1
|
Hnoonual A, Jankittunpaiboon C, Limprasert P. Screening for FMR1 CGG Repeat Expansion in Thai Patients with Autism Spectrum Disorder. BIOMED RESEARCH INTERNATIONAL 2021; 2021:4359308. [PMID: 34926684 PMCID: PMC8674057 DOI: 10.1155/2021/4359308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/07/2021] [Accepted: 11/26/2021] [Indexed: 11/30/2022]
Abstract
Autism spectrum disorder (ASD) is a complex disorder with a heterogeneous etiology. Fragile X syndrome (FXS) is recognized as the most common single gene mutation associated with ASD. FXS patients show some autistic behaviors and may be difficult to distinguish at a young age from autistic children. However, there have been no published reports on the prevalence of FXS in ASD patients in Thailand. In this study, we present a pilot study to analyze the CGG repeat sizes of the FMR1 gene in Thai autistic patients. We screened 202 unrelated Thai patients (168 males and 34 females) with nonsyndromic ASD and 212 normal controls using standard FXS molecular diagnosis techniques. The distributions of FMR1 CGG repeat sizes in the ASD and normal control groups were similar, with the two most common alleles having 29 and 30 CGG repeats, followed by an allele with 36 CGG repeats. No FMR1 full mutations or premutations were found in either ASD individuals or the normal controls. Interestingly, three ASD male patients with high normal CGG and intermediate CGG repeats (44, 46, and 53 CGG repeats) were identified, indicating that the prevalence of FMR1 intermediate alleles in Thai ASD patients was approximately 1% while these alleles were absent in the normal male controls. Our study indicates that CGG repeat expansions of the FMR1 gene may not be a common genetic cause of nonsyndromic ASD in Thai patients. However, further studies for mutations other than the CGG expansion in the FMR1 gene are required to get a better information on FXS prevalence in Thai ASD patients.
Collapse
Affiliation(s)
- Areerat Hnoonual
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla 90110, Thailand
| | | | - Pornprot Limprasert
- Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla 90110, Thailand
- Faculty of Medicine, Siam University, Bangkok 10160, Thailand
| |
Collapse
|
2
|
Alvarez-Mora MI, Madrigal I, Martinez F, Tejada MI, Izquierdo-Alvarez S, Sanchez-Villar de Saz P, Caro-Llopis A, Villate O, Rodríguez-Santiago B, Pérez Jurado LA, Rodriguez-Revenga L, Milà M. Clinical implication of FMR1 intermediate alleles in a Spanish population. Clin Genet 2018; 94:153-158. [PMID: 29604051 DOI: 10.1111/cge.13257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 03/26/2018] [Accepted: 03/28/2018] [Indexed: 11/28/2022]
Abstract
FMR1 premutation carriers (55-200 CGGs) are at risk of developing Fragile X-associated primary ovarian insufficiency as well as Fragile X-associated tremor/ataxia syndrome. FMR1 premutation alleles are also associated with a variety of disorders, including psychiatric, developmental, and neurological problems. However, there is a major concern regarding clinical implications of smaller CGG expansions known as intermediate alleles (IA) or gray zone alleles (45-54 CGG). Although several studies have hypothesized that IA may be involved in the etiology of FMR1 premutation associated phenotypes, this association still remains unclear. The aim of this study was to provide new data on the clinical implications of IA. We reviewed a total of 17 011 individuals: 1142 with primary ovarian insufficiency, 478 with movement disorders, 14 006 with neurodevelopmental disorders and 1385 controls. Similar IA frequencies were detected in all the cases and controls (cases 1.20% vs controls 1.39%, P = .427). When comparing the allelic frequencies of IA ≥ 50CGGs, a greater, albeit not statistically significant, number of alleles were detected in all the cohorts of patients. Therefore, IA below 50 CGGs should not be considered as risk factors for FMR1 premutation-associated phenotypes, at least in our population. However, the clinical implication of IA ≥ 50CGGs remains to be further elucidated.
