CALD1 encodes caldesmon 1, a cytoskeleton-associated protein that regulates actomyosin interactions and actin filament organization. The protein functions as a bridge between myosin and actin filaments, inhibiting actomyosin ATPase activity in smooth muscle by binding to F-actin 1. This inhibition is modulated by calcium-calmodulin and enhanced by tropomyosin interactions. CALD1 plays crucial roles in cytoskeletal organization, focal adhesion formation, and cell movement processes 2. In cancer contexts, CALD1 expression is dysregulated across multiple tumor types. Reduced CALD1 expression in ovarian cancer leads to fewer F-actin stress fibers, decreased focal adhesions, and enhanced cell invasiveness 2. Conversely, CALD1 upregulation occurs in idiopathic pulmonary fibrosis, where it contributes to fibroblast activation and collagen production 3. The gene shows differential splicing patterns in glioma microvasculature compared to normal brain tissue, with specific splice variants exclusively found in tumor vessels 1. CALD1 variants are associated with orofacial cleft risk, suggesting developmental roles 4. In gastric cancer, CALD1 is regulated by the miR-148a-5p pathway in cancer-associated fibroblasts, promoting tumor proliferation through collagen VI production 5. These findings establish CALD1 as a critical regulator of cytoskeletal dynamics with significant implications in development, tissue remodeling, and cancer progression.