert
- Neuro-Intensive Care Unit, Hospices Civils de Lyon, Neurological Hospital Pierre-Wertheimer, Lyon, France; University Lyon I, Villeurbanne, France
| | - Léna Guillot-Noël
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Sylvie Forlani
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Ludmila Jornea
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Anna Heinzmann
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Aude Sangare
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Department of Neurophysiology, University Hospital Group APHP-Sorbonne University, Pitié-Salpêtrière Site, Paris, France
| | - Bertrand Gaymard
- Department of Neurophysiology, University Hospital Group APHP-Sorbonne University, Pitié-Salpêtrière Site, Paris, France
| | - Lucie Guyant-Maréchal
- Neurophysiology Department, Rouen University Hospital, Rouen, France; Medical Genetics Department, Rouen University Hospital, Rouen, France
| | - Perrine Charles
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Unité de Génétique Clinique, AP-HP, Hôpital Pitié-Salpêtrière, Paris, France
| | - Cecilia Marelli
- MMDN, University Montpellier, EPHE, INSERM and Expert Center for Neurogenetic Diseases, CHU, 34095, Montpellier, France
| | - Jérôme Honnorat
- Reference Center for Paraneoplastic Neurological Syndromes and Autoimmune Encephalitis, Hospices Civils de Lyon, MeLiS Institute UMR CNRS 5284 - INSERM U1314, Université Claude Bernard Lyon 1, Lyon, France
| | - Bertrand Degos
- Neurology Department, Avicenne Hospital, APHP, Hôpitaux Universitaires de Paris-Seine Saint Denis (HUPSSD), Sorbonne Paris Nord, Réseau NS-PARK/FCRIN, Bobigny, France
| | - François Tison
- Institut des Maladies Neurodégénératives-Clinique (IMNc), University Hospital Bordeaux, Bordeaux, France; Institut des Maladies Neurodégénératives, CNRS, UMR 5293, Bordeaux University, Bordeaux, France
| | - Sophie Sangla
- Neurology Department, Hôpital Fondation Adolphe de Rothschild, Paris, France
| | - Marion Simonetta-Moreau
- Department of Neurology, University Hospital of Toulouse, 31300, Toulouse, France; Toulouse NeuroImaging Center (ToNIC), Inserm, UPS, Université de Toulouse, 31024, Toulouse, France; Clinical Investigation Center (CIC 1436), Toulouse University Hospital, INSERM, 31059, Toulouse, France
| | - François Salachas
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Département de Neurologie, Assistance Publique Hôpitaux de Paris (APHP), Centre de Référence SLA Ile de France, Hôpital de la Pitié-Salpêtrière, Paris, France
| | - Maya Tchikviladzé
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Giovanni Castelnovo
- Department of Neurology, Nîmes University Hospital, Hopital Caremeau, Nîmes, France
| | - Fanny Mochel
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Stephan Klebe
- Department of Neurology, University Hospital Essen, Essen, Germany
| | - Anna Castrioto
- Univ. Grenoble Alpes, Inserm, U1216, CHU Grenoble Alpes, Grenoble Institut Neurosciences, Neurology Department, 38000, Grenoble, France
| | - Silvia Fenu
- Unit of Rare Neurological Diseases, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Aurélie Méneret
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Département de Neurologie, Hôpital de la Pitié-Salpêtrière, Assistance Publique Hôpitaux de Paris (APHP), Paris, France
| | - Frédéric Bourdain
- Service de Neurologie, Centre Hospitalier de la Côte Basque, Bayonne, France
| | - Marion Wandzel
- Laboratoire de Génétique Médicale, CHRU Nancy, Université de Lorraine, INSERM UMR_S1256, NGERE, Nancy, France
| | - Virginie Roth
- Laboratoire de Génétique Médicale, CHRU Nancy, Université de Lorraine, INSERM UMR_S1256, NGERE, Nancy, France
| | - Céline Bonnet
- Laboratoire de Génétique Médicale, CHRU Nancy, Université de Lorraine, INSERM UMR_S1256, NGERE, Nancy, France
| | - Florence Riant
- Service de Génétique Moléculaire Neurovasculaire, AP-HP, Saint Louis Hospital, Paris, France
| | - Giovanni Stevanin
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Bordeaux University (Université de Bordeaux), Equipe « Neurogénétique Translationnelle - NRGEN », INCIA CNRS UMR5287, EPHE, 33000, Bordeaux, France
| | - Sandrine Noël
- Unité de Neurogénétique Moléculaire et Cellulaire, AP-HP, Hôpital Pitié-Salpêtrière, Paris, France
| | | | - Melanie Bahlo
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Paul J Lockhart
- Bruce Lefroy Centre, Murdoch Children's Research Institute and Department of Paediatrics, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Bernard Brais
- Department of Neurology and Neurosurgery, Montreal Neurological Hospital and Institute, McGill University, Montreal, QC, Canada
| | - Mathilde Renaud
- Service de Génétique Clinique et de Neurologie, Hôpital Brabois, Nancy, France; INSERM Unité 1256 N-GERE (Nutrition-Genetics and Environmental Risk Exposure), Université de Lorraine, Nancy, France
| | - Alexis Brice
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France
| | - Alexandra Durr
- Sorbonne Université, Paris Brain Institute - ICM, Inserm, CNRS, AP-HP, Paris, France; Unité de Génétique Clinique, AP-HP, Hôpital Pitié-Salpêtrière, Paris, France.
| |
Collapse
|
8
|
Edwards N, Combrinck C, McCaughey-Chapman A, Connor B. Directly reprogrammed fragile X syndrome dorsal forebrain precursor cells generate cortical neurons exhibiting impaired neuronal maturation. Front Cell Neurosci 2023; 17:1254412. [PMID: 37810261 PMCID: PMC10552551 DOI: 10.3389/fncel.2023.1254412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 09/01/2023] [Indexed: 10/10/2023] Open
Abstract
Introduction The neurodevelopmental disorder fragile X syndrome (FXS) is the most common monogenic cause of intellectual disability associated with autism spectrum disorder. Inaccessibility to developing human brain cells is a major barrier to studying FXS. Direct-to-neural precursor reprogramming provides a unique platform to investigate the developmental profile of FXS-associated phenotypes throughout neural precursor and neuron generation, at a temporal resolution not afforded by post-mortem tissue and in a patient-specific context not represented in rodent models. Direct reprogramming also circumvents the protracted culture times and low efficiency of current induced pluripotent stem cell strategies. Methods We have developed a chemically modified mRNA (cmRNA) -based direct reprogramming protocol to generate dorsal forebrain precursors (hiDFPs) from FXS patient-derived fibroblasts, with subsequent differentiation to glutamatergic cortical neurons and astrocytes. Results We observed differential expression of mature neuronal markers suggesting impaired neuronal development and maturation in FXS- hiDFP-derived neurons compared to controls. FXS- hiDFP-derived cortical neurons exhibited dendritic growth and arborization deficits characterized by reduced neurite length and branching consistent with impaired neuronal maturation. Furthermore, FXS- hiDFP-derived neurons exhibited a significant decrease in the density of pre- and post- synaptic proteins and reduced glutamate-induced calcium activity, suggesting impaired excitatory synapse development and functional maturation. We also observed a reduced yield of FXS- hiDFP-derived neurons with a significant increase in FXS-affected astrocytes. Discussion This study represents the first reported derivation of FXS-affected cortical neurons following direct reprogramming of patient fibroblasts to dorsal forebrain precursors and subsequently neurons that recapitulate the key molecular hallmarks of FXS as it occurs in human tissue. We propose that direct to hiDFP reprogramming provides a unique platform for further study into the pathogenesis of FXS as well as the identification and screening of new drug targets for the treatment of FXS.
Collapse
Affiliation(s)
| | | | | | - Bronwen Connor
- Department of Pharmacology and Clinical Pharmacology, Centre for Brain Research, School of Medical Science, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| |
Collapse
|
9
|
Chubick A, Wang E, Au C, Grody WW, Ophoff RA. Large-Scale Whole Genome Sequence Analysis of >22,000 Subjects Provides no Evidence of FMR1 Premutation Allele Involvement in Autism Spectrum Disorder. Genes (Basel) 2023; 14:1518. [PMID: 37628570 PMCID: PMC10454383 DOI: 10.3390/genes14081518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 07/17/2023] [Accepted: 07/21/2023] [Indexed: 08/27/2023] Open
Abstract
Expansion of a CGG repeat in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene on the X chromosome is the cause of Fragile X Syndrome (FXS). The repeat length of unaffected individuals varies between 5-40 repeats, whereas >200 repeats are observed in cases of FXS. The intermediate range between 55-200 repeats is considered the premutation range and is observed in roughly 1:300 females and 1:900 males in the general population. With the availability of large-scale whole genome sequence (WGS) data and the development of computational tools to detect repeat expansions, we systematically examined the role of FMR1 premutation alleles in autism spectrum disorder (ASD) susceptibility, assess the prevalence, and consider the allelic stability between parents and offspring. We analyzed the WGS data of 22,053 subjects, including 32 FXS positive controls, 1359 population controls, and 5467 ASD families. We observed no FMR1 full mutation range repeats among the ASD parent-offspring families but identified 180 family members with premutation range alleles, which represents a higher prevalence compared to the independent WGS control sample and previous reports in the literature. A sex-specific analysis between probands and unaffected siblings did not reveal a significant increase in the burden of premutation alleles in either males or females with ASD. PCR validation, however, suggests an overestimation of the frequency of FMR1 premutation range alleles through computational analysis of WGS data. Overall, we show the utility of large-scale repeat expansion screening in WGS data and conclude that there is no apparent evidence of FMR1 premutation alleles contributing to ASD susceptibility.
