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Mirceta M, Shum N, Schmidt MHM, Pearson CE. Fragile sites, chromosomal lesions, tandem repeats, and disease. Front Genet 2022; 13:985975. [PMID: 36468036 PMCID: PMC9714581 DOI: 10.3389/fgene.2022.985975] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 09/02/2022] [Indexed: 09/16/2023] Open
Abstract
Expanded tandem repeat DNAs are associated with various unusual chromosomal lesions, despiralizations, multi-branched inter-chromosomal associations, and fragile sites. Fragile sites cytogenetically manifest as localized gaps or discontinuities in chromosome structure and are an important genetic, biological, and health-related phenomena. Common fragile sites (∼230), present in most individuals, are induced by aphidicolin and can be associated with cancer; of the 27 molecularly-mapped common sites, none are associated with a particular DNA sequence motif. Rare fragile sites ( ≳ 40 known), ≤ 5% of the population (may be as few as a single individual), can be associated with neurodevelopmental disease. All 10 molecularly-mapped folate-sensitive fragile sites, the largest category of rare fragile sites, are caused by gene-specific CGG/CCG tandem repeat expansions that are aberrantly CpG methylated and include FRAXA, FRAXE, FRAXF, FRA2A, FRA7A, FRA10A, FRA11A, FRA11B, FRA12A, and FRA16A. The minisatellite-associated rare fragile sites, FRA10B, FRA16B, can be induced by AT-rich DNA-ligands or nucleotide analogs. Despiralized lesions and multi-branched inter-chromosomal associations at the heterochromatic satellite repeats of chromosomes 1, 9, 16 are inducible by de-methylating agents like 5-azadeoxycytidine and can spontaneously arise in patients with ICF syndrome (Immunodeficiency Centromeric instability and Facial anomalies) with mutations in genes regulating DNA methylation. ICF individuals have hypomethylated satellites I-III, alpha-satellites, and subtelomeric repeats. Ribosomal repeats and subtelomeric D4Z4 megasatellites/macrosatellites, are associated with chromosome location, fragility, and disease. Telomere repeats can also assume fragile sites. Dietary deficiencies of folate or vitamin B12, or drug insults are associated with megaloblastic and/or pernicious anemia, that display chromosomes with fragile sites. The recent discovery of many new tandem repeat expansion loci, with varied repeat motifs, where motif lengths can range from mono-nucleotides to megabase units, could be the molecular cause of new fragile sites, or other chromosomal lesions. This review focuses on repeat-associated fragility, covering their induction, cytogenetics, epigenetics, cell type specificity, genetic instability (repeat instability, micronuclei, deletions/rearrangements, and sister chromatid exchange), unusual heritability, disease association, and penetrance. Understanding tandem repeat-associated chromosomal fragile sites provides insight to chromosome structure, genome packaging, genetic instability, and disease.
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Affiliation(s)
- Mila Mirceta
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Natalie Shum
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Monika H. M. Schmidt
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Christopher E. Pearson
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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Chakraborty A, Grageda A, Kuznetsov VA, Feng W. A Double Jeopardy: Loss of FMRP Results in DSB and Down-regulated DNA Repair. 21ST CENTURY PATHOLOGY 2022; 2:125. [PMID: 36688938 PMCID: PMC9850805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Our understanding of the molecular functions of the nucleocytoplasmic FMRP protein, which, if absent or dysfunctional, causes the fragile X syndrome (FXS), largely revolves around its involvement in protein translation regulation in the cytoplasm. Recent studies have begun honing in on the nuclear and genomic functions of FMRP. We have shown that during DNA replication stress, cells derived from FXS patients sustain increased level of R-loop formation and DNA double strand breaks. Here, we describe a transcriptomic analysis of these cells in order to identify those genes most impacted by the loss of FMRP with and without replication stress. We show that FMRP loss causes transcriptomic changes previously reported in untreated conditions. Importantly, we also show that replication stress, in addition to causing excess of DSB, results in down-regulation of transcription in virtually all DNA repair pathways. This finding suggests that despite normal DNA damage response, FXS patient-derived cells experience R-loop-induced DNA breakage as well as impaired DNA repair functions, effectively a double jeopardy. We suggest that it is imperative to deepen the understanding of the nuclear functions, particularly a genome protective function, of FMRP, which will lead to discoveries of novel therapeutic interventions for the FXS.
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Affiliation(s)
- Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA,Tessera Therapeutics, Somerville, Massachusetts, USA
| | - Andre Grageda
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA,Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Vladimir A. Kuznetsov
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA,Department of Urology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA,Corresponding Author: Wenyi Feng, Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA;
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Kamimura K, Maeda N. Glypicans and Heparan Sulfate in Synaptic Development, Neural Plasticity, and Neurological Disorders. Front Neural Circuits 2021; 15:595596. [PMID: 33679334 PMCID: PMC7928303 DOI: 10.3389/fncir.2021.595596] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 01/11/2021] [Indexed: 12/16/2022] Open
Abstract
Heparan sulfate proteoglycans (HSPGs) are components of the cell surface and extracellular matrix, which bear long polysaccharides called heparan sulfate (HS) attached to the core proteins. HSPGs interact with a variety of ligand proteins through the HS chains, and mutations in HSPG-related genes influence many biological processes and cause various diseases. In particular, recent findings from vertebrate and invertebrate studies have raised the importance of glycosylphosphatidylinositol-anchored HSPGs, glypicans, as central players in the development and functions of synapses. Glypicans are important components of the synapse-organizing protein complexes and serve as ligands for leucine-rich repeat transmembrane neuronal proteins (LRRTMs), leukocyte common antigen-related (LAR) family receptor protein tyrosine phosphatases (RPTPs), and G-protein-coupled receptor 158 (GPR158), regulating synapse formation. Many of these interactions are mediated by the HS chains of glypicans. Neurexins (Nrxs) are also synthesized as HSPGs and bind to some ligands in common with glypicans through HS chains. Therefore, glypicans and Nrxs may act competitively at the synapses. Furthermore, glypicans regulate the postsynaptic expression levels of ionotropic glutamate receptors, controlling the electrophysiological properties and non-canonical BMP signaling of synapses. Dysfunctions of glypicans lead to failures in neuronal network formation, malfunction of synapses, and abnormal behaviors that are characteristic of neurodevelopmental disorders. Recent human genetics revealed that glypicans and HS are associated with autism spectrum disorder, neuroticism, and schizophrenia. In this review, we introduce the studies showing the roles of glypicans and HS in synapse formation, neural plasticity, and neurological disorders, especially focusing on the mouse and Drosophila as potential models for human diseases.
