FMR1 and fragile X syndrome: Additionally, 5-azacitidine (5-AzadC) cannot reactivate the silenced the FMR1 gene in post-mitotic neurons and can only exert its effects during the DNA replication process (Kumari et al., 2020), indicating that DNA methylation may not be the sole factor in the pathogenesis of FXS and that the role of other epigenetic modifications should not be disregarded.