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Beyond Trinucleotide Repeat Expansion in Fragile X Syndrome: Rare Coding and Noncoding Variants in FMR1 and Associated Phenotypes. Genes (Basel) 2021; 12:genes12111669. [PMID: 34828275 PMCID: PMC8623550 DOI: 10.3390/genes12111669] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 11/17/2022] Open
Abstract
FMR1 (FMRP translational regulator 1) variants other than repeat expansion are known to cause disease phenotypes but can be overlooked if they are not accounted for in genetic testing strategies. We collected and reanalyzed the evidence for pathogenicity of FMR1 coding, noncoding, and copy number variants published to date. There is a spectrum of disease-causing FMR1 variation, with clinical and functional evidence supporting pathogenicity of five splicing, five missense, one in-frame deletion, one nonsense, and four frameshift variants. In addition, FMR1 deletions occur in both mosaic full mutation patients and as constitutional pathogenic alleles. De novo deletions arise not only from full mutation alleles but also alleles with normal-sized CGG repeats in several patients, suggesting that the CGG repeat region may be prone to genomic instability even in the absence of repeat expansion. We conclude that clinical tests for potentially FMR1-related indications such as intellectual disability should include methods capable of detecting small coding, noncoding, and copy number variants.
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Watanabe N, Kitada K, Santostefano KE, Yokoyama A, Waldrop SM, Heldermon CD, Tachibana D, Koyama M, Meacham AM, Pacak CA, Terada N. Generation of Induced Pluripotent Stem Cells from a Female Patient with a Xq27.3-q28 Deletion to Establish Disease Models and Identify Therapies. Cell Reprogram 2020; 22:179-188. [PMID: 32608992 DOI: 10.1089/cell.2020.0012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Since it is extremely difficult to establish an animal model for human chromosomal abnormalities, induced pluripotent stem cells (iPSCs) provide a powerful alternative to study underlying mechanisms of these disorders and identify potential therapeutic interventions. In this study we established iPSCs from a young girl with a hemizygous deletion of Xq27.3-q28 who exhibited global developmental delay and intellectual disability from early in infancy. The deletion site on the X chromosome includes Fragile X Mental Retardation 1 (FMR1), the gene responsible for fragile X syndrome, which likely contributes to the patient's neurodevelopmental abnormalities. The FMR1 gene was expressed in approximately half of the iPSC clones we generated while it was absent in the other half due to the random inactivation of normal and abnormal X chromosomes. The normal or absent expression pattern of the FMR1 gene was not altered when the iPSCs were differentiated into neural progenitor cells (NPCs). Moreover, chromosome reactivating reagents such as 5-aza-2-deoxycytidine, trichostatin A, and UNC0638, were tested in an attempt to reactivate the suppressed FMR1 gene in affected iPSC-NPCs. The affected and control isogenic iPSCs developed in this study are ideal models with which to identify downstream consequences caused by the Xq27.3-q28 deletion and also to provide tools for high-throughput screening to identify compounds potentially improving the well-being of this patient population.
