Enables GTPase activator activity. Involved in several processes, including negative regulation of blood vessel remodeling; negative regulation of cellular extravasation; and regulation of vascular permeability. Acts upstream of or within several processes, including animal organ development; cellular response to lipopolysaccharide; and regulation of vesicle-mediated transport. Located in cytosol; plasma membrane; and postsynaptic density. Is active in Schaffer collateral - CA1 synapse and glutamatergic synapse. Is expressed in several structures, including cardiovascular system; central nervous system; forelimb bud; genitourinary system; and spleen. Human ortholog(s) of this gene implicated in acute lymphoblastic leukemia; chronic myeloid leukemia; and leukemia. Orthologous to human BCR (BCR activator of RhoGEF and GTPase). [provided by Alliance of Genome Resources, Apr 2022]