Experiences of the Molecular Diagnosis of Fragile X Syndrome in Ecuador

Fragile X syndrome (FXS) is the most common cause of hereditary intellectual disability and the second most common cause of intellectual disability of genetic etiology. This complex neurodevelopmental disorder is caused by an alteration in the CGG trinucleotide expansion in fragile X mental retardation gene 1 (FMR1) leading to gene silencing and the subsequent loss of its product: fragile X mental retardation protein 1 (FMRP). Molecular diagnosis is based on polymerase chain reaction (PCR) screening followed by Southern blotting (SB) or Triplet primer-PCR (TP-PCR) to determine the number of CGG repeats in the FMR1 gene. We performed, for the first time, screening in 247 Ecuadorian male individuals with clinical criteria to discard FXS. Analysis was carried out by the Genetics Service of the Hospital de Especialidades No. 1 de las Fuerzas Armadas (HE-1), Ecuador. The analysis was performed using endpoint PCR for CGG fragment expansion analysis of the FMR1 gene. Twenty-two affected males were identified as potentially carrying the full mutation in FMR1 and thus diagnosed with FXS that is 8.1% of the sample studied. The average age at diagnosis of the positive cases was 13 years of age, with most cases from the geographical area of Pichincha (63.63%). We confirmed the familial nature of the disease in four cases. The range of CGG variation in the population was 12–43 and followed a modal distribution of 27 repeats. Our results were similar to those reported in the literature; however, since it was not possible to differentiate between premutation and mutation cases, we can only establish a molecular screening approach to identify an expanded CGG repeat, which makes it necessary to generate national strategies to optimize molecular tests and establish proper protocols for the diagnosis, management, and follow-up of patients, families, and communities at risk of presenting FXS.

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FMRP Levels in Human Peripheral Blood Leukocytes Correlates with Intellectual Disability

Diagnostics ◽

10.3390/diagnostics11101780 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1780

Author(s):

Mark Roth ◽

Lucienne Ronco ◽

Diego Cadavid ◽

Blythe Durbin-Johnson ◽

Randi J. Hagerman ◽

...

Keyword(s):

Mental Retardation ◽

Intellectual Disability ◽

Peripheral Blood ◽

Fragile X ◽

Repeat Expansion ◽

Repeat Number ◽

Cgg Repeat ◽

Fragile X Mental Retardation ◽

Cgg Repeats ◽

Fmr1 Mrna

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability. FXS is an X-linked, neurodevelopmental disorder caused by a CGG trinucleotide repeat expansion in the 5′ untranslated region (UTR) of the Fragile X Mental Retardation gene, FMR1. Greater than 200 CGG repeats results in epigenetic silencing of the gene leading to the deficiency or absence of Fragile X mental retardation protein (FMRP). The loss of FMRP is considered the root cause of FXS. The relationship between neurological function and FMRP expression in peripheral blood mononuclear cells (PBMCs) has not been well established. Assays to detect and measure FMR1 and FMRP have been described; however, none are sufficiently sensitive, precise, or quantitative to properly characterize the relationships between cognitive ability and CGG repeat number, FMR1 mRNA expression, or FMRP expression measured in PBMCs. To address these limitations, two novel immunoassays were developed and optimized, an electro-chemiluminescence immunoassay and a multiparameter flow cytometry assay. Both assays were performed on PMBCs isolated from 27 study participants with FMR1 CGG repeats ranging from normal to full mutation. After correcting for methylation, a significant positive correlation between CGG repeat number and FMR1 mRNA expression levels and a significant negative correlation between FMRP levels and CGG repeat expansion was observed. Importantly, a high positive correlation was observed between intellectual quotient (IQ) and FMRP expression measured in PBMCs.

