Together, our findings implicate both excessive and reduced Trio activity and the resulting synaptic dysfunction in ASD-related pathogenesis, and point to the Trio-Rac1 pathway at glutamatergic synapses as a possible key point of convergence of many ASD-related genes.Trio is a RhoGEF protein that promotes actin polymerization and is implicated in the regulation of glutamatergic synapses in autism spectrum disorder (ASD).