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Jiraanont P, Zafarullah M, Sulaiman N, Espinal GM, Randol JL, Durbin-Johnson B, Schneider A, Hagerman RJ, Hagerman PJ, Tassone F. FMR1 Protein Expression Correlates with Intelligence Quotient in Both Peripheral Blood Mononuclear Cells and Fibroblasts from Individuals with an FMR1 Mutation. J Mol Diagn 2024; 26:498-509. [PMID: 38522837 DOI: 10.1016/j.jmoldx.2024.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 02/15/2024] [Accepted: 02/23/2024] [Indexed: 03/26/2024] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable form of intellectual disability and is caused by CGG repeat expansions exceeding 200 (full mutation). Such expansions lead to hypermethylation and transcriptional silencing of the fragile X messenger ribonucleoprotein 1 (FMR1) gene. As a consequence, little or no FMR1 protein (FMRP) is produced; absence of the protein, which normally is responsible for neuronal development and maintenance, causes the syndrome. Previous studies have demonstrated the causal relationship between FMRP levels and cognitive abilities in peripheral blood mononuclear cells (PBMCs) and dermal fibroblast cell lines of patients with FXS. However, it is arguable whether PBMCs or fibroblasts would be the preferred surrogate for measuring molecular markers, particularly FMRP, to represent the cognitive impairment, a core symptom of FXS. To address this concern, CGG repeats, methylation status, FMR1 mRNA, and FMRP levels were measured in both PBMCs and fibroblasts derived from 66 individuals. The findings indicated a strong association between FMR1 mRNA expression levels and CGG repeat numbers in PBMCs of premutation males after correcting for methylation status. Moreover, FMRP expression levels from both PBMCs and fibroblasts of male participants with a hypermethylated full mutation and with mosaicism demonstrated significant association between the intelligence quotient levels and FMRP levels, suggesting that PBMCs may be preferable for FXS clinical studies, because of their greater accessibility.
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Affiliation(s)
- Poonnada Jiraanont
- Division of Molecular and Cellular Medicine, Faculty of Medicine, King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand
| | - Marwa Zafarullah
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Noor Sulaiman
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Glenda M Espinal
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Jamie L Randol
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California
| | - Blythe Durbin-Johnson
- Division of Biostatistics, University of California, Davis, School of Medicine, Davis, California
| | - Andrea Schneider
- Department of Pediatrics, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California
| | - Randi J Hagerman
- Department of Pediatrics, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California
| | - Paul J Hagerman
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Davis, California; UC Davis MIND Institute, University of California, Davis, Sacramento, California.
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Randol JL, Kim K, Ponzini MD, Tassone F, Falcon AK, Hagerman RJ, Hagerman PJ. Variation of FMRP Expression in Peripheral Blood Mononuclear Cells from Individuals with Fragile X Syndrome. Genes (Basel) 2024; 15:356. [PMID: 38540415 PMCID: PMC10969917 DOI: 10.3390/genes15030356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/02/2024] [Accepted: 03/08/2024] [Indexed: 04/07/2024] Open
Abstract
Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and autism spectrum disorder. The syndrome is often caused by greatly reduced or absent protein expression from the fragile X messenger ribonucleoprotein 1 (FMR1) gene due to expansion of a 5'-non-coding trinucleotide (CGG) element beyond 200 repeats (full mutation). To better understand the complex relationships among FMR1 allelotype, methylation status, mRNA expression, and FMR1 protein (FMRP) levels, FMRP was quantified in peripheral blood mononuclear cells for a large cohort of FXS (n = 154) and control (n = 139) individuals using time-resolved fluorescence resonance energy transfer. Considerable size and methylation mosaicism were observed among individuals with FXS, with FMRP detected only in the presence of such mosaicism. No sample with a minimum allele size greater than 273 CGG repeats had significant levels of FMRP. Additionally, an association was observed between FMR1 mRNA and FMRP levels in FXS samples, predominantly driven by those with the lowest FMRP values. This study underscores the complexity of FMR1 allelotypes and FMRP expression and prompts a reevaluation of FXS therapies aimed at reactivating large full mutation alleles that are likely not capable of producing sufficient FMRP to improve cognitive function.
