Sequence analysis of long FMR1 arrays in the Japanese population: insights into the generation of long (CGG) n tracts

摘要: The human fragile-X syndrome is associated with expansions of a (CGG)n triplet repeat within the FMR1 gene. Whilst normal arrays consist variable numbers (CGG)7–13 blocks punctuated single AGG triplets, unstable contain longer uninterrupted (CGG)n. degree instability, and subsequent risk expansion to mutation, dependent upon length this repeat. Detailed analyses array structures suggest that could arise either through process gradual slippage or more dramatic loss an intervening triplet. Up 15% Japanese Chinese individuals have centred on 36 repeats in length, modal group not found Caucasians. As been high-risk haplotypes some populations, we investigated nature these larger arrays. Sequence analysis revealed unusual due presence novel (CGG)6 block array. Several haplotypically related (CGG)16 (CGG)15, consistent fusion adjacent (CGG)9 after This compatible inferences from Caucasian population mechanism by which long identical are generated.