Collapse
Affiliation(s)
- M I Alvarez-Mora
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Barcelona, Spain.,Institut d'Investigació Biomèdica August Pi I Sunyer IDIBAPS, Barcelona, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Valencia, Spain
| | - I Madrigal
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Barcelona, Spain.,Institut d'Investigació Biomèdica August Pi I Sunyer IDIBAPS, Barcelona, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Valencia, Spain
| | - F Martinez
- Genetics Unit, Hospital Universitario y Politecnico La Fe, Valencia, Spain
| | - M-I Tejada
- Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Valencia, Spain.,Molecular Genetics Laboratory, Genetics Service, Cruces University Hospital, Barakaldo, Spain.,Biocruces Health Research Institute, Barakaldo, Spain
| | - S Izquierdo-Alvarez
- Genetics department of Clinical Biochemistry Service, University Hospital Miguel Servet, Zaragoza, Spain
| | | | - A Caro-Llopis
- Genetics Unit, Hospital Universitario y Politecnico La Fe, Valencia, Spain
| | - O Villate
- Molecular Genetics Laboratory, Genetics Service, Cruces University Hospital, Barakaldo, Spain
| | | | - L A Pérez Jurado
- Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Valencia, Spain.,Genetics Unit, Universitat Pompeu Fabra, and Hospital del Mar Research Institute (IMIM), Barcelona, Spain
| | - L Rodriguez-Revenga
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Barcelona, Spain.,Institut d'Investigació Biomèdica August Pi I Sunyer IDIBAPS, Barcelona, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Valencia, Spain
| | - M Milà
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Barcelona, Spain.,Institut d'Investigació Biomèdica August Pi I Sunyer IDIBAPS, Barcelona, Spain.,Centre for Biomedical Research on Rare Diseases (CIBERER), ISCIII, Valencia, Spain
| |
Collapse
|
3
|
Debrey SM, Leehey MA, Klepitskaya O, Filley CM, Shah RC, Kluger B, Berry-Kravis E, Spector E, Tassone F, Hall DA. Clinical Phenotype of Adult Fragile X Gray Zone Allele Carriers: a Case Series. THE CEREBELLUM 2017; 15:623-31. [PMID: 27372099 DOI: 10.1007/s12311-016-0809-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Considerable research has focused on patients with trinucleotide (CGG) repeat expansions in the fragile X mental retardation 1 (FMR1) gene that fall within either the full mutation (>200 repeats) or premutation range (55-200 repeats). Recent interest in individuals with gray zone expansions (41-54 CGG repeats) has grown due to reported phenotypes that are similar to those observed in premutation carriers, including neurological, molecular, and cognitive signs. The purpose of this manuscript is to describe a series of adults with FMR1 alleles in the gray zone presenting with movement disorders or memory loss. Gray zone carriers ascertained in large FMR1 screening studies were identified and their clinical phenotypes studied. Thirty-one gray zone allele carriers were included, with mean age of symptom onset of 53 years in patients with movement disorders and 57 years in those with memory loss. Four patients were chosen for illustrative case reports and had the following diagnoses: early-onset Parkinson disease (PD), atypical parkinsonism, dementia, and atypical essential tremor. Some gray zone carriers presenting with parkinsonism had typical features, including bradykinesia, rigidity, and a positive response to dopaminergic medication. These patients had a higher prevalence of peripheral neuropathy and psychiatric complaints than would be expected. The patients seen in memory clinics had standard presentations of cognitive impairment with no apparent differences. Further studies are necessary to determine the associations between FMR1 expansions in the gray zone and various phenotypes of neurological dysfunction.
Collapse
Affiliation(s)
- Sarah M Debrey
- Department of Psychiatry, Emory University, Atlanta, GA, USA
| | - Maureen A Leehey
- Department of Neurology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Olga Klepitskaya
- Department of Neurology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Christopher M Filley
- Departments of Neurology and Psychiatry, University of Colorado School of Medicine, Aurora, CO, USA
- Denver Veterans Affairs Medical Center, Denver, CO, USA
| | - Raj C Shah
- Rush Alzheimer's Disease Center, Rush University, Chicago, IL, USA
| | - Benzi Kluger
- Departments of Neurology and Psychiatry, University of Colorado School of Medicine, Aurora, CO, USA
| | - Elizabeth Berry-Kravis
- Departments of Pediatrics and Biochemistry, Rush University, Chicago, IL, USA
- Department of Neurological Sciences, Rush University, 1725 West Harrison Street, Suite 755, Chicago, IL, 60612, USA
| | - Elaine Spector
- Denver Genetics DNA Diagnostic Laboratory at Children's Hospital Colorado, Department of Pediatrics, University of Colorado-Denver, Aurora, CO, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, University of California School of Medicine, Davis, CA, USA
- M.I.N.D. Institute, University of California-Davis Medical Center, Sacramento, CA, USA
| | - Deborah A Hall
- Department of Neurological Sciences, Rush University, 1725 West Harrison Street, Suite 755, Chicago, IL, 60612, USA.