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Affiliation(s)
- Noriko Watanabe
- Department of Pathology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Kohei Kitada
- Department of Pathology, University of Florida College of Medicine, Gainesville, Florida, USA
| | | | - Airi Yokoyama
- Department of Pathology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Sara M Waldrop
- Department of Pathology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Coy D Heldermon
- Department of Medicine, and University of Florida College of Medicine, Gainesville, Florida, USA
| | - Daisuke Tachibana
- Depertment of Obstetrics and Gynecology, Osaka City University, Graduate School of Medicine, Osaka, Japan
| | - Masayasu Koyama
- Depertment of Obstetrics and Gynecology, Osaka City University, Graduate School of Medicine, Osaka, Japan
| | - Amy M Meacham
- Department of Medicine, and University of Florida College of Medicine, Gainesville, Florida, USA
| | - Christina A Pacak
- Department of Pediatrics, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Naohiro Terada
- Department of Pathology, University of Florida College of Medicine, Gainesville, Florida, USA
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3
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Katoh K, Aiba K, Fukushi D, Yoshimura J, Suzuki Y, Mitsui J, Morishita S, Tuji S, Yamada K, Wakamatsu N. Clinical and molecular genetic characterization of two female patients harboring the Xq27.3q28 deletion with different ratios of X chromosome inactivation. Hum Mutat 2020; 41:1447-1460. [PMID: 32485067 DOI: 10.1002/humu.24058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 05/04/2020] [Accepted: 05/22/2020] [Indexed: 11/10/2022]
Abstract
A heterozygous deletion at Xq27.3q28 including FMR1, AFF2, and IDS causing intellectual disability and characteristic facial features is very rare in females, with only 10 patients having been reported. Here, we examined two female patients with different clinical features harboring the Xq27.3q28 deletion and determined the chromosomal breakpoints. Moreover, we assessed the X chromosome inactivation (XCI) in peripheral blood from both patients. Both patients had an almost overlapping deletion at Xq27.3q28, however, the more severe patient (Patient 1) showed skewed XCI of the normal X chromosome (79:21) whereas the milder patient (Patient 2) showed random XCI. Therefore, deletion at Xq27.3q28 critically affected brain development, and the ratio of XCI of the normal X chromosome greatly affected the clinical characteristics of patients with deletion at Xq27.3q28. As the chromosomal breakpoints were determined, we analyzed a change in chromatin domains termed topologically associated domains (TADs) using published Hi-C data on the Xq27.3q28 region, and found that only patient 1 had a possibility of a drastic change in TADs. The altered chromatin topologies on the Xq27.3q28 region might affect the clinical features of patient 1 by changing the expression of genes just outside the deletion and/or the XCI establishment during embryogenesis resulting in skewed XCI.
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Affiliation(s)
- Kimiko Katoh
- Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Aichi, Japan
| | - Kaori Aiba
- Department of Pediatrics, Toyohashi Municipal Hospital, Toyohashi, Aichi, Japan
| | - Daisuke Fukushi
- Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Aichi, Japan
| | - Jun Yoshimura
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Yasuyo Suzuki
- Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Aichi, Japan
| | - Jun Mitsui
- Department of Molecular Neurology, The University of Tokyo, Tokyo, Japan
| | - Shinichi Morishita
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan
| | - Shoji Tuji
- Department of Molecular Neurology, The University of Tokyo, Tokyo, Japan
| | - Kenichiro Yamada
- Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Aichi, Japan
| | - Nobuaki Wakamatsu
- Department of Genetics, Institute for Developmental Research, Aichi Developmental Disability Center, Kasugai, Aichi, Japan.,Department of Neurology, Neurology and Stroke Center, Takamatsu Municipal Hospital, Takamatsu, Kagawa, Japan.,Department of Pathology and Host Defense, Faculty of Medicine, Kagawa University, Miki, Kagawa, Japan
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Zink AM, Wohlleber E, Engels H, Rødningen OK, Ravn K, Heilmann S, Rehnitz J, Katzorke N, Kraus C, Blichfeldt S, Hoffmann P, Reutter H, Brockschmidt FF, Kreiß-Nachtsheim M, Vogt PH, Prescott TE, Tümer Z, Lee JA. Microdeletions including FMR1 in three female patients with intellectual disability - further delineation of the phenotype and expression studies. Mol Syndromol 2014; 5:65-75. [PMID: 24715853 DOI: 10.1159/000357962] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2013] [Indexed: 11/19/2022] Open
Abstract
Fragile X syndrome (FXS) is one of the most common causes of intellectual disability/developmental delay (ID/DD), especially in males. It is caused most often by CGG trinucleotide repeat expansions, and less frequently by point mutations and partial or full deletions of the FMR1 gene. The wide clinical spectrum of affected females partly depends on their X-inactivation status. Only few female ID/DD patients with microdeletions including FMR1 have been reported. We describe 3 female patients with 3.5-, 4.2- and 9.2-Mb de novo microdeletions in Xq27.3-q28 containing FMR1. X-inactivation was random in all patients, yet they presented with ID/DD as well as speech delay, macrocephaly and other features attributable to FXS. No signs of autism were present. Here, we further delineate the clinical spectrum of female patients with microdeletions. FMR1 expression studies gave no evidence for an absolute threshold below which signs of FXS present. Since FMR1 expression is known to be highly variable between unrelated females, and since FMR1 mRNA levels have been suggested to be more similar among family members, we further explored the possibility of an intrafamilial effect. Interestingly, FMR1 mRNA levels in all 3 patients were significantly lower than in their respective mothers, which was shown to be specific for patients with microdeletions containing FMR1.