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New Targeted Treatments for Fragile X Syndrome

Current Pediatric Reviews ◽

10.2174/1573396315666190625110748 ◽

2019 ◽

Vol 15 (4) ◽

pp. 251-258 ◽

Cited By ~ 1

Author(s):

Dragana Protic ◽

Maria J. Salcedo-Arellano ◽

Jeanne Barbara Dy ◽

Laura A. Potter ◽

Randi J. Hagerman

Keyword(s):

Mental Retardation ◽

Intellectual Disability ◽

Fragile X Syndrome ◽

Behavioral Problems ◽

Rna Binding ◽

Fragile X ◽

Symptomatic Treatment ◽

Fmr1 Gene ◽

Fragile X Mental Retardation ◽

Cgg Repeats

Fragile X Syndrome (FXS) is the most common cause of inherited intellectual disability with prevalence rates estimated to be 1:5,000 in males and 1:8,000 in females. The increase of >200 Cytosine Guanine Guanine (CGG) repeats in the 5’ untranslated region of the Fragile X Mental Retardation 1 (FMR1) gene results in transcriptional silencing on the FMR1 gene with a subsequent reduction or absence of fragile X mental retardation protein (FMRP), an RNA binding protein involved in the maturation and elimination of synapses. In addition to intellectual disability, common features of FXS are behavioral problems, autism, language deficits and atypical physical features. There are still no currently approved curative therapies for FXS, and clinical management continues to focus on symptomatic treatment of comorbid behaviors and psychiatric problems. Here we discuss several treatments that target the neurobiological pathway abnormal in FXS. These medications are clinically available at present and the data suggest that these medications can be helpful for those with FXS.

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An “Omic” Overview of Fragile X Syndrome

Biology ◽

10.3390/biology10050433 ◽

2021 ◽

Vol 10 (5) ◽

pp. 433

Author(s):

Olivier Dionne ◽

François Corbin

Keyword(s):

Mental Retardation ◽

Fragile X Syndrome ◽

Molecular Mechanisms ◽

Rna Binding ◽

Fragile X ◽

Neurodevelopmental Disorder ◽

Medical Problems ◽

Biochemical Alterations ◽

Fragile X Mental Retardation ◽

Wide Range

Fragile X syndrome (FXS) is a neurodevelopmental disorder associated with a wide range of cognitive, behavioral and medical problems. It arises from the silencing of the fragile X mental retardation 1 (FMR1) gene and, consequently, in the absence of its encoded protein, FMRP (fragile X mental retardation protein). FMRP is a ubiquitously expressed and multifunctional RNA-binding protein, primarily considered as a translational regulator. Pre-clinical studies of the past two decades have therefore focused on this function to relate FMRP’s absence to the molecular mechanisms underlying FXS physiopathology. Based on these data, successful pharmacological strategies were developed to rescue fragile X phenotype in animal models. Unfortunately, these results did not translate into humans as clinical trials using same therapeutic approaches did not reach the expected outcomes. These failures highlight the need to put into perspective the different functions of FMRP in order to get a more comprehensive understanding of FXS pathophysiology. This work presents a review of FMRP’s involvement on noteworthy molecular mechanisms that may ultimately contribute to various biochemical alterations composing the fragile X phenotype.

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Fragile X mental retardation protein interactions with a G quadruplex structure in the 3′-untranslated region of NR2B mRNA

Molecular BioSystems ◽

10.1039/c5mb00423c ◽

2015 ◽

Vol 11 (12) ◽

pp. 3222-3230 ◽

Cited By ~ 23

Author(s):

Snezana Stefanovic ◽

Brett A. DeMarco ◽

Ayana Underwood ◽

Kathryn R. Williams ◽

Gary J. Bassell ◽

...

Keyword(s):

Mental Retardation ◽

Intellectual Disability ◽

Protein Interactions ◽

Untranslated Region ◽

Fragile X ◽

Common Cause ◽

Fragile X Mental Retardation ◽

Quadruplex Structure ◽

G Quadruplex ◽

Mental Retardation Protein

Fragile X syndrome, the most common cause of inherited intellectual disability, is caused by a trinucleotide CGG expansion in the 5′-untranslated region of the FMR1 gene, which leads to the loss of expression of the fragile X mental retardation protein (FMRP).

