Autism is a neurodevelopmental disorder characterized by impaired communication skills, social behavior abnormalities, and stereotypies, with a prevalence of ∼1/150 children [1]. It is considered to be one of the most highly genetic neuropsychiatric disorders with a heritability of 40–80% [2], [3]. Family studies show that siblings of autistic children are at a ∼25-fold higher risk to develop autism than the general population [4], and twin studies show concordance of the autism phenotype in 20–30% of dizygotic twins and ∼60% of monozygotic twins [3], [4]. Genome-wide linkage and association studies, and candidate gene approaches have identified several susceptibility loci and implicated potential autism genes [5]–[7]. The fact that no single genetic aberration accounts for more than 1% of cases suggests extreme genetic heterogeneity [8], [9], posing a major challenge to identifying causative genes. To date genes have been identified on the basis of overlap with other syndromic neurodevelopmental disorders (e.g. Fragile X syndrome, Angelman syndrome, Rett syndrome), chromosomal abnormalities and copy number variation, and as causes for nonsyndromic autism (e.g. NRXN1, NLGN3/4X, SHANK3) [4], [10]. In a few cases, autism
