Fragile X Syndrome (FXS)

In order to provide the best possible care to patients with a rare condition, it is essential that global knowledge about the condition is gathered. Nationwide, centers of expertise have been set up to stimulate care for rare disorders and to gather knowledge. For the formal recognition of an expertise center by the Ministry of Health, an important condition is that the expertise center gathers, analyzes and shares knowledge through publications. These can be publications in scientific journals, but also treatment guidelines for health care professionals or information brochures for patients or caregivers. We optimize care and research within ENCORE through standardized follow-up and close collaboration between doctors and researchers. That way, we can ultimately develop better treatments for rare conditions. You may therefore be asked to participate in research. Participation in research is always on a voluntary basis. The data obtained is stored and analyzed in an anonymous form. All research has been approved in advance by an ethics review committee.

Genetic testing will be performed on all Fragile X Syndrome patients seen in our center of expertise to determine the genetic cause and to be able to support and advise the parents. If genetic testing has already been done elsewhere, it will not be repeated. This genetic knowledge also helps us to better understand the effect of the genetic change ("mutation") on the severity of symptoms. We can then also investigate which treatment works best for a particular mutation. In rare cases, the genetic analysis is inconclusive. In these cases, the genetic change will be further investigated in the laboratory.

Detailed knowledge about the course of the Fragile X Syndrome is of great importance for drug research (trials). We also want to determine the best way to measure the effectiveness of treatments (outcome measures for research). After all, only if we can demonstrate that a new drug improves the quality of life compared to an untreated patient, will the drug actually be approved and reimbursed.

In addition to permission to record these clinical data, you may be asked to provide a tube of blood for research. This blood is used to generate iPSC (induced Pluripotent Stem Cells) for research. Brain cells can be grown from these iPS cells. See the pre-clinical research page on this website for more information about iPS research.

Ongoing research
One of the studies within ENCORE that is currently focusing on children and young people with Fragile X Syndrome is the Special X study. The aim of this research is to get a better picture of the autism characteristics and the mental and social skills of children with Fragile X Syndrome, and the underlying biological causes thereof. Click here for more information about this study.

Müller AR, (2024) Cannabidiol (Epidyolex®) for severe behavioral manifestations in patients with tuberous sclerosis complex, mucopolysaccharidosis type III and fragile X syndrome: protocol for a series of randomized, placebo-controlled N-of-1 trials. BMC Psychiatry. Pubmed

Lubbers K, (2022) Autism Symptoms in Children and Young Adults With Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis Complex, and Neurofibromatosis Type 1: A Cross-Syndrome Comparison. Front Psychiatry. Pubmed

Ottenhoff MJ, (2020) Considerations for Clinical Therapeutic Development of Statins for Neurodevelopmental Disorders. eNeuro. 7; 1-5. Pubmed

Van Remmerden MC, et al. (2020) Growing up with Fragile X Syndrome: Concerns and Care Needs of Young Adult Patients and Their Parents. J Autism Dev Disord. Pubmed

Zeidler S, Fragile X Syndrome: new therapeutic strategies. Tijdschr Psychiatr. 60(5); 338-42 Link

Zeidler S, (2017) Leidraad voor diagnostiek en behandeling van kinderen met het Fragiele X Syndroom. Expertisecentrum ENCORE. Link

van der Vaart T, (2015) Treatment of Cognitive Deficits in Genetic Disorders: A Systematic Review of Clinical Trials of Diet and Drug Treatments. JAMA Neurol 72; 1052–60. Pubmed

Pop, A.S. et al. (2013) Fragile X syndrome: a preclinical review on metabotropic glutamate receptor 5 (mGluR5) antagonists and drug development. Psychopharmacology (Berl.) Pubmed

de Esch, C.E.F. et al. (2013) Translational endpoints in fragile X syndrome. Neurosci Biobehav Rev. Pubmed

Pop, A.S. et al. (2012) Rescue of dendritic spine phenotype in Fmr1 KO mice with the mGluR5 antagonist AFQ056/Mavoglurant. Psychopharmacology (Berl.) Pubmed

