Epigenetic switch controls social actions.

Mutations in epigenetic factors are associated with autism spectrum disorder (ASD). In this issue of Neuron, Yan et al. (2022) show that the antagonism of ASH1L and PRC2 switches the equilibrium of histone methylation at the ephrin receptor A7 locus, causing decreased EphA7 expression, deficits in synaptic pruning, and ASD-like behaviors.