Molecular-intelligence correlations in young fragile X males with a mild CGG repeat expansion in the FMR1 gene

✍ Scribed by Steyaert, Jean; Borghgraef, Martine; Legius, Eric; Fryns, Jean-Pierre

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 484 KB
• Volume: 64
• Category: Article
• ISSN: 0148-7299
• DOI: 10.1002/(sici)1096-8628(19960809)64:2<274::aid-ajmg8>3.0.co;2-u

✦ Synopsis

Several mechanisms can explain the occurrence of full-mutation fragile X males with an I& level above -2 SD below mean, also called "high-functioning fragile X males." Incomplete methylation of the CpG island at the 5' end of the FMRl gene is one of these mechanisms. The present study describes the physical and behavior phenotypes in 7 fragile X boys with CGG repeat insertions in the FMRl gene between 600-2,400 base pairs. The degree of methylation at the FMR1-associated CpG island ranges in peripheral blood lymphocytes from &95%. Subjects with a low degree of methylation at this site have mild or absent physical characteristics of the fragile X syndrome, while subjects with a high degree of methylation at this site have more severe physical characteristics. In this range of CGG repeat insertion (600-2,400 base pairs), the degree of methylation at the FMR1-associated CpG island is a good predictor of intelligence, while CGG repeat insertion length is not.