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Acero-Garcés DO, Saldarriaga W, Cabal-Herrera AM, Rojas CA, Hagerman RJ. Fragile X Syndrome in children. Colomb Med (Cali) 2023; 54:e4005089. [PMID: 37664646 PMCID: PMC10469670 DOI: 10.25100/cm.v54i2.5089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 11/28/2022] [Accepted: 05/14/2023] [Indexed: 09/05/2023] Open
Abstract
Fragile X syndrome is caused by the expansion of CGG triplets in the FMR1 gene, which generates epigenetic changes that silence its expression. The absence of the protein coded by this gene, FMRP, causes cellular dysfunction, leading to impaired brain development and functional abnormalities. The physical and neurologic manifestations of the disease appear early in life and may suggest the diagnosis. However, it must be confirmed by molecular tests. It affects multiple areas of daily living and greatly burdens the affected individuals and their families. Fragile X syndrome is the most common monogenic cause of intellectual disability and autism spectrum disorder; the diagnosis should be suspected in every patient with neurodevelopmental delay. Early interventions could improve the functional prognosis of patients with Fragile X syndrome, significantly impacting their quality of life and daily functioning. Therefore, healthcare for children with Fragile X syndrome should include a multidisciplinary approach.
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Affiliation(s)
| | - Wilmar Saldarriaga
- Universidad del Valle, Facultad de Salud, Escuela de Medicina, Cali, Colombia
- Universidad del Valle, Facultad de Salud, Escuela de Ciencias Básicas, Cali, Colombia
| | | | - Christian A. Rojas
- Universidad del Valle, Facultad de Salud, Escuela de Medicina, Cali, Colombia
| | - Randi J. Hagerman
- University of California, Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Sacramento, CA, USA
- Davis Medical Center, Sacramento, CA, USA
- University of California, Department of Pediatrics, Davis, CA, USA
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Rajaratnam A, Shergill J, Salcedo-Arellano M, Saldarriaga W, Duan X, Hagerman R. Fragile X syndrome and fragile X-associated disorders. F1000Res 2017; 6:2112. [PMID: 29259781 PMCID: PMC5728189 DOI: 10.12688/f1000research.11885.1] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/20/2017] [Indexed: 12/26/2022] Open
Abstract
Fragile X syndrome (FXS) is caused by a full mutation on the
FMR1 gene and a subsequent lack of FMRP, the protein product of
FMR1. FMRP plays a key role in regulating the translation of many proteins involved in maintaining neuronal synaptic connections; its deficiency may result in a range of intellectual disabilities, social deficits, psychiatric problems, and dysmorphic physical features. A range of clinical involvement is also associated with the
FMR1 premutation, including fragile X-associated tremor ataxia syndrome, fragile X-associated primary ovarian insufficiency, psychiatric problems, hypertension, migraines, and autoimmune problems. Over the past few years, there have been a number of advances in our knowledge of FXS and fragile X-associated disorders, and each of these advances offers significant clinical implications. Among these developments are a better understanding of the clinical impact of the phenomenon known as mosaicism, the revelation that various types of mutations can cause FXS, and improvements in treatment for FXS.
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Affiliation(s)
| | | | | | - Wilmar Saldarriaga
- MIND Institute, UC Davis Health, Sacramento, CA, USA.,Department of Morphology and Obstetrics & Gynecology, Universidad del Valle, School of Medicine, Cali, Valle del Cauca, Colombia
| | - Xianlai Duan
- MIND Institute, UC Davis Health, Sacramento, CA, USA.,Department of Neurology, The Third Hospital of Changsha, Hunan Sheng, China
| | - Randi Hagerman
- MIND Institute, UC Davis Health, Sacramento, CA, USA.,Department of Pediatrics, University of California, Davis, School of Medicine, Sacramento, CA, USA
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Barasoain M, Barrenetxea G, Ortiz-Lastra E, González J, Huerta I, Télez M, Ramírez JM, Domínguez A, Gurtubay P, Criado B, Arrieta I. Single nucleotide polymorphism and FMR1 CGG repeat instability in two Basque valleys. Ann Hum Genet 2012; 76:110-20. [PMID: 22211843 DOI: 10.1111/j.1469-1809.2011.00696.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fragile X Syndrome (FXS, MIM 309550) is mainly due to the expansion of a CGG trinucleotide repeat sequence, found in the 5' untranslated region of the FMR1 gene. Some studies suggest that stable markers, such as single nucleotide polymorphisms (SNPs) and the study of populations with genetic identity, could provide a distinct advance to investigate the origin of CGG repeat instability. In this study, seven SNPs (WEX28 rs17312728:G>T, WEX70 rs45631657:C>T, WEX1 rs10521868:A>C, ATL1 rs4949:A>G, FMRb rs25707:A>G, WEX17 rs12010481:C>T and WEX10 ss71651741:C>T) have been analyzed in two Basque valleys (Markina and Arratia). We examined the association between these SNPs and the CGG repeat size, the AGG interruption pattern and two microsatellite markers (FRAXAC1 and DXS548). The results suggest that in both valleys WEX28-T, WEX70-C, WEX1-C, ATL1-G, and WEX10-C are preferably associated with cis-acting sequences directly influencing instability. But comparison of the two valleys reveals also important differences with respect to: (1) frequency and structure of "susceptible" alleles and (2) association between "susceptible" alleles and STR and SNP haplotypes. These results may indicate that, in Arratia, SNP status does not identify a pool of susceptible alleles, as it does in Markina. In Arratia valley, the SNP haplotype association reveals also a potential new "protective" factor.
