We compared phenotypes of Patient 2 with those of MPS II cases with deletion of the IDS gene alone reported previously, suggesting that the early-onset MR might be affected by the additional deletion of FMR2.
We correlate loss of FMR2 expression with (CCG)n expansion at FRAXE, demonstrating that this is a gene associated with the CpG island adjacent to FRAXE and contributes for FRAXE-associated mild mental retardation.
Expansion and methylation status at FRAXE can be detected on EcoRI blots used for FRAXA diagnosis: analysis of four FRAXE families with mild mental retardation in males.
Mental status in FRAXE individuals is highly variable and, although mild mental retardation is observed in most cases, several carrier males are apparently normal.
Expansion of a (CGG)n trinucleotide repeat unit at FRAXE, a newly defined fragile site distal to FRAXA, at Xq28, is reported to be associated with mild mental retardation.