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Affiliation(s)
- A M Zink
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - E Wohlleber
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - H Engels
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - O K Rødningen
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
| | - K Ravn
- Applied Human Molecular Genetics, Kennedy Center, Glostrup, Denmark
| | - S Heilmann
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Department of Genomics, Life & Brain Center, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - J Rehnitz
- Molecular Genetics and Infertility Unit, Department of Gynecology, Endocrinology and Reproductive Medicine, University Women Hospital, Heidelberg, Germany
| | - N Katzorke
- Molecular Genetics and Infertility Unit, Department of Gynecology, Endocrinology and Reproductive Medicine, University Women Hospital, Heidelberg, Germany
| | - C Kraus
- Institute of Human Genetics, Friedrich-Alexander-University, Erlangen-Nuremberg, Germany
| | - S Blichfeldt
- Pediatric Department L55, Glostrup University Hospital, Glostrup, Denmark
| | - P Hoffmann
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Department of Genomics, Life & Brain Center, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Medical Genetics, Department of Biomedicine, University Hospital, Basel, Switzerland
| | - H Reutter
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Department of Neonatology, Children's Hospital, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - F F Brockschmidt
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Department of Genomics, Life & Brain Center, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - M Kreiß-Nachtsheim
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany
| | - P H Vogt
- Molecular Genetics and Infertility Unit, Department of Gynecology, Endocrinology and Reproductive Medicine, University Women Hospital, Heidelberg, Germany
| | - T E Prescott
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway
| | - Z Tümer
- Applied Human Molecular Genetics, Kennedy Center, Glostrup, Denmark ; Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark
| | - J A Lee
- Institute of Human Genetics, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Department of Genomics, Life & Brain Center, Rheinische Friedrich-Wilhelms-University, Bonn, Germany ; Greenwood Genetic Center, Greenwood, S.C., USA
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Marshall LS, Simon J, Wood T, Peng M, Owen R, Feldman GS, Zaragoza MV. Deletion Xq27.3q28 in female patient with global developmental delays and skewed X-inactivation. BMC MEDICAL GENETICS 2013; 14:49. [PMID: 23634718 PMCID: PMC3643848 DOI: 10.1186/1471-2350-14-49] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 04/25/2013] [Indexed: 01/28/2023]
Abstract
BACKGROUND Global developmental delay and mental retardation are associated with X-linked disorders including Hunter syndrome (mucopolysaccharidosis type II) and Fragile X syndrome (FXS). Single nucleotide mutations in the iduronate 2-sulfatase (IDS) gene at Xq28 most commonly cause Hunter syndrome while a CGG expansion in the FMR1 gene at Xq27.3 is associated with Fragile X syndrome. Gene deletions of the Xq27-28 region are less frequently found in either condition with rare reports in females. Additionally, an association between Xq27-28 deletions and skewed X-inactivation of the normal X chromosome observed in previous studies suggested a primary role of the Xq27-28 region in X-inactivation. CASE PRESENTATION We describe the clinical, molecular and biochemical evaluations of a four year-old female patient with global developmental delay and a hemizygous deletion of Xq27.3q28 (144,270,614-154,845,961 bp), a 10.6 Mb region that contains >100 genes including IDS and FMR1. A literature review revealed rare cases with similar deletions that included IDS and FMR1 in females with developmental delay, variable features of Hunter syndrome, and skewed X-inactivation of the normal X chromosome. In contrast, our patient exhibited skewed X-inactivation of the deleted X chromosome and tested negative for Hunter syndrome. CONCLUSIONS This is a report of a female with a 10.6 Mb Xq27-28 deletion with skewed inactivation of the deleted X chromosome. Contrary to previous reports, our observations do not support a primary role of the Xq27-28 region in X-inactivation. A review of the genes in the deletion region revealed several potential genes that may contribute to the patient's developmental delays, and sequencing of the active X chromosome may provide insight into the etiology of this clinical presentation.
