Monogenic models of ASD, such as Fragile X Syndrome (FXS) Fmr1 mutant mice, Tuberous Sclerosis Complex (TSC) TSC1 or TSC2 mutant mice and Rett Syndrome Mecp2 mutant mice, provide good construct validity for exploring potential therapeutic avenues. Here, MECP2 is linked to atypical Rett syndrome.