FMR1 and fragile X syndrome: For instance, integrative Genomics Viewer reveals that the binding of Tet1 and 5 hmC levels on Fmr1 locus in WT is decreased in Tet1-knockdown ESCs by analysis of published data GEO datasets (GSE24841) (Williams et al., 2011), likely reducing expression of Fmr1. Indeed, blocking DNA methylation by 5-azacytidine (5-azaC or 5-azadC) has achieved a significant reactivation of FMR1 gene expression in fragile X syndrome cellular models (Bar-Nur et al., 2012).