FMR1 and fragile X syndrome: Recently, targeted epigenetic editing utilizing CRISPR/dCas9 and the TET1 demethylase has effectively demethylated the FMR1 promoter/CGG region and reactivated endogenous FMR1 in neurons derived from human FXS-induced pluripotent stem cells (iPSCs), simultaneously restoring aberrant electrophysiological characteristics.