ARHGAP12 (Rho GTPase activating protein 12) functions as a negative regulator of Rho family GTPases, particularly Rac and Cdc42, by catalyzing their conversion from active GTP-bound to inactive GDP-bound states 12. The protein contains multiple functional domains including rhoGAP, SH3, PH, and two WW domains, and is ubiquitously expressed across human tissues 1. ARHGAP12 plays critical roles in cytoskeletal regulation and cellular morphology. At epithelial tight junctions, it suppresses N-WASP-mediated F-actin assembly through its WW domains, thereby controlling paracellular permeability of the leak pathway without affecting ion transport 3. In neuronal synapses, ARHGAP12 functions as a developmental brake, negatively regulating spine size and promoting AMPA receptor endocytosis, preventing precocious synapse maturation 4. The protein's GAP activity is modulated by G-actin binding, creating a negative feedback loop that couples Rac activity to actin dynamics 2. Disease relevance includes roles in cancer progression, where ARHGAP12 suppresses metastatic behaviors like invadopodia formation 2 and regulates morphological transitions in glioma 5. Additionally, ARHGAP12 serves as an independent prognostic factor in pancreatic adenocarcinoma 6 and contributes to intestinal protection during ischemia/reperfusion injury 7.