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Affiliation(s)
- Keisuke Kamimura
- Developmental Neuroscience Project, Department of Brain and Neurosciences, Tokyo Metropolitan Institute of Medical Science, Setagaya, Japan
| | - Nobuaki Maeda
- Developmental Neuroscience Project, Department of Brain and Neurosciences, Tokyo Metropolitan Institute of Medical Science, Setagaya, Japan
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Tanna M, Aqeilan RI. Modeling WWOX Loss of Function in vivo: What Have We Learned? Front Oncol 2018; 8:420. [PMID: 30370248 PMCID: PMC6194312 DOI: 10.3389/fonc.2018.00420] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/10/2018] [Indexed: 12/21/2022] Open
Abstract
The WW domain–containing oxidoreductase (WWOX) gene encompasses a common fragile sites (CFS) known as FRA16D, and is implicated in cancer. WWOX encodes a 46kDa adaptor protein, which contains two N-terminal WW–domains and a catalytic domain at its C–terminus homologous to short–chain dehydrogenase/reductase (SDR) family proteins. A high sequence conservation of WWOX orthologues from insects to rodents and ultimately humans suggest its significant role in physiology and homeostasis. Indeed, data obtained from several animal models including flies, fish, and rodents demonstrate WWOX in vivo requirement and that its deregulation results in severe pathological consequences including growth retardation, post–natal lethality, neuropathy, metabolic disorders, and tumorigenesis. Altogether, these findings set WWOX as an essential protein that is necessary to maintain normal cellular/physiological homeostasis. Here, we review and discuss lessons and outcomes learned from modeling loss of WWOX expression in vivo.
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Affiliation(s)
- Mayur Tanna
- Faculty of Medicine, The Lautenberg Center for Immunology and Cancer Research, Institute for Medical Research, Israel-Canada (IMRIC), Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rami I Aqeilan
- Faculty of Medicine, The Lautenberg Center for Immunology and Cancer Research, Institute for Medical Research, Israel-Canada (IMRIC), Hebrew University of Jerusalem, Jerusalem, Israel.,Department of Cancer Biology & Genetics, Ohio State University Wexner Medical Center, Columbus, OH, United States
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Feng W, Chakraborty A. Fragility Extraordinaire: Unsolved Mysteries of Chromosome Fragile Sites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1042:489-526. [PMID: 29357071 DOI: 10.1007/978-981-10-6955-0_21] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chromosome fragile sites are a fascinating cytogenetic phenomenon now widely implicated in a slew of human diseases ranging from neurological disorders to cancer. Yet, the paths leading to these revelations were far from direct, and the number of fragile sites that have been molecularly cloned with known disease-associated genes remains modest. Moreover, as more fragile sites were being discovered, research interests in some of the earliest discovered fragile sites ebbed away, leaving a number of unsolved mysteries in chromosome biology. In this review we attempt to recount some of the early discoveries of fragile sites and highlight those phenomena that have eluded intense scrutiny but remain extremely relevant in our understanding of the mechanisms of chromosome fragility. We then survey the literature for disease association for a comprehensive list of fragile sites. We also review recent studies addressing the underlying cause of chromosome fragility while highlighting some ongoing debates. We report an observed enrichment for R-loop forming sequences in fragile site-associated genes than genomic average. Finally, we will leave the reader with some lingering questions to provoke discussion and inspire further scientific inquiries.
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Affiliation(s)
- Wenyi Feng
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA.
| | - Arijita Chakraborty
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
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Summers SM, Cogswell J, Goodrich JE, Mu Y, Nguyen DV, Brass SD, Hagerman RJ. Prevalence of restless legs syndrome and sleep quality in carriers of the fragile X premutation. Clin Genet 2015; 86:181-4. [PMID: 25180401 DOI: 10.1111/cge.12249] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This study examined the relationship between the fragile X premutation and restless legs syndrome (RLS). Demographic, medical history and survey responses related to sleep were collected from 213 participants (127 carriers and 86 age matched controls). Subjects were asked about the presence of the four formal diagnostic criteria for RLS. Individuals with the premutation were 1.9 times as likely to meet criteria for RLS (95% CI 1.1–3.2, p=0.025) as controls. Premutation carriers with RLS also experienced significantly worse symptoms than matched controls with adjusted mean scores of 15.1±8.8 vs 7.9±4.4, respectively on the International Restless Legs Scale (IRLS). As markers for domains of sleep disturbance, all subjects completed the Epworth Sleepiness Scale (ESS), the Insomnia Severity Index (ISA) and the Pittsburgh Sleep Quality Index (PSQI). Premutation carriers demonstrated significantly more pathology on these tests except for the ESS where there was a trend towards increased daytime sleepiness in carriers. RLS joins a host of other conditions that should be carefully screened for in those carrying the fragile X premutation and sleep should be a focus for clinicians providing care to them.
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Affiliation(s)
- Patricia A. Jacobs
- Wessex Regional Genetics Laboratory, Salisbury NHS Foundation Trust, SP2 8BJ Salisbury, United Kingdom;
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Leman AR, Noguchi E. The replication fork: understanding the eukaryotic replication machinery and the challenges to genome duplication. Genes (Basel) 2014; 4:1-32. [PMID: 23599899 PMCID: PMC3627427 DOI: 10.3390/genes4010001] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic cells must accurately and efficiently duplicate their genomes during each round of the cell cycle. Multiple linear chromosomes, an abundance of regulatory elements, and chromosome packaging are all challenges that the eukaryotic DNA replication machinery must successfully overcome. The replication machinery, the “replisome” complex, is composed of many specialized proteins with functions in supporting replication by DNA polymerases. Efficient replisome progression relies on tight coordination between the various factors of the replisome. Further, replisome progression must occur on less than ideal templates at various genomic loci. Here, we describe the functions of the major replisome components, as well as some of the obstacles to efficient DNA replication that the replisome confronts. Together, this review summarizes current understanding of the vastly complicated task of replicating eukaryotic DNA.
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Affiliation(s)
- Adam R. Leman
- Authors to whom correspondence should be addressed; E-Mails: (A.R.L.); (E.N.); Tel.: +1-215-762-4825 (E.N.); Fax: +1-215-762-4452 (E.N.)
| | - Eishi Noguchi
- Authors to whom correspondence should be addressed; E-Mails: (A.R.L.); (E.N.); Tel.: +1-215-762-4825 (E.N.); Fax: +1-215-762-4452 (E.N.)
