Zdisc

The Z-disc, also called the Z-line, is a structural boundary that marks the ends of each sarcomere in striated muscle. It serves as the anchor for thin actin filaments from adjacent sarcomeres and provides a site for lateral force transmission, helping to maintain the alignment and integrity of myofibrils during contraction.

Molecularly, the Z-disc is a protein-rich complex. The primary cross-linker is α-actinin, which binds actin filaments from neighboring sarcomeres. Other components include CapZ, which caps the plus ends of actin, and Z-disc–associated proteins such as ZASP, telethonin (TCAP), myotilin, and various titin isoforms that extend toward the Z-disc. Desmin and other intermediate filaments also connect the Z-disc to the cell’s cytoskeleton, linking the contractile apparatus to the broader cellular framework.

Functionally, the Z-disc stabilizes sarcomere structure, participates in sarcomere assembly, and facilitates efficient force transmission across the myofiber. It is a hub for mechanosensitive signaling and participates in the remodeling and adaptation of muscle tissue in response to mechanical load.

Pathology commonly involves Z-disc components. Mutations and abnormal remodeling of Z-disc proteins are associated with muscular dystrophies and cardiomyopathies, including Z-disc–related dilated cardiomyopathy and various idiopathic myopathies. Disruption of Z-disc integrity can impair force transmission and promote sarcomere disarray, contributing to muscle weakness and cardiac dysfunction.