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Affiliation(s)
- Maitane Barasoain
- Department of Genetics, Physical Anthropology and Animal physiology, Faculty of Science and Technology, University of the Basque Country, Bilbao, Spain
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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.
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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.
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5
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Datta S, Alam MP, Majumdar SS, Mehta AK, Maiti S, Wadhwa N, Brahmachari V. Nucleosomal occupancy and CGG repeat expansion: a comparative analysis of triplet repeat region from mouse and human fragile X mental retardation gene 1. Chromosome Res 2011; 19:445-55. [PMID: 21499798 DOI: 10.1007/s10577-011-9206-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/21/2011] [Accepted: 03/21/2011] [Indexed: 10/18/2022]
Abstract
The expansion of CGG repeats in the 5'-untranslated region (5'UTR) of FMR1 gene is the molecular basis of fragile X syndrome in most of the patients. The nature of the flanking sequences in addition to the length and interruption pattern of repeats is predicted to influence CGG repeat instability in the FMR1 gene. We investigated nucleosome occupancy as a contributor to CGG repeat instability in a transgenic mouse model containing unstable (CGG)(26,) from human FMR1 cloned downstream of nucleosome-excluding sequence. We observe that the transgene has an open chromatin structure compared to the stable endogenous mouse Fmr1 within the same nucleus. CGG repeats in mouse Fmr1 are flanked by nucleosomes unlike the repeats in the transgene in all the tissues examined. Further in vitro chromatin reconstitution experiments show that DNA fragment without the SV40ori/EPR (nucleosome-excluding sequence) forms more stable chromatin than the one containing it, despite having the same number of CGG repeats. The correlation between nucleosomal organisation of the FMR1 gene and CGG repeat instability was supported by significantly lower frequency of repeat expansion in mice containing an identical transgene without the SV40ori/EPR. Our studies demonstrate that flanking DNA sequences can influence repeat instability through modulation of nucleosome occupancy in the region.
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Affiliation(s)
- Sonal Datta
- Dr. B. R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi, 110007, India
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Peprah EK, Allen EG, Williams SM, Woodard LM, Sherman SL. Genetic diversity of the fragile X syndrome gene (FMR1) in a large Sub-Saharan West African population. Ann Hum Genet 2010; 74:316-25. [PMID: 20597902 DOI: 10.1111/j.1469-1809.2010.00582.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fragile X syndrome (OMIM #300624) is caused by the expansion of a CGG trinucleotide repeat found in the 5' untranslated region of the X-linked FMR1 gene. Although examinations of characteristics associated with repeat instability and expansion of the CGG repeat upon transmission from parent to offspring has occurred in various world populations, none has been conducted in large Sub-Saharan African populations. We have examined the FMR1 CGG repeat structure in a sample of 350 males drawn from the general population of Ghana. We found that Ghanaians and African Americans have similar allele frequency distributions of CGG repeat and its flanking STR markers, DXS548 and FRAXAC1. However, the distribution of the more complex marker, FRAXAC2, is significantly different. The haplotype structure of the FMR1 locus indicated that Ghanaians share several haplotypes with African Americans and Caucasians that are associated with the expanded full mutation. In Ghanaians, the majority of repeat structures contained two AGG interruptions, however, the majority of intermediate alleles (35-49) lacked AGG interruptions. Overall, we demonstrate that allelic diversity of the FMR1 locus among Ghanaians is comparable to African Americans, but includes a minority of CGG array structures not found in other populations.
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Affiliation(s)
- Emmanuel K Peprah
- Department of Human Genetics, Emory University, Atlanta, Georgia 30322, USA.
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Chakraborty SS, Mondal BC, Das S, Das K, Dasgupta UB. Haplotype analysis at the FRAXA locus in an Indian population. Am J Med Genet A 2008; 146A:1980-5. [PMID: 18627041 DOI: 10.1002/ajmg.a.32108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The FRAXA locus is flanked by three polymorphic STR markers DXS548, FRAXAC1, and FRAXAC2. Allele frequencies of these markers were determined on a population representing the eastern part of India comprising of 69 normal controls and 69 unrelated subjects with mental retardation, among whom 21 were fragile X patients. These frequencies were compared with published data on other Indian population and the major populations of the world. The allele and haplotype distribution of the studied population were significantly different in some respects from the major populations of the world. The increase of heterozygosities in fragile X samples (DXS548 67.5%, FRAXAC1 63.5%, FRAXAC2 68.5%) relative to the controls (DXS548 63.3%, FRAXAC1 51.0%, FRAXAC2 67.2%) suggests a multimodal distribution of fragile X associated alleles. Haplotype analyses with DXS548 and FRAXAC1 markers revealed that haplotype distribution in the normal controls and fragile X groups were significantly different, suggesting a weak founder effect.