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Crum-Bailey JM, Dennison DH, Weiner WJ, Hawley JS. The neurology and corresponding genetics of fragile X disorders: insights into the genetics of neurodegeneration. FUTURE NEUROLOGY 2013. [DOI: 10.2217/fnl.12.92] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
There have been significant advances in understanding how the fragile X gene (FMR1) can lead to distinct neurological syndromes. Clinical features of two disorders – fragile X syndrome and fragile X-associated tremor ataxia syndrome (FXTAS) – are highlighted in this article. These two disorders – one a neurodevelopmental disorder, the other a neurodegenerative disorder – are caused by a single expanded CGG repeat sequence within the FMR1 gene. Minor differences in repeat length result in the markedly different phenotypes. Understanding the action of FMR1 in FXTAS and fragile X syndrome has yielded significant insights into the genetics of neurodegeneration. Moreover, the genetic model in FXTAS is similar to several other neurologic genetic disorders, suggesting there are common pathways shared by many phenotypically diverse progressive neurodegenerative disorders. Finally, it is possible that targeted therapies for disorders such as FXTAS may also be effective in other neurodegenerative disorders that share similar mechanisms of pathogenesis.
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Affiliation(s)
- Jennifer M Crum-Bailey
- Walter Reed National Military Medical Center, 8901 Wisconsin Avenue, Department of Neurology, Bethesda, MD 20889, USA
| | - David H Dennison
- Walter Reed National Military Medical Center, 8901 Wisconsin Avenue, Department of Neurology, Bethesda, MD 20889, USA
| | - William J Weiner
- University of Maryland School of Medicine, Department of Neurology, 110 S Paca Street 3-S-124, Baltimore MD 21201, USA
| | - Jason S Hawley
- Walter Reed National Military Medical Center, 8901 Wisconsin Avenue, Department of Neurology, Bethesda, MD 20889, USA.
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Lubs HA, Stevenson RE, Schwartz CE. Fragile X and X-linked intellectual disability: four decades of discovery. Am J Hum Genet 2012; 90:579-90. [PMID: 22482801 DOI: 10.1016/j.ajhg.2012.02.018] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/03/2012] [Accepted: 02/17/2012] [Indexed: 01/18/2023] Open
Abstract
X-Linked intellectual disability (XLID) accounts for 5%-10% of intellectual disability in males. Over 150 syndromes, the most common of which is the fragile X syndrome, have been described. A large number of families with nonsyndromal XLID, 95 of which have been regionally mapped, have been described as well. Mutations in 102 X-linked genes have been associated with 81 of these XLID syndromes and with 35 of the regionally mapped families with nonsyndromal XLID. Identification of these genes has enabled considerable reclassification and better understanding of the biological basis of XLID. At the same time, it has improved the clinical diagnosis of XLID and allowed for carrier detection and prevention strategies through gamete donation, prenatal diagnosis, and genetic counseling. Progress in delineating XLID has far outpaced the efforts to understand the genetic basis for autosomal intellectual disability. In large measure, this has been because of the relative ease of identifying families with XLID and finding the responsible mutations, as well as the determined and interactive efforts of a small group of researchers worldwide.
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Affiliation(s)
- Herbert A Lubs
- Greenwood Genetic Center, JC Self Research Institute of Human Genetics, 113 Gregor Mendel Circle, Greenwood, SC 29646, USA
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Lac operator repeats generate a traceable fragile site in mammalian cells. EMBO Rep 2011; 12:1032-8. [PMID: 21836640 DOI: 10.1038/embor.2011.158] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 06/21/2011] [Accepted: 07/08/2011] [Indexed: 11/08/2022] Open
Abstract
One limitation for the study of chromosomal fragile sites is that they must be studied on metaphase spreads, after the breakage. We show here that bacterial lac operator (lacO) repeats are prone to spontaneous breakage, which when combined with a fluorescent lac repressor (lacR) has allowed us to track a fragile site through the cell cycle. By using this system, we show that Plk1-interacting checkpoint helicase (PICH) is already present at fragile sites during interphase, suggesting roles for this helicase beyond mitosis. In addition, we report that the oncogene Myc promotes the formation of anaphase bridges and micronuclei containing fragile-site sequences.
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Stevenson RE, Schwartz CE. X-linked intellectual disability: unique vulnerability of the male genome. ACTA ACUST UNITED AC 2010; 15:361-8. [PMID: 20014364 DOI: 10.1002/ddrr.81] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
X-linked intellectual disability (XLID) accounts for approximately 16% of males with intellectual disability (ID). This is, in part, related to the fact that males have a single X chromosome. Progress in the clinical and molecular characterization of XLID has outpaced progress in the delineation of ID due to genes on the other 22 chromosomes. Almost half of the estimated 200 XLID genes have been identified and another 20% have been regionally mapped. These advances have had immediate benefits for families, allowing for carrier testing, genetic counseling, prenatal diagnosis, and preimplantation genetic diagnosis. Additionally, the combination of clinical delineation with gene identification and the development of gene panels for screening nonsyndromal XLID has been able to limit unproductive laboratory testing. Most importantly for the patients, some of the gene discoveries have pointed to potential strategies for treatment.
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Affiliation(s)
- Roger E Stevenson
- J.C. Self Research Institute, Greenwood Genetic Center, Greenwood, SC 29646, USA
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Abstract
Chromosomal fragile sites are specific loci that preferentially exhibit gaps and breaks on metaphase chromosomes following partial inhibition of DNA synthesis. Their discovery has led to novel findings spanning a number of areas of genetics. Rare fragile sites are seen in a small proportion of individuals and are inherited in a Mendelian manner. Some, such as FRAXA in the FMR1 gene, are associated with human genetic disorders, and their study led to the identification of nucleotide-repeat expansion as a frequent mutational mechanism in humans. In contrast, common fragile sites are present in all individuals and represent the largest class of fragile sites. Long considered an intriguing component of chromosome structure, common fragile sites have taken on novel significance as regions of the genome that are particularly sensitive to replication stress and that are frequently rearranged in tumor cells. In recent years, much progress has been made toward understanding the genomic features of common fragile sites and the cellular processes that monitor and influence their stability. Their study has merged with that of cell cycle checkpoints and DNA repair, and common fragile sites have provided insight into understanding the consequences of replication stress on DNA damage and genome instability in cancer cells.
