In mouse models of Rett syndrome, the expression of normal levels of wild-type MeCP2 or specifically truncated forms of MeCP2, through genetic activation or virus-mediated delivery to the brains of mutant mice has been shown to reverse symptoms and restore many normal functions (Tillotson et al, 2017; Tillotson and Bird, 2020). The gene discussed is MECP2; the disease is atypical Rett syndrome.