FMR1 and fragile X syndrome: In FXS, the epigenetic silencing of the fragile X messenger ribonucleoprotein 1 (FMR1) gene, specifically by DNA methylation and histone modifications, results in the loss of the encoded protein, FMRP, with genome-wide consequences due to the role of FMRP in regulating the expression of several coding and non-coding RNAs [34].