Myotilin, a sarcomeric protein that is encoded by the gene mapping to human chromosome 5q31, binds to a-actinin and is localized in the Z-line of myofibrils. Myotilin is expressed in skeletal and cardiac muscle, and it co-localizes with a-actinin in the sarcomeric I-bands where it directly interacts with a-actinin. Defects in the myotilin gene are reported to cause a form of autosomal dominant limb-girdle muscular dystrophy (LGMD). Symptoms of adult onset LGMD are progressive weakness of the hip and shoulder girdles as well as a distinctive dysarthric pattern of speech. The muscle of affected individuals with LGMD shows degeneration of myofibers, variations in fiber size, fiber splitting, centrally located myonuclei and an enhanced number of autophagic vesicles.