Collapse
Affiliation(s)
- Alex Chubick
- Department of Human Genetics, University of California Los Angeles, Los Angeles, CA 90095, USA (W.W.G.)
| | - Evan Wang
- Center for Neurobehavioral Genetics, Jane and Terry Semel Institute for Neuroscience and Human Behavior Los Angeles, University of California Los Angeles, Los Angeles, CA 90024, USA;
| | - Cora Au
- Department of Pathology & Laboratory Medicine, University of California Los Angeles, Los Angeles, CA 90024, USA;
| | - Wayne W. Grody
- Department of Human Genetics, University of California Los Angeles, Los Angeles, CA 90095, USA (W.W.G.)
- Department of Pathology & Laboratory Medicine, University of California Los Angeles, Los Angeles, CA 90024, USA;
- Department of Pediatrics, University of California Los Angeles, Los Angeles, CA 90024, USA
| | - Roel A. Ophoff
- Department of Human Genetics, University of California Los Angeles, Los Angeles, CA 90095, USA (W.W.G.)
- Center for Neurobehavioral Genetics, Jane and Terry Semel Institute for Neuroscience and Human Behavior Los Angeles, University of California Los Angeles, Los Angeles, CA 90024, USA;
- Department of Psychiatry, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands
| |
Collapse
|
10
|
Ciobanu CG, Nucă I, Popescu R, Antoci LM, Caba L, Ivanov AV, Cojocaru KA, Rusu C, Mihai CT, Pânzaru MC. Narrative Review: Update on the Molecular Diagnosis of Fragile X Syndrome. Int J Mol Sci 2023; 24:ijms24119206. [PMID: 37298158 DOI: 10.3390/ijms24119206] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 04/30/2023] [Accepted: 05/20/2023] [Indexed: 06/12/2023] Open
Abstract
The diagnosis and management of fragile X syndrome (FXS) have significantly improved in the last three decades, although the current diagnostic techniques are not yet able to precisely identify the number of repeats, methylation status, level of mosaicism, and/or the presence of AGG interruptions. A high number of repeats (>200) in the fragile X messenger ribonucleoprotein 1 gene (FMR1) results in hypermethylation of promoter and gene silencing. The actual molecular diagnosis is performed using a Southern blot, TP-PCR (Triplet-Repeat PCR), MS-PCR (Methylation-Specific PCR), and MS-MLPA (Methylation-Specific MLPA) with some limitations, with multiple assays being necessary to completely characterise a patient with FXS. The actual gold standard diagnosis uses Southern blot; however, it cannot accurately characterise all cases. Optical genome mapping is a new technology that has also been developed to approach the diagnosis of fragile X syndrome. Long-range sequencing represented by PacBio and Oxford Nanopore has the potential to replace the actual diagnosis and offers a complete characterization of molecular profiles in a single test. The new technologies have improved the diagnosis of fragile X syndrome and revealed unknown aberrations, but they are a long way from being used routinely in clinical practice.
Collapse
Affiliation(s)
- Cristian-Gabriel Ciobanu
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Irina Nucă
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
- Investigatii Medicale Praxis, St. Moara de Vant No 35, 700376 Iasi, Romania
| | - Roxana Popescu
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
- Medical Genetics Department, "Saint Mary" Emergency Children's Hospital, St. Vasile Lupu No 62, 700309 Iasi, Romania
| | - Lucian-Mihai Antoci
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Lavinia Caba
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Anca Viorica Ivanov
- Pediatrics Department, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Karina-Alexandra Cojocaru
- Department of Biochemistry, Faculty of Dental Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
| | - Cristina Rusu
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
- Medical Genetics Department, "Saint Mary" Emergency Children's Hospital, St. Vasile Lupu No 62, 700309 Iasi, Romania
| | | | - Monica-Cristina Pânzaru
- Medical Genetics Department, Faculty of Medicine, "Grigore T. Popa" University of Medicine and Pharmacy, University Street No 16, 700115 Iasi, Romania
- Medical Genetics Department, "Saint Mary" Emergency Children's Hospital, St. Vasile Lupu No 62, 700309 Iasi, Romania
| |
Collapse
|
11
|
Ryan NM, Heron EA. Evidence for parent-of-origin effects in autism spectrum disorder: a narrative review. J Appl Genet 2023; 64:303-317. [PMID: 36710277 PMCID: PMC10076404 DOI: 10.1007/s13353-022-00742-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/08/2022] [Accepted: 12/15/2022] [Indexed: 01/31/2023]
Abstract
Autism spectrum disorder (ASD) is a heterogeneous group of early-onset neurodevelopmental disorders known to be highly heritable with a complex genetic architecture. Abnormal brain developmental trajectories that impact synaptic functioning, excitation-inhibition balance and brain connectivity are now understood to play a central role in ASD. Ongoing efforts to identify the genetic underpinnings still prove challenging, in part due to phenotypic and genetic heterogeneity.This review focuses on parent-of-origin effects (POEs), where the phenotypic effect of an allele depends on its parental origin. POEs include genomic imprinting, transgenerational effects, mitochondrial DNA, sex chromosomes and mutational transmission bias. The motivation for investigating these mechanisms in ASD has been driven by their known impacts on early brain development and brain functioning, in particular for the most well-documented POE, genomic imprinting. Moreover, imprinting is implicated in syndromes such as Angelman and Prader-Willi, which frequently share comorbid symptoms with ASD. In addition to other regions in the genome, this comprehensive review highlights the 15q11-q13 and 7q chromosomal regions as well as the mitochondrial DNA as harbouring the majority of currently identified POEs in ASD.
Collapse
Affiliation(s)
- Niamh M Ryan
- Neuropsychiatric Genetics Research Group, Department of Psychiatry, Trinity College Dublin, Dublin, Ireland
| | - Elizabeth A Heron
- Neuropsychiatric Genetics Research Group, Department of Psychiatry, Trinity College Dublin, Dublin, Ireland.
| |
Collapse
|
12
|
Bypassing Mendel's First Law: Transmission Ratio Distortion in Mammals. Int J Mol Sci 2023; 24:ijms24021600. [PMID: 36675116 PMCID: PMC9863905 DOI: 10.3390/ijms24021600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/15/2023] Open
Abstract
Mendel's law of segregation states that the two alleles at a diploid locus should be transmitted equally to the progeny. A genetic segregation distortion, also referred to as transmission ratio distortion (TRD), is a statistically significant deviation from this rule. TRD has been observed in several mammal species and may be due to different biological mechanisms occurring at diverse time points ranging from gamete formation to lethality at post-natal stages. In this review, we describe examples of TRD and their possible mechanisms in mammals based on current knowledge. We first focus on the differences between TRD in male and female gametogenesis in the house mouse, in which some of the most well studied TRD systems have been characterized. We then describe known TRD in other mammals, with a special focus on the farmed species and in the peculiar common shrew species. Finally, we discuss TRD in human diseases. Thus far, to our knowledge, this is the first time that such description is proposed. This review will help better comprehend the processes involved in TRD. A better understanding of these molecular mechanisms will imply a better comprehension of their impact on fertility and on genome evolution. In turn, this should allow for better genetic counseling and lead to better care for human families.
Collapse
|
13
|
Yousuf A, Ahmed N, Qurashi A. Non-canonical DNA/RNA structures associated with the pathogenesis of Fragile X-associated tremor/ataxia syndrome and Fragile X syndrome. Front Genet 2022; 13:866021. [PMID: 36110216 PMCID: PMC9468596 DOI: 10.3389/fgene.2022.866021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 07/22/2022] [Indexed: 11/13/2022] Open
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) and fragile X syndrome (FXS) are primary examples of fragile X-related disorders (FXDs) caused by abnormal expansion of CGG repeats above a certain threshold in the 5′-untranslated region of the fragile X mental retardation (FMR1) gene. Both diseases have distinct clinical manifestations and molecular pathogenesis. FXTAS is a late-adult-onset neurodegenerative disorder caused by a premutation (PM) allele (CGG expansion of 55–200 repeats), resulting in FMR1 gene hyperexpression. On the other hand, FXS is a neurodevelopmental disorder that results from a full mutation (FM) allele (CGG expansions of ≥200 repeats) leading to heterochromatization and transcriptional silencing of the FMR1 gene. The main challenge is to determine how CGG repeat expansion affects the fundamentally distinct nature of FMR1 expression in FM and PM ranges. Abnormal CGG repeat expansions form a variety of non-canonical DNA and RNA structures that can disrupt various cellular processes and cause distinct effects in PM and FM alleles. Here, we review these structures and how they are related to underlying mutations and disease pathology in FXS and FXTAS. Finally, as new CGG expansions within the genome have been identified, it will be interesting to determine their implications in disease pathology and treatment.
Collapse
|
14
|
Hwang YH, Hayward BE, Zafarullah M, Kumar J, Durbin Johnson B, Holmans P, Usdin K, Tassone F. Both cis and trans-acting genetic factors drive somatic instability in female carriers of the FMR1 premutation. Sci Rep 2022; 12:10419. [PMID: 35729184 PMCID: PMC9213438 DOI: 10.1038/s41598-022-14183-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 05/18/2022] [Indexed: 11/30/2022] Open
Abstract
The fragile X mental retardation (FMR1) gene contains an expansion-prone CGG repeat within its 5' UTR. Alleles with 55-200 repeats are known as premutation (PM) alleles and confer risk for one or more of the FMR1 premutation (PM) disorders that include Fragile X-associated Tremor/Ataxia Syndrome (FXTAS), Fragile X-associated Primary Ovarian Insufficiency (FXPOI), and Fragile X-Associated Neuropsychiatric Disorders (FXAND). PM alleles expand on intergenerational transmission, with the children of PM mothers being at risk of inheriting alleles with > 200 CGG repeats (full mutation FM) alleles) and thus developing Fragile X Syndrome (FXS). PM alleles can be somatically unstable. This can lead to individuals being mosaic for multiple size alleles. Here, we describe a detailed evaluation of somatic mosaicism in a large cohort of female PM carriers and show that 94% display some evidence of somatic instability with the presence of a series of expanded alleles that differ from the next allele by a single repeat unit. Using two different metrics for instability that we have developed, we show that, as with intergenerational instability, there is a direct relationship between the extent of somatic expansion and the number of CGG repeats in the originally inherited allele and an inverse relationship with the number of AGG interruptions. Expansions are progressive as evidenced by a positive correlation with age and by examination of blood samples from the same individual taken at different time points. Our data also suggests the existence of other genetic or environmental factors that affect the extent of somatic expansion. Importantly, the analysis of candidate single nucleotide polymorphisms (SNPs) suggests that two DNA repair factors, FAN1 and MSH3, may be modifiers of somatic expansion risk in the PM population as observed in other repeat expansion disorders.
Collapse
Affiliation(s)
- Ye Hyun Hwang
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Sacramento, CA, 95817, USA
| | - Bruce Eliot Hayward
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Marwa Zafarullah
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Sacramento, CA, 95817, USA
| | - Jay Kumar
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Sacramento, CA, 95817, USA
| | - Blythe Durbin Johnson
- Department of Public Health Sciences, University of California, Davis, School of Medicine, Sacramento, CA, 95817, USA
| | - Peter Holmans
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurology, School of Medicine, Cardiff University, Cardiff, UK
| | - Karen Usdin
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, University of California Davis, School of Medicine, Sacramento, CA, 95817, USA. .,MIND Institute, University of California Davis Medical Center, Sacramento, CA, 95817, USA.
| |
Collapse
|
15
|
Rajan-Babu IS, Lian M, Chong SS. Triplet-Primed PCR Assays for Accurate Screening of FMR1 CGG Repeat Expansion and Genotype Verification. Curr Protoc 2022; 2:e427. [PMID: 35609145 DOI: 10.1002/cpz1.427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fragile X syndrome and other fragile X-associated disorders are caused by the full-mutation (>200 copies) and premutation (55 to 200 copies) expansion, respectively, of the CGG short tandem repeat in the fragile X messenger ribonucleoprotein 1 (FMR1) gene. Clinical diagnostic laboratories use Southern blot analysis and polymerase chain reaction (PCR)-based tests to detect and/or size the FMR1 CGG repeats. The development of sensitive and high-throughput triplet-primed PCR (TP-PCR) assays has diminished the need to subject all samples to Southern blot analysis, which is both labor- and time-intensive. In this article, we describe two direct TP-PCR (dTP-PCR) assays for the detection of FMR1 CGG repeat expansions. We outline a protocol that is based on melting curve analysis of dTP-PCR amplicons for a rapid and cost-effective first-tier screening and identification of individuals with premutation and full-mutation expansions. We also describe a protocol that employs capillary electrophoresis to resolve the dTP-PCR amplicon fragments and to estimate the repeat sizes of normal (5 to 44 copies), intermediate (45 to 54 copies), and premutation alleles, as well as to detect full mutations and determine the structure of the FMR1 alleles. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Direct triplet-primed PCR master mix preparation and amplification of the FMR1 CGG repeat locus for melting curve analysis Basic Protocol 2: Melting curve analysis of direct triplet-primed PCR amplicons on the Rotor-Gene Q MD × 5plex high-resolution melt platform Alternate Protocol: Melting curve analysis of direct triplet-primed PCR amplicons on the LightCycler 480 system Basic Protocol 3: Generation of direct triplet-primed PCR melting curve analysis profiles Basic Protocol 4: Direct triplet-primed PCR master mix preparation and amplification of the FMR1 CGG repeat locus for capillary electrophoresis Basic Protocol 5: Generation of control FMR1 plasmids for direct triplet-primed PCR melting curve analysis Basic Protocol 6: Sanger sequencing assay to verify FMR1 CGG repeat size and structure of plasmid DNA controls.
Collapse
Affiliation(s)
- Indhu-Shree Rajan-Babu
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada.,Children's & Women's Hospital, Vancouver, British Columbia, Canada
| | - Mulias Lian
- Khoo Teck Puat-National University Children's Medical Institute, National University Hospital, Singapore, Singapore
| | - Samuel S Chong
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Obstetrics and Gynecology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Department of Laboratory Medicine, National University Hospital, Singapore, Singapore
| |
Collapse
|
16
|
Tabolacci E, Nobile V, Pucci C, Chiurazzi P. Mechanisms of the FMR1 Repeat Instability: How Does the CGG Sequence Expand? Int J Mol Sci 2022; 23:ijms23105425. [PMID: 35628235 PMCID: PMC9141726 DOI: 10.3390/ijms23105425] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022] Open
Abstract
A dynamic mutation in exon 1 of the FMR1 gene causes Fragile X-related Disorders (FXDs), due to the expansion of an unstable CGG repeat sequence. Based on the CGG sequence size, two types of FMR1 alleles are possible: “premutation” (PM, with 56-200 CGGs) and “full mutation” (FM, with >200 triplets). Premutated females are at risk of transmitting a FM allele that, when methylated, epigenetically silences FMR1 and causes Fragile X syndrome (FXS), a very common form of inherited intellectual disability (ID). Expansions events of the CGG sequence are predominant over contractions and are responsible for meiotic and mitotic instability. The CGG repeat usually includes one or more AGG interspersed triplets that influence allele stability and the risk of transmitting FM to children through maternal meiosis. A unique mechanism responsible for repeat instability has not been identified, but several processes are under investigations using cellular and animal models. The formation of unusual secondary DNA structures at the expanded repeats are likely to occur and contribute to the CGG expansion. This review will focus on the current knowledge about CGG repeat instability addressing the CGG sequence expands.
Collapse
Affiliation(s)
- Elisabetta Tabolacci
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Veronica Nobile
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Cecilia Pucci
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
| | - Pietro Chiurazzi
- Dipartimento Scienze della Vita e Sanità Pubblica, Sezione di Medicina Genomica, Università Cattolica del Sacro Cuore, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy; (E.T.); (V.N.); (C.P.)
- UOC Genetica Medica, Fondazione Policlinico Universitario “A. Gemelli” IRCCS, 00168 Rome, Italy
- Correspondence: ; Tel.: +39-06-3015-4606
| |
Collapse
|
17
|
Trinh J, Lüth T, Schaake S, Laabs BH, Schlüter K, Laβ J, Pozojevic J, Tse R, König I, Jamora RD, Rosales RL, Brüggemann N, Saranza G, Diesta CCE, Kaiser FJ, Depienne C, Pearson CE, Westenberger A, Klein C. Mosaic divergent repeat interruptions in XDP influence repeat stability and disease onset. Brain 2022; 146:1075-1082. [PMID: 35481544 PMCID: PMC9976955 DOI: 10.1093/brain/awac160] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 03/14/2022] [Accepted: 04/14/2022] [Indexed: 11/14/2022] Open
Abstract
While many genetic causes of movement disorders have been identified, modifiers of disease expression are largely unknown. X-linked dystonia-parkinsonism (XDP) is a neurodegenerative disease caused by a SINE-VNTR-Alu(AGAGGG)n retrotransposon insertion in TAF1, with a polymorphic (AGAGGG)n repeat. Repeat length and variants in MSH3 and PMS2 explain ∼65% of the variance in age at onset (AAO) in XDP. However, additional genetic modifiers are conceivably at play in XDP, such as repeat interruptions. Long-read nanopore sequencing of PCR amplicons from XDP patients (n = 202) was performed to assess potential repeat interruption and instability. Repeat-primed PCR and Cas9-mediated targeted enrichment confirmed the presence of identified divergent repeat motifs. In addition to the canonical pure SINE-VNTR-Alu-5'-(AGAGGG)n, we observed a mosaic of divergent repeat motifs that polarized at the beginning of the tract, where the divergent repeat interruptions varied in motif length by having one, two, or three nucleotides fewer than the hexameric motif, distinct from interruptions in other disease-associated repeats, which match the lengths of the canonical motifs. All divergent configurations occurred mosaically and in two investigated brain regions (basal ganglia, cerebellum) and in blood-derived DNA from the same patient. The most common divergent interruption was AGG [5'-SINE-VNTR-Alu(AGAGGG)2AGG(AGAGGG)n], similar to the pure tract, followed by AGGG [5'-SINE-VNTR-Alu(AGAGGG)2AGGG(AGAGGG)n], at median frequencies of 0.425 (IQR: 0.42-0.43) and 0.128 (IQR: 0.12-0.13), respectively. The mosaic AGG motif was not associated with repeat number (estimate = -3.8342, P = 0.869). The mosaic pure tract frequency was associated with repeat number (estimate = 45.32, P = 0.0441) but not AAO (estimate = -41.486, P = 0.378). Importantly, the mosaic frequency of the AGGG negatively correlated with repeat number after adjusting for age at sampling (estimate = -161.09, P = 3.44 × 10-5). When including the XDP-relevant MSH3/PMS2 modifier single nucleotide polymorphisms into the model, the mosaic AGGG frequency was associated with AAO (estimate = 155.1063, P = 0.047); however, the association dissipated after including the repeat number (estimate = -92.46430, P = 0.079). We reveal novel mosaic divergent repeat interruptions affecting both motif length and sequence (DRILS) of the canonical motif polarized within the SINE-VNTR-Alu(AGAGGG)n repeat. Our study illustrates: (i) the importance of somatic mosaic genotypes; (ii) the biological plausibility of multiple modifiers (both germline and somatic) that can have additive effects on repeat instability; and (iii) that these variations may remain undetected without assessment of single molecules.
