SYNGAP1 is a ras GTPase-activating protein that is critical for cognition and synapse function. Mutations in humans cause mental retardation.

Several mutations in the SYNGAP1 gene were identified as the cause of mental retardation. Mental retardation is sometimes associated with syndromes of other defects caused by the same gene, but SYNGAP1-associated mental retardation is not; it is therefore called non-syndromic mental retardation. Since neither of the parents of children with this condition have the mutation, this means it was a sporadic mutation that occurred during division of the parents' gametes (meiosis) or fertilization of the egg. It is a dominant mutation, which means that the individual will be retarded if only one allele is mutated.