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Affiliation(s)
- S Saha Chakraborty
- Department of Biophysics, Molecular Biology and Genetics, University of Calcutta, Kolkata, India
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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.
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Affiliation(s)
- R J Mitchell
- Department of Genetics and Human Variation, School of Molecular Sciences, La Trobe University, Melbourne, Australia.
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Tzeng CC, Tsai LP, Hwu WL, Lin SJ, Chao MC, Jong YJ, Chu SY, Chao WC, Lu CL. Prevalence of theFMR1 mutation in Taiwan assessed by large-scale screening of newborn boys and analysis of DXS548-FRAXAC1 haplotype. Am J Med Genet A 2005; 133A:37-43. [PMID: 15637705 DOI: 10.1002/ajmg.a.30528] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
If carrier women could be identified in time and take appropriate measures, fragile X syndrome (FXS) can be prevented. Wide screening of women to be or in their early pregnancy was considered a good approach to identify carriers without misdetection. Nevertheless, we argued against the cost-effectiveness of implementing such a screening program in Taiwan, due to the lower carrier rate found in our pilot study. To reliably estimate the prevalence of mutant FMR1 gene in Taiwan, we anonymously screened 10,046 newborn boys using bloodspot polymerase chain reaction (PCR). Among them, the sample from one boy, who was most likely had FXS, failed repeatedly in PCR amplification. The estimated prevalence of premutation (55-200 CGG repeats) and intermediate alleles (45-54 CGG repeats) was 1:1,674 (n = 6) and 1:143 (n = 70), respectively. All these estimates were constantly lower than that reported in Caucasian populations, with variable statistic significance. Furthermore, when comparing analyses of the distribution of alleles at the two most often investigated microsatellite loci, DXS548 and FRAXAC1, between 100 control and 28 unrelated fragile X chromosomes, we found no apparent founder haplotype prevalent among the fragile X patients. Because a few founder haplotypes were reportedly prevalent in two thirds of fragile X alleles in Caucasians and in Chinese from Central China, we thus suggested that lack of founder fragile X chromosomes might result in a relatively low prevalence of mutant FMR1 gene in a population, as observed in Taiwan.
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Affiliation(s)
- Ching-Cherng Tzeng
- Department of Pathology, Chi Mei Medical Center, Tainan, Taiwan, Republic of China.
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Mandel JL, Biancalana V. Fragile X mental retardation syndrome: from pathogenesis to diagnostic issues. Growth Horm IGF Res 2004; 14 Suppl A:S158-S165. [PMID: 15135801 DOI: 10.1016/j.ghir.2004.03.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Fragile X (FRAXA) syndrome is the most common cause of familial (monogenic) mental retardation and is widespread in human populations. This syndrome is characterised by an unusual mode of transmission for an X-linked disease. In affected families, one frequently finds clinically normal transmitting males, whose daughters - also clinically normal - have a high risk of having affected children. The risk of developing the disease (penetrance) thus appears to increase in successive generations of the same family through maternal transmission. As shown by molecular cloning of the fragile X locus, Fragile X mutations are unstable expansions of a CGG trinucleotide repeat, located in the first exon (non-protein-coding) of the FMR1 gene (for Fragile X Mental Retardation). Two main types of mutation are observed in affected families. A full mutation is found in patients with mental retardation and corresponds to large expansions of the repeat. Premutations are moderate expansions and are found in normal transmitting males and in the majority of clinically normal carrier females. About 15% of patients show a mosaic pattern consisting of both full mutations and premutations. Although analysis of the CGG expansion has led to the establishment of reliable tests for diagnosis and genetic counseling of Fragile X syndrome, care must be exercised to use these tools to answer the concerns of the families and avoid doing harm. In our opinion, testing in children should be restricted to those who show a developmental delay, cognitive deficits and/or abnormal behavior evocative of the syndrome. A carrier diagnosis in a girl who is clinically normal should probably only be performed at an age where she can understand the consequences for family planning and the options of prenatal diagnosis. When testing children with borderline cognitive deficits, a positive diagnosis should be used to improve educational strategies for the children - and not to stigmatise them.
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Affiliation(s)
- J L Mandel
- Institut de Génétique et Biologie Moléculaire et Cellulaire, INSERM/CNRS/Université Louis Pasteur, Faculté de Médecine and Hôpitaux Universitaires Strasbourg, Illkirch-Cedex, Strasbourg 67404, France.
