FARP1 (FERM, ARH/RhoGEF and pleckstrin domain protein 1) functions as a guanine nucleotide exchange factor (GEF) that activates the small GTPases Rac1 and Cdc42 1. Its N-terminal FERM domain mediates membrane localization through phospholipid binding via a conserved positively charged surface patch, enabling recruitment to postsynaptic sites 2. FARP1 regulates neuronal morphogenesis by controlling dendritic filopodia dynamics, dendritic spine formation, and synapse assembly, operating through the Wnt/PCP pathway in coordination with scaffold protein ANKK1 3. In cancer biology, FARP1 drives Rac1-dependent cell motility in lung adenocarcinoma downstream of receptor tyrosine kinases (EGFR, c-Met), operating non-redundantly with other Rac-GEFs to control ruffle dynamics 4. A circular RNA variant (circFARP1) derived from FARP1 promotes gemcitabine resistance in pancreatic cancer by stabilizing CAV1 and enhancing LIF secretion 5. Genetic variants affecting FARP1 alternative splicing (rs35861926) reduce lung adenocarcinoma risk by downregulating the FARP1-011 transcript, which promotes cancer cell migration and proliferation 6. FARP1 also functions in endothelial vascular leakage by localizing Cdc42 activators to the plasma membrane in a tetraspanin-cholesterol-dependent manner 7. Elevated FARP1 expression correlates with poor survival in multiple solid tumors.