Desmin is a type III intermediate filament found near the Z line in sarcomeres. It was first purified in 1977, the gene was characterized in 1989, and the first knock-out mouse was created in 1996. Desmin is only expressed in vertebrates, however homologous proteins are found in many organisms. It is a 52kD protein that is a subunit of intermediate filaments in skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue.