While inhibition studies implicate p110δ in aspects of neuronal development (Eickholt et al., 2007; Low et al., 2014; Schmidt et al., 2014), a significant gap in knowledge remains as to the impact of increased p110δ on the development of mammalian neuronal morphology, which is of direct relevance to the role of p110δ in diverse neurodevelopmental disorders. Here, PIK3CD is linked to neurodevelopmental disorder.