Enables GTP binding activity and mitogen-activated protein kinase kinase kinase binding activity. Involved in several processes, including Cdc42 protein signal transduction; actin filament branching; and regulation of synapse organization. Located in Golgi membrane; plasma membrane; and secretory granule. Is active in Schaffer collateral - CA1 synapse. Biomarker of temporal lobe epilepsy. Human ortholog(s) of this gene implicated in fibrosarcoma. Orthologous to human CDC42 (cell division cycle 42). [provided by Alliance of Genome Resources, Apr 2022]