| |
Collapse
|
4
|
Alvarez-Mora MI, Calvo Escalona R, Puig Navarro O, Madrigal I, Quintela I, Amigo J, Martinez-Elurbe D, Linder-Lucht M, Aznar Lain G, Carracedo A, Mila M, Rodriguez-Revenga L. Comprehensive molecular testing in patients with high functioning autism spectrum disorder. Mutat Res 2016; 784-785:46-52. [PMID: 26845707 DOI: 10.1016/j.mrfmmm.2015.12.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 12/28/2015] [Accepted: 12/30/2015] [Indexed: 10/22/2022]
Abstract
Autism spectrum disorders (ASD) include a range of complex neurodevelopmental disorders with extreme genetic heterogeneity. Exome and target sequencing studies have shown to be an effective tool for the discovery of new ASD genes. The aim of this study was to design an ASD candidate gene panel that covers 44 of the top ASD candidate genes. As a pilot study we performed comprehensive molecular diagnostic testing, including the study of the FMR1 and FMR2 repeat regions, copy number variant analysis in a collection of 50 Spanish ASD cases and mutation screening using targeted next generation sequencing-based techniques in 44 out of the total cohort. We evaluated and clinically selected our cohort, with most of the cases having high functioning ASD without facial dysmorphic features. The results of the present study allowed the detection of copy number and single nucleotide variants not yet identified. In addition, our results underscore the difficulty of the molecular diagnosis of ASD and confirm its genetic heterogeneity. The information gained from this and other genetic screenings is necessary to unravel the clinical interpretation of novel variants.
Collapse
Affiliation(s)
- Maria Isabel Alvarez-Mora
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain; CIBER of Rare Diseases (CIBERER), Villarroel 170, 08036 Barcelona, Spain; IDIBAPS, Rosselló 149, 08036 Barcelona, Spain.
| | - Rosa Calvo Escalona
- Child and Adolescent Psychiatry Department, Hospital Clinic, SGR-1119, CIBERSAM, Villarroel 170, 08036 Barcelona, Spain.
| | - Olga Puig Navarro
- Child and Adolescent Psychiatry Department, Hospital Clinic, SGR-1119, CIBERSAM, Villarroel 170, 08036 Barcelona, Spain.
| | - Irene Madrigal
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain; CIBER of Rare Diseases (CIBERER), Villarroel 170, 08036 Barcelona, Spain; IDIBAPS, Rosselló 149, 08036 Barcelona, Spain.
| | - Ines Quintela
- Genomic Medicine Group-Santiago de Compostela University, CEGEN-PRB2-ISCIII, Travesía da Choupana, s/n, 15706 Santiago de Compostela, A Coruña, Spain.
| | - Jorge Amigo
- Genomic Medicine Group-Santiago de Compostela University, CEGEN-PRB2-ISCIII, Travesía da Choupana, s/n, 15706 Santiago de Compostela, A Coruña, Spain; Genomic Medicine Group, CIBERER, Fundacion Publica Galega de Medicina Xenomica-SERGAS, Travesía da Choupana, s/n, 15706 Santiago de Compostela, A Coruña, Spain.
| | - Dei Martinez-Elurbe
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain.
| | - Michaela Linder-Lucht
- Pediatric Service, Hospital del Mar, Passeig Marítim, 25-29, 08003 Barcelona, Spain.
| | - Gemma Aznar Lain
- Pediatric Service, Hospital del Mar, Passeig Marítim, 25-29, 08003 Barcelona, Spain; Autonoma University of Barcelona, Cerdanyola del Vallès, 08193 Barcelona, Spain.
| | - Angel Carracedo
- Genomic Medicine Group-Santiago de Compostela University, CEGEN-PRB2-ISCIII, Travesía da Choupana, s/n, 15706 Santiago de Compostela, A Coruña, Spain; Genomic Medicine Group, CIBERER, Fundacion Publica Galega de Medicina Xenomica-SERGAS, Travesía da Choupana, s/n, 15706 Santiago de Compostela, A Coruña, Spain; King Abdulaziz University, Center of Excellence in Genomic Medicine Research, Abdullah Sulayman, Jeddah 22254, Saudi Arabia.
