scholarly journals Common Variant Associations with Fragile X Syndrome

2017 ◽  
Author(s):  
James J Crowley ◽  
Jin Szatkiewicz ◽  
Anna K Kähler ◽  
Paola Giusti-Rodriguez ◽  
NaEshia Ancalade ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Odds Ratio ◽  
De Novo ◽  
Fragile X ◽  
De Novo Mutation ◽  
Risk Haplotype ◽  
Functional Genomic ◽  
Cgg Repeats ◽  
Genome Wide ◽  
Protective Haplotype

AbstractFragile X syndrome is a common cause of intellectual disability. It is usually caused by a de novo mutation which often occur on multiple haplotypes and should not be detectible using genome-wide association (GWA). We conducted GWA 89 male FXS cases and 266 male controls, and detected multiple genome-wide significant signals near FMR1 (odds ratio=8.10, P=2.5×10−10). These findings withstood robust attempts at falsification. Fine-mapping did not serve to narrow the interval (minimum P=1.13×l0−14), and functional genomic integration (including 5C data we generated for this region) did not provide a mechanistic hypothesis. Controls carrying a risk haplotype had significantly longer and more variable FMR1 CGG repeats than controls with the protective haplotype (P=4.75×10−5) which may predispose toward increases in CGG number to the pre-mutation range over many generations. This is a salutary reminder of the complexity of even “simple” monogenetic disorders.

scholarly journals Spatially coordinated heterochromatinization of distal short tandem repeats in fragile X syndrome

2021 ◽  
Author(s):  
Linda Zhou ◽  
Chunmin Ge ◽  
Thomas Malachowski ◽  
Ji Hun Kim ◽  
Keerthivasan Raanin Chandradoss ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Short Tandem Repeats ◽  
Tandem Repeats ◽  
Fragile X ◽  
Repeat Expansion ◽  
Genome Wide ◽  
A Genome ◽  
In Trans ◽  
Surveillance Mechanism ◽  
Short Tandem

AbstractShort tandem repeat (STR) instability is causally linked to pathologic transcriptional silencing in a subset of repeat expansion disorders. In fragile X syndrome (FXS), instability of a single CGG STR tract is thought to repress FMR1 via local DNA methylation. Here, we report the acquisition of more than ten Megabase-sized H3K9me3 domains in FXS, including a 5-8 Megabase block around FMR1. Distal H3K9me3 domains encompass synaptic genes with STR instability, and spatially co-localize in trans concurrently with FMR1 CGG expansion and the dissolution of TADs. CRISPR engineering of mutation-length FMR1 CGG to normal-length preserves heterochromatin, whereas cut-out to pre-mutation-length attenuates a subset of H3K9me3 domains. Overexpression of a pre-mutation-length CGG de-represses both FMR1 and distal heterochromatinized genes, indicating that long-range H3K9me3-mediated silencing is exquisitely sensitive to STR length. Together, our data uncover a genome-wide surveillance mechanism by which STR tracts spatially communicate over vast distances to heterochromatinize the pathologically unstable genome in FXS.One-Sentence SummaryHeterochromatinization of distal synaptic genes with repeat instability in fragile X is reversible by overexpression of a pre-mutation length CGG tract.

scholarly journals Analysis of unstable DNA sequence in FMR1 gene in Polish families with fragile X syndrome.

1996 ◽  
Vol 43 (2) ◽  
pp. 383-388
Author(s):  
M Milewski ◽  
M Zygulska ◽  
J Bal ◽  
W H Deelen ◽  
E Obersztyn ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Dna Sequence ◽  
Clinical Features ◽  
Fragile Site ◽  
Fragile X ◽  
Fmr1 Gene ◽  
Repeat Number ◽  
Full Mutation ◽  
Cgg Repeats ◽  
Large Expansion

