Common genetic risk factors for both ASD and schizophrenia include genes encoding neurotrophic factors such as neurexin-1 (38) and synaptic proteins such as PSD-95 (39) and copy number variations in several genomic regions (e.g., 1q21, 16p11.2, and 22q11) regulating synaptic structure and function (40). Here, DLG4 is linked to schizophrenia.