Myotilin is a sarcomeric protein mutated in two forms of muscle disease, limb-girdle muscular dystrophy type 1A and myofibrillar myopathy. Myotilin is expressed late during human myofibrillogenesis and localizes to Z-discs in mature sarcomere. It interacts with alpha-actinin, actin, and filamin C, and has strong F-actin-bundling activity. These features suggest an important role for myotilin in sarcomere organization. In our effort towards the construction of a genetic model for myotilin-related muscle disorders, we have cloned mouse myotilin, including its promoter region, and studied the expression in various tissues. Mouse myotilin is 90% identical with the human orthologue. Northern blot analysis revealed strong mRNA transcripts in skeletal and cardiac muscle, and weak expression in liver and lung tissue. Western blot and RT-PCR analysis showed the presence of one major product in mouse tissues. Analysis of the 5'-flanking region revealed a number of putative regulatory elements that drive expression in differentiating myoblasts. Finally, endogenous myotilin is induced at later stages of Z-disc assembly in C(2)C(12) cells indicating conservation between mouse and human promoter region.