Esanov et al. (2016) further elucidated the role of 5hmC in the epigenetic regulation of the FMR1 gene in FXS, revealing significant increases in 5hmC levels at the FMR1 promoter in full-mutation FXS patient brains compared to pre-mutation carriers and controls, with this enrichment being neuron-specific. This evidence concerns the gene FMR1 and fragile X syndrome.