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Affiliation(s)
- Sandra G Durkin
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-0618, USA.
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Abstract
Fragile X syndrome is one of the most common forms of inherited mental retardation. In most cases the disease is caused by the methylation-induced transcriptional silencing of the fragile X mental retardation 1 (FMR1) gene that occurs as a result of the expansion of a CGG repeat in the gene's 5'UTR and leads to the loss of protein product fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that associates with translating polyribosomes as part of a large messenger ribonucleoprotein (mRNP) and modulates the translation of its RNA ligands. Pathological studies from the brains of patients and from Fmr1 knockout mice show abnormal dendritic spines implicating FMRP in synapse formation and function. Evidence from both in vitro and in vivo neuronal studies indicates that FMRP is located at the synapse and the loss of FMRP alters synaptic plasticity. As synaptic plasticity has been implicated in learning and memory, analysis of synapse abnormalities in patients and Fmr1 knockout mice should prove useful in studying the pathogenesis of fragile X syndrome and understanding learning and cognition in general. If an appreciable portion of the total variance (in IQ) is due to sex linked genes, it is of more importance that a boy should have a clever mother than a clever father. Hogben 1932 (quoted in Lehrke 1974)
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Affiliation(s)
- William T O'Donnell
- Howard Hughes Medical Institute and Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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Sabaratnam M, Vroegop PG, Gangadharan SK. Epilepsy and EEG findings in 18 males with fragile X syndrome. Seizure 2001; 10:60-3. [PMID: 11181100 DOI: 10.1053/seiz.2000.0492] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Of the 24 males identified as having fragile X syndrome in the Northeast Essex screening programme, 25% had epilepsy. Epilepsy in individuals with fragile X syndrome is known to follow a benign course with seizures disappearing before the age of 20. However, half of our sample with a history of epilepsy continued to have seizures after the age of 20. We reviewed the EEG reports of 18 of the 24 individuals (aged between 13 and 63 years) including all six individuals with epilepsy. We had 32 EEG recordings from 18 subjects, with nine people having more than one recording at different points. The EEG showed a definite improvement in only five individuals. Three individuals who had serial recordings (one with epilepsy) showed no significant changes over time and the EEG of one subject with epilepsy deteriorated. The most common abnormal EEG findings were rhythmic theta activity (50%) and a slowing of background activity (28%). There were no characteristic features in the sleep EEGs performed on four subjects. The possible implications of these preliminary findings are discussed.
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Affiliation(s)
- M Sabaratnam
- Imperial College, London, and Ealing Community Team for People with Learning Disabilities, 62 Green Lane, Hanwell, London, W7 2PB, UK.
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Musumeci SA, Hagerman RJ, Ferri R, Bosco P, Dalla Bernardina B, Tassinari CA, De Sarro GB, Elia M. Epilepsy and EEG findings in males with fragile X syndrome. Epilepsia 1999; 40:1092-9. [PMID: 10448821 DOI: 10.1111/j.1528-1157.1999.tb00824.x] [Citation(s) in RCA: 186] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE AND METHODS One hundred and ninety-two fragile X male patients were investigated for seizures and EEG findings, 168 in a retrospective and 24 in another prospective study, to characterize the natural history of seizures, epilepsy, and EEG abnormalities in males with this syndrome. RESULTS Seizures were documented in 35 (18.2%) of 192 patients; they never started before the age of 2 years or after the age of 9 years. Seizures were frequently of the complex partial type and less frequently of the partial motor and generalized type. Seizures involving frontal and temporal lobes were commonly seen and were usually well controlled by anticonvulsants. In the majority of young fragile X patients studied, an age-related paroxysmal EEG pattern was found, which showed neurophysiologic characteristics very similar to those of the centrotemporal spikes. CONCLUSIONS These findings confirm that fragile X syndrome can be considered a genetic model of epilepsy.
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Affiliation(s)
- S A Musumeci
- Oasi Institute for Research on Mental Retardation and Brain Aging, Troina (EN), Italy
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Miezejeski CM, Heaney G, Belser R, Brown WT, Jenkins EC, Sersen EA. Longer brainstem auditory evoked response latencies of individuals with fragile X syndrome related to sedation. AMERICAN JOURNAL OF MEDICAL GENETICS 1997; 74:167-71. [PMID: 9129717 DOI: 10.1002/(sici)1096-8628(19970418)74:2<167::aid-ajmg10>3.0.co;2-g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Brainstem auditory evoked response latencies were studies in 75 males (13 with fragile X syndrome, 18 with mental retardation due to other causes, and 44 with no disability). Latency values were obtained for each ear for the positive deflections of waves I (P1), III (P3), and V (P5). Some individuals with mental retardation required sedation. Contrary to previous report, latencies obtained for individuals with fragile X did not differ from those obtained for persons without mental retardation. Persons receiving sedation, whether or not their retardation was due to fragile X, had longer latencies for wave P5 than persons who did not receive sedation. This effect of sedation may also explain the previously reported increased latencies for persons with fragile X.
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Affiliation(s)
- C M Miezejeski
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314, USA
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Murray J, Cuckle H, Taylor G, Hewison J. Screening for fragile X syndrome: information needs for health planners. J Med Screen 1997; 4:60-94. [PMID: 9275266 DOI: 10.1177/096914139700400204] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- J Murray
- Centre for Reproduction, Growth & Development, Research School of Medicine, University of Leeds, United Kingdom
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Giovannucci Uzielli ML, Guarducci S, Cecconi A, Lenzi S, Ricci U, Balestrieri C, Petrocelli P, Lapi E. Diagnosis and prevention of fragile-X syndrome. From the family study to the population screening programme: eighteen years of activity. ACTA GENETICAE MEDICAE ET GEMELLOLOGIAE 1996; 45:303-8. [PMID: 8872054 DOI: 10.1017/s0001566000001537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Fragile-X syndrome, which derives its name from the expression of a fragile site (FRAXA) at Xq27.3 associated with the phenotype, has achieved distinction as the most common inherited cause of mental retardation. It is the first disorder shown to be due to dynamic mutation in heritable instable DNA.In 1991 the mutation responsible for Fragile-X syndrome was delineated as an expansion of the trinucleotide (CGG) sequence within an evolutionarily conserved gene, at the position of the fragile-X site.The DNA of the promoter in the 5' UTR region of FMR-1 gene becomes abnormally methylated when the CGG sequence exceeds approximately 230 repeats, resulting in the transcriptional suppression of FMR-1. Based on the length of CGG repeat in the FMR-1 gene, the alleles are usually classified as normal, premutation or full mutation. CGG instability correlates with the length of repeats and number of AGGs within the FMR-1 CGG tract. In a minority of cases the Fragile-X syndrome may be due to deletion, or to point mutation in the FMR-1 gene.
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20
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Simonoff E, Bolton P, Rutter M. Mental retardation: genetic findings, clinical implications and research agenda. J Child Psychol Psychiatry 1996; 37:259-80. [PMID: 8707910 DOI: 10.1111/j.1469-7610.1996.tb01404.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The most important genetic advances in the field of mental retardation include the discovery of the novel genetic mechanism responsible for the Fragile X syndrome, and the imprinting involved in the Prader-Willi and Angelman syndromes, but there have also been advances in our understanding of the pathogenesis of Down syndrome and phenylketonuria. Genetic defects (both single gene Mendelizing disorders and cytogenetic abnormalities) are involved in a substantial proportion of cases of mild as well as severe mental retardation, indicating that the previous equating of severe mental retardation with pathology, and of mild retardation with normal variation, is a misleading over-simplication. Within the group in which no pathological cause can be detected, behaviour genetic studies indicate that genetic influences are important, but that their interplay with environmental factors, which are also important, is at present poorly understood. Research into the joint action of genetic and environmental influences in this group will be an important research area in the future.
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Affiliation(s)
- E Simonoff
- MRC Child Psychiatry Unit and Centre for Social, Genetic and Developmental Psychiatry, Institute of Psychiatry, London, U.K
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21
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Arrieta MI, Echarri E, Nuñez T, Gil A, Criado B, Martinez B. Cytogenetics of autosomal fragile sites: A Basque population study. Am J Hum Biol 1996; 8:473-481. [DOI: 10.1002/(sici)1520-6300(1996)8:4<473::aid-ajhb7>3.0.co;2-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/1994] [Accepted: 10/20/1995] [Indexed: 11/11/2022] Open
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22
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Jones C, Penny L, Mattina T, Yu S, Baker E, Voullaire L, Langdon WY, Sutherland GR, Richards RI, Tunnacliffe A. Association of a chromosome deletion syndrome with a fragile site within the proto-oncogene CBL2. Nature 1995; 376:145-9. [PMID: 7603564 DOI: 10.1038/376145a0] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The fragile site FRA11B has been localized to the p(CCG)n repeat of the CBL2 proto-oncogene. A proportion of Jacobsen (11q-) syndrome patients inherited a chromosome carrying a CBL2 p(CCG)n expansion, which was truncated close to FRA11B. These results have broad implications for the role of p(CCG)n repeat expansion in the aetiology of genetic disease involving chromosome rearrangements.
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Affiliation(s)
- C Jones
- Department of Pathology, University of Cambridge, UK
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23
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Chary-Reddy S, Prasad VS, Ahuja YR. Expression of common fragile sites in untreated non-Hodgkin's lymphoma with aphidicolin and folate deficiency. Cancer Lett 1994; 86:111-7. [PMID: 7954347 DOI: 10.1016/0304-3835(94)90187-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The frequency and distribution of aphidicolin induced and folate sensitive common fragile sites on chromosomes of peripheral blood lymphocytes in untreated non-Hodgkin's lymphoma patients and healthy controls showed a considerable overlap in the expression of common fragile sites between the two groups. However, a significant increase in the expression of 16 aphidicolin induced common fragile sites was seen in untreated lymphoma patients. In the folate deficient cultures only, the common fragile sites 2q22, 8q24, 11q13, 12q21, 16q22, 17p12 and 20p12 were found in both the groups under study. The fragile sites at 8q22, 8q24, 11q13 and 18q21 in patients showed an increased expression over the control group. Interestingly these fragile sites were located in the same chromosomal bands as the oncogenes, MOS, MYC, BCL-1 and BCL-2 as well as cancer breakpoints specifically associated with non-Hodgkin's lymphoma, suggesting the possibility that fragile sites may play a critical role in the pathogenesis of non-Hodgkin's lymphoma.
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Affiliation(s)
- S Chary-Reddy
- Department of Microbiology and Immunology, University of Oklahoma, Oklahoma City 73190
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24
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Nistal M, Martínez-García F, Regadera J, Cobo P, Paniagua R. Macro-orchidism: a clinicopathological approach. J Urol 1994; 151:1155-61. [PMID: 8158750 DOI: 10.1016/s0022-5347(17)35203-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- M Nistal
- Department of Morphology, School of Medicine, Autonomous University of Madrid, Spain
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25
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Schwartz CE. X-linked mental retardation: in pursuit of a gene map. Am J Hum Genet 1993; 52:1025-31. [PMID: 8503437 PMCID: PMC1682268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
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26
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Sutherland GR, Mulley JC, Richards RI. Fragile X syndrome: The most common cause of familial intellectual handicap. Med J Aust 1993. [DOI: 10.5694/j.1326-5377.1993.tb137582.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Gram R Sutherland
- Department of Cytogenetics and Molecular GeneticsCentre for Medical GeneticsWomen's and Children's HospitalNorth AdelaideSA5006
| | - John C Mulley
- Department of Cytogenetics and Molecular GeneticsCentre for Medical GeneticsWomen's and Children's HospitalNorth AdelaideSA5006
| | - Robert I Richards
- Department of Cytogenetics and Molecular GeneticsCentre for Medical GeneticsWomen's and Children's HospitalNorth AdelaideSA5006
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27
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Abstract
The fragile X syndrome is recognized as the most common heritable condition resulting in mental retardation. The disabilities are substantial, and therefore early detection is mandatory to assist with reproductive counseling of families in which the fragile X syndrome has occurred. Highly accurate, direct DNA diagnostic testing can now be performed to diagnose the fragile X syndrome without the involvement of individual family members, as was the situation with the use of DNA linkage analysis. Such testing is rapidly becoming a standard diagnostic tool for screening of individuals with suspected fragile X syndrome, of potential unaffected carriers, and of patients with undefined mental retardation. Fragile X testing should be considered for all children with developmental delay of unknown cause. Autistic children will occasionally be found to have mutations in FMR-1. Detection of affected individuals will allow early intervention for these individuals and will assist families with their reproductive decisions (including prevention) in subsequent offspring. An understanding of the molecular genetics of fragile X syndrome has resulted in the resolution of the Sherman paradox and is the first molecular characterization of a chromosomal fragile site, a finding that almost certainly will be important in understanding the cause of chromosomal rearrangements involving fragile sites. In addition, molecular details of the fragile X mutations have yielded insight into "heritable unstable elements," of which the fragile X chromosome is one of the first characterized examples. Thus a similar molecular mechanism involving a trinucleotide repeat may explain the genetics of myotonic dystrophy and spinal-bulbar muscular atrophy (Kennedy disease); it seems reasonable to assume that other genetic diseases also may result from disruption of genes by inherited unstable elements.