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Yachelevich N, Gittler JK, Klugman S, Feldman B, Martin J, Brooks SS, Dobkin C, Nolin SL. Terminal deletions of the long arm of chromosome X that include the FMR1 gene in female patients: A case series. Am J Med Genet A 2011; 155A:870-4. [DOI: 10.1002/ajmg.a.33936] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2010] [Accepted: 01/14/2011] [Indexed: 11/07/2022]
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Coffee B, Ikeda M, Budimirovic DB, Hjelm LN, Kaufmann WE, Warren ST. Mosaic FMR1 deletion causes fragile X syndrome and can lead to molecular misdiagnosis: a case report and review of the literature. Am J Med Genet A 2008; 146A:1358-67. [PMID: 18412117 DOI: 10.1002/ajmg.a.32261] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The most common cause of fragile X syndrome is expansion of a CGG trinucleotide repeat in the 5'UTR of FMR1. This expansion leads to transcriptional silencing of the gene. However, other mutational mechanisms, such as deletions of FMR1, also cause fragile X syndrome. The result is the same for both the expansion mediated silencing and deletion, absence of the gene product, FMRP. We report here on an 11-year-old boy with a cognitive and behavioral profile with features compatible with, but not specific to, fragile X syndrome. A mosaic deletion of 1,013,395 bp was found using high-density X chromosome microarray analysis followed by sequencing of the deletion breakpoints. We review the literature of FMR1 deletions and present this case in the context of other FMR1 deletions having mental retardation that may or may not have the classic fragile X phenotype.
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Affiliation(s)
- Bradford Coffee
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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8
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Arthus MF, Lonergan M, Crumley MJ, Naumova AK, Morin D, DE Marco LA, Kaplan BS, Robertson GL, Sasaki S, Morgan K, Bichet DG, Fujiwara TM. Report of 33 novel AVPR2 mutations and analysis of 117 families with X-linked nephrogenic diabetes insipidus. J Am Soc Nephrol 2000; 11:1044-1054. [PMID: 10820168 DOI: 10.1681/asn.v1161044] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
X-linked nephrogenic diabetes insipidus (NDI) is a rare disease caused by mutations in the arginine vasopressin receptor 2 gene (AVPR2). Thirty-three novel AVPR2 mutations were identified in 62 families that were not included in our previous studies. This study describes the diversity of mutations observed in a total of 117 families, the number of affected people at the time of diagnosis, skewed X chromosome inactivation in severely affected females, the inferred parental origin of de novo mutations, and it provides estimates of incidence. Among 117 families, there were 82 different putative disease-causing mutations. Based on haplotype analysis, it can be inferred that when the same AVPR2 mutation is identified in different families that were not known to be related, the mutations most likely arose independently. More than half of the families had only one affected male; two families presented with a severely affected female and no family history of NDI. A de novo mutation arose during oogenesis in the mother in 20% of isolated cases. The estimate of about 8.8 per million male live births of the incidence of X-linked NDI in the province of Quebec, Canada may be representative of the general population except in Nova Scotia and New Brunswick, where the incidence is more than six times higher. Documentation of the diversity of mutations will assist in revealing the full spectrum of clinical variation. Discussion of genetic and population genetic aspects of X-linked NDI may contribute to early diagnosis and treatment.
