Gammaactins

Gammaactins are a subfamily of actin proteins that form part of the cellular cytoskeleton. In humans, the gamma-actin subfamily is encoded by two genes, ACTG1 and ACTG2, producing gamma-actin 1 and gamma-actin 2 isoforms. These proteins are highly conserved cytoplasmic actins that polymerize into filamentous structures (F-actin) involved in a wide range of cellular processes.

Expression patterns differ between the two genes. ACTG1 is widely expressed in many cell types and serves as a general cytoplasmic actin, contributing to the maintenance of cell shape, polarity, and basic motility. ACTG2 expression is stronger in smooth muscle tissues and certain visceral tissues, where gamma-actin contributes to the contractile apparatus and structural integrity of smooth muscle fibers.

Functions of gamma-actins include supporting the cortical cytoskeleton, enabling cell migration, and participating in cytokinesis during cell division. They interact with a variety of actin-binding proteins that regulate polymerization, filament stability, and organization into networks such as stress fibers, lamellipodia, and microvilli. Although beta-actin and other actins fulfill overlapping roles, gamma-actins provide tissue- and context-specific contributions to cytoskeletal dynamics.

Clinical significance links gamma-actin genes to several disorders. Mutations in ACTG1 have been associated with Baraitser-Winter syndrome and certain forms of hereditary deafness. Pathogenic variants in ACTG2 are linked to visceral myopathy, megacystis-microcolon-intestinal hypoperistalsis syndrome, and related smooth muscle defects. Research continues to clarify the precise mechanisms by which gamma-actin variants contribute to these conditions.