Vinueza Veloz, M.F. et al. (2012) The effect of an mGluR5 inhibitor on procedural memory and avoidance discrimination impairments in Fmr1 KO mice. Genes Brain Behav 11, 325–331. Pubmed

Castrén, E. et al. (2012) Treatment of neurodevelopmental disorders in adulthood. J Neurosci 32, 14074–14079. Link

Levenga, J. et al. (2011) AFQ056, a new mGluR5 antagonist for treatment of fragile X syndrome. Neurobiol Dis 42, 311–317. Pubmed

Levenga, J. et al. (2011) Subregion-specific dendritic spine abnormalities in the hippocampus of Fmr1 KO mice. Neurobiol Learn Mem 95, 467–472. Pubmed

Levenga, J. et al. (2010) Potential therapeutic interventions for fragile X syndrome. Trends Mol Med 16, 516–527. Pubmed

Brouwer, J.R. et al. (2009) The FMR1 gene and fragile X-associated tremor/ataxia syndrome. Am. J. Med Genet B Neuropsychiatr Genet, 150, 782–798. Pubmed

Levenga, J. et al. (2009) Ultrastructural analysis of the functional domains in FMRP using primary hippocampal mouse neurons. Neurobiol Dis 35, 241–250. Pubmed

Van’t Padje, S. et al. (2009) Reduction in fragile X related 1 protein causes cardiomyopathy and muscular dystrophy in zebrafish. J. Exp. Biol. 212, 2564–2570. Pubmed

Brouwer, J.R. et al. (2008) CGG-repeat length and neuropathological and molecular correlates in a mouse model for fragile X-associated tremor/ataxia syndrome. J Neurochem 107, 1671–1682. Pubmed

Smit, A.E. et al. (2008) Savings and extinction of conditioned eyeblink responses in fragile X syndrome. Genes Brain Behav 7, 770–777. Pubmed

de Vrij, F.M.S. et al. (2008) Rescue of behavioral phenotype and neuronal protrusion morphology in Fmr1 KO mice. Neurobiol Dis 31, 127–132. Pubmed

Brouwer, J.R. et al. (2008) Altered hypothalamus-pituitary-adrenal gland axis regulation in the expanded CGG-repeat mouse model for fragile X-associated tremor/ataxia syndrome. Psychoneuroendocrinology 33, 863–873. Pubmed

Govaerts, L.C.P. et al. (2007) Exceptional good cognitive and phenotypic profile in a male carrying a mosaic mutation in the FMR1 gene. Clin Genet 72, 138–144. Pubmed

Brouwer, J.R. et al. (2007) Elevated Fmr1 mRNA levels and reduced protein expression in a mouse model with an unmethylated Fragile X full mutation. Exp Cell Res 313, 244–253. Pubmed

Mientjes, E.J. et al. (2006) The generation of a conditional Fmr1 knock out mouse model to study Fmrp function in vivo. Neurobiol Dis 21, 549–555. Pubmed

Koekkoek, S.K.E. et al. (2005) Deletion of FMR1 in Purkinje cells enhances parallel fiber LTD, enlarges spines, and attenuates cerebellar eyelid conditioning in Fragile X syndrome. Neuron 47, 339–352. Pubmed

van ’t Padje, S. et al. (2005) Characterisation of Fmrp in zebrafish: evolutionary dynamics of the fmr1 gene. Dev. Genes Evol. 215, 198–206. Pubmed

Blonden, L. et al. (2005) Two members of the Fxr gene family, Fmr1 and Fxr1, are differentially expressed in Xenopus tropicalis. Int. J. Dev. Biol. 49, 437–441. Pubmed

Stoyanova, V. et al. (2004) Loss of FMR1 hypermethylation in somatic cell heterokaryons. FASEB J. 18, 1964–1966. Pubmed

Schrier, M. et al. (2004) Transport kinetics of FMRP containing the I304N mutation of severe fragile X syndrome in neurites of living rat PC12 cells. Exp Neurol 189, 343–353. Pubmed

Mientjes, E.J. et al. (2004) Fxr1 knockout mice show a striated muscle phenotype: implications for Fxr1p function in vivo. Hum Mol Genet 13, 1291–1302. Pubmed