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Affiliation(s)
- Marie-Françoise Arthus
- Department of Medicine, Université de Montréal and Research Centre, Hôpital du Sacré-Coeur de Montréal, Montreal, Canada
| | - Michèle Lonergan
- Department of Medicine, Université de Montréal and Research Centre, Hôpital du Sacré-Coeur de Montréal, Montreal, Canada
| | - M Joyce Crumley
- Montreal General Hospital Research Institute, Montreal, Canada
| | - Anna K Naumova
- Department of Medicine, McGill University, Montreal, Canada
- Department of Obstetrics and Gynecology, McGill University, Montreal, Canada
| | - Denis Morin
- Unité 469, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique-INSERM de Pharmacologie-Endocrinologie, Montpellier, France
| | - Luiz A DE Marco
- Department of Pharmacology, University Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Bernard S Kaplan
- Division of Nephrology, The Children's Hospital of Philadelphia and Department of Pediatrics, The University of Pennsylvania, Philadelphia, Pennsylvania
| | - Gary L Robertson
- Clinical Research Center and Northwestern University Medical School, Chicago, Illinois
| | - Sei Sasaki
- Second Department of Internal Medicine, School of Medicine, Tokyo Medical and Dental University, Tokyo, Japan
| | - Kenneth Morgan
- Department of Human Genetics, McGill University, Montreal, Canada
- Department of Medicine, McGill University, Montreal, Canada
- Montreal General Hospital Research Institute, Montreal, Canada
| | - Daniel G Bichet
- Department of Medicine, Université de Montréal and Research Centre, Hôpital du Sacré-Coeur de Montréal, Montreal, Canada
| | - T Mary Fujiwara
- Department of Human Genetics, McGill University, Montreal, Canada
- Department of Medicine, McGill University, Montreal, Canada
- Montreal General Hospital Research Institute, Montreal, Canada
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9
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Buller RE, Sood AK, Lallas T, Buekers T, Skilling JS. Association between nonrandom X-chromosome inactivation and BRCA1 mutation in germline DNA of patients with ovarian cancer. J Natl Cancer Inst 1999; 91:339-46. [PMID: 10050867 DOI: 10.1093/jnci/91.4.339] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Most human female cells contain two X chromosomes, only one of which is active. The process of X-chromosome inactivation, which occurs early in development, is usually random, producing tissues with equal mixtures of cells having active X chromosomes of either maternal or paternal origin. However, nonrandom inactivation may occur in a subset of females. If a tumor suppressor gene were located on the X chromosome and if females with a germline mutation in one copy of that suppressor gene experienced nonrandom X-chromosome inactivation, then some or all of the tissues of such women might lack the wild-type suppressor gene function. This scenario could represent a previously unrecognized mechanism for development of hereditary cancers. We investigated whether such a mechanism might contribute to the development of hereditary ovarian cancers. METHODS Patterns of X-chromosome inactivation were determined by means of polymerase chain reaction amplification of the CAG-nucleotide repeat of the androgen receptor (AR) gene after methylation-sensitive restriction endonuclease digestion of blood mononuclear cell DNA from patients with invasive (n = 213) or borderline (n = 44) ovarian cancer and control subjects without a personal or family history of cancer (n = 50). BRCA1 gene status was determined by means of single-strand conformational polymorphism analysis and DNA sequencing. All statistical tests were two-sided. RESULTS AND CONCLUSIONS Among individuals informative for the AR locus, nonrandom X-chromosome inactivation was found in the DNA of 53% of those with invasive cancer versus 28% of those with borderline cancer (P = .005) and 33% of healthy control subjects (P = .016). Nonrandom X-chromosome inactivation can be a heritable trait. Nine of 11 AR-informative carriers of germline BRCA1 mutations demonstrated nonrandom X-chromosome inactivation (.0002 < P < .008, for simultaneous occurrence of both). IMPLICATIONS Nonrandom X-chromosome inactivation may be a predisposing factor for the development of invasive, but not borderline, ovarian cancer.
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Affiliation(s)
- R E Buller
- Department of Pharmacology, The University of Iowa Hospitals and Clinics, Iowa City 52242-1009, USA.
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10
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Kooy RF, Oostra BA, Willems PJ. The fragile X syndrome and other fragile site disorders. Results Probl Cell Differ 1998; 21:1-46. [PMID: 9670313 DOI: 10.1007/978-3-540-69680-3_1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- R F Kooy
- Department of Medical Genetics, University of Antwerp, Belgium.
