FMR1 and fragile X syndrome: Interestingly, our analyses revealed 5hmC enrichment in control over FXS samples within four FMR1 locus genomic regions located (1) upstream of FMR1, (2) at the TSS, (3) throughout the first intron, and (4) in a region located between introns 13 and 16 (Fig. 1c, Table 1), highlighting FMR1 hypo-hydroxymethylation as a novel features of fragile X syndrome.