CDC42EP4 (CDC42 effector protein 4) is a cytoskeletal regulatory protein that functions downstream of the small GTPase CDC42 to organize the actin cytoskeleton and regulate cell morphology 1. The protein plays important roles in actin filament assembly and pseudopodia formation, contributing to cell shape changes and cytoskeletal dynamics 2. CDC42EP4 interacts with septins and influences cytoskeletal organization, affecting cellular processes including dendritic spine formation in neurons 3. In disease contexts, CDC42EP4 expression is dysregulated across multiple conditions. In schizophrenia, CDC42EP4 mRNA levels are significantly upregulated in cortical layer 3 pyramidal cells, potentially contributing to dendritic spine deficits and synaptic dysfunction 13. Conversely, CDC42EP4 acts as a tumor suppressor in prostate cancer, where its expression is reduced and overexpression inhibits cell proliferation, migration, and invasion through suppression of the ERK signaling pathway 4. The protein has also been identified as a potential diagnostic biomarker for hypertrophic cardiomyopathy 5 and shows upregulation in helper T cells from obese asthmatic children, suggesting involvement in TH1-polarized inflammation 6. These findings highlight CDC42EP4's diverse roles in cytoskeletal regulation, neuronal function, and disease pathogenesis.