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Hammond LS, Macias MM, Tarleton JC, Pai GS. Fragile X syndrome and deletions in FMR1: New case and review of the literature. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/(sici)1096-8628(19971112)72:4<430::aid-ajmg11>3.0.co;2-s] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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12
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Schmidt M. Comparison of female and male interstitial deletions in the distal Xq. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:166-8. [PMID: 8826468 DOI: 10.1002/(sici)1096-8628(19960712)64:1<166::aid-ajmg28>3.0.co;2-k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Abstract
The expression of X-linked genes in females heterozygous for X-linked defects can be modulated by epigenetic control mechanisms that constitute the X chromosome inactivation pathway. At least four different effects have been found to influence, in females, the phenotypic expression of genes responsible for X-linked mental retardation (XLMR). First, non-random X inactivation, due either to stochastic or genetic factors, can result in tissues in which one cell type (for example, that in which the X chromosome carrying a mutant XLMR gene is active) dominates, instead of the normal mosaic cell population expected as a result of random X inactivation. Second, skewed inactivation of the normal X in individuals carrying a deletion of part of the X chromosome has been documented in a number of mentally retarded females. Third, functional disomy of X-linked genes that are expressed inappropriately due to the absence of X inactivation has been found in mentally retarded females with structurally abnormal X chromosomes that do not contain the X inactivation center. And fourth, dose-dependent overexpression of X-linked genes that normally "escape" X inactivation may account for the mental and developmental delay associated with increasing numbers of otherwise inactive X chromosomes in individuals with X chromosome aneuploidy.
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Affiliation(s)
- H F Willard
- Department of Genetics, Case Western Reserve University School of Medicine and University Hospitals of Cleveland, OH 44106, USA
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14
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Migeon BR, Stetten G, Tuck-Muller C, Axelman J, Jani M, Dungy D. Molecular characterization of a deleted X chromosome (Xq13.3-Xq21.31) exhibiting random X inactivation. SOMATIC CELL AND MOLECULAR GENETICS 1995; 21:113-20. [PMID: 7570183 DOI: 10.1007/bf02255786] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
As a result of selection following random X chromosome inactivation in human females, X chromosomes with visible deletions are usually inactive in every somatic cell. We have studied a female with mental retardation and dysmorphic features whose karyotype includes an X chromosome with a visible interstitial deletion in the proximal long arm. Based on cytogenetic analysis, the proximal breakpoint appeared to be in band Xq13.1, and the distal one in band q21.3. However, molecular analyses show that less of the q13 band is missing than cytogenetic studies indicated, as the deletion includes only loci from the region Xq13.3 to Xq21.31. Unexpectedly, studies of chromosome replication show that the pattern of X inactivation is random. Whereas the deleted X chromosome is late replicating in some cells from all tissues studied, it is early replicating in the majority of blood lymphocytes and skin fibroblasts, and is the active X chromosome in many of the hybrids derived from skin fibroblasts. As this chromosome is able to inactivate, it must include those DNA sequences from the X-inactivation center (XIC) that are essential for cis X inactivation. Molecular studies show that the XIC region, at Xq13.2, is present, so it is unlikely that the lack of consistent inactivation of this chromosome is attributable to close proximity of the breakpoint to the XIC. Supporting this conclusion is the similarity of the breakpoints to those of the other chromosomes we studied, whose deletions clearly do not interfere with the ability to inactivate. Our results show that deletions distal to DXS441 in Xq13.2 do not interfere with cis X inactivation. We attribute the random pattern of X inactivation reported here to the fact that in the tissues studied, cells with this interstitial deletion are not at a selective disadvantage.
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Affiliation(s)
- B R Migeon
- Center for Medical Genetics, Johns Hopkins University, Baltimore, Maryland 21287-3914, USA
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Abbadi N, Philippe C, Chery M, Gilgenkrantz H, Tome F, Collin H, Theau D, Recan D, Broux O, Fardeau M. Additional case of female monozygotic twins discordant for the clinical manifestations of Duchenne muscular dystrophy due to opposite X-chromosome inactivation. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 52:198-206. [PMID: 7802009 DOI: 10.1002/ajmg.1320520215] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A pair of female monozygotic (MZ) twins, heterozygous carriers for a deletion in the DMD gene and discordant for the clinical manifestations of Duchenne muscular dystrophy, were analyzed by molecular studies, in situ hybridization, and methylation pattern of X chromosomes to search for opposite X inactivation as an explanation of their clinical discordance. Results in lymphocytes and skin fibroblast cell lines suggest a partial mirror inactivation with the normal X chromosome preferentially active in the unaffected twin, and the maternal deleted X chromosome preferentially active in the affected twin. A review shows that MZ female twins discordant for X-linked diseases are not uncommon. Twinning and X inactivation may be interrelated and could explain the female twins discordant for X-linked traits.
