Document Detail

Sequence analysis of long FMR1 arrays in the Japanese population: insights into the generation of long (CGG)n tracts.
MedLine Citation:
PMID:  9402973     Owner:  NLM     Status:  MEDLINE    
The human fragile-X syndrome is associated with expansions of a (CGG)n triplet repeat within the FMR1 gene. Whilst normal FMR1 arrays consist of variable numbers of (CGG)7-13 blocks punctuated with single AGG triplets, unstable arrays contain longer blocks of uninterrupted (CGG)n. The degree of instability, and subsequent risk of expansion to the fragile-X mutation, is dependent upon the length of this uninterrupted repeat. Detailed analyses of normal FMR1 array structures suggest that longer uninterrupted blocks of repeat could arise either through a process of gradual slippage or a more dramatic loss of an intervening AGG triplet. Up to 15% of Japanese and Chinese individuals have FMR1 triplet arrays centred on 36 repeats in length, a modal group not found in Caucasians. As longer FMR1 arrays have been associated with high-risk fragile-X haplotypes in some populations, we investigated the nature of these larger arrays. Sequence analysis revealed that the unusual length is due to the presence of a novel (CGG)6 block within the array. Several haplotypically related arrays contain blocks of (CGG)16 or (CGG)15, consistent with the fusion of adjacent (CGG)9 and (CGG)6 blocks after loss of the intervening AGG triplet. This is compatible with inferences from the Caucasian population that AGG loss is a mechanism by which long blocks of identical repeats are generated.
M C Hirst; T Arinami; C D Laird
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Human genetics     Volume:  101     ISSN:  0340-6717     ISO Abbreviation:  Hum. Genet.     Publication Date:  1997 Dec 
Date Detail:
Created Date:  1998-01-08     Completed Date:  1998-01-08     Revised Date:  2009-09-29    
Medline Journal Info:
Nlm Unique ID:  7613873     Medline TA:  Hum Genet     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  214-8     Citation Subset:  IM    
Institute of Molecular Medicine, John Radcliffe, Headington, Oxford, UK.
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MeSH Terms
Dinucleotide Repeats
Fragile X Mental Retardation Protein
Fragile X Syndrome / genetics*
Nerve Tissue Proteins / genetics*
Polymerase Chain Reaction
RNA-Binding Proteins*
Sequence Analysis, DNA
Trinucleotide Repeats*
Grant Support
//Wellcome Trust
Reg. No./Substance:
0/FMR1 protein, human; 0/Nerve Tissue Proteins; 0/RNA-Binding Proteins; 139135-51-6/Fragile X Mental Retardation Protein

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