| | - Montserrat Mila
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain; CIBER of Rare Diseases (CIBERER), Villarroel 170, 08036 Barcelona, Spain; IDIBAPS, Rosselló 149, 08036 Barcelona, Spain.
| | - Laia Rodriguez-Revenga
- Biochemistry and Molecular Genetics Department, Hospital Clinic, Villarroel 170, 08036 Barcelona, Spain; CIBER of Rare Diseases (CIBERER), Villarroel 170, 08036 Barcelona, Spain; IDIBAPS, Rosselló 149, 08036 Barcelona, Spain.
| |
Collapse
|
5
|
Tassone F, Choudhary NS, Tassone F, Durbin-Johnson B, Hansen R, Hertz-Picciotto I, Pessah I. Identification of expanded alleles of the FMR1 Gene in the CHildhood Autism Risks from Genes and Environment (CHARGE) study. J Autism Dev Disord 2013; 43:530-9. [PMID: 22767137 DOI: 10.1007/s10803-012-1580-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fragile X syndrome (FXS) is a neuro-developmental disorder characterized by intellectual disabilities and autism spectrum disorders (ASD). Expansion of a CGG trinucleotide repeat (>200 repeats) in the 5'UTR of the fragile X mental retardation gene, is the single most prevalent cause of cognitive disabilities. Several screening studies for FXS, among individuals with ID from different ethnic populations, have indicated that the prevalence of the syndrome varies between 0.5 and 16 %. Because the high co-morbidity with autism, we have conducted a screening study of the cohort from CHARGE, a large-scale, population-based, case control study. We have identified six subjects carrying an expanded allele, which emphasize the importance of screening for FXS in a population with intellectual disabilities and ASD.
Collapse
Affiliation(s)
- Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, 2700 Stockton Blvd, Suite 2102, Sacramento, CA 95817, USA.
| | | | | | | | | | | | | |
Collapse
|
6
|
Loesch D, Hagerman R. Unstable Mutations in the FMR1 Gene and the Phenotypes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 769:78-114. [DOI: 10.1007/978-1-4614-5434-2_6] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
|
7
|
Abstract
Fragile X syndrome (FXS) is characterized by moderate to severe intellectual disability, which is accompanied by macroorchidism and distinct facial morphology. FXS is caused by the expansion of the CGG trinucleotide repeat in the 5' untranslated region of the fragile X mental retardation 1 (FMR1) gene. The syndrome has been studied in ethnically diverse populations around the world and has been extensively characterized in several populations. Similar to other trinucleotide expansion disorders, the gene-specific instability of FMR1 is not accompanied by genomic instability. Currently we do not have a comprehensive understanding of the molecular underpinnings of gene-specific instability associated with tandem repeats. Molecular evidence from in vitro experiments and animal models supports several pathways for gene-specific trinucleotide repeat expansion. However, whether the mechanisms reported from other systems contribute to trinucleotide repeat expansion in humans is not clear. To understand how repeat instability in humans could occur, the CGG repeat expansion is explored through molecular analysis and population studies which characterized CGG repeat alleles of FMR1. Finally, the review discusses the relevance of these studies in understanding the mechanism of trinucleotide repeat expansion in FXS.
Collapse
Affiliation(s)
- Emmanuel Peprah
- Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institute of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
8
|
Abstract
During the last few years, several studies have reported an excess of intermediate FMR1 alleles in patients with cognitive and/or behavioural phenotypes. Here, we report the frequency of intermediate alleles (IAs) in three pathologies, intellectual disabilities (IDs), attention-deficit/hyperactivity disorder and autism, from different Spanish regions. We found 142 IAs among 9015 patients with ID (1.6%), 4 among the 415 ADHD patients (0.96%) and 4 among the 300 autistic patients (1.3%), similar to the frequency reported in our control population. No evidence was found of an excess of IA at the FRAXA locus in any of the study populations, although geographical variability was detected. Moreover, the analysis of 100 transmissions of IAs showed that 95% of these alleles were stable. Only 3% expanded within the same range and 2% expanded to a full mutation in two generations. No evidence of an association between IAs and behavioural or cognitive phenotypes was found, suggesting that IAs are not clearly implicated in these pathologies.
