These disorders include inherited forms of epilepsy caused by presynaptic proteins such as MUNC18–1 [encoded by syntaxin-binding protein 1 (STXBP1)] (3,4), Synapsin I (SYN1) (5,6), syntaxin 1B (STX1B) (7,8) and synaptosome-associated protein 25B (SNAP25B) (9), and there are clues from studies in model organisms that many more SV-associated genes will play a central role in diseases characterized by seizures and/or neurodevelopmental delay (10,11). This evidence concerns the gene SYN1 and Neurodevelopmental delay.