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The Feasibility and Utility of Hair Follicle Sampling To Measure FMRP and FMR1 mRNA in Children With or Without Fragile X Syndrome

10.21203/rs.3.rs-1128569/v1 ◽

2021 ◽

Author(s):

Isha Jalnapurkar ◽

Jean A. Frazier ◽

Mark Roth ◽

David M. Cochran ◽

Ann Foley ◽

...

Keyword(s):

Mental Retardation ◽

Hair Follicle ◽

Fragile X Syndrome ◽

Fragile X ◽

Hair Follicles ◽

Buccal Swab ◽

Typically Developing ◽

Cgg Repeat ◽

Fragile X Mental Retardation ◽

Fmr1 Mrna

Abstract Background: Fragile X syndrome (FXS) is the most common cause inherited cause of intellectual disability in males and the most common single gene cause of autism. This X-linked disorder is caused by an expansion of a trinucleotide CGG repeat (>200 base pairs) on the promotor region of the fragile X mental retardation 1 gene (FMR1). This leads to the deficiency or absence of the encoded protein, Fragile X mental retardation protein (FMRP). FMRP has a central role in the translation of mRNAs involved in synaptic connections and plasticity. Recent studies have demonstrated the benefit of therapeutics focused on reactivation of the FMR1 locus towards improving key clinical phenotypes via restoration of FMRP and ultimately disease modification. A key step in future studies directed towards this effort is the establishment of proof of concept (POC) for FMRP reactivation in individuals with FXS. For this it is key to determine the feasibility of repeated collection of tissues or fluids to measure FMR1 and FMRP. Methods: Individuals, ages 3 to 22 years of age, with FXS and those who were typically developing participated in this single-site pilot clinical biomarker study. The repeated collection of hair follicles was compared with the collection of blood and buccal swabs for detection of FMR1 mRNA and FMRP and related molecules. Results: There were n = 15 participants, of whom 10 had a diagnosis of FXS (7.0 ± 3.56 years) and 5 were typically developing (8.2 ± 2.77 years). Absolute levels of FMRP and FMR1 mRNA were substantially higher in healthy participants compared to full mutation and mosaic FXS participants, and lowest in the FXS boys. Measurement of FMR1 and FMRP levels by any method did not show any notable variation by collection location at home versus office across the various sample collection methodologies of hair follicle, blood sample, and buccal swab. Conclusion: Findings demonstrated that repeated sampling of hair follicles in individuals with FXS, in both, home and office settings, is feasible, repeatable, and can be used for measurement of FMR1 and FMRP in longitudinal studies.

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Fragile X Syndrome

Colombia Medica ◽

10.25100/cm.v45i4.1810 ◽

2014 ◽

pp. 190-198 ◽

Cited By ~ 45

Author(s):

Wilmar Saldarriaga ◽

Flora Tassone ◽

Laura Yuriko González-Teshima ◽

Jose Vicente Forero-Forero ◽

Sebastián Ayala-Zapata ◽

...

Keyword(s):

