COBL (cordon-bleu WH2 repeat protein) is a calcium-regulated actin nucleator critical for neuronal morphogenesis and cytoskeletal dynamics. Primary Function: COBL nucleates actin polymerization by assembling three actin monomers in cross-filament orientation, promoting barbed-end growth while also mediating depolymerization and filament severing 1. It regulates dendritic and axonal branching, increases neuronal arborization, and promotes cell ruffles through coordinated control of actin filament networks. Mechanism: COBL's nucleation activity requires all three WH2 domains for actin monomer binding 1. Its functions are tightly controlled by calcium/calmodulin signaling, which modulates actin-binding properties and promotes interactions with the membrane-shaping protein syndapin I 12. Arginine methylation by PRMT2 also regulates COBL's actin-binding capacity and dendritogenesis 3. Syndapin I recruits COBL to membranes via its F-BAR domain, and COBL functionally intertwines with the Arp2/3 complex during neuromorphogenesis 2. Disease Relevance: COBL expression correlates with brown adipose tissue development and metabolic dysfunction markers in obese children, including adipocyte size and insulin resistance 4. Clinical Significance: COBL's involvement in neurodevelopmental processes and metabolic regulation suggests potential relevance to neurodevelopmental and metabolic disorders, though direct disease associations require further investigation.