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Smith A, Beran RG. Chromosome fragility in the Lennox-Gastaut epilepsy syndrome. JOURNAL OF INTELLECTUAL DISABILITY RESEARCH : JIDR 1992; 36 ( Pt 5):435-41. [PMID: 1458000 DOI: 10.1111/j.1365-2788.1992.tb00561.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Chromosome fragility was sought in a well-defined cohort of patients with Lennox-Gastaut epilepsy syndrome. Twenty-five patients plus 25 age- and sex-matched normal controls had cytogenetic studies performed. All patients were taking sodium valproate, and four were also on hydantoin. Blood cultures from both patients and controls were set up simultaneously in an appropriate medium designed to elicit fragile-sites. Harvesting took place after 96 h by standard techniques. In addition to routine banded analysis, at least 50 cells were scored for chromosome breaks and gaps from each patient and control. Results showed no difference between the patients and the control group in the overall occurrence of fragility or the type of aberration detected. No fragile-X syndrome was detected. This study found no effect due to sodium valproate on the occurrence of chromosome aberrations.
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Affiliation(s)
- A Smith
- Cytogenetics Unit, Oliver Latham Laboratory, Sydney, Australia
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Affiliation(s)
- W T Brown
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York
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30
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Affiliation(s)
- G R Sutherland
- Department of Cytogenetics and Molecular Genetics, Adelaide Children's Hospital, Australia
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31
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Nicklas JA, Hunter TC, O'Neill JP, Albertini RJ. Fine structure mapping of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene region of the human X chromosome (Xq26). Am J Hum Genet 1991; 49:267-78. [PMID: 1678246 PMCID: PMC1683319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Xq26-q27 region of the X chromosome is interesting, as an unusually large number of genes and anonymous RFLP probes have been mapped in this area. A number of studies have used classical linkage analysis in families to map this region. Here, we use mutant human T-lymphocyte clones known to be deleted for all or part of the hypoxanthine-guanine phosphoribosyltransferase (hprt) gene, to order anonymous probes known to map to Xq26. Fifty-seven T-cell clones were studied, including 44 derived from in vivo mutation and 13 from in vitro irradiated T-lymphocyte cultures. Twenty anonymous probes (DXS10, DXS11, DXS19, DXS37, DXS42, DXS51, DXS53, DXS59, DXS79, DXS86, DXS92, DXS99, DXS100d, DXS102, DXS107, DXS144, DXS172, DXS174, DXS177, and DNF1) were tested for codeletion with the hprt gene by Southern blotting methods. Five of these probes (DXS10, DXS53, DXS79, DXS86 and DXS177) showed codeletion with hprt in some mutants. The mutants established the following unambiguous ordering of the probes relative to the hprt gene: DXS53-DXS79-5'hprt3'-DXS86-DXS10-DXS177 . The centromere appears to map proximal to DXS53. These mappings order several closely linked but previously unordered probes. In addition, these studies indicate that rather large deletions of the functionally haploid X chromosome can occur while still retaining T-cell viability.
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Affiliation(s)
- J A Nicklas
- Department of Medicine, University of Vermont, Burlington
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32
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Abstract
Non-specific X linked mental retardation (MRX) is mental retardation in persons of normal physical appearance who have no recognisable features apart from a characteristic pedigree. Review of published reports shows that there is clinical variability in the degree of mental retardation within families and genetic heterogeneity, based on gene localisation, between families. We propose a classification based on genetic localisation and a set of minimal clinical features that should be recorded in the hope of identifying possible specific phenotypes.
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Affiliation(s)
- B Kerr
- Department of Medical Genetics, Prince of Wales Children's Hospital, Randwick, NSW, Australia
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Czeizel A, Sankaranarayanan K, Szondy M. The load of genetic and partially genetic diseases in man. III. Mental retardation. Mutat Res 1990; 232:291-303. [PMID: 2215538 DOI: 10.1016/0027-5107(90)90136-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This paper summarizes estimates of detriment associated with different etiologic categories of mental retardation (MR) in Hungary. The basic data derive from an earlier study carried out in Budapest on 1276 school-age mentally retarded children (with some etiologic reclassification based on recent studies). Detriment associated with these different categories of MR is expressed in terms of years of lost and impaired life. About 30 per 10(3) school-age children in Hungary are mentally retarded (mild + severe MR), one-tenth of whom have severe MR (IQ less than or equal to 50); 50% of the latter are institutionalized. The breakdown on the basis of etiology is as follows: gene mutations and chromosomal abnormalities, about 4 per 10(3); 'familial' (multifactorial) causes, 12 per 10(3); adverse pre-, peri- and post-natal causes, 11 per 10(3); and 'causes as yet unknown', the remainder. The estimates of mean number of years of lost life range from 42 to 68 (depending on the etiologic category), with an overall mean of 58. The total number of years of lost life is about 36,000 per 10(4) live births of which over 70% is due to pre-, peri- and post-natal causes, 18% due to 'familial' causes and the remainder due to Mendelian and chromosomal diseases. The total number of years of impaired life is about 7300 per 10(4) livebirths, 50% of which is due to 'familial' causes. While admittedly approximate, these estimates suggest that detriment associated with MR-related causes is not inconsiderable. Additionally, they provide some indication of causes of MR which are minimizable.
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Affiliation(s)
- A Czeizel
- Department of Human Genetics and Teratology, National Institute of Hygiene, Budapest, Hungary
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Abstract
A diagnostic survey was undertaken of children aged 11 to 19 years in Tameside with severe learning difficulties (intelligence quotient less than or equal to 50). Eighty-two children were identified and their medical records reviewed. A specific diagnosis for the retardation was documented in 25 (30%) of the children, 18 of whom had Down's syndrome. A probable aetiology or a disorder of unknown aetiology had been identified in a further 21 (26%) children. To confirm the existing diagnosis, identify new diagnoses, and offer genetic counselling, the parents of 63 children were offered detailed reassessment of their child. Fifty three children were reviewed, and a specific disorder identified in 25 out of 31 previously undiagnosed children. The most frequent diagnoses made were fragile X syndrome and Rett's syndrome. On completion of the survey, 61 of the 82 children (74%) had a specific diagnosis or probable aetiology identified, 12 (15%) had associated disorders such as cerebral palsy, and in only nine of the 82 children (11%) were there no clues at all to the cause of their retardation.