Mental Retardation ◽

Intellectual Disability ◽

Fragile X Syndrome ◽

Fragile X ◽

Gene Promoter ◽

Molecular Techniques ◽

Pharmaceutical Management ◽

Developmental Problems ◽

Fragile X Mental Retardation ◽

Cgg Repeats

Fragile X Syndrome (FXS) is a genetic disease due to a CGG trinucleotide expansion, named full mutation (greater than 200 CGG repeats), in the fragile X mental retardation 1 gene locus Xq27.3; which leads to an hypermethylated region in the gene promoter therefore silencing it and lowering the expression levels of the fragile X mental retardation 1, a protein involved in synaptic plasticity and maturation. Individuals with FXS present with intellectual disability, autism, hyperactivity, long face, large or prominent ears and macroorchidism at puberty and thereafter. Most of the young children with FXS will present with language delay, sensory hyper arousal and anxiety. Girls are less affected than boys, only 25% have intellectual disability. Given the genomic features of the syndrome, there are patients with a number of triplet repeats between 55 and 200, known as premutation carriers. Most carriers have a normal IQ but some have developmental problems. The diagnosis of FXS has evolved from karyotype with special culture medium, to molecular techniques that are more sensitive and specific including PCR and Southern Blot. During the last decade, the advances in the knowledge of FXS, has led to the development of investigations on pharmaceutical management or targeted treatments for FXS. Minocycline and sertraline have shown efficacy in children.

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Clinical Development of Targeted Fragile X Syndrome Treatments: An Industry Perspective

Brain Sciences ◽

10.3390/brainsci8120214 ◽

2018 ◽

Vol 8 (12) ◽

pp. 214 ◽

Cited By ~ 16

Author(s):

Anna Lee ◽

Pamela Ventola ◽

Dejan Budimirovic ◽

Elizabeth Berry-Kravis ◽

Jeannie Visootsak

Keyword(s):

Clinical Trials ◽

Mental Retardation ◽

Intellectual Disability ◽

Fragile X Syndrome ◽

Fragile X ◽

Basic Research ◽

Autism Spectrum ◽

Pharmacological Agents ◽

Fragile X Mental Retardation ◽

Wide Range

Fragile X syndrome (FXS) is the leading known cause of inherited intellectual disability and autism spectrum disorder. It is caused by a mutation of the fragile X mental retardation 1 (FMR1) gene, resulting in a deficit of fragile X mental retardation protein (FMRP). The clinical presentation of FXS is variable, and is typically associated with developmental delays, intellectual disability, a wide range of behavioral issues, and certain identifying physical features. Over the past 25 years, researchers have worked to understand the complex relationship between FMRP deficiency and the symptoms of FXS and, in the process, have identified several potential targeted therapeutics, some of which have been tested in clinical trials. Whereas most of the basic research to date has been led by experts at academic institutions, the pharmaceutical industry is becoming increasingly involved with not only the scientific community, but also with patient advocacy organizations, as more promising pharmacological agents are moving into the clinical stages of development. The objective of this review is to provide an industry perspective on the ongoing development of mechanism-based treatments for FXS, including identification of challenges and recommendations for future clinical trials.

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Molecular Biomarkers in Fragile X Syndrome

Brain Sciences ◽

10.3390/brainsci9050096 ◽

2019 ◽

Vol 9 (5) ◽

pp. 96 ◽

Cited By ~ 5

Author(s):

Zafarullah ◽

Tassone

Keyword(s):

Clinical Trials ◽

Mental Retardation ◽

Intellectual Disability ◽

Fragile X Syndrome ◽

Fragile X ◽

Autism Spectrum ◽

Molecular Biomarkers ◽

Synaptic Function ◽

Primary Role ◽

Fragile X Mental Retardation

Fragile X syndrome (FXS) is the most common inherited form of intellectual disability (ID) and a known monogenic cause of autism spectrum disorder (ASD). It is a trinucleotide repeat disorder, in which more than 200 CGG repeats in the 5’ untranslated region (UTR) of the fragile X mental retardation 1 (FMR1) gene causes methylation of the promoter with consequent silencing of the gene, ultimately leading to the loss of the encoded fragile X mental retardation 1 protein, FMRP. FMRP is an RNA binding protein that plays a primary role as a repressor of translation of various mRNAs, many of which are involved in the maintenance and development of neuronal synaptic function and plasticity. In addition to intellectual disability, patients with FXS face several behavioral challenges, including anxiety, hyperactivity, seizures, repetitive behavior, and problems with executive and language performance. Currently, there is no cure or approved medication for the treatment of the underlying causes of FXS, but in the past few years, our knowledge about the proteins and pathways that are dysregulated by the loss of FMRP has increased, leading to clinical trials and to the path of developing molecular biomarkers for identifying potential targets for therapies. In this paper, we review candidate molecular biomarkers that have been identified in preclinical studies in the FXS mouse animal model and are now under validation for human applications or have already made their way to clinical trials.