Collapse
Affiliation(s)
- Joanne Trinh
- Correspondence to: Joanne Trinh, PhD University of Lübeck, Ratzeburger Allee 160 23538 Lübeck, Germany E-mail:
| | - Theresa Lüth
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Susen Schaake
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Björn-Hergen Laabs
- Institute of Medical Biometry and Statistics, University of Lübeck, Lübeck, Germany
| | - Kathleen Schlüter
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Joshua Laβ
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Jelena Pozojevic
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Ronnie Tse
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Inke König
- Institute of Medical Biometry and Statistics, University of Lübeck, Lübeck, Germany
| | - Roland Dominic Jamora
- Department of Neurosciences, College of Medicine—Philippine General Hospital, University of the Philippines Manila, Manila, Philippines
| | - Raymond L Rosales
- Department of Neurology and Psychiatry, University of Santo Tomas and the CNS-Metropolitan Medical Center, Manila, Philippines
| | - Norbert Brüggemann
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany,Department of Neurology, University of Lübeck, Lübeck, Germany
| | - Gerard Saranza
- Section of Neurology, Department of Internal Medicine, Chong Hua Hospital, Cebu, Philippines
| | - Cid Czarina E Diesta
- Department of Neurosciences, Movement Disorders Clinic, Makati Medical Center, Makati City, Philippines
| | - Frank J Kaiser
- Institute for Human Genetics at the University Hospital Essen, Essen, Germany,Center for Rare Diseases (Essenser Zentrum für Seltene Erkrankungen—EZSE) at the University Hospital Essen, Essen, Germany
| | - Christel Depienne
- Institute for Human Genetics at the University Hospital Essen, Essen, Germany
| | - Christopher E Pearson
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Canada,University of Toronto, Program of Molecular Genetics, Toronto, Canada
| | - Ana Westenberger
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| | - Christine Klein
- Institute of Neurogenetics, University of Lübeck and University Hospital Schleswig-Holstein, Lübeck, Germany
| |
Collapse
|
18
|
Boivin M, Charlet-Berguerand N. Trinucleotide CGG Repeat Diseases: An Expanding Field of Polyglycine Proteins? Front Genet 2022; 13:843014. [PMID: 35295941 PMCID: PMC8918734 DOI: 10.3389/fgene.2022.843014] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 01/31/2022] [Indexed: 12/30/2022] Open
Abstract
Microsatellites are repeated DNA sequences of 3–6 nucleotides highly variable in length and sequence and that have important roles in genomes regulation and evolution. However, expansion of a subset of these microsatellites over a threshold size is responsible of more than 50 human genetic diseases. Interestingly, some of these disorders are caused by expansions of similar sequences, sizes and localizations and present striking similarities in clinical manifestations and histopathological features, which suggest a common mechanism of disease. Notably, five identical CGG repeat expansions, but located in different genes, are the causes of fragile X-associated tremor/ataxia syndrome (FXTAS), neuronal intranuclear inclusion disease (NIID), oculopharyngodistal myopathy type 1 to 3 (OPDM1-3) and oculopharyngeal myopathy with leukoencephalopathy (OPML), which are neuromuscular and neurodegenerative syndromes with overlapping symptoms and similar histopathological features, notably the presence of characteristic eosinophilic ubiquitin-positive intranuclear inclusions. In this review we summarize recent finding in neuronal intranuclear inclusion disease and FXTAS, where the causing CGG expansions were found to be embedded within small upstream ORFs (uORFs), resulting in their translation into novel proteins containing a stretch of polyglycine (polyG). Importantly, expression of these polyG proteins is toxic in animal models and is sufficient to reproduce the formation of ubiquitin-positive intranuclear inclusions. These data suggest the existence of a novel class of human genetic pathology, the polyG diseases, and question whether a similar mechanism may exist in other diseases, notably in OPDM and OPML.
Collapse
|
19
|
Owens KM, Terhaar C, Zdrodowski J, Johnson LR, Eveleigh D. Refining reproductive risk for FMR1 premutation carriers in the general obstetric population. Am J Med Genet A 2022; 188:1476-1481. [PMID: 35129870 DOI: 10.1002/ajmg.a.62666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 08/31/2021] [Accepted: 01/06/2022] [Indexed: 11/08/2022]
Abstract
Female FMR1 premutation (FMR1 PM) carriers for fragile X syndrome (FXS) are at risk to have a child with FXS based on their CGG repeat size and AGG interruption number. Studies examining this risk in unselected populations of female PM carriers are lacking. This retrospective cohort study analyzed carrier status, CGG repeat length, AGG interruption result, and reproductive risk refinement in a population of female patients who underwent routine carrier screening for FXS. A total of 1536 PM carriers (0.43%) were identified, 95% of whom had between 55 and 90 CGG repeats. A number of 1334 carriers underwent AGG interruption testing. The majority had at least one AGG interruption and received a lower reproductive risk for FXS following AGG interruption testing (89% and 85%, respectively) as compared to their risk calculated based on CGG repeat size alone. The average change in risk across the population following AGG interruption testing was -3.4%, with a range from -50.8% to 48.9%. This article describes the range of CGG repeats and AGG interruptions in an unselected population of female PM carriers and suggests that most carriers would benefit from AGG interruption testing to refine their reproductive risk of having a child with FXS.
Collapse
|
20
|
Annear DJ, Vandeweyer G, Sanchis-Juan A, Raymond FL, Kooy RF. Non-Mendelian inheritance patterns and extreme deviation rates of CGG repeats in autism. Genome Res 2022; 32:1967-1980. [PMID: 36351771 PMCID: PMC9808627 DOI: 10.1101/gr.277011.122] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 10/14/2022] [Indexed: 11/10/2022]
Abstract
As expansions of CGG short tandem repeats (STRs) are established as the genetic etiology of many neurodevelopmental disorders, we aimed to elucidate the inheritance patterns and role of CGG STRs in autism-spectrum disorder (ASD). By genotyping 6063 CGG STR loci in a large cohort of trios and quads with an ASD-affected proband, we determined an unprecedented rate of CGG repeat length deviation across a single generation. Although the concept of repeat length being linked to deviation rate was solidified, we show how shorter STRs display greater degrees of size variation. We observed that CGG STRs did not segregate by Mendelian principles but with a bias against longer repeats, which appeared to magnify as repeat length increased. Through logistic regression, we identified 19 genes that displayed significantly higher rates and degrees of CGG STR expansion within the ASD-affected probands (P < 1 × 10-5). This study not only highlights novel repeat expansions that may play a role in ASD but also reinforces the hypothesis that CGG STRs are specifically linked to human cognition.
Collapse
Affiliation(s)
- Dale J. Annear
- Department of Medical Genetics, University of Antwerp, 2600 Antwerp, Belgium
| | - Geert Vandeweyer
- Department of Medical Genetics, University of Antwerp, 2600 Antwerp, Belgium
| | - Alba Sanchis-Juan
- NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, United Kingdom;,Department of Haematology, University of Cambridge, NHS Blood and Transplant Centre, Cambridge, CB2 0PT, United Kingdom
| | - F. Lucy Raymond
- NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, United Kingdom;,Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - R. Frank Kooy
- Department of Medical Genetics, University of Antwerp, 2600 Antwerp, Belgium
| |
Collapse
|
21
|
Hnoonual A, Jankittunpaiboon C, Limprasert P. Screening for FMR1 CGG Repeat Expansion in Thai Patients with Autism Spectrum Disorder. BIOMED RESEARCH INTERNATIONAL 2021; 2021:4359308. [PMID: 34926684 PMCID: PMC8674057 DOI: 10.1155/2021/4359308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/07/2021] [Accepted: 11/26/2021] [Indexed: 11/30/2022]
Abstract
Autism spectrum disorder (ASD) is a complex disorder with a heterogeneous etiology. Fragile X syndrome (FXS) is recognized as the most common single gene mutation associated with ASD. FXS patients show some autistic behaviors and may be difficult to distinguish at a young age from autistic children. However, there have been no published reports on the prevalence of FXS in ASD patients in Thailand. In this study, we present a pilot study to analyze the CGG repeat sizes of the FMR1 gene in Thai autistic patients. We screened 202 unrelated Thai patients (168 males and 34 females) with nonsyndromic ASD and 212 normal controls using standard FXS molecular diagnosis techniques. The distributions of FMR1 CGG repeat sizes in the ASD and normal control groups were similar, with the two most common alleles having 29 and 30 CGG repeats, followed by an allele with 36 CGG repeats. No FMR1 full mutations or premutations were found in either ASD individuals or the normal controls. Interestingly, three ASD male patients with high normal CGG and intermediate CGG repeats (44, 46, and 53 CGG repeats) were identified, indicating that the prevalence of FMR1 intermediate alleles in Thai ASD patients was approximately 1% while these alleles were absent in the normal male controls. Our study indicates that CGG repeat expansions of the FMR1 gene may not be a common genetic cause of nonsyndromic ASD in Thai patients. However, further studies for mutations other than the CGG expansion in the FMR1 gene are required to get a better information on FXS prevalence in Thai ASD patients.