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Affiliation(s)
- N Abbadi
- Laboratoire de Génétique Université de Nancy, France
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Schmidt M, Robertson A, Crawford M. X inactivation pattern in interstitial deletions of the fragile X region. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 51:451. [PMID: 7943016 DOI: 10.1002/ajmg.1320510429] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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17
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Tommerup N. Mendelian cytogenetics. Chromosome rearrangements associated with mendelian disorders. J Med Genet 1993; 30:713-27. [PMID: 8411066 PMCID: PMC1016528 DOI: 10.1136/jmg.30.9.713] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- N Tommerup
- Danish Centre for Human Genome Research, John F Kennedy Institute, Glostrup, Denmark
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18
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Gedeon AK, Baker E, Robinson H, Partington MW, Gross B, Manca A, Korn B, Poustka A, Yu S, Sutherland GR. Fragile X syndrome without CCG amplification has an FMR1 deletion. Nat Genet 1992; 1:341-4. [PMID: 1302032 DOI: 10.1038/ng0892-341] [Citation(s) in RCA: 143] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We describe a patient with typical clinical features of the fragile X syndrome, but without cytogenetic expression of the fragile X or an amplified CCG trinucleotide repeat fragment. The patient has a previously uncharacterized submicroscopic deletion encompassing the CCG repeat, the entire FMR1 gene and about 2.5 megabases of flanking sequences. This finding confirms that the fragile X phenotype can exist, without amplification of the CCG repeat or cytogenetic expression of the fragile X, and that fragile X syndrome is a genetically homogeneous disorder involving FMR1. We also found random X-inactivation in the mother of the patient who was shown to be a carrier of this deletion.
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Affiliation(s)
- A K Gedeon
- Department of Cytogenetics and Molecular Genetics, Adelaide Children's Hospital, South Australia
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19
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Abstract
X-chromosome inactivation is a unique developmental event that results in the cis-limited transcriptional inactivation of most genes on one of the two X chromosomes in female mammals. Studies in both human and mouse have demonstrated that X inactivation requires the presence in cis of a locus, the X-inactivation center, that is thought to be involved in the initiation and/or spreading of the inactivation signal in early development. Identification and characterization of a gene, XIST, which is located at or near the X-inactivation center and which is expressed specifically from the inactive X chromosome in both humans and mouse, suggests that it may be involved in X inactivation.
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Affiliation(s)
- A Ballabio
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030
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20
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Schmidt M. Do sequences in Xq27.3 play a role in X inactivation? AMERICAN JOURNAL OF MEDICAL GENETICS 1992; 43:279-81. [PMID: 1605201 DOI: 10.1002/ajmg.1320430143] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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21
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Hulsebos TJ, Oostra BA, Broersen S, Smits A, van Oost BA, Westerveld A. New distal marker closely linked to the fragile X locus. Hum Genet 1991; 87:369-72. [PMID: 1677926 DOI: 10.1007/bf00200922] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have isolated II-10, a new X-chromosomal probe that identifies a highly informative two-allele TaqI restriction fragment length polymorphism at locus DXS466. Using somatic cell hybrids containing distinct portions of the long arm of the X chromosome, we could localize DXS466 between DXS296 and DXS304, both of which are closely linked distal markers for fragile X. This regional localization was supported by the analysis, in fragile X families, of recombination events between these three loci, the fragile X locus and locus DXS52, the latter being located at a more distal position. DXS466 is closely linked to the fragile X locus with a peak lod score of 7.79 at a recombination fraction of 0.02. Heterozygosity of DXS466 is approximately 50%. Its close proximity and relatively high informativity make DXS466 a valuable new diagnostic DNA marker for fragile X.
