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Ann Hum Genet. 2012 Mar;76(2):178-91. doi: 10.1111/j.1469-1809.2011.00694.x. Epub 2011 Dec 21.

Fragile X syndrome: the FMR1 CGG repeat distribution among world populations.

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  • 1Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institute of Health, Bethesda, MD 20892, USA. peprahek@mail.nih.gov

Abstract

Fragile X syndrome (FXS) is characterized by moderate to severe intellectual disability, which is accompanied by macroorchidism and distinct facial morphology. FXS is caused by the expansion of the CGG trinucleotide repeat in the 5' untranslated region of the fragile X mental retardation 1 (FMR1) gene. The syndrome has been studied in ethnically diverse populations around the world and has been extensively characterized in several populations. Similar to other trinucleotide expansion disorders, the gene-specific instability of FMR1 is not accompanied by genomic instability. Currently we do not have a comprehensive understanding of the molecular underpinnings of gene-specific instability associated with tandem repeats. Molecular evidence from in vitro experiments and animal models supports several pathways for gene-specific trinucleotide repeat expansion. However, whether the mechanisms reported from other systems contribute to trinucleotide repeat expansion in humans is not clear. To understand how repeat instability in humans could occur, the CGG repeat expansion is explored through molecular analysis and population studies which characterized CGG repeat alleles of FMR1. Finally, the review discusses the relevance of these studies in understanding the mechanism of trinucleotide repeat expansion in FXS.

Annals of Human Genetics © 2011 Blackwell Publishing Ltd/University College London Published 2011. This article is a US Government work and is in the public domain in the USA.

PMID:
22188182
[PubMed - indexed for MEDLINE]
PMCID:
PMC3288311
Free PMC Article
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