SYNGAP1 and schizophrenia: SynGAP is a negative regulator of small GTPases, such as Ras and Rap, and is essential for synaptic development, structure, function, and plasticity Mutations in SYNGAP1, which encodes the SynGAP protein, are a major cause of genetically defined childhood brain disorders, and are found in individuals with ID, ASD, severe epilepsy, and schizophrenia [139,140].