Collapse
|
9
|
Loesch DZ, Bui QM, Huggins RM, Mitchell RJ, Hagerman RJ, Tassone F. Transcript levels of the intermediate size or grey zone fragile X mental retardation 1 alleles are raised, and correlate with the number of CGG repeats. J Med Genet 2006; 44:200-4. [PMID: 16905681 PMCID: PMC2598026 DOI: 10.1136/jmg.2006.043950] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Grey zone or intermediate alleles are one of the three recognised classes of the X-linked fragile X mental retardation 1 (FMR1) gene showing intergenerational instability. These classes are defined according to the number of CGG repeats in the FMR1 5'-untranslated region. Although large CGG expansions (>200 repeats) cause a neurodevelopmental anomaly through silencing of the gene, resulting in a deficit of FMR1 specific protein, smaller expansions (approximately 55-200 repeats) are associated with an increased transcription and late-onset specific phenotypes. Those alleles with a CGG repeat number ranging between approximately 41 and 55 are relatively poorly defined with regard to both transcriptional and translational activity, and also potential phenotypic effects. METHODS AND RESULTS Based on a sample of 33 males carrying FMR1 alleles within the grey zone range, defined here as 41-60 CGGs, we show an increased transcriptional activity relative to that seen in common alleles (5-40 CGGS). This is the first study to report a significant relationship between FMR1 mRNA levels and CGG repeat number within the grey zone range (p<0.001). From a piecewise linear regression model, the threshold for onset of the increase in mRNA levels as a function of CGG repeat size has been determined at approximately 39 repeats (standard error (SE) 3.24), and that for the reduction in the rate of this increase at approximately 54 repeats (SE 4.27). CONCLUSIONS The ambiguities associated with the definition and transcription dynamics of the FMR1 gene within the grey zone range are dealt with. There may be specific phenotypes associated with the toxic "gain-of-function" effect of raised mRNA.
Collapse
Affiliation(s)
- Danuta Z Loesch
- School of Psychological Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | | | | | | | | | | |
Collapse
|
10
|
Steiner CE, Guerreiro MM, Marques-de-Faria AP, Lopes-Cendes I. Laboratorial diagnosis of fragile-X syndrome: experience in a sample of individuals with pervasive developmental disorders. ARQUIVOS DE NEURO-PSIQUIATRIA 2005; 63:564-70. [PMID: 16172701 DOI: 10.1590/s0004-282x2005000400002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fragile X syndrome is a frequent genetic disease associated to developmental disorders, including learning disability, mental retardation, behavioral problems and pervasive developmental disorders (autism and related conditions). We studied a sample of 82 individuals (69 males and 13 females) presenting with pervasive developmental disorders using three techniques for the diagnosis of fragile X syndrome (FXS). Cytogenetic analysis detected the fragile site in four males, but only one showed a consistent positive rate. Molecular study based on the PCR technique was inconclusive for most females (92.3%), which where latter submitted to Southern blotting analysis, and for one male (1.4%), excluding the FRAXA mutation in the remaining male individuals (98.6%). Molecular tests using the Southern blotting technique confirmed only one positive case (1.2%) in a male subject. These results showed that Southern blotting analysis of the FRAXA mutation has the best sensitivity and specificity for the diagnosis of FXS but also validated the PCR technique as a confinable screening test.
Collapse
Affiliation(s)
- Carlos Eduardo Steiner
- Departamento de Genética Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
| | | | | | | |
Collapse
|
11
|
Mitchell RJ, Holden JJA, Zhang C, Curlis Y, Slater HR, Burgess T, Kirkby KC, Carmichael A, Heading KD, Loesch DZ. FMR1 alleles in Tasmania: a screening study of the special educational needs population. Clin Genet 2005; 67:38-46. [PMID: 15617547 DOI: 10.1111/j.1399-0004.2004.00344.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The distribution of fragile X mental retardation-1 (FMR1) allele categories, classified by the number of CGG repeats, in the population of Tasmania was investigated in 1253 males with special educational needs (SEN). The frequencies of these FMR1 categories were compared with those seen in controls as represented by 578 consecutive male births. The initial screening was based on polymerase chain reaction analysis of dried blood spots. Inconclusive results were verified by Southern analysis of a venous blood sample. The frequencies of common FMR1 alleles in both samples, and of grey zone alleles in the controls, were similar to those in other Caucasian populations. Consistent with earlier reports, we found some (although insignificant) increase of grey zone alleles in SEN subjects compared with controls. The frequencies of predisposing flanking haplotypes among grey zone males FMR1 alleles were similar to those seen in other Caucasian SEN samples. Contrary to expectation, given the normal frequency of grey zone alleles, no premutation (PM) or full mutation (FM) allele was detected in either sample, with only 15 fragile X families diagnosed through routine clinical admissions registered in Tasmania up to 2002. An explanation of this discrepancy could be that the C19th founders of Tasmania carried few PM or FM alleles. The eight to ten generations since white settlement of Tasmania has been insufficient time for susceptible grey zone alleles to evolve into the larger expansions.
