In order to assess whether SIRT1 was involved in FMR1 gene silencing, we transfected plasmids encoding a human SIRT1 protein and a dominant negative version of this construct (dnSIRT1) [21] into fibroblast cells from 3 different males, 1 who was unaffected and 2 with FXS. This evidence concerns the gene SIRT1 and fragile X syndrome.