Collapse
Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla 90110, Thailand
| | | | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla 90110, Thailand
- Faculty of Medicine, Siam University, Bangkok 10160, Thailand
| |
Collapse
|
22
|
Hayward BE, Usdin K. Mechanisms of Genome Instability in the Fragile X-Related Disorders. Genes (Basel) 2021; 12:genes12101633. [PMID: 34681027 PMCID: PMC8536109 DOI: 10.3390/genes12101633] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/12/2021] [Accepted: 10/14/2021] [Indexed: 12/17/2022] Open
Abstract
The Fragile X-related disorders (FXDs), which include the intellectual disability fragile X syndrome (FXS), are disorders caused by expansion of a CGG-repeat tract in the 5′ UTR of the X-linked FMR1 gene. These disorders are named for FRAXA, the folate-sensitive fragile site that localizes with the CGG-repeat in individuals with FXS. Two pathological FMR1 allele size classes are distinguished. Premutation (PM) alleles have 54–200 repeats and confer the risk of fragile X-associated tremor/ataxia syndrome (FXTAS) and fragile X-associated primary ovarian insufficiency (FXPOI). PM alleles are prone to both somatic and germline expansion, with female PM carriers being at risk of having a child with >200+ repeats. Inheritance of such full mutation (FM) alleles causes FXS. Contractions of PM and FM alleles can also occur. As a result, many carriers are mosaic for different sized alleles, with the clinical presentation depending on the proportions of these alleles in affected tissues. Furthermore, it has become apparent that the chromosomal fragility of FXS individuals reflects an underlying problem that can lead to chromosomal numerical and structural abnormalities. Thus, large numbers of CGG-repeats in the FMR1 gene predisposes individuals to multiple forms of genome instability. This review will discuss our current understanding of these processes.
Collapse
|
23
|
Bartlett E, Archibald AD, Francis D, Ling L, Thomas R, Chandler G, Ward L, O'Farrell G, Pandelache A, Delatycki MB, Bennetts BH, Ho G, Fisk K, Baker EK, Amor DJ, Godler DE. Paternal retraction of a fragile X allele to normal size, showing normal function over two generations. Am J Med Genet A 2021; 188:304-309. [PMID: 34545686 DOI: 10.1002/ajmg.a.62500] [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: 04/08/2021] [Revised: 08/09/2021] [Accepted: 08/18/2021] [Indexed: 11/09/2022]
Abstract
The FMR1 premutation (PM:55-199 CGG) is associated with fragile X-associated tremor/ataxia syndrome (FXTAS) and when maternally transmitted is at risk of expansion to a hypermethylated full mutation (FM: ≥ 200 CGG) that causes fragile X syndrome (FXS). We describe a maternally transmitted PM (77 CGG) that was passed to a son (103 CGG), and to a daughter (220-1822 CGG), who were affected with FXTAS and FXS, respectively. The male with the PM showed low-level mosaicism for normal size of 30 and 37 CGG. This male had two offspring: one female mosaic for PM and FM (56, 157, >200 CGG) and another with only a 37 CGG allele detected in multiple tissues, neither with a clinical phenotype. The female with the 37 CGG allele showed normal levels of FMR1 methylation and mRNA and passed this 37 CGG allele to one of her daughters, who was also unaffected. These findings show that post-zygotic paternal retraction can lead to low-level mosaicism for normal size alleles, with these normal alleles being functional when passed over two generations.
Collapse
Affiliation(s)
- Essra Bartlett
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Alison D Archibald
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Faculty of Medicine, Dentistry and Health Sciences, Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.,Bruce Lefroy Centre, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - David Francis
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Ling Ling
- Diagnosis and Development, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Rob Thomas
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Gabrielle Chandler
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Lisa Ward
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Gemma O'Farrell
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Alison Pandelache
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Martin B Delatycki
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Faculty of Medicine, Dentistry and Health Sciences, Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.,Bruce Lefroy Centre, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - Bruce H Bennetts
- Sydney Genome Diagnostics-Molecular Genetics, Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Discipline of Genetic Medicine, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Gladys Ho
- Sydney Genome Diagnostics-Molecular Genetics, Children's Hospital at Westmead, Sydney, New South Wales, Australia.,Discipline of Genetic Medicine, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Katrina Fisk
- Sydney Genome Diagnostics-Molecular Genetics, Children's Hospital at Westmead, Sydney, New South Wales, Australia
| | - Emma K Baker
- Diagnosis and Development, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Faculty of Medicine, Dentistry and Health Sciences, Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.,School of Psychology and Public Health, La Trobe University, Melbourne, Victoria, Australia
| | - David J Amor
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Faculty of Medicine, Dentistry and Health Sciences, Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia.,Neurodisability and Rehabilitation, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia
| | - David E Godler
- Diagnosis and Development, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, Victoria, Australia.,Faculty of Medicine, Dentistry and Health Sciences, Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
| |
Collapse
|
24
|
Zhao X, Usdin K. (Dys)function Follows Form: Nucleic Acid Structure, Repeat Expansion, and Disease Pathology in FMR1 Disorders. Int J Mol Sci 2021; 22:ijms22179167. [PMID: 34502075 PMCID: PMC8431139 DOI: 10.3390/ijms22179167] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 12/26/2022] Open
Abstract
Fragile X-related disorders (FXDs), also known as FMR1 disorders, are examples of repeat expansion diseases (REDs), clinical conditions that arise from an increase in the number of repeats in a disease-specific microsatellite. In the case of FXDs, the repeat unit is CGG/CCG and the repeat tract is located in the 5' UTR of the X-linked FMR1 gene. Expansion can result in neurodegeneration, ovarian dysfunction, or intellectual disability depending on the number of repeats in the expanded allele. A growing body of evidence suggests that the mutational mechanisms responsible for many REDs share several common features. It is also increasingly apparent that in some of these diseases the pathologic consequences of expansion may arise in similar ways. It has long been known that many of the disease-associated repeats form unusual DNA and RNA structures. This review will focus on what is known about these structures, the proteins with which they interact, and how they may be related to the causative mutation and disease pathology in the FMR1 disorders.
Collapse
Affiliation(s)
- Xiaonan Zhao
- Correspondence: (X.Z.); (K.U.); Tel.: +1-301-451-6322 (X.Z.); +1-301-496-2189 (K.U.)
| | - Karen Usdin
- Correspondence: (X.Z.); (K.U.); Tel.: +1-301-451-6322 (X.Z.); +1-301-496-2189 (K.U.)
| |
Collapse
|
25
|
Guo Q, Chang YY, Huang CH, Hsiao YS, Hsiao YC, Chiu IF, Zhou Y, Zhang H, Ko TM. Population-based carrier screening and prenatal diagnosis of fragile X syndrome in East Asian populations. J Genet Genomics 2021; 48:1104-1110. [PMID: 34412977 DOI: 10.1016/j.jgg.2021.04.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/13/2021] [Accepted: 04/28/2021] [Indexed: 10/21/2022]
Abstract
Identification of carriers of fragile X syndrome (FXS) with the subsequent prenatal diagnosis and knowledge of FXS-associated genetic profiles are essential for intervention in specific populations. We report the results of carrier screening of 39,458 East Asian adult women and prenatal diagnosis from 87 FXS carriers. The prevalence of FXS carriers and full mutation fetuses was estimated to be 1/581 and 1/3124 in East Asian populations, respectively. We confirmed the validity of the current threshold of CGG trinucleotide repeats for FMR1 categorization; the integral risks of full mutation expansion were approximately 6.0%, 43.8%, and 100% for premutation alleles with 55-74, 75-89, and ≥90 CGG repeats, respectively. The protective effect of AGG (adenine-guanine-guanine nucleotides) interruption in East Asian populations was validated, which is important in protecting premutation alleles with 75-89 CGG repeats from full mutation expansion. Finally, family history was shown not an effective indicator for FXS carrier screening in East Asian populations, and population-based screening was more cost-effective. This study provides an insight into the largest carrier screening and prenatal diagnosis for FXS in East Asian populations to date. The FXS-associated genetic profiles of East Asian populations are delineated, and population-based carrier screening is shown to be promising for FXS intervention.
Collapse
Affiliation(s)
- Qiwei Guo
- United Diagnostic and Research Center for Clinical Genetics, Women and Children's Hospital, School of Medicine & School of Public Health, Xiamen University, Xiamen, Fujian 361102, China.
| | - Yih-Yuan Chang
- Genephile Bioscience Laboratory, Ko's Obstetrics and Gynecology, Taipei 100, Taiwan, China
| | - Chien-Hao Huang
- Genephile Bioscience Laboratory, Ko's Obstetrics and Gynecology, Taipei 100, Taiwan, China
| | - Yu-Shan Hsiao
- Genephile Bioscience Laboratory, Ko's Obstetrics and Gynecology, Taipei 100, Taiwan, China
| | - Yu-Chiao Hsiao
- Biofast Biotechnology Co., Ltd., Xiamen, Fujian 361102, China
| | - I-Fan Chiu
- Biofast Biotechnology Co., Ltd., Xiamen, Fujian 361102, China
| | - Yulin Zhou
- United Diagnostic and Research Center for Clinical Genetics, Women and Children's Hospital, School of Medicine & School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Haixia Zhang
- United Diagnostic and Research Center for Clinical Genetics, Women and Children's Hospital, School of Medicine & School of Public Health, Xiamen University, Xiamen, Fujian 361102, China
| | - Tsang-Ming Ko
- Genephile Bioscience Laboratory, Ko's Obstetrics and Gynecology, Taipei 100, Taiwan, China.
| |
Collapse
|
26
|
Nolin SL, Napoli E, Flores A, Hagerman RJ, Giulivi C. Deficits in Prenatal Serine Biosynthesis Underlie the Mitochondrial Dysfunction Associated with the Autism-Linked FMR1 Gene. Int J Mol Sci 2021; 22:ijms22115886. [PMID: 34070950 PMCID: PMC8198117 DOI: 10.3390/ijms22115886] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 05/25/2021] [Accepted: 05/27/2021] [Indexed: 12/22/2022] Open
Abstract
Fifty-five to two hundred CGG repeats (called a premutation, or PM) in the 5′-UTR of the FMR1 gene are generally unstable, often expanding to a full mutation (>200) in one generation through maternal inheritance, leading to fragile X syndrome, a condition associated with autism and other intellectual disabilities. To uncover the early mechanisms of pathogenesis, we performed metabolomics and proteomics on amniotic fluids from PM carriers, pregnant with male fetuses, who had undergone amniocentesis for fragile X prenatal diagnosis. The prenatal metabolic footprint identified mitochondrial deficits, which were further validated by using internal and external cohorts. Deficits in the anaplerosis of the Krebs cycle were noted at the level of serine biosynthesis, which was confirmed by rescuing the mitochondrial dysfunction in the carriers’ umbilical cord fibroblasts using alpha-ketoglutarate precursors. Maternal administration of serine and its precursors has the potential to decrease the risk of developing energy shortages associated with mitochondrial dysfunction and linked comorbidities.
