FMR1 and fragile X syndrome: To further investigate epigenetic changes and pathways associated with FMR1 silencing in FXS PBMCs, and based on Coriell fibroblast ChIP-array data, native-ChIP assays using antibodies for histone PTMs, associated with and contributing to transcriptional gene repression (H3K9me2, H3K9me3) and gene activation (H3K4me2, H4K20me1), were carried out on fractionated chromatin from eight clinical FXS and three control PBMC samples.