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Hnoonual A, Plong-On O, Worachotekamjorn J, Charalsawadi C, Limprasert P. Clinical and molecular characteristics of FMR1 microdeletion in patient with fragile X syndrome and review of the literature. Clin Chim Acta 2024; 553:117728. [PMID: 38142803 DOI: 10.1016/j.cca.2023.117728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 12/09/2023] [Accepted: 12/16/2023] [Indexed: 12/26/2023]
Abstract
BACKGROUND Fragile X syndrome (FXS) is mainly caused by FMR1 CGG repeat expansions. Other types of mutations, particularly deletions, are also responsible for FXS phenotypes, however these mutations are often missed by routine clinical testing. MATERIALS AND METHODS Molecular diagnosis in cases of suspected FXS was a combination of PCR and Southern blot. Measurement of the FMRP protein level was useful for detecting potentially deleterious impact. RESULTS PCR analysis and Southern blot revealed a case with premutation and suspected deletion alleles. Sanger sequencing showed that the deletion involved 313 bp upstream of repeats and some parts of CGG repeat tract, leaving transcription start site. FMRP was detected in 5.5 % of blood lymphocytes. CONCLUSION According to our review of case reports, most patients carrying microdeletion and full mutation had typical features of FXS. To our knowledge, our case is the first to describe mosaicism of a premutation and microdeletion in the FMR1 gene. The patient was probably protected from the effects of the deletion by mosaicism with premutation allele, leading to milder phenotype. It is thus important to consider appropriate techniques for detecting FMR1 variants other than repeat expansions which cannot be detected by routine FXS diagnosis.
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Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Oradawan Plong-On
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | | | - Chariyawan Charalsawadi
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
| | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand; Genomic Medicine Center, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
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Detection and Quantification of the Fragile X Mental Retardation Protein 1 (FMRP). Genes (Basel) 2016; 7:genes7120121. [PMID: 27941672 PMCID: PMC5192497 DOI: 10.3390/genes7120121] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 01/11/2023] Open
Abstract
The final product of FMR1 gene transcription, Fragile X Mental Retardation Protein 1 (FMRP), is an RNA binding protein that acts as a repressor of translation. FMRP is expressed in several tissues and plays important roles in neurogenesis, synaptic plasticity, and ovarian functions and has been implicated in a number of neuropsychological disorders. The loss of FMRP causes Fragile X Syndrome (FXS). In most cases, FXS is due to large expansions of a CGG repeat in FMR1—normally containing 6–54 repeats—to over 200 CGGs and identified as full mutation (FM). Hypermethylation of the repeat induces FMR1 silencing and lack of FMRP expression in FM male. Mosaic FM males express low levels of FMRP and present a less severe phenotype that inversely correlates with FMRP levels. Carriers of pre-mutations (55–200 CGG) show increased mRNA, and normal to reduced FMRP levels. Alternative splicing of FMR1 mRNA results in 24 FMRP predicted isoforms whose expression are tissues and developmentally regulated. Here, we summarize the approaches used by several laboratories including our own to (a) detect and estimate the amount of FMRP in different tissues, developmental stages and various pathologies; and (b) to accurately quantifying FMRP for a direct diagnosis of FXS in adults and newborns.
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Kazdoba TM, Leach PT, Silverman JL, Crawley JN. Modeling fragile X syndrome in the Fmr1 knockout mouse. Intractable Rare Dis Res 2014; 3:118-33. [PMID: 25606362 PMCID: PMC4298642 DOI: 10.5582/irdr.2014.01024] [Citation(s) in RCA: 161] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 11/28/2014] [Indexed: 11/05/2022] Open
Abstract
Fragile X Syndrome (FXS) is a commonly inherited form of intellectual disability and one of the leading genetic causes for autism spectrum disorder. Clinical symptoms of FXS can include impaired cognition, anxiety, hyperactivity, social phobia, and repetitive behaviors. FXS is caused by a CGG repeat mutation which expands a region on the X chromosome containing the FMR1 gene. In FXS, a full mutation (> 200 repeats) leads to hypermethylation of FMR1, an epigenetic mechanism that effectively silences FMR1 gene expression and reduces levels of the FMR1 gene product, fragile X mental retardation protein (FMRP). FMRP is an RNA-binding protein that is important for the regulation of protein expression. In an effort to further understand how loss of FMR1 and FMRP contribute to FXS symptomology, several FXS animal models have been created. The most well characterized rodent model is the Fmr1 knockout (KO) mouse, which lacks FMRP protein due to a disruption in its Fmr1 gene. Here, we review the behavioral phenotyping of the Fmr1 KO mouse to date, and discuss the clinical relevance of this mouse model to the human FXS condition. While much remains to be learned about FXS, the Fmr1 KO mouse is a valuable tool for understanding the repercussions of functional loss of FMRP and assessing the efficacy of pharmacological compounds in ameliorating the molecular and behavioral phenotypes relevant to FXS.