Collapse
Affiliation(s)
- Sarah L. Nolin
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY 10314, USA;
| | - Eleonora Napoli
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; (E.N.); (A.F.)
| | - Amanda Flores
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; (E.N.); (A.F.)
- Medical Sciences Campus, Department of Biochemistry, University of Puerto Rico, San Juan PR00936, Puerto Rico
| | - Randi J. Hagerman
- Department of Pediatrics, University of California Davis Medical Center, Sacramento, CA 95817, USA;
- The MIND Institute, University of California Davis Medical Center, Sacramento, CA 95817, USA
| | - Cecilia Giulivi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA; (E.N.); (A.F.)
- The MIND Institute, University of California Davis Medical Center, Sacramento, CA 95817, USA
- Correspondence: ; Tel.: +1-530-754-8603
| |
Collapse
|
27
|
Erbs E, Fenger-Grøn J, Jacobsen CM, Lildballe DL, Rasmussen M. Spontaneous rescue of a FMR1 repeat expansion and review of deletions in the FMR1 non-coding region. Eur J Med Genet 2021; 64:104244. [PMID: 34022415 DOI: 10.1016/j.ejmg.2021.104244] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 04/16/2021] [Accepted: 05/02/2021] [Indexed: 12/07/2022]
Abstract
Fragile X syndrome (FXS) is caused by CGG-repeat expansion in the 5' UTR of FMR1 of >200 repeats. Rarely, FXS is caused by deletions; however, it is not clear whether deletions including only the non-coding region of FMR1 are pathogenic. We report a deletion in the 5' UTR of FMR1 in an unaffected male infant and review 12 reported deletions involving only the non-coding region of FMR1. Genetic testing was requested in a male infant born to a mother harbouring a FMR1 full mutation. The maternal grandmother carried a FMR1 premutation. FMR1 CGG repeats were analysed using repeat-primed PCR. Only a short PCR fragment was amplified and subsequent Sanger sequencing detected an 88 bp deletion in hemizygous form. The deletion included all CGG repeats and flanking sequences but no FMR1 exons. Linkage analysis using STR markers revealed that the deletion had occurred on the allele, which was expanded in the mother and the maternal grandmother. Reverse transcription and quantitative PCR showed normal FMR1 mRNA levels. Grønskov et al. reported a 157 bp deletion of all CGG repeats and flanking sequences in a female without FXS hemizygous for the FMR1 gene due to a deletion on the other X chromosome. Protein expression was unaffected by the deletion. The reported deletion comprises the deletion detected in the male infant. At almost 2 years of age he is unaffected. Based on these observations and the normal FMR1 mRNA level, we conclude that a spontaneous rescue of an FMR1 repeat expansion has occurred.
Collapse
Affiliation(s)
- Emilie Erbs
- Department of Clinical Genetics, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark.
| | - Jesper Fenger-Grøn
- Department of Paediatrics, Lillebaelt Hospital, University Hospital of Southern Denmark, Kolding, Denmark
| | - Cecilie Mondrup Jacobsen
- Department of Clinical Genetics, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark
| | - Dorte Launholt Lildballe
- Department of Clinical Genetics, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark
| | - Maria Rasmussen
- Department of Clinical Genetics, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark; Department of Regional Health Research, University of Southern Denmark, Odense M, Denmark
| |
Collapse
|
28
|
Depienne C, Mandel JL. 30 years of repeat expansion disorders: What have we learned and what are the remaining challenges? Am J Hum Genet 2021; 108:764-785. [PMID: 33811808 DOI: 10.1016/j.ajhg.2021.03.011] [Citation(s) in RCA: 162] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 03/05/2021] [Indexed: 12/13/2022] Open
Abstract
Tandem repeats represent one of the most abundant class of variations in human genomes, which are polymorphic by nature and become highly unstable in a length-dependent manner. The expansion of repeat length across generations is a well-established process that results in human disorders mainly affecting the central nervous system. At least 50 disorders associated with expansion loci have been described to date, with half recognized only in the last ten years, as prior methodological difficulties limited their identification. These limitations still apply to the current widely used molecular diagnostic methods (exome or gene panels) and thus result in missed diagnosis detrimental to affected individuals and their families, especially for disorders that are very rare and/or clinically not recognizable. Most of these disorders have been identified through family-driven approaches and many others likely remain to be identified. The recent development of long-read technologies provides a unique opportunity to systematically investigate the contribution of tandem repeats and repeat expansions to the genetic architecture of human disorders. In this review, we summarize the current and most recent knowledge about the genetics of repeat expansion disorders and the diversity of their pathophysiological mechanisms and outline the perspectives of developing personalized treatments in the future.
Collapse
|
29
|
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: 18] [Impact Index Per Article: 6.0] [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).
Collapse
|
30
|
Movaghar A, Page D, Scholze D, Hong J, DaWalt LS, Kuusisto F, Stewart R, Brilliant M, Mailick M. Artificial intelligence-assisted phenotype discovery of fragile X syndrome in a population-based sample. Genet Med 2021; 23:1273-1280. [PMID: 33772223 PMCID: PMC8257481 DOI: 10.1038/s41436-021-01144-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 03/01/2021] [Accepted: 03/02/2021] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Fragile X syndrome (FXS), the most prevalent inherited cause of intellectual disability, remains underdiagnosed in the general population. Clinical studies have shown that individuals with FXS have a complex health profile leading to unique clinical needs. However, the full impact of this X-linked disorder on the health of affected individuals is unclear and the prevalence of co-occurring conditions is unknown. METHODS We mined the longitudinal electronic health records from more than one million individuals to investigate the health characteristics of patients who have been clinically diagnosed with FXS. Additionally, using machine-learning approaches, we created predictive models to identify individuals with FXS in the general population. RESULTS Our discovery-oriented approach identified the associations of FXS with a wide range of medical conditions including circulatory, endocrine, digestive, and genitourinary, in addition to mental and neurological disorders. We successfully created predictive models to identify cases five years prior to clinical diagnosis of FXS without relying on any genetic or familial data. CONCLUSION Although FXS is often thought of primarily as a neurological disorder, it is in fact a multisystem syndrome involving many co-occurring conditions, some primary and some secondary, and they are associated with a considerable burden on patients and their families.
Collapse
Affiliation(s)
- Arezoo Movaghar
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - David Page
- Department of Biostatistics and Bioinformatics, Duke University, Durham, NC, USA
| | - Danielle Scholze
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA.,Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Jinkuk Hong
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | | | | | - Ron Stewart
- Morgridge Institute for Research, Madison, WI, USA
| | - Murray Brilliant
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA.,Marshfield Clinic Research Institute, Marshfield, WI, USA
| | - Marsha Mailick
- Waisman Center, University of Wisconsin-Madison, Madison, WI, USA.
| |
Collapse
|
31
|
'Essential Tremor' Phenotype in FMR1 Premutation/Gray Zone Sibling Series: Exploring Possible Genetic Modifiers. Twin Res Hum Genet 2021; 24:95-102. [PMID: 33757613 DOI: 10.1017/thg.2021.10] [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] [Indexed: 12/20/2022]
Abstract
Fragile X-associated tremor/ataxia syndrome (FXTAS) occurs in carriers of fragile X mental retardation 1 (FMR1) X-linked small CGG expansion (gray zone [GZ] and premutation [PM]) alleles, containing 41-200 repeats. Major features comprise kinetic tremor, gait ataxia, cognitive decline and cerebellar peduncular white matter lesions, but atypical/incomplete FXTAS may occur. We explored the possibility of polygenic effects modifying the FXTAS spectrum phenotypes. We used three motor scales and selected cognitive tests in a series of three males and three females from a single sibship carrying PM or GZ alleles (44 to 75 repeats). The molecular profiles from these siblings were determined by genomewide association study with single-nucleotide polymorphism (SNP) genotyping by Illumina Global Screening Array. Nonparametric linkage analysis was applied and Parkinson's disease (PD) polygenic risk scores (PRSs) were calculated for all the siblings, based on 107 known risk variants. All male and female siblings manifested similar kinetic tremor phenotypes. In contrast to FXTAS, they showed negligible gait ataxia, and few white matter lesions on MRI. Cognitive functioning was unaffected. Suggestive evidence of linkage to a broad region of the short arm of chromosome 10 was obtained, and median PD PRS for the sibship fell within the top 30% of a sample of over 500,000 UK and Australian controls. The genomewide study results are suggestive of modifying effects of genetic risk loci linked to PD, on the neurological phenotype of FMR1-CGG small expansion carriers, resulting in an oligosymptomatic kinetic tremor seen in FXTAS spectrum, but also consistent with essential tremor.
Collapse
|
32
|
Abstract
Neurodevelopmental disorders are the most prevalent chronic medical conditions encountered in pediatric primary care. In addition to identifying appropriate descriptive diagnoses and guiding families to evidence-based treatments and supports, comprehensive care for individuals with neurodevelopmental disorders includes a search for an underlying etiologic diagnosis, primarily through a genetic evaluation. Identification of an underlying genetic etiology can inform prognosis, clarify recurrence risk, shape clinical management, and direct patients and families to condition-specific resources and supports. Here we review the utility of genetic testing in patients with neurodevelopmental disorders and describe the three major testing modalities and their yields - chromosomal microarray, exome sequencing (with/without copy number variant calling), and FMR1 CGG repeat analysis for fragile X syndrome. Given the diagnostic yield of genetic testing and the potential for clinical and personal utility, there is consensus that genetic testing should be offered to all patients with global developmental delay, intellectual disability, and/or autism spectrum disorder. Despite this recommendation, data suggest that a minority of children with autism spectrum disorder and intellectual disability have undergone genetic testing. To address this gap in care, we describe a structured but flexible approach to facilitate integration of genetic testing into clinical practice across pediatric specialties and discuss future considerations for genetic testing in neurodevelopmental disorders to prepare pediatric providers to care for patients with such diagnoses today and tomorrow.