The unstable DNA sequence in the FMR1 gene was analyzed in 85 individuals from Polish families with fragile X syndrome in order to characterize mutations responsible for the disease in Poland. In all affected individuals classified on the basis of clinical features and expression of the fragile site at X(q27.3) a large expansion of the unstable sequence (full mutation) was detected. About 5% (2 of 43) of individuals with full mutation did not express the fragile site. Among normal alleles, ranging in size from 20 to 41 CGG repeats, allele with 29 repeats was the most frequent (37%). Transmission of premutated and fully mutated alleles to the offspring was always associated with size increase. No change in repeat number was found when normal alleles were transmitted.

scholarly journals Cascade Testing for Fragile X Syndrome in a Rural Setting in Cameroon (Sub-Saharan Africa)

Genes ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 136
Author(s):  
Karen Kengne Kamga ◽  
Séraphin Nguefack ◽  
Khuthala Minka ◽  
Edmond Wonkam Tingang ◽  
Alina Esterhuizen ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Fragile X ◽  
Autism Spectrum ◽  
Sub Saharan Africa ◽  
Rural Setting ◽  
Premature Menopause ◽  
Molecular Testing ◽  
Full Mutation ◽  
Cgg Repeat ◽  
Cgg Repeats

Fragile X Syndrome (FXS), an X-linked dominant monogenic condition, is the main genetic cause of intellectual disability (ID) and autism spectrum disorder (ASD). FXS is associated with an expansion of CGG repeat sequence in the Fragile X Mental Retardation gene 1 (FMR1) on chromosome X. Following a neuropediatric assessment of two male siblings who presented with signs of FXS that was confirmed with molecular testing, we provided cascade counselling and testing to the extended family. A total of 46 individuals were tested for FXS; among them, 58.70% (n = 27) were females. The mean age was 9.4 (±5) years for children and 45.9 (±15.9) years for adults. Pedigree analysis suggested that the founder of these families was likely a normal transmitting male. Four out of 19 males with clinical ID were confirmed to have a full mutation for FXS, while 14/27 females had a pathologic CGG expansion (>56 CGG repeats) on one of their X chromosomes. Two women with premature menopause were confirmed of being carriers of premutation (91 and 101 CGG repeats). We also identified maternal alleles (91 and 126 CGG repeats) which expanded to a full mutation in their offspring (>200 CGG repeats). This study is a rare report on FXS from Africa and illustrates the case scenario of implementing genetic medicine for a neurogenetic condition in a rural setting.

scholarly journals Early Intervention Combined with Targeted Treatment Promotes Cognitive and Behavioral Improvements in Young Children with Fragile X Syndrome

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Tri Indah Winarni ◽  
Andrea Schneider ◽  
Mariya Borodyanskara ◽  
Randi J. Hagerman
Keyword(s):  
Young Children ◽  
Fragile X Syndrome ◽  
Dendritic Spine ◽  
Environmental Enrichment ◽  
Fragile X ◽  
Educational Interventions ◽  
Targeted Treatment ◽  
Pharmacological Intervention ◽  
Cgg Repeats ◽  
And Behavior

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability due to an expansion in the full mutation range (>200 CGG repeats) of the promoter region of theFMR1gene leading to gene silencing. Lack of FMRP, a critical protein for dendritic spine formation and maturation, will cause FXS. Early environmental enrichment combined with pharmacological intervention has been proven to rescue dendritic spine abnormalities in the animal model of FXS. Here we report on 2 young children with FXS who were treated early with a combination of targeted treatment and intensive educational interventions leading to improvement in their cognition and behavior and a normal IQ.

scholarly journals Altered steady state and activity-dependent de novo protein expression in fragile X syndrome

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Heather Bowling ◽  
Aditi Bhattacharya ◽  
Guoan Zhang ◽  
Danyal Alam ◽  
Joseph Z. Lebowitz ◽  
...  
Keyword(s):  
Steady State ◽  
Protein Expression ◽  
Fragile X Syndrome ◽  
De Novo ◽  
Fragile X ◽  
Activity Dependent

scholarly journals Genome-wide analysis validates aberrant methylation in fragile X syndrome is specific to the FMR1locus

