Instability of a premutation-sized CGG repeat in FMR1 YAC transgenic mice.
Fragile X syndrome results from the massive expansion of a CGG repeat in the 5' untranslated region of the gene FMR1. Data suggest that the hyperexpansion properties of FMR1 CGG repeats may depend on flanking cis-acting elements. We have therefore used homologous recombination in yeast to introduce an in situ CGG expansion corresponding to a premutation-sized allele into a human YAC carrying the FMR1 locus. Several transgenic lines were generated that carried repeats of varying lengths and amounts of flanking sequence. Length-dependent instability in the form of small expansions and contractions was observed in both male and female transmissions over five generations. No parent-of-origin effect or somatic instability was observed. Alterations in tract length were found to occur exclusively in the 3' uninterrupted CGG tract. Large expansion events indicative of a transition from a premutation to a full mutation were not observed. Overall, our results indicate both similarities and differences between the behavior of a premutation-sized repeat in mouse and that in human.
Peier
Andrea M
AM
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
Nelson
David L
DL
D000818:Animals; D018244:Chromosomes, Artificial, Yeast; D004195:Disease Models, Animal; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1; D005600:Fragile X Syndrome / Q000235:genetics*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010375:Pedigree; D016601:RNA-Binding Proteins; D018911:Trinucleotide Repeats
D051860:Fragile X Messenger Ribonucleoprotein 1; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; C497684:Fmr1 protein, mouse