Collapse
Affiliation(s)
- Juliann M. Savatt
- Autism & Developmental Medicine Institute, Geisinger, Danville, PA, United States
| | | |
Collapse
|
33
|
Tassanakijpanich N, Hagerman RJ, Worachotekamjorn J. Fragile X premutation and associated health conditions: A review. Clin Genet 2021; 99:751-760. [PMID: 33443313 DOI: 10.1111/cge.13924] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/10/2021] [Accepted: 01/11/2021] [Indexed: 12/17/2022]
Abstract
Fragile X syndrome (FXS) is the most common single gene disorder, which causes autism and intellectual disability. The fragile X mental retardation 1 (FMR1) gene is silenced when cytosine-guanine-guanine (CGG) triplet repeats exceed 200, which is the full mutation that causes FXS. Carriers of FXS have a CGG repeat between 55 and 200, which is defined as a premutation and transcription of the gene is overactive with high levels of the FMR1 mRNA. Most carriers of the premutation have normal levels of fragile X mental retardation protein (FMRP) and a normal intelligence, but in the upper range of the premutation (120-200) the FMRP level may be lower than normal. The clinical problems associated with the premutation are caused by the RNA toxicity associated with increased FMR1 mRNA levels, although for some mildly lowered FMRP can cause problems associated with FXS. The RNA toxicity causes various health problems in the carriers including but not limited to fragile X-associated tremor/ataxia syndrome, fragile X-associated primary ovarian insufficiency, and fragile X-associated neuropsychiatric disorders. Since some individuals with neuropsychiatric problems do not meet the severity for a diagnosis of a "disorder" then the condition can be labeled as fragile X premutation associated condition (FXPAC). Physicians must be able to recognize these health problems in the carriers and provide appropriate management.
Collapse
Affiliation(s)
| | - Randi J Hagerman
- UC Davis MIND Institute, UC Davis Health, Sacramento, California, USA.,Department of Pediatrics, University of California, Davis, School of Medicine, Sacramento, California, USA
| | | |
Collapse
|
34
|
Wright GEB, Black HF, Collins JA, Gall-Duncan T, Caron NS, Pearson CE, Hayden MR. Interrupting sequence variants and age of onset in Huntington's disease: clinical implications and emerging therapies. Lancet Neurol 2020; 19:930-939. [PMID: 33098802 DOI: 10.1016/s1474-4422(20)30343-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 08/23/2020] [Accepted: 08/25/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Huntington's disease is a fatal neurodegenerative disorder that is caused by CAG-CAA repeat expansion, encoding polyglutamine, in the huntingtin (HTT) gene. Current age-of-clinical-onset prediction models for Huntington's disease are based on polyglutamine length and explain only a proportion of the variability in age of onset observed between patients. These length-based assays do not interrogate the underlying genetic variation, because known genetic variants in this region do not alter the protein coding sequence. Given that individuals with identical repeat lengths can present with Huntington's disease decades apart, the search for genetic modifiers of clinical age of onset has become an active area of research. RECENT DEVELOPMENTS Results from three independent genetic studies of Huntington's disease have shown that glutamine-encoding CAA variants that interrupt DNA CAG repeat tracts, but do not alter polyglutamine length or polyglutamine homogeneity, are associated with substantial differences in age of onset of Huntington's disease in carriers. A variant that results in the loss of CAA interruption is associated with early onset and is particularly relevant to individuals that carry alleles in the reduced penetrance range (ie, CAG 36-39). Approximately a third of clinically manifesting carriers of reduced penetrance alleles, defined by current diagnostics, carry this variant. Somatic repeat instability, modified by interrupted CAG tracts, is the most probable cause mediating this effect. This relationship is supported by genome-wide screens for disease modifiers, which have revealed the importance of DNA-repair genes in Huntington's disease (ie, FAN1, LIG1, MLH1, MSH3, PMS1, and PMS2). WHERE NEXT?: Focus needs to be placed on refining our understanding of the effect of the loss-of-interruption and duplication-of-interruption variants and other interrupting sequence variants on age of onset, and assessing their effect in disease-relevant brain tissues, as well as in diverse population groups, such as individuals from Africa and Asia. Diagnostic tests should be augmented or updated, since current tests do not assess the underlying DNA sequence variation, especially when assessing individuals that carry alleles in the reduced penetrance range. Future studies should explore somatic repeat instability and DNA repair as new therapeutic targets to modify age of onset in Huntington's disease and in other repeat-mediated disorders. Disease-modifying therapies could potentially be developed by therapeutically targeting these processes. Promising approaches include therapeutically targeting the expanded repeat or directly perturbing key DNA-repair genes (eg, with antisense oligonucleotides or small molecules). Targeting the CAG repeat directly with naphthyridine-azaquinolone, a compound that induces contractions, and altering the expression of MSH3, represent two viable therapeutic strategies. However, as a first step, the capability of such novel therapeutic approaches to delay clinical onset in animal models should be assessed.
Collapse
Affiliation(s)
- Galen E B Wright
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada; BC Children's Hospital Research Institute, Vancouver, BC, Canada; Neuroscience Research Program, Kleysen Institute for Advanced Medicine, Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB, Canada
| | - Hailey Findlay Black
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada; BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Jennifer A Collins
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada; BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Terence Gall-Duncan
- Program of Genetics and Genome Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Nicholas S Caron
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada; BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Christopher E Pearson
- Program of Genetics and Genome Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada; Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Michael R Hayden
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada; BC Children's Hospital Research Institute, Vancouver, BC, Canada.
| |
Collapse
|
35
|
Frequency of the loss of CAA interruption in the HTT CAG tract and implications for Huntington disease in the reduced penetrance range. Genet Med 2020; 22:2108-2113. [PMID: 32741964 PMCID: PMC7708297 DOI: 10.1038/s41436-020-0917-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/17/2020] [Accepted: 07/17/2020] [Indexed: 11/27/2022] Open
Abstract
Purpose In some Huntington disease (HD) patients, the “loss of interruption” (LOI) variant eliminates an interrupting codon in the HTT CAG-repeat tract, which causes earlier age of onset (AOO). The magnitude of this effect is uncertain, since previous studies included few LOI carriers, and the variant also causes CAG size misestimation. We developed a rapid LOI detection screen, enabling unbiased frequency estimation among manifest HD patients. Additionally, we combined published data with clinical data from newly identified patients to accurately characterize the LOI’s effect on AOO. Methods We developed a LOI detection polymerase chain reaction (PCR) assay, and screened patients to estimate the frequency of the LOI variant and its effect on AOO. Results Mean onset for LOI carriers (n = 49) is 20.4 years earlier than expected based on diagnosed CAG size. After correcting for CAG size underestimation, the variant is still associated with onset 9.5 years earlier. The LOI is present in 1.02% of symptomatic HD patients, and in 32.2% of symptomatic reduced penetrance (RP) range patients (36–39 CAGs). Conclusion The LOI causes significantly earlier onset, greater than expected by CAG length, particularly in persons with 36–39 CAG repeats. Detection of this variant has implications for HD families, especially for those in the RP range.
Collapse
|
36
|
Villate O, Ibarluzea N, Maortua H, de la Hoz AB, Rodriguez-Revenga L, Izquierdo-Álvarez S, Tejada MI. Effect of AGG Interruptions on FMR1 Maternal Transmissions. Front Mol Biosci 2020; 7:135. [PMID: 32766278 PMCID: PMC7381193 DOI: 10.3389/fmolb.2020.00135] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 06/05/2020] [Indexed: 12/30/2022] Open
Abstract
There are four classes of CGG repeat alleles in the FMR1 gene: normal alleles have up to 44 repeats; patients with Fragile X Syndrome have more than 200 repeats; those between 55 and 200 CGGs are considered FMR1 premutation alleles, because they are associated with maternal expansions of the number of CGGs in the next generation and finally, alleles between 45 and 54 CGGs are called intermediate or gray zone alleles. In these last categories, the stability depends on the presence of AGG interruptions, which usually occurs between 9 and 10 CGGs. In this context, we have studied retrospectively 66 women with CGG repeats between 45 and 65, and their offspring. In total 87 transmissions were analyzed with triplet repeat primed PCR using AmplideX® FMR1 PCR (Asuragen, Austin, TX, USA) and we found that alleles with CGG repeats between 45 and 58 do not expand in the next generation except two cases with 56 repeats and 0 AGG interruptions. Furthermore, we have found four females with alleles with more than 59 CGG repeats and 2 AGG interruptions that do not expand either. Alleles from 56 CGG repeats without AGGs expand in all cases. In light of these results and those of the literature, we consider that the risk of unstable transmissions should be based on the presence or absence of AGG interruptions and not on the classical cutoffs which define each category of FMR1 alleles. The application of these results in the genetic and reproductive counseling is essential and AGG interruptions should always be studied.
