Rare inherited variation in autism: beginning to see the forest and a few trees.

In this issue of Neuron, two papers (Lim et al., 2013; Yu et al., 2013) use whole-exome sequencing (WES) to elucidate the contribution of inherited variation to the risk for autism by leveraging the increased penetrance of homozygous and compound heterozygous rare variants in autosomes and hemizygous rare variants in the X chromosome of males. Together, they expand our knowledge about the genetic architecture of ASD, verify previously identified genes, and identify novel mutations that will guide the discovery of the critical biological processes disrupted in autism.