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An ‘’Omic’’ Overview of Fragile X Syndrome

10.20944/preprints202103.0643.v1 ◽

2021 ◽

Author(s):

Olivier Dionne ◽

François Corbin

Keyword(s):

Mental Retardation ◽

Fragile X Syndrome ◽

Molecular Mechanisms ◽

Rna Binding ◽

Fragile X ◽

Neurodevelopmental Disorder ◽

Therapeutic Approaches ◽

Medical Problems ◽

Fragile X Mental Retardation ◽

Wide Range

Fragile X syndrome (FXS) is a neurodevelopmental disorder associated with a wide range of cognitive, behavioral and medical problems. It arises from the silencing of the fragile X mental retardation 1 (FMR1) gene, and consequently, in the absence of its encoded protein, FMRP (Fragile X Mental Retardation Protein). FMRP is a ubiquitously expressed and multifunctional RNA-binding protein, primarily considered as a translational regulator. Pre-clinical studies of the past two decades have therefore focus on this function to relate FMRP’s absence to the molecular mechanisms underlying FXS physiopathology. Based on these data, successful pharmacological strategies were developed to rescue fragile X phenotype in animal models. Unfortunately, these results did not translate into human, as clinical trials using same therapeutic approaches did not reach the expected outcomes. These failures highlight the need to put into perspectives the different functions of FMRP in order to get a more comprehensive understanding of FXS pathophysiology. In this review, FMRP’s involvement on noteworthy molecular mechanisms are pointed out; ultimately contributing to various biochemicals alterations composing the fragile X phenotype.

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ASFMR1splice variant

Neurology Genetics ◽

10.1212/nxg.0000000000000246 ◽

2018 ◽

Vol 4 (4) ◽

pp. e246 ◽

Cited By ~ 6

Author(s):

Padmaja Vittal ◽

Shrikant Pandya ◽

Kevin Sharp ◽

Elizabeth Berry-Kravis ◽

Lili Zhou ◽

...

Keyword(s):

Mental Retardation ◽

Splice Variant ◽

Messenger Rna ◽

Clinical Symptoms ◽

Fragile X ◽

Cgg Repeat ◽

Men And Women ◽

Fragile X Mental Retardation ◽

Repeat Size ◽

Ataxia Syndrome

ObjectiveTo explore the association of a splice variant of theantisense fragile X mental retardation 1(ASFMR1) gene, loss offragile X mental retardation 1(FMR1) AGG interspersions andFMR1CGG repeat size with manifestation, and severity of clinical symptoms of fragile X-associated tremor/ataxia syndrome (FXTAS).MethodsPremutation carriers (PMCs) with FXTAS, without FXTAS, and normal controls (NCs) had a neurologic evaluation and collection of skin and blood samples. Expression ofASFMR1transcript/splice variant 2 (ASFMR1-TV2), nonsplicedASFMR1, totalASFMR1, andFMR1messenger RNA were quantified and compared using analysis of variance. Least absolute shrinkage and selection operator (LASSO) logistic regression and receiver operating characteristic analyses were performed.ResultsPremutation men and women both with and without FXTAS had higherASFMR1-TV2 levels compared with NC men and women (n = 135,135,p< 0.0001), andASFMR1-TV2 had good discriminating power for FXTAS compared with NCs but not for FXTAS from PMC. After adjusting for age, loss of AGG, larger CGG repeat size (in men), and elevatedASFMR1-TV2 level (in women) were strongly associated with FXTAS compared with NC and PMC (combined).ConclusionsThis study found elevated levels ofASFMR1-TV2and loss of AGG interruptions in both men and women with FXTAS. Future studies will be needed to determine whether these variables can provide useful diagnostic or predictive information.

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