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Affiliation(s)
- J C Asthana
- Community Child Health, Tameside and Glossop Health Authority
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36
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Fundia AF, Larripa IB. Coincidence in fragile site expression with fluorodeoxyuridine and bromodeoxyuridine. CANCER GENETICS AND CYTOGENETICS 1989; 41:41-8. [PMID: 2527595 DOI: 10.1016/0165-4608(89)90106-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Fragile site expression induced by 10 micrograms/ml or 20 micrograms/ml fluorodeoxyuridine (FudR) and 25 micrograms/ml or 50 micrograms/ml bromodeoxyuridine (BrdU) was studied in lymphocyte cultures of six healthy individuals. A significant decrease in mitotic indexes in respect to control cultures was observed with both FudR concentrations used. The cells showing chromosome aberrations and the total number of cytogenetic alterations were significantly increased both in FudR (p less than 0.001) and BrdU (25 micrograms/ml) (p less than 0.05) treated cultures with respect to the control culture. A site showing a gap or a break was defined as fragile if it appeared in 1% of the cells analyzed and in at least three of the six individuals studied with the same culture treatment. Using these criteria, fragile sites 4q31, 5q15, 6p22, 7p13, 7q32, 13q21, and 14q24 were induced in different proportions by both chemical agents. Although these drugs act via different mechanisms, they both substitute for thymidine in DNA. Our findings suggest that FudR is a more potent common fragile site inducer than BrdU.
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Affiliation(s)
- A F Fundia
- Department of Cytogenetics, Instituto de Investigaciones Hematológicas Mariano R. Castex, Academía Nacional de Medicina de Buenos Aires, Argentina
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37
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Vieregge P, Froster-Iskenius U. Clinico-neurological investigations in the fra(X) form of mental retardation. J Neurol 1989; 236:85-92. [PMID: 2709058 DOI: 10.1007/bf00314402] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A clinical, neurological and electroencephalographic investigation was undertaken in 29 previously cytogenetically verified hemizygous males with the fra(X) form of mental retardation (age range 3.5 to 59 years); in addition, 6 heterozygous females were examined. All male patients displayed the known physical aspects of this syndrome together with associated abnormalities of the palate, skeleton, connective tissue and endocrine system. The most prominent neurological features were different forms of oculomotor disturbances, minor motor and pyramidal signs, incoordination, muscle hypotonia, gait and speech abnormalities. There was no increased frequency either in seizures or in epileptic EEG discharges. Some patients had a slowing of background activity in EEG. About 50% of all patients displayed autistic-like behaviour, short attention span and/or hyperactivity. In accordance with the literature, the findings indicate that there are no neurological, electroencephalographic or neuroradiological features which occur specifically in this syndrome. The need to differentiate the findings from those resulting from encephalopathic mechanisms during the gestational and perinatal period is stressed. A distinct typing of seizures and EEG changes is needed in each patient, before definite conclusions about an association of seizures and fra(X) syndrome are drawn. In view of the lack of correlation between IQ and the clinical-neurological measures, a more practical approach to quantifying the mental impairment is proposed.
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Affiliation(s)
- P Vieregge
- Klinik für Neurologie, Medizinische Universität zu Lübeck, Federal Republic of Germany
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Thode A, Laing S, Partington MW, Turner G. Is there a fragile(X) negative Martin-Bell syndrome? AMERICAN JOURNAL OF MEDICAL GENETICS 1988; 30:459-71. [PMID: 3052069 DOI: 10.1002/ajmg.1320300149] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
During the course of the preventative screening program for the fra(X) syndrome, we identified 32 men with the phenotype but who were fra(X) negative. These were reviewed and none fitted the full criteria, so we were unable to confirm the existence of the fra(X) negative Martin-Bell syndrome. The literature and 4 families previously thought to have the fra(X) negative Martin-Bell syndrome were also reviewed. We were unable to make a concrete diagnosis of the fra(X) negative Martin-Bell syndrome.
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Affiliation(s)
- A Thode
- Department of Medical Genetics, Prince of Wales Children's Hospital, Randwick, New South Wales, Australia
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40
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Milone G, Conti L, Rizzo R, Sanfilippo S, Sammito V, Romano C. A dermatoglyphic study of a group of Sicilian children with fragile-X syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS 1988; 30:177-83. [PMID: 3177443 DOI: 10.1002/ajmg.1320300116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In a dermatoglyphic study of 14 fra(X) boys (compared with a control group of 191 normal schoolboys), we observed the following statistically significant (p less than 0.01) differences: 1) lower frequency of ulnar loops on the fingertips, particularly on the 2nd and 3rd fingers, with a corresponding increase of whorls; 2) transverse course of main line A; 3) increased frequency of abnormal palmar creases. The log score index of Simpson et al [1984] identified 71.4% of our patients and that of Rodewald et al [1986] 64.2%. The different values of these indexes can probably be attributed to ethnic differences. We think that by combining the results of dermatoglyphic analysis from several centers a more discriminatory log score index can be obtained.
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Affiliation(s)
- G Milone
- Paediatric Clinic, University of Catania, Italy
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41
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Musumeci SA, Colognola RM, Ferri R, Gigli GL, Petrella MA, Sanfilippo S, Bergonzi P, Tassinari CA. Fragile-X syndrome: a particular epileptogenic EEG pattern. Epilepsia 1988; 29:41-7. [PMID: 3338421 DOI: 10.1111/j.1528-1157.1988.tb05096.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A clinical and EEG study of 12 fragile-X syndrome subjects (six with epilepsy) is presented. All subjects had clinical-family history examinations, EEG evaluations, and karyotyping. Spikes were present in the sleep EEG of one nonepileptic and four epileptic subjects: these spikes were similar in location, occurrence, voltage, frequency, and morphology (and similar to those of the Rolandic spikes). These data, together with the clinical similarities (type of epilepsy, responses to drugs, ages of seizure onset, etc.), have resulted in the postulation of EEG characteristics of epileptic and nonepileptic fragile-X patients. However, further studies with fragile-X patients are needed to confirm this hypothesis.
