Autism spectrum disorder (ASD) is a disorder of brain development with onset early in life, characterized by impairments in social communication and restricted interests and/or repetitive behaviors. The biological pathways and developmental events underlying ASD remain poorly understood, hindering the design of effective therapies. However, recent studies have identified dozens of genes containing disruptive mutations that confer risk for ASD, providing an entry point for understanding ASD biology. Many ASD risk genes regulate gene expression, and these risk genes are specifically enriched in gene co-expression networks in mid-fetal human cortex¬. This suggests that disruption of regulatory genes in ASD results in aberrant gene expression in the developing brain, thereby contributing to ASD. The goal of this proposal is to identify regulatory networks harboring risk for ASD and the biological pathways they impact during early brain development. We recently identified the targets of the ASD risk gene CHD8 in the mid-fetal human brain, and found that CHD8 directly regulates other regulatory genes associated with ASD. Disruptive mutations in CHD8 may thus contribute to ASD risk by altering the expression of other ASD risk genes in a common ASD-associated regulatory network. Using genome editing coupled with functional genomic and bioinformatics approaches developed in our laboratory, we will characterize regulatory networks of ASD risk genes controlled by CHD8 in human neural stem cells and in mouse models of the developing human brain. To evaluate the impact of ASD-associated loss of function in these genes, we will integrate gene target maps with expression studies in CHD8 mutant mice, and in neural stem cells where expression of CHD8 and other ASD risk genes has been reduced. Our results will reveal common regulatory pathways underlying ASD, providing fundamental biological insights into the origins of the disorder and new avenues for the treatment of individuals with autism.