MYO9B encodes an unconventional myosin that functions as both an actin-based motor protein and a GTPase-activating protein (GAP) for RhoA. The protein binds actin with high affinity and its mechanochemical activity is inhibited by calcium ions. As a RhoA GAP, MYO9B negatively regulates Rho activity; its motor activity recruits MYO9B to lamellipodial extensions where it locally suppresses RhoA to promote directional cell migration. MYO9B also interacts with the SLIT2 receptor ROBO1, which modulates its GAP activity and regulates cell migration. In disease contexts, MYO9B variants associate with coronary artery disease (CAD)—an enhancer variant was experimentally validated to regulate vascular cell motility 1. MYO9B polymorphisms show population-specific associations with inflammatory bowel disease susceptibility in Caucasian populations 2, and the R133Q polymorphism associates with increased type 1 diabetes risk and enhanced dendritic cell function 3. Additionally, MYO9B suppression of RhoA activity promotes cancer cell invasion and metastasis in prostate and breast cancer models 4. These findings implicate MYO9B in vascular biology, immune regulation, and cancer progression, establishing it as a potential therapeutic target for cardiovascular and malignant disease.