The fragile X syndrome.
The fragile X syndrome is characterised by mental retardation, behavioural features, and physical features, such as a long face with large protruding ears and macro-orchidism. In 1991, after identification of the fragile X mental retardation (FMR1) gene, the cytogenetic marker (a fragile site at Xq27.3) became replaced by molecular diagnosis. The fragile X syndrome was one of the first examples of a "novel" class of disorders caused by a trinucleotide repeat expansion. In the normal population, the CGG repeat varies from six to 54 units. Affected subjects have expanded CGG repeats (>200) in the first exon of the FMR1 gene (the full mutation). Phenotypically normal carriers of the fragile X syndrome have a repeat in the 43 to 200 range (the premutation). The cloning of the FMR1 gene led to the characterisation of its protein product FMRP, encouraged further clinical studies, and opened up the possibility of more accurate family studies and fragile X screening programmes.
Department of Clinical Genetics, University Hospital Dijkzigt and Erasmus University, Rotterdam, The Netherlands.
B B
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de Vries
D J
DJ
Halley
B A
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Oostra
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Niermeijer
D043283:Chromosome Fragile Sites; D002873:Chromosome Fragility; D004252:DNA Mutational Analysis; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D005820:Genetic Testing; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D008297:Male; D018598:Minisatellite Repeats; D009419:Nerve Tissue Proteins / Q000235:genetics; D010641:Phenotype; D016601:RNA-Binding Proteins; D014960:X Chromosome / Q000235:genetics
D051860:Fragile X Messenger Ribonucleoprotein 1; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; C497683:FMR1 protein, human