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Sharma D, Gupta M, Thelma BK. FMR1 haplotype analyses among Indians: a weak founder effect and other findings. Hum Genet 2003; 112:262-71. [PMID: 12596051 DOI: 10.1007/s00439-002-0872-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2002] [Accepted: 10/23/2002] [Indexed: 11/24/2022]
Abstract
This study on allelic/haplotypic fragile X associations evaluated using STR (DXS548, FRAXAC1, FRAXAC2) and SNP (ATL1) markers flanking the (CGG)(n) locus of FMR1is the first report from the large ethnically complex Indian population. Results have been compared with allele/haplotype distributions reported for other major ethnic groups, including White Caucasians, Africans, and Pacific Asians. Though overall allele frequency distributions at the individual loci are more similar to Western Caucasians compared with others, significant differences are observed in haplotypic associations with the mutated X. The striking findings are: (1) high diversity and heterozygosity of haplotypes among fragile X chromosomes ( n=40) and controls ( n=262), including four haplotypes found exclusively in this study sample; (2) weak association of DXS548-FRAXAC1-FRAXAC2 haplotypes, 2-1-3, 6-3-3+ and 7-4-6+ with the disorder, and absence of White Caucasian fragile X haplotypes 6-4-4 and 6-4-5; (3) weak founder effect for the fragile X expansion mutation in the Indians; (4) lack of a continuum of haplotype-based FMR1 alleles between intermediate (CGG)(n) size ranges and expanded alleles; (5) exclusion of ATL1 as a candidate genetic indicator of FMR1 instability. The high STR-based haplotype diversity observed among fragile X lineages, irrespective of ethnic alliances, strongly suggests the inappropriateness of using STR haplotypes to infer predisposition to instability among ethnically separated fragile X pedigrees and may reiterate the need for identifying newer SNPs from this region to not only determine true founder effects for the fragile X mutation, but also decipher possible mechanisms leading to CGG instability.
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Affiliation(s)
- Deepti Sharma
- Department of Genetics, University of Delhi South Campus, New Delhi, India
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Arrieta I, Peñagarikano O, Télez M, Ortega B, Flores P, Criado B, Veiga I, Peixoto AL, Lostao CM. The FMR1 CGG repeat and linked microsatellite markers in two Basque valleys. Heredity (Edinb) 2003; 90:206-11. [PMID: 12634803 DOI: 10.1038/sj.hdy.6800218] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Fragile X syndrome is associated with an unstable CGG repeat sequence in the 5' untranslated region of the first exon of the FMR1 gene. The present study involved the evaluation of factors implicated in CGG repeat stability in a normal sample from two Basque valleys (Markina and Arratia), to discover whether the Basque population shows allelic diversity and to identify factors involved, by using the data in conjunction with previous findings. The study was based on a sample of 204 and 58 X chromosomes from the Markina and Arratia valleys, respectively. The CGG repeat, the AGG interspersion and two flanking microsatellite markers, FRAXAC1 and DXS548, were examined. In the Markina valley, gray zone alleles (> or =35 CGG repeats) were associated with anchoring AGGs, with the longest 3' pure CGG repeats of the valley (=15), with the 5' instability structure 9+n and with one principal fragile X FRAXAC1-DXS548 haplotype 42-50. In the Arratia valley, gray zone alleles (> or =35 CGG repeats) showed the highest frequency among the Basque samples analyzed, and were associated with anchoring AGGs, with the longest 3' pure repeats (> or =20), with the 5' instability structure 9+n and with one "normal" FRAXAC1-DXS548 haplotype 38-40 (these data from Arratia suggest the existence of a "protective" haplotype). The results showed, on the one hand, differences between Markina and Arratia in factors implicated in CGG repeat instability and, on the other hand, a great similarity between the general Basque sample from Biscay and the Markina valley.
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Affiliation(s)
- I Arrieta
- Dipartamento Biología Animal y Genética, Facultad de Ciencias, Universidad del País Vasco, Apdo 644, Bilbao 48080, Spain.
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Weisman-Shomer P, Cohen E, Fry M. Interruption of the fragile X syndrome expanded sequence d(CGG)(n) by interspersed d(AGG) trinucleotides diminishes the formation and stability of d(CGG)(n) tetrahelical structures. Nucleic Acids Res 2000; 28:1535-41. [PMID: 10710419 PMCID: PMC102797 DOI: 10.1093/nar/28.7.1535] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/1999] [Revised: 02/15/2000] [Accepted: 02/15/2000] [Indexed: 11/14/2022] Open
Abstract
Fragile X syndrome is caused by expansion of a d(CGG) trinucleotide repeat sequence in the 5' untranslated region of the first exon of the FMR1 gene. Repeat expansion is thought to be instigated by formation of d(CGG)(n)secondary structures. Stable FMR1 d(CGG)(n)runs in normal individuals consist of 6-52 d(CGG) repeats that are interrupted every 9-11 triplets by a single d(AGG) trinucleotide. By contrast, individuals having fragile X syndrome premutation or full mutation present >54-200 or >200-2000 monotonous d(CGG) repeats, respectively. Here we show that the presence of interspersed d(AGG) triplets diminished in vitro formation of bimolecular tetrahelical structures of d(CGG)(18)oligomers. Tetraplex structures formed by d(CGG)(n)oligomers containing d(AGG) interspersions had lower thermal stability. In addition, tetraplex structures of d(CGG)(18)oligomers interspersed by d(AGG) triplets were unwound by human Werner syndrome DNA helicase at rates and to an extent that exceeded the unwinding of tetraplex form consisting of monotonous d(CGG)(18). Diminished formation and stability of tetraplex structures of d(AGG)-containing FMR1 d(CGG)(2-50)tracts might restrict their expansion in normal individuals.