Collapse
Affiliation(s)
- R J Mitchell
- Department of Genetics and Human Variation, School of Molecular Sciences, La Trobe University, Melbourne, Australia.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
van Karnebeek CDM, Jansweijer MCE, Leenders AGE, Offringa M, Hennekam RCM. Diagnostic investigations in individuals with mental retardation: a systematic literature review of their usefulness. Eur J Hum Genet 2005; 13:6-25. [PMID: 15523501 DOI: 10.1038/sj.ejhg.5201279] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
There are no guidelines available for diagnostic studies in patients with mental retardation (MR) established in an evidence-based manner. Here we report such study, based on information from original studies on the results with respect to detected significant anomalies (yield) of six major diagnostic investigations, and evaluate whether the yield differs depending on setting, MR severity, and gender. Results for cytogenetic studies showed the mean yield of chromosome aberrations in classical cytogenetics to be 9.5% (variation: 5.4% in school populations to 13.3% in institute populations; 4.1% in borderline-mild MR to 13.3% in moderate-profound MR; more frequent structural anomalies in females). The median yield of subtelomeric studies was 4.4% (also showing female predominance). For fragile X screening, yields were 5.4% (cytogenetic studies) and 2.0% (molecular studies) (higher yield in moderate-profound MR; checklist use useful). In metabolic investigations, the mean yield of all studies was 1.0% (results depending on neonatal screening programmes; in individual populations higher yield for specific metabolic disorders). Studies on neurological examination all showed a high yield (mean 42.9%; irrespective of setting, degree of MR, and gender). The yield of neuroimaging studies for abnormalities was 30.0% (higher yield if performed on an indicated basis) and the yield for finding a diagnosis based on neuroradiological studies only was 1.3% (no data available on value of negative findings). A very high yield was found for dysmorphologic examination (variation 39-81%). The data from this review allow conclusions for most types of diagnostic investigations in MR patients. Recommendations for further studies are provided.
Collapse
Affiliation(s)
- Clara D M van Karnebeek
- Department of Paediatrics/Emma Children's Hospital, Academic Medical Center, Amsterdam, The Netherlands
| | | | | | | | | |
Collapse
|
13
|
Crawford DC, Meadows KL, Newman JL, Taft LF, Scott E, Leslie M, Shubek L, Holmgreen P, Yeargin-Allsopp M, Boyle C, Sherman SL. Prevalence of the fragile X syndrome in African-Americans. AMERICAN JOURNAL OF MEDICAL GENETICS 2002; 110:226-33. [PMID: 12116230 DOI: 10.1002/ajmg.10427] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Since the development of a molecular diagnosis for the fragile X syndrome in the early 1990s, several population-based studies in Caucasians of mostly northern European descent have established that the prevalence is probably between one in 6,000 to one in 4,000 males in the general population. Reports of increased or decreased prevalence of the fragile X syndrome exist for a few other world populations; however, many of these are small and not population-based. We present here the final results of a 4-year study in the metropolitan area of Atlanta, Georgia, establishing the prevalence of the fragile X syndrome and the frequency of CGG repeat variants in a large Caucasian and African-American population. Results demonstrate that one-quarter to one-third of the children identified with the fragile X syndrome attending Atlanta public schools are not diagnosed before the age of 10 years. Also, a revised prevalence for the syndrome revealed a higher point estimate for African-American males (1/2,545; 95% CI: 1/5,208-1/1,289) than reported previously, although confidence intervals include the prevalence estimated for Caucasians from this (1/3,717; 95% CI: 1/7,692-1/1,869) and other studies. Further population-based studies in diverse populations are necessary to explore the possibility that the prevalence of the fragile X syndrome differs among world populations.