2013 ◽  
Vol 14 (1) ◽  
Author(s):  
Reid S Alisch ◽  
Tao Wang ◽  
Pankaj Chopra ◽  
Jeannie Visootsak ◽  
Karen N Conneely ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Fragile X ◽  
Aberrant Methylation ◽  
Genome Wide Analysis ◽  
Genome Wide

scholarly journals Simplified Molecular Diagnosis of Fragile X Syndrome by Fluorescent Methylation-Specific PCR and GeneScan Analysis

2006 ◽  
Vol 52 (8) ◽  
pp. 1492-1500 ◽  
Author(s):  
Youyou Zhou ◽  
Josephine MS Lum ◽  
Gare-Hoon Yeo ◽  
Jennifer Kiing ◽  
Stacey KH Tay ◽  
...  
Keyword(s):  
Fragile X Syndrome ◽  
Southern Blot ◽  
Molecular Diagnosis ◽  
Blot Analysis ◽  
Southern Blot Analysis ◽  
Fragile X ◽  
Molecular Diagnostic ◽  
Methylation Specific Pcr ◽  
Specific Pcr ◽  
Cgg Repeats

Abstract Background: Fragile X syndrome (FXS), the most common cause of inherited mental impairment, is most commonly related to hyperexpansion and hypermethylation of a polymorphic CGG trinucleotide repeat in the 5′ untranslated region of the FMR1 gene. Southern blot analysis is the most commonly used method for molecular diagnosis of FXS. We describe a simplified strategy based on fluorescent methylation-specific PCR (ms-PCR) and GeneScan™ analysis for molecular diagnosis of fragile X syndrome. Methods: We used sodium bisulfite treatment to selectively modify genomic DNA from fragile X and normal lymphoblastoid cell lines and from patients. We then performed ms-PCR amplification using fluorescently-labeled primers complementary to modified methylated or unmethylated DNA. Amplification products were resolved by capillary electrophoresis. FMR1 mutational status was determined by a combination of fluorescent peak sizes and patterns on the GeneScan electropherogram. Results: DNA samples from male and female persons with known NL, PM, and FM FMR1 CGG repeats were analyzed. Each FMR1 genotype produced a unique GeneScan electropherogram pattern, thus providing a way to identify the various disease states. The number of CGG repeats in all NL and PM alleles were determined accurately. Analysis by both the new assay and Southern blot of a family segregating with FXS showed complete concordance between both methods. Conclusions: This simplified molecular diagnostic test, based on fluorescent methylation-specific PCR, may be a suitable alternative or complement to Southern blot analysis for the diagnosis of FXS.

scholarly journals Beyond Trinucleotide Repeat Expansion in Fragile X Syndrome: Rare Coding and Noncoding Variants in FMR1 and Associated Phenotypes

Genes ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1669
Author(s):  
Cedrik Tekendo-Ngongang ◽  
Angela Grochowsky ◽  
Benjamin D. Solomon ◽  
Sho T. Yano
Keyword(s):  
Copy Number ◽  
Trinucleotide Repeat ◽  
De Novo ◽  
Fragile X ◽  
Copy Number Variants ◽  
Repeat Expansion ◽  
Full Mutation ◽  
Cgg Repeat ◽  
Testing Strategies ◽  
Cgg Repeats

FMR1 (FMRP translational regulator 1) variants other than repeat expansion are known to cause disease phenotypes but can be overlooked if they are not accounted for in genetic testing strategies. We collected and reanalyzed the evidence for pathogenicity of FMR1 coding, noncoding, and copy number variants published to date. There is a spectrum of disease-causing FMR1 variation, with clinical and functional evidence supporting pathogenicity of five splicing, five missense, one in-frame deletion, one nonsense, and four frameshift variants. In addition, FMR1 deletions occur in both mosaic full mutation patients and as constitutional pathogenic alleles. De novo deletions arise not only from full mutation alleles but also alleles with normal-sized CGG repeats in several patients, suggesting that the CGG repeat region may be prone to genomic instability even in the absence of repeat expansion. We conclude that clinical tests for potentially FMR1-related indications such as intellectual disability should include methods capable of detecting small coding, noncoding, and copy number variants.

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