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Affiliation(s)
- P Weisman-Shomer
- Unit of Biochemistry, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, PO Box 9649, Haifa 31096, Israel
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14
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Mingroni-Netto RC, Costa SS, Angeli CB, Vianna-Morgante AM. DXS548/FRAXAC1 haplotypes in fragile X chromosomes in the Brazilian population. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-8628(19990528)84:3<204::aid-ajmg7>3.0.co;2-j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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16
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Mornet E, Chateau C, Simon-Bouy B, Serre JL. The intermediate alleles of the fragile X CGG repeat in patients with mental retardation. Clin Genet 1998; 53:200-1. [PMID: 9630074 DOI: 10.1111/j.1399-0004.1998.tb02676.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have analysed the size of the non-expanded FRAXA CGG repeat in 385 male patients affected by mental retardation and in 182 unrelated normal chromosomes as control. The results show that intermediate alleles with more than 40 repeats were not significantly more frequent in patients than in controls. These data do not corroborate previous findings supporting the idea that intermediate alleles may have a deleterious effect on mental retardation.
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Affiliation(s)
- E Mornet
- Centre d'Etudes de Biologie Prénatale-SESEP, Université de Versailles-Saint Quentin, Versailles, France.
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17
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Cossée M, Schmitt M, Campuzano V, Reutenauer L, Moutou C, Mandel JL, Koenig M. Evolution of the Friedreich's ataxia trinucleotide repeat expansion: founder effect and premutations. Proc Natl Acad Sci U S A 1997; 94:7452-7. [PMID: 9207112 PMCID: PMC23842 DOI: 10.1073/pnas.94.14.7452] [Citation(s) in RCA: 219] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Friedreich's ataxia, the most frequent inherited ataxia, is caused, in the vast majority of cases, by large GAA repeat expansions in the first intron of the frataxin gene. The normal sequence corresponds to a moderately polymorphic trinucleotide repeat with bimodal size distribution. Small normal alleles have approximately eight to nine repeats whereas a more heterogeneous mode of large normal alleles ranges from 16 to 34 GAA. The latter class accounts for approximately 17% of normal alleles. To identify the origin of the expansion mutation, we analyzed linkage disequilibrium between expansion mutations or normal alleles and a haplotype of five polymorphic markers within or close to the frataxin gene; 51% of the expansions were associated with a single haplotype, and the other expansions were associated with haplotypes that could be related to the major one by mutation at a polymorphic marker or by ancient recombination. Of interest, the major haplotype associated with expansion is also the major haplotype associated with the larger alleles in the normal size range and was almost never found associated with the smaller normal alleles. The results indicate that most if not all large normal alleles derive from a single founder chromosome and that they represent a reservoir for larger expansion events, possibly through "premutation" intermediates. Indeed, we found two such alleles (42 and 60 GAA) that underwent cataclysmic expansion to pathological range in a single generation. This stepwise evolution to large trinucleotide expansions already was suggested for myotonic dystrophy and fragile X syndrome and may relate to a common mutational mechanism, despite sequence motif differences.
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Affiliation(s)
- M Cossée
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale/Centre National de la Recherche Scientifique/Université Louis Pasteur, Strasbourg, France
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18
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Murray A, Macpherson JN, Pound MC, Sharrock A, Youings SA, Dennis NR, McKechnie N, Linehan P, Morton NE, Jacobs PA. The role of size, sequence and haplotype in the stability of FRAXA and FRAXE alleles during transmission. Hum Mol Genet 1997; 6:173-84. [PMID: 9063737 DOI: 10.1093/hmg/6.2.173] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Factors involved in the stability of trinucleotide repeats during transmission were studied in 139 families in which a full mutation, premutation or intermediate allele at either FRAXA or FRAXE was segregating. The transmission of alleles at FRAXA, FRAXE and four microsatellite loci were recorded for all individuals. Instability within the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for FRAXE) was extremely rare; only one example was observed, an increased in size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were unstably transmitted. Instability was more frequent for FRAXA intermediate alleles that had a tract of pure CGG greater than 37 although instability only occurred in two of 13 such transmissions: the changes observed were limited to only one or two repeats. Premutation FRAXA alleles over 100 repeats expanded to a full mutation during female transmission in 100% of cases, in agreement with other published series. There was no clear correlation between haplotype and probability of expansion of FRAXA premutations. Instability at FRAXA or FRAXE was more often observed in conjunction with a second instability at an independent locus suggesting genomic instability as a possible mechanism by which at least some FRAXA and FRAXE mutations arise.
