In Vitro Reactivation of the FMR1 Gene Involved in Fragile X Syndrome
Abstract
Fragile X syndrome is the most frequent cause of heritable mental retardation. Most patients have a mutation in the 5' untranslated region of the FMR1 gene, consisting of the amplification of a polymorphic (CGG)nrepeat sequence, and cytogenetically express the folate-sensitive fragile site FRAXA in Xq27.3. Fragile X patients harbour an expanded sequence with >200 CGG repeats (full mutation), accompanied by methylation of most cytosines of the sequence itself and of the upstream CpG island. This abnormal hypermethylation of the promoter suppresses gene transcription, resulting in the absence of the FMR1 protein. Rare individuals of normal intelligence were shown to carry a completely or partially unmethylated full mutation and to express the FMR1 protein. Given this observation and knowing that the open reading frame of the mutated FMR1 gene is intact, we decided to investigate whether its activity could be restored in vitro by inducing DNA demethylation with 5-azadeoxycytidine (5-azadC) in fragile X patients' lymphoblastoid cells. We report that treatment with 5-azadC causes reactivation of fully mutated FMR1 genes with 300-800 repeats, as shown by the restoration of specific mRNA and protein production. This effect correlates with the extent of promoter demethylation, determined by restriction analysis with methylation-sensitive enzymes. These results confirm the critical role of FMR1 promoter hypermethylation in the pathogenesis of the fragile X syndrome, provide an additional explanation for the normal IQ of the rare males with unmethylated full mutations and pave the way to future attempts at pharmacologically restoring mutant FMR1 gene activity in vivo.
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5-aza-deoxycytidine restored transcription and translation of FMR1 in cells derived from patients with fragile X syndrome.
“The first compound tested on cells derived from patients with FXS was the drug 5-aza-deoxycytidine (5-azadC, a methyltransferase inhibitor; Figure 3A), which restored transcription and translation of the FMR1 gene (95).”
From Fragile X syndrome: causes, diagnosis, mechanisms, and therapeutics (2012) · cites this paper as [95]
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Self-citation
- Authors
- Chiurazzi, P., Pomponi, M. G., Willemsen, R., Oostra, B. A., & Neri, G.
- Affiliations
- Università Cattolica del Sacro Cuore (IT)
- Erasmus University Rotterdam (NL)
- Corresponding author
- Neri, G.
- Venue
- Human Molecular Genetics
- Publisher
- Oxford University Press (OUP)
- Published
- 1998-01-01
- Volume
- 7
- Issue
- 1
- Pages
- 109-113
- ISSN
- 0964-6906 (ISSN-L)
- 1460-2083
- OpenAlex
- W2119787118
- Cited by
- 198
- References
- 30
- Citations by year
- 2026: 2 · 2025: 6 · 2024: 6 · 2023: 5 · 2022: 2 · 2021: 8 · 2020: 5 · 2019: 6 · 2018: 6 · 2017: 4 · 2016: 12 · 2015: 6 · 2014: 12 · 2013: 13 · 2012: 6
- FWCI
- 6.11
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Human Molecular Genetics (publishedVersion)
- PubMed (publishedVersion)
- EUR Research Repository (Erasmus University Rotterdam) (submittedVersion)
- HighWire Press Open Archive (submittedVersion)
- Funders
- Erasmus Universiteit Rotterdam
- Erasmus+
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetics and Neurodevelopmental Disorders
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Epigenetics and DNA Methylation
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Genetic Neurodegenerative Diseases
- Keywords
- fragile X syndrome, FMR1 gene, CGG repeat expansion, promoter hypermethylation, DNA demethylation, azacitidine, gene reactivation, CpG islands, FMRP
- MeSH terms
- Cell Line, Female, Fragile X Syndrome, Gene Expression Regulation, Humans, Nerve Tissue Proteins, RNA-Binding Proteins, Gene Transfer Techniques, Fragile X Mental Retardation Protein, Fragile X Messenger Ribonucleoprotein 1
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