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Affiliation(s)
- Jamie L. Randol
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Kyoungmi Kim
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Matthew D. Ponzini
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Flora Tassone
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
| | - Alexandria K. Falcon
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Randi J. Hagerman
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
- Department of Pediatrics, School of Medicine, University of California, Davis, Sacramento, CA 95817, USA
| | - Paul J. Hagerman
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Davis, CA 95616, USA
- Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, UC Davis Health, Sacramento, CA 95817, USA
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Shankar VG, Klann E. Size matters: Fighting repeat expansion size in fragile X syndrome using antisense oligonucleotides. Proc Natl Acad Sci U S A 2023; 120:e2309678120. [PMID: 37440569 PMCID: PMC10372623 DOI: 10.1073/pnas.2309678120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/15/2023] Open
Affiliation(s)
| | - Eric Klann
- Center for Neural Science, New York University, New York, NY10003
- New York University Neuroscience Institute, New York University Grossman School of Medicine, New York, NY10016
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Schmitt LM, Will M, Shaffer R, Erickson C. A Paradigm Shifting View of Intellectual Disability: A Near Normal Distribution of IQ in Fragile X Syndrome. RESEARCH SQUARE 2023:rs.3.rs-2869313. [PMID: 37205401 PMCID: PMC10187411 DOI: 10.21203/rs.3.rs-2869313/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Fragile X Syndrome (FXS) is an X-linked disorder leading to the loss of expression of FMR1-protein product, FMRP. The absence or deficiency of FMRP is thought to result in the characteristic FXS phenotypes, including intellectual disability. Identifying the relationship between FMRP levels and IQ may be critical to better understand underlying mechanisms and advance treatment development and planning. A sample of 80 individuals with FXS (67% male), aged 8-45 years, completed IQ testing and blood draw via venipuncture to determine the relationship between IQ scores and FMRP levels as well as the normalcy of IQ distributions. In females with FXS only, higher FMRP levels were associated with higher IQ. In contrast, males with FXS showed a downward shifted but otherwise normal distribution of IQ scores. Our findings offer a paradigm-shifting views of FXS-males with FXS have normally distributed IQ that is downshifted 5 standard deviations. Our novel work provides evidence of a "FXS standard curve", and is a critical step towards establishing molecular markers of disease severity in FXS. There is much future work to better understand the mechanism by which FMRP loss leads to intellectual disability and what biological/genetic and socio-environmental factors contribute to variation in IQ.
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Jalnapurkar I, Frazier JA, Roth M, Cochran DM, Foley A, Merk T, Venuti L, Ronco L, Raines S, Cadavid D. The feasibility and utility of hair follicle sampling to measure FMRP and FMR1 mRNA in children with or without fragile X syndrome: a pilot study. J Neurodev Disord 2022; 14:57. [PMID: 36494616 PMCID: PMC9733195 DOI: 10.1186/s11689-022-09465-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 10/26/2022] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Fragile X syndrome (FXS) is the most common 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 messenger ribonucleoprotein 1 gene (FMR1). This leads to the deficiency or absence of the encoded protein, fragile X messenger ribonucleoprotein 1 (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 mRNA 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 mRNA 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 mRNA and FMRP in longitudinal studies.
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Affiliation(s)
- Isha Jalnapurkar
- grid.410516.70000 0001 0707 2056Department of Psychiatry, EK Shriver Center, University of Massachusetts Medical School, Worcester, MA USA
| | - Jean A. Frazier
- grid.410516.70000 0001 0707 2056Department of Psychiatry, EK Shriver Center, University of Massachusetts Medical School, Worcester, MA USA
| | - Mark Roth
- grid.509699.a0000 0004 5907 6392Fulcrum Therapeutics, Cambridge, MA USA
| | - David M. Cochran
- grid.410516.70000 0001 0707 2056Department of Psychiatry, EK Shriver Center, University of Massachusetts Medical School, Worcester, MA USA
| | - Ann Foley
- grid.410516.70000 0001 0707 2056Department of Psychiatry, EK Shriver Center, University of Massachusetts Medical School, Worcester, MA USA
| | - Taylor Merk
- grid.410516.70000 0001 0707 2056Department of Psychiatry, EK Shriver Center, University of Massachusetts Medical School, Worcester, MA USA
| | - Lauren Venuti
- grid.410516.70000 0001 0707 2056Department of Psychiatry, EK Shriver Center, University of Massachusetts Medical School, Worcester, MA USA
| | - Lucienne Ronco
- grid.509699.a0000 0004 5907 6392Fulcrum Therapeutics, Cambridge, MA USA
| | - Shane Raines
- grid.509699.a0000 0004 5907 6392Fulcrum Therapeutics, Cambridge, MA USA
| | - Diego Cadavid
- grid.509699.a0000 0004 5907 6392Fulcrum Therapeutics, Cambridge, MA USA
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Optimization, validation and initial clinical implications of a Luminex-based immunoassay for the quantification of Fragile X Protein from dried blood spots. Sci Rep 2022; 12:5617. [PMID: 35379866 PMCID: PMC8980090 DOI: 10.1038/s41598-022-09633-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/17/2022] [Indexed: 02/03/2023] Open
Abstract
Fragile X Syndrome (FXS) is caused by a trinucleotide expansion leading to silencing of the FMR1 gene and lack of expression of Fragile X Protein (FXP, formerly known as Fragile X Mental Retardation Protein, FMRP). Phenotypic presentation of FXS is highly variable, and the lack of reproducible, sensitive assays to detect FXP makes evaluation of peripheral FXP as a source of clinical variability challenging. We optimized a Luminex-based assay to detect FXP in dried blot spots for increased reproducibility and sensitivity by improving reagent concentrations and buffer conditions. The optimized assay was used to quantify FXP in 187 individuals. We show that the optimized assay is highly reproducible and detects a wide range of FXP levels. Mosaic individuals had, on average, higher FXP levels than fully methylated individuals, and trace amounts of FXP were consistently detectable in a subset of individuals with full mutation FXS. IQ scores were positively correlated with FXP levels in males and females with full mutation FXS demonstrating the clinical utility of this method. Our data suggest trace amounts of FXP detectable in dried blood spots of individuals with FXS could be clinically relevant and may be used to stratify individuals with FXS for optimized treatment.
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