For example, defects in neuronal migration, synaptic spines and neuronal morphology such as those we have demonstrated here, have been suggested to underpin ID in conditions such as lissencephaly,18 Down’s syndrome31 and Rett syndrome.32 While we are not suggesting that Katnal1 is causative for these conditions, similarities in symptoms and neuronal phenotypes between these conditions and those linked to Katnal1 dysfunction should be appreciated. Here, KATNAL1 is linked to atypical Rett syndrome.