Collapse
Affiliation(s)
- Olatz Villate
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Nekane Ibarluzea
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Hiart Maortua
- Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Ana Belén de la Hoz
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| | - Laia Rodriguez-Revenga
- Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain.,Biochemistry and Molecular Genetics Department, Hospital Clinic, Barcelona, Spain.,Institut d'Investigació Biomèdica August Pi i Sunyer IDIBAPS, Barcelona, Spain
| | - Silvia Izquierdo-Álvarez
- Genetics Department of Clinical Biochemistry, Hospital Universitario Miguel Servet, Zaragoza, Spain
| | - María Isabel Tejada
- Biocruces Bizkaia Health Research Institute, Barakaldo, Spain.,Genetics Service, Cruces University Hospital, Osakidetza Basque Health Service, Barakaldo, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Madrid, Spain
| |
Collapse
|
37
|
Khristich AN, Mirkin SM. On the wrong DNA track: Molecular mechanisms of repeat-mediated genome instability. J Biol Chem 2020; 295:4134-4170. [PMID: 32060097 PMCID: PMC7105313 DOI: 10.1074/jbc.rev119.007678] [Citation(s) in RCA: 148] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Expansions of simple tandem repeats are responsible for almost 50 human diseases, the majority of which are severe, degenerative, and not currently treatable or preventable. In this review, we first describe the molecular mechanisms of repeat-induced toxicity, which is the connecting link between repeat expansions and pathology. We then survey alternative DNA structures that are formed by expandable repeats and review the evidence that formation of these structures is at the core of repeat instability. Next, we describe the consequences of the presence of long structure-forming repeats at the molecular level: somatic and intergenerational instability, fragility, and repeat-induced mutagenesis. We discuss the reasons for gender bias in intergenerational repeat instability and the tissue specificity of somatic repeat instability. We also review the known pathways in which DNA replication, transcription, DNA repair, and chromatin state interact and thereby promote repeat instability. We then discuss possible reasons for the persistence of disease-causing DNA repeats in the genome. We describe evidence suggesting that these repeats are a payoff for the advantages of having abundant simple-sequence repeats for eukaryotic genome function and evolvability. Finally, we discuss two unresolved fundamental questions: (i) why does repeat behavior differ between model systems and human pedigrees, and (ii) can we use current knowledge on repeat instability mechanisms to cure repeat expansion diseases?
Collapse
Affiliation(s)
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, Massachusetts 02155.
| |
Collapse
|
38
|
Reversion to Normal of FMR1 Expanded Alleles: A Rare Event in Two Independent Fragile X Syndrome Families. Genes (Basel) 2020; 11:genes11030248. [PMID: 32111011 PMCID: PMC7140891 DOI: 10.3390/genes11030248] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/12/2020] [Accepted: 02/24/2020] [Indexed: 01/12/2023] Open
Abstract
Fragile X syndrome (FXS) is mostly due to the expansion and subsequent methylation of a polymorphic CGG repeat in the 5’ UTR of the FMR1 gene. Full mutation alleles (FM) have more than 200 repeats and result in FMR1 gene silencing and FXS. FMs arise from maternal premutations (PM) that have 56–200 CGGs; contractions of a maternal PM or FM are rare. Here, we describe two unaffected boys in two independent FXS families who inherited a non-mosaic allele in the normal and intermediate range, respectively, from their mothers who are carriers of an expanded CGG allele. The first boy inherited a 51 CGG allele (without AGG interruptions) from his mother, who carries a PM allele with 72 CGGs. The other boy inherited from his FM mother an unusual allele with 19 CGGs resulting from a deletion, removing 85 bp upstream of the CGG repeat. Given that transcription of the deleted allele was found to be preserved, we assume that the binding sites for FMR1 transcription factors are excluded from the deletion. Such unusual cases resulting in non-mosaic reduction of maternal CGG expansions may help to clarify the molecular mechanisms underlying the instability of the FMR1 gene.
Collapse
|
39
|
Suardi GAM, Haddad LA. FMRP ribonucleoprotein complexes and RNA homeostasis. ADVANCES IN GENETICS 2020; 105:95-136. [PMID: 32560791 DOI: 10.1016/bs.adgen.2020.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The Fragile Mental Retardation 1 gene (FMR1), at Xq27.3, encodes the fragile mental retardation protein (FMRP), and displays in its 5'-untranslated region a series of polymorphic CGG triplet repeats that may undergo dynamic mutation. Fragile X syndrome (FXS) is the leading cause of inherited intellectual disability among men, and is most frequently due to FMR1 full mutation and consequent transcription repression. FMR1 premutations may associate with at least two other clinical conditions, named fragile X-associated primary ovarian insufficiency (FXPOI) and tremor and ataxia syndrome (FXTAS). While FXPOI and FXTAS appear to be mediated by FMR1 mRNA accumulation, relative reduction of FMRP, and triplet repeat translation, FXS is due to the lack of the RNA-binding protein FMRP. Besides its function as mRNA translation repressor in neuronal and stem/progenitor cells, RNA editing roles have been assigned to FMRP. In this review, we provide a brief description of FMR1 transcribed microsatellite and associated clinical disorders, and discuss FMRP molecular roles in ribonucleoprotein complex assembly and trafficking, as well as aspects of RNA homeostasis affected in FXS cells.
Collapse
Affiliation(s)
- Gabriela Aparecida Marcondes Suardi
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Luciana Amaral Haddad
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
| |
Collapse
|
40
|
Johansen Taber K, Lim-Harashima J, Naemi H, Goldberg J. Fragile X syndrome carrier screening accompanied by genetic consultation has clinical utility in populations beyond those recommended by guidelines. Mol Genet Genomic Med 2019; 7:e1024. [PMID: 31694075 PMCID: PMC6900367 DOI: 10.1002/mgg3.1024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 08/30/2019] [Accepted: 10/01/2019] [Indexed: 01/12/2023] Open
Abstract
Background Fragile X syndrome (FXS) is the most common inherited form of intellectual disability. Many providers offer preconception or prenatal FXS carrier screening. However, guidelines recommend screening only for those with a family history or undergoing fertility evaluation. Wider screening has been resisted because of concerns about patient understanding of FXS‐associated inheritance patterns and phenotypes. Additionally, the clinical utility has been questioned. Methods We addressed these concerns by analyzing reproductive decision‐making and pregnancy management informed by post‐test genetic consultation among 122 FMR1 premutation carriers identified by expanded carrier screening. Results Sixty‐three percent of those screened met guidelines screening criteria; the remaining 37% did not. Ninety‐eight percent had undergone post‐test genetic consultation. Of respondents screened preconceptionally, 74% reported planning or pursuing actions to reduce the risk of an affected pregnancy; the extent to which couples planned/pursued these actions was not significantly different between those meeting either screening criterion (76%) versus those meeting neither criterion (55%). Of respondents screened prenatally, 41% pursued prenatal diagnostic testing; the extent to which couples pursued prenatal diagnosis was not significantly different between those who met either screening criterion (37%) versus those who met neither criterion (31%). Conclusion These results support the expansion of FXS screening criteria in guidelines.
Collapse
Affiliation(s)
| | | | | | - Jim Goldberg
- Myriad Women's Health, South San Francisco, CA, USA
| |
Collapse
|
41
|
Nolin SL, Glicksman A, Tortora N, Allen E, Macpherson J, Mila M, Vianna‐Morgante AM, Sherman SL, Dobkin C, Latham GJ, Hadd AG. Expansions and contractions of the FMR1 CGG repeat in 5,508 transmissions of normal, intermediate, and premutation alleles. Am J Med Genet A 2019; 179:1148-1156. [PMID: 31050164 PMCID: PMC6619443 DOI: 10.1002/ajmg.a.61165] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 03/21/2019] [Accepted: 04/11/2019] [Indexed: 12/15/2022]
Abstract
Instability of the FMR1 repeat, commonly observed in transmissions of premutation alleles (55-200 repeats), is influenced by the size of the repeat, its internal structure and the sex of the transmitting parent. We assessed these three factors in unstable transmissions of 14/3,335 normal (~5 to 44 repeats), 54/293 intermediate (45-54 repeats), and 1561/1,880 premutation alleles. While most unstable transmissions led to expansions, contractions to smaller repeats were observed in all size classes. For normal alleles, instability was more frequent in paternal transmissions and in alleles with long 3' uninterrupted repeat lengths. For premutation alleles, contractions also occurred more often in paternal than maternal transmissions and the frequency of paternal contractions increased linearly with repeat size. All paternal premutation allele contractions were transmitted as premutation alleles, but maternal premutation allele contractions were transmitted as premutation, intermediate, or normal alleles. The eight losses of AGG interruptions in the FMR1 repeat occurred exclusively in contractions of maternal premutation alleles. We propose a refined model of FMR1 repeat progression from normal to premutation size and suggest that most normal alleles without AGG interruptions are derived from contractions of maternal premutation alleles.
Collapse
Affiliation(s)
- Sarah L. Nolin
- Department of Human GeneticsNew York State Institute for Basic Research in Developmental DisabilitiesStaten IslandNew York
| | - Anne Glicksman
- Department of Human GeneticsNew York State Institute for Basic Research in Developmental DisabilitiesStaten IslandNew York
| | - Nicole Tortora
- Department of Human GeneticsNew York State Institute for Basic Research in Developmental DisabilitiesStaten IslandNew York
| | - Emily Allen
- Department of Human GeneticsEmory University School of MedicineAtlantaGeorgia
| | - James Macpherson
- Wessex Regional Genetics LaboratorySalisbury NHS District HospitalSalisburyUnited Kingdom
| | - Montserrat Mila
- Biochemical and Molecular GeneticsHospital Clinic de Barcelona, IDIBAPS and CIBERERBarcelonaSpain
| | - Angela M. Vianna‐Morgante
- Department of Genetics and Evolutionary Biology, Institute of BiosciencesUniversidade de São PauloSão PauloBrazil
| | | | - Carl Dobkin
- Department of Human GeneticsNew York State Institute for Basic Research in Developmental DisabilitiesStaten IslandNew York
| | | | | |
Collapse
|