Actins are globular multi-functional proteins which can be detected in all eukaryotic cells. In vertebrates, there are three main groups of actins that possess slightly different functions: alpha, beta, and gamma. The alpha actins, found in muscle tissues, are a major constituent of the contractile apparatus. Beta-actin, found at the expanding edge of cells, uses the projection of its cellular structure as its mean of mobility. Gamma-actin is found in the filaments of stress fibres. ACTA2 is an alpha actin that is found in skeletal muscle. Expression of alpha skeletal, alpha cardiac, alpha vascular, and gamma enteric actins are restricted to specialized muscle cell type. Smooth muscle alpha actin is of further interest because it is one of a few genes whose expression is relatively restricted to vascular smooth muscle cells. Further more, expression of smooth muscle alpha actin is regulated by hormones, cell proliferation, and altered by pathological conditions including oncogenic transformation and atherosclerosis.