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Affiliation(s)
- Tatiana M. Kazdoba
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
- Address correspondence to: Dr. Tatiana M. Kazdoba, MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, Research II Building 96, 4625 2nd Avenue, Sacramento, CA 95817, USA. E-mail:
| | - Prescott T. Leach
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
| | - Jill L. Silverman
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
| | - Jacqueline N. Crawley
- MIND Institute, Department of Psychiatry and Behavioral Sciences, University of California, Davis, School of Medicine, Sacramento, CA, USA
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Kuru K, Niranjan M, Tunca Y, Osvank E, Azim T. Biomedical visual data analysis to build an intelligent diagnostic decision support system in medical genetics. Artif Intell Med 2014; 62:105-18. [PMID: 25262492 DOI: 10.1016/j.artmed.2014.08.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 08/15/2014] [Accepted: 08/16/2014] [Indexed: 11/30/2022]
Abstract
BACKGROUND In general, medical geneticists aim to pre-diagnose underlying syndromes based on facial features before performing cytological or molecular analyses where a genotype-phenotype interrelation is possible. However, determining correct genotype-phenotype interrelationships among many syndromes is tedious and labor-intensive, especially for extremely rare syndromes. Thus, a computer-aided system for pre-diagnosis can facilitate effective and efficient decision support, particularly when few similar cases are available, or in remote rural districts where diagnostic knowledge of syndromes is not readily available. METHODS The proposed methodology, visual diagnostic decision support system (visual diagnostic DSS), employs machine learning (ML) algorithms and digital image processing techniques in a hybrid approach for automated diagnosis in medical genetics. This approach uses facial features in reference images of disorders to identify visual genotype-phenotype interrelationships. Our statistical method describes facial image data as principal component features and diagnoses syndromes using these features. RESULTS The proposed system was trained using a real dataset of previously published face images of subjects with syndromes, which provided accurate diagnostic information. The method was tested using a leave-one-out cross-validation scheme with 15 different syndromes, each of comprised 5-9 cases, i.e., 92 cases in total. An accuracy rate of 83% was achieved using this automated diagnosis technique, which was statistically significant (p<0.01). Furthermore, the sensitivity and specificity values were 0.857 and 0.870, respectively. CONCLUSION Our results show that the accurate classification of syndromes is feasible using ML techniques. Thus, a large number of syndromes with characteristic facial anomaly patterns could be diagnosed with similar diagnostic DSSs to that described in the present study, i.e., visual diagnostic DSS, thereby demonstrating the benefits of using hybrid image processing and ML-based computer-aided diagnostics for identifying facial phenotypes.
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Affiliation(s)
- Kaya Kuru
- Department of Communication, Electronics, and Information Systems, Gülhane Military Medical Academy, Etlik, Ankara 06010, Turkey.
| | - Mahesan Niranjan
- School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BF, UK
| | - Yusuf Tunca
- Department of Medical Genetics, Gülhane Military Medical Academy, Etlik, Ankara 06010, Turkey
| | - Erhan Osvank
- Institute of Informatics, Middle East Technical University, Balgat, Ankara 06531, Turkey
| | - Tayyaba Azim
- School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BF, UK
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Kim SY, Burris J, Bassal F, Koldewyn K, Chattarji S, Tassone F, Hessl D, Rivera SM. Fear-specific amygdala function in children and adolescents on the fragile x spectrum: a dosage response of the FMR1 gene. Cereb Cortex 2012; 24:600-13. [PMID: 23146966 DOI: 10.1093/cercor/bhs341] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations of the fragile X mental retardation 1 (FMR1) gene are the genetic cause of fragile X syndrome (FXS). The presence of significant socioemotional problems has been well documented in FXS although the brain basis of those deficits remains unspecified. Here, we investigated amygdala dysfunction and its relation to socioemotional deficits and FMR1 gene expression in children and adolescents on the FX spectrum (i.e., individuals whose trinucleotide CGG repeat expansion from 55 to over 200 places them somewhere within the fragile X diagnostic range from premutation to full mutation). Participants performed an fMRI task in which they viewed fearful, happy, and scrambled faces. Neuroimaging results demonstrated that FX participants revealed significantly attenuated amygdala activation in Fearful > Scrambled and Fearful > Happy contrasts compared with their neurotypical counterparts, while showing no differences in amygdala volume. Furthermore, we found significant relationships between FMR1 gene expression, anxiety/social dysfunction scores, and reduced amygdala activation in the FX group. In conclusion, we report novel evidence regarding a dosage response of the FMR1 gene on fear-specific functions of the amygdala, which is associated with socioemotional deficits in FXS.
