The FMR1 promoter in FXS patient cells is also associated with a decrease in the levels of active histone marks that include acetylation of histone H3 at lysine 9 (H3K9ac), di-methylation of lysine 4 (H3K4me2), and acetylation of histone H4 at lysine 16 (H4K16ac) [46,47,58]. The gene discussed is FMR1; the disease is fragile X syndrome.