SYT1. To continue our series on SNAREopathies—developmental disorders caused by genes encoding proteins involved in the SNARE complex—we next provide a brief overview of SYT1-related disorders. The gene SYT1 encodes synaptotagmin-1 (SYT1), which belongs to the group of synaptotagmin proteins that are essential for neurotransmission. Disease-causing mutations in SYT1 have a spectrum of clinical presentations ranging in severity and phenotypic complexity but also with certain unifying features, making SYT1-related disorders a complex neurodevelopmental SNAREopathy.