smooth muscle actin a smooth muscle cell-specific protein is also known as aortic smooth muscle or a smooth muscle actin (SMA SMactin SM-actin ASMA). It belongs to the actin family.It is predominantly found in cells of the smooth muscle lineages. It has been reported that smooth muscle actin was also found in certain non-muscle cells in particular fibroblasts i.e. myofibroblasts. Actin a conserved eukaryotic protein is the major cytoskeletal component and is expressed as six different isoforms in mammals and birds. It is mapped to human chromosome 10q23.31.The antibody reacts with normal and neoplastic human vascular and visceral smooth muscle cells. It reacts with normal myoepithelial cells pericytes eye lens cells hair follicle cells and certain stromal cells in the intestine testis lymphoid organs liver ovary and bone marrow. The antibody also reacts with stromal myofibroblasts in hypertrophic scars and in neoplastic tissues. smooth muscle actin is tr