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Affiliation(s)
- T J Hulsebos
- Institute of Human Genetics, University of Amsterdam, The Netherlands
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22
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Hirst MC, Roche A, Flint TJ, MacKinnon RN, Bassett JH, Nakahori Y, Watson JE, Bell MV, Patterson MN, Boyd Y. Linear order of new and established DNA markers around the fragile site at Xq27.3. Genomics 1991; 10:243-9. [PMID: 2045104 DOI: 10.1016/0888-7543(91)90506-a] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have used recombinant clones derived from microdissection of the fragile X region to characterize breakpoints around the fragile site at Xq27.3. So far, no microdissection markers derived from Xq28 material have been found, thus allowing a rapid screening for clones surrounding the fragile site by their presence in a somatic cell hybrid containing Xq27.2-Xqter. A total of 43 new DNA markers from Xq27 have been sublocalized within this chromosome band. Of these new DNA markers, 5 lie in an interval defined as containing the fragile X region. The saturation of Xq27 with DNA markers by microdissection demonstrates the power of this technique and provides the resources for generating a complete physical map of the region.
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Affiliation(s)
- M C Hirst
- Molecular Genetics Group, John Radcliffe Hospital, Headington, Oxford, United Kingdom
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23
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Spano LM, Opitz JM. Bibliography on X-linked mental retardation, the fragile X, and related subjects V (1991). AMERICAN JOURNAL OF MEDICAL GENETICS 1991; 38:173-85. [PMID: 2018055 DOI: 10.1002/ajmg.1320380203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- L M Spano
- Department of Medical Genetics, Shodair Children's Hospital, Helena, Montana 59604
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24
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Oostra BA, Majoor-Krakauer DF, van Hemel JO, Bakker E, Callen DF, Schmidt M, van Oost BA. Mapping of a new RFLP marker RN1 (DXS369) close to the fragile site FRAXA on Xq27-q28. AMERICAN JOURNAL OF MEDICAL GENETICS 1991; 38:332-5. [PMID: 1673306 DOI: 10.1002/ajmg.1320380233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A new polymorphic DNA marker RN1, defining locus DXS369, was recently isolated. Using different somatic cell hybrids, RN1 was mapped between markers 4D-8 and U6.2. We have narrowed the localization of RN1 to the region between 4D-8 and FRAXA by genetic mapping in fragile X [fra(X)] families. Combined with information from other reports, the following order of loci on Xq27-q28 is suggested: cen-F9-(DXS105-DXS152)-DXS98-DXS369-FRAXA- DXS304-(DXS52-DXS15-F8)-tel. The locus DXS369 is closely linked to FRAXA, with a peak lodscore of 18.5 at a recombination fraction of 0.05. Therefore, RN1 is a useful probe for carrier detection and prenatal diagnosis in fra(X) families.
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Affiliation(s)
- B A Oostra
- Department of Cell Biology, Erasmus University, Rotterdam, The Netherlands
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25
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Schmidt M, Du Sart D, Kalitsis P, Fraser N, Leversha M, Voullaire L, Foster D, Davies J, Hills L, Petrovic V. X chromosome inactivation in fibroblasts of mentally retarded female carriers of the fragile site Xq27.3: application of the probe M27 beta to evaluate X inactivation status. AMERICAN JOURNAL OF MEDICAL GENETICS 1991; 38:411-5. [PMID: 1673316 DOI: 10.1002/ajmg.1320380252] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Over 30% of female carriers of the fragile X [fra(X)] syndrome are clinically affected. A nonrandom X chromosome inactivation in these cases could be a plausible explanation. A review of previous studies addressing this question showed inconclusive results; thus, we analysed the X inactivation pattern in fibroblasts of 4 unrelated, mentally retarded fra(X) carriers with a high expression of the fragile site Xq27.3. Using Southern analysis with a highly polymorphic probe M27 beta that recognizes methylation differences between the active and inactive X chromosome we found a 50/50 inactivation pattern in 2 cases and skewed patterns in the other 2. As biased patterns were also observed in control females we conclude that at present no evidence exists for a nonrandom X chromosome inactivation in the fra(X) syndrome in females.
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Affiliation(s)
- M Schmidt
- Murdoch Institute, Royal Children's Hospital, Parkville, Melbourne, Australia
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