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Affiliation(s)
- S A Musumeci
- Oasi, Istituto di Ricerca sul Ritardo Mentale, Troina, Italy
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42
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Abstract
The fragile X syndrome is the most common inherited form of mental retardation known. Its phenotype includes large or prominent ears, macroorchidism, and characteristic behavioral problems. It has attracted the interest of cytogeneticists and molecular biologists because of its characteristic fragile site on the X chromosome. It has puzzled geneticists because of its unusual inheritance pattern involving nonpenetrant males. This syndrome has also spearheaded an appreciation of cytogenetic abnormalities in the etiology of all degrees of developmental delay.
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Affiliation(s)
- R J Hagerman
- University of Colorado Health Sciences Center, Denver
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Veenema H, Geraedts JP, Beverstock GC, Pearson PL. The fragile X syndrome in a large family. I. Cytogenetic and clinical investigations. J Med Genet 1987; 24:23-31. [PMID: 3492604 PMCID: PMC1049852 DOI: 10.1136/jmg.24.1.23] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Cytogenetic and clinical investigations were performed in 85 members of a large family, in which 18 males and seven females were mentally retarded. In the male patients the fragile site Xq27 was found in 6 to 44% (mean 22.5%) of peripheral blood lymphocytes. One non-retarded male expressed the cytogenetic abnormality in 6% of his cells. In 21 females the fra(X) was found in 3 to 28% (mean 8.7%) of their cells. Two obligate carriers did not express the fragile site. A significant difference in expression between the seven retarded (mean 16.7%) and seven non-retarded female carriers of corresponding age (mean 6.3%) was found (alpha = 0.01). No significant correlation between expression and age could be established, either in males or in females. The cytogenetic results appeared to be consistent. To avoid false positives, a cut-off point was chosen: males were considered to be fra(X) negative if no more than one in 100 cells showed the abnormality; for females the cut-off point was two in 100 cells. Segregation analysis did not detect significant deviations from the expected ratios. The putative presence of a transmitting male is discussed. The results of recombinant DNA analysis will be published elsewhere. Clinical investigations confirmed the findings of others. CT scans showed an enlargement of the ventricular system that exceeded the expected age changes.
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Brown WT, Jenkins EC, Krawczun MS, Wisniewski K, Rudelli R, Cohen IL, Fisch G, Wolf-Schein E, Miezejeski C, Dobkin C. The fragile X syndrome. Ann N Y Acad Sci 1986; 477:129-50. [PMID: 3545014 DOI: 10.1111/j.1749-6632.1986.tb40329.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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46
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Wright HH, Young SR, Edwards JG, Abramson RK, Duncan J. Fragile X syndrome in a population of autistic children. JOURNAL OF THE AMERICAN ACADEMY OF CHILD PSYCHIATRY 1986; 25:641-4. [PMID: 3760413 DOI: 10.1016/s0002-7138(09)60288-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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47
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Rodewald A, Froster-Iskenius U, Käb E, Langenbeck U, Schinzel A, Schmidt A, Schwinger E, Steinbach P, Veenema H, Wegner RD. Dermatoglyphic peculiarities in families with X-linked mental retardation and fragile site Xq27: a collaborative study. Clin Genet 1986; 30:1-13. [PMID: 3757292 DOI: 10.1111/j.1399-0004.1986.tb00563.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The dermatoglyphic patterns of fingertips, palms and soles of 75 male patients with X-linked mental retardation and fra-Xq27 and of 28 obligate female heterozygotes were analyzed and compared with the data from 200 male and 200 female control individuals. The results show that there is a strong association between the fra-X-syndrome and dermatoglyphic peculiarities observed in male patients and also in female heterozygotes. The characteristic dermatoglyphic features of the fra-X-syndrome are: increased frequencies of radial loops, whorls and arches on the fingertips, a pronounced transversal course of palmar ridges, lower a-b RC, absence of c-triradii on the palms, abnormal palmar and plantar creases, dysplasia of the papillary ridges and low frequencies of true patterns on the soles. Some of these patterns were found in the female carriers of fra-Xq27 also. The combination of palmar and plantar patterns, expressed by a "log. score-Index", provides a high degree of discrimination between the male patients with fra-X-syndrome and the control group. A preliminary log. score-Index was developed also for the female heterozygotes. A "phantom picture" of the dermatoglyphic stigmata is constructed. We suggest that dermatoglyphic examination of the members of families suspected for fra-Xq27-syndrome can be useful for predicting this state and for diagnosing male hemizygotes and carrier females.
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Partington MW. X-linked mental retardation: caveats in genetic counselling. AMERICAN JOURNAL OF MEDICAL GENETICS 1986; 23:101-9. [PMID: 3953640 DOI: 10.1002/ajmg.1320230105] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Thake A, Todd J, Bundey S, Webb T. Is it possible to make a clinical diagnosis of the fragile X syndrome in a boy? Arch Dis Child 1985; 60:1001-7. [PMID: 4073931 PMCID: PMC1777630 DOI: 10.1136/adc.60.11.1001] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Clinical observations were made on a series of 156 boys with severe mental retardation, before cytogenetic results were known. The clinical features that helped to distinguish the 14 boys with the fragile X chromosome from those without were: head circumference over the 50th centile, postpubertal testicular volume over the 50th centile, and an IQ between 35 and 70. If the above clinical features were all present, then the chance of finding the fragile X chromosome was 1 in 3.6, whereas the chance of finding this abnormality in any boy with severe idiopathic mental retardation, regardless of his clinical features, was 1 in 9. Two boys with fragile X syndrome did not, however, possess any of the above clinical features. Moreover, some of the other retarded boys had clinical features of the syndrome, or an X linked pedigree, but lacked the chromosome abnormality.
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Abstract
The fragile sites of human chromosomes are specific sites that are characterized by a tendency to show gaps, multiradial figures, acentric fragments, and deleted chromosomes on microscopy. These characteristics seem to reflect an inherent fragility at the site, although the underlying biochemical cause of fragile sites is unknown. Investigators have proposed several categories of fragile sites: "rare" or "heritable," "common," and "constitutive." Although the clinical significance of most fragile sites is unknown, fragile site Xq27.3 is associated with one form of X-linked mental retardation. In this article, the three types of chromosome fragile sites are described, and their possible relevance to chromosomal breakage that results in birth defects or cancer is discussed.
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