The Fragile X Syndrome

Laetitia Davidovic, Université de Nice, Nice, France
Barthélémy Tournier, Université Laval, Québec, Canada
Edouard W Khandjian, Université Laval, Québec, Canada

Published online: July 2007

DOI: 10.1002/9780470015902.a0005533

Fragile X syndrome is the most common form of inherited mental retardation affecting approximately 1/7000 females and 1/4000 males worldwide. The syndrome is due to the silencing/dysfuntion of a single gene, the FRAGILE X MENTAL RETARDATION 1 gene, and affected patients display a variety of physical and mental abnormalities. In the last 15 years, research advances in the fragile X syndrome field have lead to a better understanding of its molecular basis as well as of the pleiotropic phenotypic effects caused by the absence of the fragile X mental retardation protein.

Keywords: mental retardation; fragile X; neuron; RNA translation; RNA trafficking

Figure 1. Portraits of children affected with fragile X syndrome. Courtesy of Dr. Carlo Paribello MD, President of the Fragile X Research Foundation of Canada.
Figure 2. Molecular basis of the fragile X Syndrome. A normal and an affected X-chromosome are represented, and the consequences induced by the massive expansion of the CGG repeats are illustrated.
Figure 3. Morphology of neurons carrying spines from a knockout (left) as compared to normal neurons from a wild-type mice (right). Note the long, thin and tortuous dendritic spines and the increased spine density in the knock-out neuron, characteristics of developing immature spines. With permission from Comery TA et al. (1997) Proceedings of the National Academy of Sciences of the USA 94: 5401–5414. Copyright 1997, National Academy of Sciences, USA.
Figure 4. Model proposing the involvement of FMRP in trafficking of neuronal granules that are exported to distal locations such as dendritic spines or synapses (one dendritic spine forms half a synapse). High levels of FMRP are present in granules to chaperone the mRNA. Adapted from Bardoni B, Davidovic L, Bensaid M and Khandjian EW (2006) The fragile X syndrome. Expert Reviews in Molecular Medicine, 8: 1–16. With permission from Cambridge University Press.
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 Further Reading
    Bardoni B, Davidovic L, Bensaid M and Khandjian EW (2006) The fragile X syndrome: exploring its molecular basis and seeking a treatment. Expert Reviews in Molecular Medicine 8: 1–16.
    Beckel-Mitchener A and Greenough WT (2004) Correlates across the structural, functional, and molecular phenotypes of fragile X syndrome. Mental Retardation and Developmental Disabilities Research Reviews 10: 53–59.
    Chelly J and Mandel JL (2001) Monogenic causes of X-linked mental retardation. Nature Reviews Genetics 2: 669–680.
    book Hagerman RJ and Hagerman PJ (eds) 2002) Fragile X syndrome. Baltimore and London: The Johns Hopkins University Press.
    Hagerman PJ and Hagerman RJ (2004) Fragile X-associated tremor/ataxia syndrome (FXTAS). Mental Retardation Developmental and Disabilities Research Reviews 10: 25–30.
    O'Donnell WT and Warren ST (2002) A decade of molecular studies of fragile X syndrome. Annual Review of Neuroscience 25: 315–338.
    other Sung Y-J and Denman RB (eds) (2005) The Molecular Basis of Fragile X Syndrome Research Signpost. Kerala, India. ISBN: 81-7736-257-7.
    book Tranfaglia M (2004) Medication Guide for Fragile X. Newburyport: FRAXA Research Foundation.
    Visootsak J, Warren ST, Anido A and Graham JM Jr (2005) Fragile X syndrome: an update and review for the primary pediatrician. Clinical Pediatrics (Phila) 44: 371–381.
    de Vries BB, Halley DJ, Oostra BA and Niermeijer MF (1998) The fragile X syndrome. Journal of Medical Genetics 35: 579–589.
 Web Links
    other Fragile X patients support organisations in some countries:
    ePath Association Nationale du Syndrome X Fragile. http://www.xfra.org/ (France).
    ePath Association Syndrome X Fragile. http://www.x-fragile.be (Belgium).
    ePath Conquer Fragile X. http://www.cfxf.org (USA).
    ePath Foreningen fragile X. http://www.fragilex.se/ (Sweden).
    ePath Fragile X Assocition of Australia. http://www.fragilex.org.au (Australia).
    ePath Fragile X Research Foundation of Canada. http://www.fragile-x.ca (Canada).
    ePath Sindrome X-Fragile. http://www.xfragile.net/ (Italy).
    ePath The Fragile X Research Foundation. http://www.fraxa.org (USA).
    ePath The National Fragile X Foundation. http://www.fragilex.org (UK).

Related Sub-Topics:

Neurobiology of Disease | Nervous System Development | Specific Genetic Disorders | Mutational Mechanisms of Genetic Disease | Gene and Genome Structure and Organisation | DNA Damage and Repair
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Article Title: The Fragile X Syndrome
 
How to Cite close
Davidovic, Laetitia, Tournier, Barthélémy, and Khandjian, Edouard W(Jul 2007) The Fragile X Syndrome. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0005533]