Collapse
Affiliation(s)
- Dana C Crawford
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Sharma D, Gupta M, Thelma BK. Expansion mutation frequency and CGG/GCC repeat polymorphism in FMR1 and FMR2 genes in an Indian population. Genet Epidemiol 2001; 20:129-144. [PMID: 11119302 DOI: 10.1002/1098-2272(200101)20:1<129::aid-gepi11>3.0.co;2-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Based on molecular screening, we estimated the frequencies of fragile X syndrome and FRAXE syndrome in an institutionalized population (n = 130) in New Delhi, India. Eligibility criteria for inclusion of subjects in the study were mild/moderate mental retardation, with/without family history, and the fragile X clinical phenotype. Screening by Southern hybridization revealed an overall frequency of 0.077 of the syndrome in the sample population. The disorder was observed with a high frequency (0.1) among males as compared to females (0.027). No expansions of FMR2 allele were observed in the same study sample. CGG/GCC allelic polymorphism of FMR1 and FMR2 were established from a total of 392 X chromosomes, using the radioactive polymerase chain reaction-polyacrylamide gel electrophoresis method. Distinct repeat sizes, repeat ranges, and repeat modes characterised the FMR1 and FMR2 alleles. In the X chromosomes of both MR individuals and unaffected controls, unimodal values of 29 and 15 repeats in FMR1 and FMR2 genes, respectively, were observed. Allele frequency distribution was symmetrical at the FMR1 locus whereas a significant positive skew was observed for the FMR2 alleles. The observed heterozygosity of the FMR1 gene was 0.772 compared to 0.839 of FMR2. Correlation of CGG/GCC repeats of FMR1 and FMR2 did not show any association of repeat sizes at these two loci (correlation coefficient, rho = 0.09). CGG/GCC repeat variation at FMR1 and FMR2 loci observed in this study sample are different from that reported for the other Caucasian and Asian populations.
Collapse
Affiliation(s)
- D Sharma
- Department of Genetics, University of Delhi South Campus, New Delhi, India
| | | | | |
Collapse
|
15
|
Abstract
The fragile X syndrome, an X-linked dominant disorder with reduced penetrance, is one of the most common forms of inherited mental retardation. The cognitive, behavioral, and physical phenotype varies by sex, with males being more severely affected because of the X-linked inheritance of the mutation. The disorder-causing mutation is the amplification of a CGG repeat in the 5' untranslated region of FMR1 located at Xq27.3. The fragile X CGG repeat has four forms: common (6-40 repeats), intermediate (41-60 repeats), premutation (61-200 repeats), and full mutation (>200-230 repeats). Population-based studies suggest that the prevalence of the full mutation, the disorder-causing form of the repeat, ranges from 1/3,717 to 1/8,918 Caucasian males in the general population. The full mutation is also found in other racial/ethnic populations; however, few population-based studies exist for these populations. No population-based studies exist for the full mutation in a general female population. In contrast, several large, population-based studies exist for the premutation or carrier form of the disorder, with prevalence estimates ranging from 1/246 to 1/468 Caucasian females in the general population. For Caucasian males, the prevalence of the premutation is approximately 1/1,000. Like the full mutation, little information exists for the premutation in other populations. Although no effective cure or treatment exists for the fragile X syndrome, all persons affected with the syndrome are eligible for early intervention services. The relatively high prevalence of the premutation and full mutation genotypes coupled with technological advances in genetic testing make the fragile X syndrome amenable to screening. The timing as well as benefits and harms associated with the different screening strategies are the subject of current research and discussion.
Collapse
Affiliation(s)
- Dana C. Crawford
- Centers for Disease Control and Prevention, Epidemic Intelligence Service, Division of Applied Public Health Training, Epidemiology Program Office
- Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities
| | - Juan M. Acuña
- Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Reproductive Health, CDC Assignee to the Louisiana Office of Public Health
- National University of Colombia
| | | |
Collapse
|
16
|
Mazzocco MM. Advances in research on the fragile X syndrome. MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 2000; 6:96-106. [PMID: 10899802 DOI: 10.1002/1098-2779(2000)6:2<96::aid-mrdd3>3.0.co;2-h] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Fragile X syndrome is a neurodevelopmental disorder that results from a single gene mutation on the X chromosome. The purpose of this review is to summarize key advances made in understanding the fragile X premutation gene seen in carriers and the full mutation gene seen in persons with the syndrome. DNA testing has replaced cytogenetic testing as the primary method for identification of fragile X, although the efficacy of protein level screening is being explored. The premutation is associated with no effects, although there is evidence of physical effects-primarily premature menopause and mild outward features of the fragile X syndrome-among premutation carriers. There is much controversy regarding premutation effects on psychological development. The few experimental studies carried out to date do not suggest noticeable or significant effects. One challenge in addressing this controversy is the sometimes ambiguous differentiation between premutation and full mutation genes. There is a well-established yet highly variable phenotype of the full mutation. Research from this decade has helped to address specific aspects of this phenotype, including the early course of its development in males, the influence of home and family environments, the nature of social difficulties and autistic features seen in boys and girls with fragile X, and the potential role of hyperarousal or hyper-reactivity. Studies in these areas, and on the role of FMR protein, will contribute towards ongoing advances in our understanding of fragile X syndrome and its mechanisms. The variability in physical, social, and cognitive features, as described in this review, is one that prohibits clear-cut screening guidelines designed to avoid high rates of both false positives and false negatives. Results from recent studies indicate the need to consider behavioral features in selecting candidates for fragile X screening. MRDD Research Reviews 2000;6:96-106.