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Affiliation(s)
- A Murray
- Wessex Regional Genetics Laboratory, Salisbury District Hospital, Wiltshire, UK
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19
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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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20
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Chiurazzi P, Genuardi M, Kozak L, Giovannucci-Uzielli ML, Bussani C, Dagna-Bricarelli F, Grasso M, Perroni L, Sebastio G, Sperandeo MP, Oostra BA, Neri G. Fragile X founder chromosomes in Italy: a few initial events and possible explanation for their heterogeneity. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:209-15. [PMID: 8826478 DOI: 10.1002/(sici)1096-8628(19960712)64:1<209::aid-ajmg38>3.0.co;2-p] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A total of 137 fragile X and 235 control chromosomes from various regions of Italy were haplotyped by analyzing two neighbouring marker microsatellites, FRAXAC1 and DXS548. The number of CGG repeats at the 5' end of the FMR1 gene was also assessed in 141 control chromosomes and correlated with their haplotypes. Significant linkage disequilibrium between some "major" haplotypes and fragile X was observed, while other "minor" haplotypes may have originated by subsequent mutation at the marker microsatellite loci and/or recombination between them. Recent evidence suggests that the initial mechanism leading to CGG instability might consist of rare (10 (-6/-7)) CGG repeat slippage events and/or loss of a stabilizing AGG via A-to-C transversion. Also, the apparently high variety of fragile X chromosomes may be partly due to the relatively high mutation rate (10 (-4/-5)) of the microsatellite markers used in haplotyping. Our fragile X sample also showed a higher than expected heterozygosity when compared to the control sample and we suggest that this might be explained by the chance occurrence of the few founding events on different chromosomes, irrespective of their actual frequency in the population. Alternatively, a local mechanism could enhance the microsatellite mutation rate only on fragile X chromosomes, or fragile X mutations might occur more frequently on certain background haplotypes.
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Affiliation(s)
- P Chiurazzi
- Istituto di Genetica Medica, Università Cattolica, Rome, Italy
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21
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Zhong N, Kajanoja E, Smits B, Pietrofesa J, Curley D, Wang D, Ju W, Nolin S, Dobkin C, Ryynänen M, Brown WT. Fragile X founder effects and new mutations in Finland. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:226-33. [PMID: 8826481 DOI: 10.1002/(sici)1096-8628(19960712)64:1<226::aid-ajmg41>3.0.co;2-m] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The apparent associations between fragile X mutations and nearby microsatellites may reflect both founder effects and microsatellite instability. To gain further insight into their relative contributions, we typed a sample of 56 unrelated control and 37 fragile X chromosomes from an eastern Finnish population for FMR1 CGG repeat lengths, AGG interspersion patterns, DXS548, FRAXAC1, FRAXE and a new polymorphic locus, Alu-L. In the controls, the most common FMR1 allele was 30 repeats with a range of 20 to 47 and a calculated heterozygosity of 88%. A strong founder effect was observed for locus DXS548 with 95% of fragile X chromosomes having the 21 CA repeat (196 bp) allele compared to 17% of controls, while none of the fragile X but 69% of controls had the 20 repeat allele. Although the FRAXAC1 locus is much closer than DXS548 to FMR1 (7 kb vs. 150 kb), there was no significant difference between fragile X and control FRAXAC1 allele distributions. The FRAXE repeat, located 600 kb distal to FMR1, was found to show strong linkage disequilibrium as well. A newly defined polymorphism, Alu-L, located at approximately 40 kb distal to the FMR1 repeat, showed very low polymorphism in the Finnish samples. Analysis of the combined loci DXS548-FRAXAC1-FRAXE showed three founder haplotypes. Haplotype 21-19-16 was found on 27 (75%) of fragile X chromosomes but on none of controls. Three (8.4%) fragile X chromosomes had haplotypes 21-19-15, 21-19-20, and 21-19-25 differing from the common fragile X haplotype only in FRAXE. These could have arisen by recombination or from mutations of FRAXE. A second haplotype 21-18-17 was found in four (11.1%) fragile X chromosomes but only one (1.9%) control. This may represent a more recent founder mutation. A third haplotype 25-21-15, seen in two fragile X chromosomes (5.6%) and one (1.9%) control, was even less common and thus may represent an even more recent mutation or admixture of immigrant types. Analysis of the AGG interspersions within the FMR1 CGG repeat showed that 7/8 premutation chromosomes lacked an AGG whereas all controls had at least one AGG. This supports the hypothesis that the mutation of AGG to CGG leads to repeat instability and mutational expansion.
