Enables GTPase activator activity. Involved in negative regulation of fibroblast proliferation. Acts upstream of or within several processes, including animal organ development; modulation of chemical synaptic transmission; and nervous system development. Located in cytoplasm. Is expressed in several structures, including alimentary system; central nervous system; genitourinary system; heart; and integumental system. Used to study juvenile myelomonocytic leukemia and neurofibromatosis. Human ortholog(s) of this gene implicated in autistic disorder; hematologic cancer (multiple); nervous system cancer (multiple); neurofibromatosis 1; and neurofibromatosis-Noonan syndrome. Orthologous to human NF1 (neurofibromin 1). [provided by Alliance of Genome Resources, Apr 2022]