Collapse
Affiliation(s)
- M M Mazzocco
- Department of Developmental Cognitive Neurology, Kennedy Krieger Institute; Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
| |
Collapse
|
17
|
Youings SA, Murray A, Dennis N, Ennis S, Lewis C, McKechnie N, Pound M, Sharrock A, Jacobs P. FRAXA and FRAXE: the results of a five year survey. J Med Genet 2000; 37:415-21. [PMID: 10851251 PMCID: PMC1734610 DOI: 10.1136/jmg.37.6.415] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We report the results of a five year survey of FRAXA and FRAXE mutations among boys aged 5 to 18 with special educational needs (SEN) related to learning disability. We tested their mothers using the X chromosome not transmitted to the son as a control chromosome, and the X chromosome inherited by the son to provide information on stability of transmission. We tested 3738 boys and 2968 mothers and found 20 FRAXA and one FRAXE full mutations among the boys and none among the mothers. This gives an estimated prevalence of full mutations in males of 1 in 5530 for FRAXA and 1 in 23 423 for FRAXE. We found an excess of intermediate and premutation alleles for both FRAXA and FRAXE. For FRAXA this was significant at the 0.001 level but the excess for FRAXE was significant only at the 0.03 level. We conclude that the excess of intermediate and premutation sized alleles for FRAXA may well be a contributing factor to the boys' mental impairment, while that for FRAXE may be a chance finding. We studied approximately 3000 transmissions from mother to son and found five instabilities of FRAXA in the common or intermediate range and three instabilities of FRAXE in the intermediate range. Thus instabilities in trinucleotide repeat size for FRAXA and FRAXE are rare, especially among alleles in the common size range.
Collapse
Affiliation(s)
- S A Youings
- Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, Wiltshire SP2 8BJ, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
González-del Angel A, Vidal S, Saldaña Y, del Castillo V, Angel Alcántara M, Macías M, Pedro Luna J, Orozco L. Molecular diagnosis of the fragile X and FRAXE syndromes in patients with mental retardation of unknown cause in Mexico. ANNALES DE GENETIQUE 2000; 43:29-34. [PMID: 10818218 DOI: 10.1016/s0003-3995(00)00018-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The fragile X syndrome (Fra-X) is the most common cause of inherited mental retardation with X-linked semi-dominant inheritance. The prevalence of Fra-X in the Mexican population is unknown. The aim of this population screening study was to determine if Fra-X or FRAXE mutations are the cause of a number of cases of mental retardation in a sample of Mexican children with mental retardation of unknown cause (MRUC) and to stress the importance of performing molecular analysis of the FMR-1 gene in all patients with MRUC. We report here the direct analysis of CGG and GCC repeats within the FMR-1 and FMR-2 genes, respectively, in 62 unrelated patients with MRUC. Two male index cases had the CGG expansion, although they did not express the Xq27.3 fragile site cytogenetically. Fra-X diagnosis was highly suspected on a clinical basis in one of the patients, but not in the other. Both mothers were found to be premutation carriers. The molecular studies of FMR-1 showed that the proportion of MRUC patients with Fra-X is 3.2%. This frequency was not significantly different to that reported in most populations. As reported in other series, no patients with FRAXE were found in our sample. Our findings confirm that the molecular analysis of the FMR-1 gene is necessary in MRUC patients to achieve unequivocal diagnosis of fragile X syndrome, carrier premutation detection and for accurate genetic counseling.
Collapse
Affiliation(s)
- A González-del Angel
- Molecular Biology Laboratory, Department of Research in Human Genetics, National Institute of Pediatrics, Mexico City, Mexico
| | | | | | | | | | | | | | | |
Collapse
|