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Affiliation(s)
- So-Yeon Kim
- Center for Mind and Brain, University of California, Davis, CA 95618, USA
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Rousseau F, Labelle Y, Bussières J, Lindsay C. The fragile x mental retardation syndrome 20 years after the FMR1 gene discovery: an expanding universe of knowledge. Clin Biochem Rev 2011; 32:135-162. [PMID: 21912443 PMCID: PMC3157949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The fragile X mental retardation (FXMR) syndrome is one of the most frequent causes of mental retardation. Affected individuals display a wide range of additional characteristic features including behavioural and physical phenotypes, and the extent to which individuals are affected is highly variable. For these reasons, elucidation of the pathophysiology of this disease has been an important challenge to the scientific community. 1991 marks the year of the discovery of both the FMR1 gene mutations involved in this disease, and of their dynamic nature. Although a mouse model for the disease has been available for 16 years and extensive research has been performed on the FMR1 protein (FMRP), we still understand little about how the disease develops, and no treatment has yet been shown to be effective. In this review, we summarise current knowledge on FXMR with an emphasis on the technical challenges of molecular diagnostics, on its prevalence and dynamics among populations, and on the potential of screening for FMR1 mutations.
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Affiliation(s)
- François Rousseau
- Réseau de Médecine Génétique Appliquée, Fonds de Recherche en Santé du Québec
- The APOGEE-Net/CanGèneTest Research and Knowledge Network (www.cangenetest.org)
- Unité de recherche en génétique humaine et moléculaire, Axe de recherche en évaluation des technologies et transfert des connaissances, Centre de recherche du CHUQ-Hôpital-Saint-François-d’Assise
- Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de Médecine, Université Laval, CRCHUQ-Hôpital St-François d’Assise, 10 rue de l’Espinay, Québec, Qc, Canada G1L 3L5
| | - Yves Labelle
- The APOGEE-Net/CanGèneTest Research and Knowledge Network (www.cangenetest.org)
- Unité de recherche en génétique humaine et moléculaire, Axe de recherche en évaluation des technologies et transfert des connaissances, Centre de recherche du CHUQ-Hôpital-Saint-François-d’Assise
- Département de biologie moléculaire, biochimie médicale et pathologie, Faculté de Médecine, Université Laval, CRCHUQ-Hôpital St-François d’Assise, 10 rue de l’Espinay, Québec, Qc, Canada G1L 3L5
| | - Johanne Bussières
- Unité de recherche en génétique humaine et moléculaire, Axe de recherche en évaluation des technologies et transfert des connaissances, Centre de recherche du CHUQ-Hôpital-Saint-François-d’Assise
| | - Carmen Lindsay
- Unité de recherche en génétique humaine et moléculaire, Axe de recherche en évaluation des technologies et transfert des connaissances, Centre de recherche du CHUQ-Hôpital-Saint-François-d’Assise
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Romero-Espinoza P, Rosales-Reynoso MA, Willemsen R, Barros-Núñez P. FMR1Protein Expression in Blood Smears for Fragile X Syndrome Diagnosis in a Mexican Population Sample. Genet Test Mol Biomarkers 2010; 14:511-4. [DOI: 10.1089/gtmb.2009.0172] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | - Mónica A. Rosales-Reynoso
- División de Medicina Molecular, Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, México
| | - Rob Willemsen
- CBG-Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
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Iwahashi C, Tassone F, Hagerman RJ, Yasui D, Parrott G, Nguyen D, Mayeur G, Hagerman PJ. A quantitative ELISA assay for the fragile x mental retardation 1 protein. J Mol Diagn 2009; 11:281-9. [PMID: 19460937 DOI: 10.2353/jmoldx.2009.080118] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Non-coding (CGG-repeat) expansions in the fragile X mental retardation 1 (FMR1) gene result in a spectrum of disorders involving altered neurodevelopment (fragile X syndrome), neurodegeneration (late-onset fragile X-associated tremor/ataxia syndrome), or primary ovarian insufficiency. While reliable and quantitative assays for the number of CGG repeats and FMR1 mRNA levels are now available, there has been no scalable, quantitative assay for the FMR1 protein (FMRP) in non-transformed cells. Using a combination of avian and murine antibodies to FMRP, we developed a sensitive and highly specific sandwich enzyme-linked immunosorbent assay (ELISA) for FMRP in peripheral blood lymphocytes. This ELISA method is capable of quantifying FMRP levels throughout the biologically relevant range of protein concentrations and is specific for the intact FMRP protein. Moreover, the ELISA is well-suited for replicate protein determinations across serial dilutions in non-transformed cells and is readily scalable for large sample numbers. The FMRP ELISA is potentially a powerful tool in expanding our understanding of the relationship between FMRP levels and the various FMR1-associated clinical phenotypes.