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Affiliation(s)
- N Zhong
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314, USA
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22
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Chiurazzi P, Macpherson J, Sherman S, Neri G. Significance of linkage disequilibrium between the fragile X locus and its flanking markers. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 64:203-8. [PMID: 8826477 DOI: 10.1002/(sici)1096-8628(19960712)64:1<203::aid-ajmg37>3.0.co;2-p] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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23
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Abstract
Fragile X syndrome is the most common cause of interited mental retardation in humans, with a frequency of approximately 1 in 1200 males and 1 in 2500 females [1]. It is second only to Down syndrome as a genetic cause of mental retardation, which has an overall frequency of 1 in 600. These frequency estimates suggest that fragile X syndrome accounts for approximately 3% of mental retardation in males, and perhaps as much as 20% in males with IQs between 30 and 55 [2]. The disease derives its name from the observation of a fragile site at Xq27.3 in cultured lymphocytes, fibroblasts and amniocytes [3].The phenotype of the fragile X syndrome is mental retardation, usually with an IQ in the 4-70 range [4] and a number of dysmorphic features: long face, everted ears and large testicles [for review see ref. 5] (Fig. 1). Not every patient shows all the physical symptoms, which are generally more apparent after childhood. Macroorchidism is a common feature of fragile X syndrome in more than 90% of postpuberal males. Some patients show hyperactivity and attention deficits as well as avoidance behaviour similar to autism. Affected females generally have a less severe clinical presentation, and their IQ scores are generally higher, with typically borderline IQs or mild mental retardation.No gross pathological abnormalities have been described in the brains of fragile X patients. Only a few post-mortem brain studies of fragile X males have been described and the information is very limited, presenting only non-specific findings such as brain atrophy, ventricular dilatation and pyramidal neurons with abnormal dendritic spines. It has been shown that the volume of the hippocampus was enlarged compared to controls [6], while a significantly decreased size of the posterior cerebellar vermis and increased size of the fourth ventricle was found [7]. Using magnetic resonance imaging it was shown that fragile X patients have an increased volume of the caudate nucleus [8]. The caudate volume is correlated with IQ and methylation status of the FMR1 gene.
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Affiliation(s)
- B A Oostra
- Department of Clinical Genetics, Erasmus University, Rotterdam, The Netherlands
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24
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Wijesuriya SD, Evans K, Jay MR, Davison C, Weber BH, Bird AC, Bhattacharya SS, Gregory CY. Sorsby's fundus dystrophy in the British Isles: demonstration of a striking founder effect by microsatellite-generated haplotypes. Genome Res 1996; 6:92-101. [PMID: 8919688 DOI: 10.1101/gr.6.2.92] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Sorsby's fundus dystrophy (SFD) has been mapped to a genetic interval of 8 cM between loci D22S275 and D22S278. A total of 15 families, unrelated on the basis of genealogy and expressing the SFD phenotype were identified from a large data base of genetic eye disease families originating from diverse parts of the British Isles. The identification of the same Ser181Cys mutation cosegregating with disease in each family led us to consider the hypothesis of a founder effect being present. In all families studied, the same relatively infrequent allele (occurring in just 11% of the control group) was associated with disease at marker locus D22S280. A highly significant disease-associated haplotype, spanning across 3 cM of the SFD locus, was conserved in 11 of the 15 families (68% of all affected chromosomes); a further extended haplotype spanning up to 7 cM, was identified in 5 families (27% of SFD-associated chromosomes) and possibly represents the ancestral haplotype. This haplotype analysis has refined the TIMP3 gene localization to a 1- to 3-cM interval between marker loci D22S273 and D22S281 and provides strong evidence for a single mutational event being responsible for the majority of SFD identified in the British Isles.
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Affiliation(s)
- S D Wijesuriya
- Department of Molecular Genetics, Institute of Ophthalmology, Southampton, UK
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25
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Abstract
Rare haplotypes for close flanking markers are associated with increased allele size and frequency of the fragile X mutation. Exceptional founder haplotypes can be identified, but many haplotypes with rare alleles contribute to full mutations. A transition matrix constructed from the data predicts that a population with reduced variability will manifest a slowly increasing frequency of premutations and full mutations, reach a distribution close to the observed one after a few hundred generations, and then slowly be depleted of these alleles. This prediction is opposite to less well supported inference of increasing frequency of progressive amplification, but the data are inadequate to reach any firm conclusions. Factors that may determine the evolution of these systems, but cannot now be evaluated, are discussed.
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Affiliation(s)
- A Morris
- Human Genetics Centre, Princess Anne Hospital, University of Southampton
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26
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Flannery AV, Hirst MC, Knight SJ, Ritchie RJ, Davies KE. The fragile X syndrome. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1271:293-303. [PMID: 7605796 DOI: 10.1016/0925-4439(95)00046-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- A V Flannery
- Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, UK
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27
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Schaap T. Confidentiality in counseling for X-linked conditions. Clin Genet 1995; 47:155-7. [PMID: 7634539 DOI: 10.1111/j.1399-0004.1995.tb03949.x] [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] [Indexed: 01/26/2023]
Abstract
Genetic counseling in a synthetic fragile-X family is used to illustrate some dilemmas which may arise from the genetic counselor's wish to respect the patient's confidence. What is the counselor's obligation towards family members who are unaware that they are carriers? Should the counselor try to avoid disclosing information concerning such family members to the patient, and if so-how? May the future father of an affected fetus be prevented from participating in the reproductive decisions concerning that fetus, out of respect for the mother's wishes?
