BAIAP2 (BAR/IMD domain containing adaptor protein 2) is a multi-domain scaffolding protein that functions as a critical regulator of actin cytoskeleton dynamics and neuronal development. Mechanistically, BAIAP2 links membrane-bound small G-proteins (CDC42 and RAC1) to cytoplasmic effector proteins, mediating actin reorganization and filopodia formation through interactions with WASF family members and the Arp2/3 complex 1. The protein plays essential roles in dendritic spine morphogenesis, excitatory synapse formation, and neuronal migration during cortical development 23. Disease relevance of BAIAP2 is substantial and diverse. De novo missense variants in BAIAP2 cause developmental and epileptic encephalopathies (DEEs) through gain-of-function mechanisms, increasing neuronal excitability and synaptic transmission 2. Loss-of-function variants impair neuronal migration and cause lissencephaly, a neurodevelopmental disorder marked by absent brain surface convolutions 3. BAIAP2 polymorphisms associate with altered default-mode network connectivity and anger dysregulation in ADHD adults 4, while methylation changes in BAIAP2 correlate with asthma exacerbations 5. Clinically, BAIAP2 emerges as a therapeutic target in urothelial bladder cancer, where overexpression promotes tumor aggressiveness, migration, invasion, and epithelial-mesenchymal transition through cytoskeletal remodeling 6. Additionally, BAIAP2 responds to nanoparticle mechanical properties in tumor-associated macrophages, representing a potential immunotherapy strategy 7.