Causes likely converge at the synapse, as indicated by mutations of synaptic genes or by mutations causing quantitative alterations in synaptic protein expression, half-life or degradation, and are reflected by a virtually autism-pathognomonic neuronal excitation–inhibition dysbalance.4, 11, 12, 13, 14, 15 Neuroligin-4 mutations, for instance, belong to the most common causes of monogenetic heritable autism.16 Construct-valid and face-valid mouse models of autism, building on monogenetic grounds, have helped in approaching the underlying common biology.17, 18. The gene discussed is NLGN4X; the disease is autism.