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Affiliation(s)
- T Schaap
- Department of Human Genetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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28
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29
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Monckton DG, Neumann R, Guram T, Fretwell N, Tamaki K, MacLeod A, Jeffreys AJ. Minisatellite mutation rate variation associated with a flanking DNA sequence polymorphism. Nat Genet 1994; 8:162-70. [PMID: 7842015 DOI: 10.1038/ng1094-162] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Human minisatellite mutation in the male germline frequently involves complex interallelic gene conversion events restricted to one end of the tandem repeat array. Some alleles at minisatellite MS32 show reduced variability in human populations and are associated with a G to C transversion upstream of the array. Analysis of single sperm demonstrated a frequently profound reduction in mutation rate at alleles carrying the C variant. This mutation suppression acts in cis, but does not affect the ability of an allele to act as sequence donor during gene conversion. This mutation rate polymorphism provides strong evidence for elements near the minisatellite that regulate tandem repeat instability.
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Affiliation(s)
- D G Monckton
- Department of Genetics, University of Leicester, UK
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30
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31
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Sutherland GR, Brown WT, Hagerman R, Jenkins E, Lubs H, Mandel JL, Nelson D, Neri G, Partington MW, Richards RI. Sixth international workshop on the fragile X and X-linked mental retardation. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 51:281-93. [PMID: 7942989 DOI: 10.1002/ajmg.1320510402] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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32
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Zhong N, Ye L, Dobkin C, Brown WT. Fragile X founder chromosome effects: linkage disequilibrium or microsatellite heterogeneity? AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 51:405-11. [PMID: 7943008 DOI: 10.1002/ajmg.1320510421] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Previous studies of founder chromosome effects in fragile X have been based on linkage disequilibrium with either FRAXAC1 or DXS548 alone or combined with FRAXAC2. Recently, we found no linkage disequilibrium of FMR-1 with FRAXAC2, but rather, found FRAXAC2 was complex and highly mutable. Therefore, we have now analyzed FRAXAC1 and DXS548 together for haplotypes, two markers which have not been jointly analyzed previously, to test for disequilibrium. We typed 315 fragile X (FX) chromosomes and controls, further subdivided into large controls (LC) and small controls (SC) with < or = 35 repeats and identified 26 different haplotypes. Two were more frequent and one less frequent in FX than SCs, thus confirming apparent linkage disequilibrium in fragile X. However, we noted increased FX microsatellite heterozygosity, either individually (results quite similar to previous studies) or as haplotypes. This heterozygosity covaried with FX > LC > SC, which may indicate alternative explanation exists for the apparent disequilibrium. We hypothesize that large FMR-1 CGG repeat allele genes may be associated with the generation of new microsatellite mutations. Possible mechanisms include gene conversions between CGG repeats and flanking microsatellites involving unequal double cross-overs, the expansion of small control CGGs to larger sizes associated with episodic generalized microsatellite instability or as a direct result of mutant FMR-1 gene function. We conclude that the founder effects observed with the use of these CA repeats is likely to reflect both linkage disequilibrium and increased microsatellite instability of fragile X chromosomes.
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Affiliation(s)
- N Zhong
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314
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33
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Zhong N, Liu X, Gou S, Houck GE, Li S, Dobkin C, Brown WT. Distribution of FMR-1 and associated microsatellite alleles in a normal Chinese population. AMERICAN JOURNAL OF MEDICAL GENETICS 1994; 51:417-22. [PMID: 7943010 DOI: 10.1002/ajmg.1320510423] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The CGG repeat size distribution of the fragile X mental retardation gene (FMR-1) was studied in a population of normal Chinese X chromosomes along with that of two proximal microsatellite polymorphic markers: FRAXAC1 and DXS548. The most common CGG repeat allele was 29 (47.2%) with 30 being second most common (26%). This distribution was different from that seen in Caucasian controls, where the most common allele was 30 repeats. Other differences with Caucasian controls included a secondary modal peak at 36 repeats and the absence of peaks at 20 or 23 repeats. There were only two FRAXAC1 and five DXS548 alleles found in the Chinese sample. A striking linkage disequilibrium of FMR-1 alleles with FRAXAC1 alleles was observed, in that 90% of the 29 CGG repeat alleles but only 41% of the 30 CGG repeat alleles had the FRAXAC1 152 bp allele (18 AC repeats). This disequilibrium suggests that slippage between the closely spaced normal CGG repeat alleles, 29 and 30, and between 152 and 154 FRAXAC1 alleles is very rare. This study lays the groundwork for an understanding of founder chromosome effects in comparing Asian and Caucasian populations.
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Affiliation(s)
- N Zhong
- Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314
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34
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35
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Mornet E, Chateau C, Taillandier A, Montagnon M, Simon-Bouy B, Serre JL, Boué A. FRAXAC2 instability. Nat Genet 1994; 7:122-3. [PMID: 7920626 DOI: 10.1038/ng0694-122b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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36
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Richards RI, Holman K, Friend K, Staples A, Sutherland GR, Oudet C, Biancalana V, Mandel JL. FRAXAC2 instability. Nat Genet 1994; 7:122; author reply 123. [PMID: 7802803 DOI: 10.1038/ng0694-122a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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37
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