Actin proteins are major components of the eukaryotic cytoskeleton. At least six vertebrate actin isoforms have been identified. The cytoplasmic β- and γ-actin proteins are referred to as “non-muscle” actin proteins because they are predominantly expressed in non-muscle cells, where they control cell structure and motility. The α-cardiac and α-skeletal actin proteins are expressed in striated cardiac and skeletal muscle. The smooth muscle α-actin and γ-actin proteins are mainly found in vascular smooth muscle and enteric smooth muscle, respectively. The α-smooth muscle actin (ACTA2) is also known as aortic smooth muscle actin. These actin isoforms regulate contractile potential.