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Affiliation(s)
- Christine Iwahashi
- Department of Biochemistry and Molecular Medicine, UC Davis, School of Medicine, Davis, CA 95616, USA
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Mínguez M, Ibáñez B, Ribate MP, Ramos F, García-Alegría E, Fernández-Rivas A, Ruiz-Parra E, Poch M, Alonso A, Martinez-Bouzas C, Beristain E, Tejada MI. Risk of cognitive impairment in female premutation carriers of fragile X premutation: analysis by means of robust segmented linear regression models. Am J Med Genet B Neuropsychiatr Genet 2009; 150B:262-70. [PMID: 18563710 DOI: 10.1002/ajmg.b.30803] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This report describes a study focused on the relationship between CGG repeat length, FMRP, mRNA levels and cognitive functioning in premutation carriers (PM) carriers of Fragile X Syndrome (FXS). We studied 60 females-43 with PM and 17 with normal (N) alleles-from 25 FXS Spanish families. The Wechsler scales were administered to all subjects and new blood samples and hair roots were taken to study mRNA and FMRP levels. Using lowess curves together with segmented models we showed that within the premutation range, IQ scores tend to decrease when the number of CGG repeats increases and the FMRP values decrease. Furthermore, we discovered cut-off points in the molecular variables that seem to change the probability of having some cognitive impairment. Specifically, for those PM females in the upper premutation range (CGG > or = 100) and with FMRP expression < 60% in hair roots, a 10% decrement of FMRP expression represents a significant decrease in IQ scores of about six points, which is more evident for Full-Scale IQ (P-value = 0.035) and Performance IQ (P-value = 0.045) than for Verbal IQ (P-value = 0.074). On the contrary, we did not find any significant correlation between FMR1 mRNA levels and the IQ scores, probably due to the fact that mRNA levels were measured in blood. In conclusion, our findings suggest that the PM can have some effect on cognitive ability in female carriers, although these effects may be subtle. In these cases, it would be advisable to carry out a hair root analysis of FMRP.
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Abstract
PURPOSE OF REVIEW The purpose of this review is to present the latest findings on fragile X syndrome and to put them into perspective. Fragile X syndrome is a relatively common form of inherited mental retardation, caused by loss of function of the FMR1 gene on the long arm of the X chromosome. The molecular mechanisms underlying the syndrome are complex and continue to surprise researchers more than 12 years after the cloning of the gene. RECENT FINDINGS We will specifically discuss the various aspects of the clinical phenotype, reassessed with the employment of functional imaging and electrophysiological techniques. The unexpected finding of a pathologic phenotype in premutation carriers is highlighted, as it represents a new and distinct condition with a different presentation in males and females. The third section deals briefly with the various functions of the FMRP protein, an RNA-binding protein interacting with multiple RNA molecules as well as proteins. It is important to realize that FMRP is probably changing partners several times, depending on its localization, on posttranslational modifications and on the available interacting proteins. In the following section, we present in short recent discoveries on the defective neuronal circuits in the fragile X syndrome. Most of these new data were made available by the study of animal models, mostly the Fmr1 knockout mouse, but also Drosophila. SUMMARY We briefly discuss the alternative options for treating fragile X syndrome. Presently, a neuropharmacological approach acting on either critical receptors or aimed at reactivating the silenced FMR1 gene appears promising.
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