De Diego Otero, Y. et al. (2002) Transport of fragile X mental retardation protein via granules in neurites of PC12 cells. Mol Cell Biol 22, 8332–8341. Pubmed

Willemsen, R. et al. (2002) Timing of the absence of FMR1 expression in full mutation chorionic villi. Hum Genet 110, 601–605. Pubmed

Bontekoe, C.J.M. et al. (2002) Knockout mouse model for Fxr2: a model for mental retardation. Hum Mol Genet 11, 487–498. Pubmed

Bontekoe, C.J. et al. (2001) Instability of a (CGG)98 repeat in the Fmr1 promoter. Hum Mol Genet 10, 1693–1699. Pubmed

Willemsen, R. et al. (2000) Twin sisters, monozygotic with the fragile X mutation, but with a different phenotype. J Med Genet 37, 603–604. Pubmed

Bakker, C.E. et al. (2000) Immunocytochemical and biochemical characterization of FMRP, FXR1P, and FXR2P in the mouse. Exp Cell Res 258, 162–170. Pubmed

Tamanini, F. et al. (2000) The fragile X-related proteins FXR1P and FXR2P contain a functional nucleolar-targeting signal equivalent to the HIV-1 regulatory proteins. Hum Mol Genet 9, 1487–1493. Pubmed

Willemsen, R. et al. (1999) Noninvasive test for fragile X syndrome, using hair root analysis. Am J Hum Genet 65, 98–103. Pubmed

de Vries, B.B. et al. (1999) Screening for the fragile X syndrome among the mentally retarded: a clinical study. The Collaborative Fragile X Study Group. J Med Genet 36, 467–470. Pubmed

Tamanini, F. et al. (1999) Different targets for the fragile X-related proteins revealed by their distinct nuclear localizations. Hum Mol Genet 8, 863–869. Pubmed

de Vries, B.B. et al. (1999) Dilemmas in counselling females with the fragile X syndrome. J Med Genet 36, 167–170. Pubmed

Wildhagen, M.F. et al. (1999) Efficacy of cascade testing for fragile X syndrome. J Med Screen 6, 70–76. Pubmed

de Vries, B.B. et al. (1998) Screening with the FMR1 protein test among mentally retarded males. Hum Genet 103, 520–522. Pubmed

Verheij, C. et al. (1993) Characterization and localization of the FMR-1 gene product associated with fragile X syndrome. Nature 363, 722–724. Pubmed

Reyniers, E. et al. (1993) The full mutation in the FMR-1 gene of male fragile X patients is absent in their sperm. Nat Genet 4, 143–146. Pubmed

Verkerk, A.J. et al. (1993) Alternative splicing in the fragile X gene FMR1. Hum Mol Genet 2, 399–404. Pubmed

De Boulle, K. et al. (1993) A point mutation in the FMR-1 gene associated with fragile X mental retardation. Nat Genet 3, 31–35. Pubmed

de Vries, B.B. et al. (1993) Mental status and fragile X expression in relation to FMR-1 gene mutation. Eur J Hum Genet 1, 72–79. Pubmed

Willems, P.J. et al. (1992) Segregation of the fragile X mutation from an affected male to his normal daughter. Hum Mol Genet 1, 511–515. Pubmed

Verkerk, A.J. et al. (1992) Intragenic probe used for diagnostics in fragile X families. Am J Med Genet 43, 192–196. Pubmed

Oostra, B.A. and Verkerk, A.J. (1992) The fragile X syndrome: isolation of the FMR-1 gene and characterization of the fragile X mutation. Chromosoma 101, 381–387. Pubmed

Faust, C.J. et al. (1992) Genetic mapping on the mouse X chromosome of human cDNA clones for the fragile X and Hunter syndromes. Genomics 12, 814–817. Pubmed

Verkerk, A.J. et al. (1991) Identification of a gene (FMR-1) containing a CGG repeat coincident with a breakpoint cluster region exhibiting length variation in fragile X syndrome. Cell 65, 905–914. Pubmed

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