We first investigated known syndromic causes of ASD in all identified ASD-affected individuals, namely, fragile X syndrome (caused by CGG expansion in FMR1), Rett syndrome (caused by mutations in MECP2), and Tuberous Sclerosis (caused by mutations in TSC1 or TSC2), as explained in Figure 1. Here, MECP2 is linked to atypical Rett syndrome.