Several studies have hypothesized differences in the fragile X spectrum may be due to either CGG amplification length or methylation status. This study looked at three categories of males with the fragile X full mutation - full mutation with full methylation (FM), full mutation with partial methylation <50% (PM) and mosaic mutations (MM) and found several statistically significant differences between the groups in behavioral, physical and cognitive areas. This study found no correlation between the phenotype and CGG amplification length in any of the three groups. The PM group consistently showed less involvement in the clinical phenotype than either the MM or FM group when examined in the postpubertal age group (> 12 years). These differences did not exist in the prepubertal age group. The PM showed the highest IQ of all the groups (p=.0001 ) with a mean of 88.2, followed by MM with a mean of 60 and FM with a mean of 41.1. Behaviorally, PM had less hand flapping (p=.002) than the other groups and were more shy (p=.01) than the FM group. In terms of the physical phenotype, the PM group was much taller than either of the two other groups with a mean percentile height of 87.2 (p=.001). Both the PM group and MM group showed a smaller (p=.01) physical index score, a measure of 10 physical indicators of fragile X syndrome with the PM group showing the smallest overall mean score (3.8). This information indicates the strong influence that methylation plays in the fragile X phenotype and points towards the important role of protein levels in these patients.
|Original language||English (US)|
|Journal||Journal of Investigative Medicine|
|State||Published - 1996|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)