TNNC2

TNNC2 is the gene that encodes the fast skeletal muscle isoform of troponin C, a calcium-binding component of the troponin complex in skeletal muscle. Troponin C, together with troponin I and troponin T, sits on the actin-containing thin filament and regulates muscle contraction in response to intracellular calcium levels.

Functionally, TNNC2-derived protein binds calcium and participates in the calcium-triggered switch that moves tropomyosin away from myosin-binding sites on actin. This allows cross-bridge cycling and contraction in fast-twitch (type II) skeletal muscle fibers. The protein is part of the conserved troponin C family of EF-hand calcium-binding proteins, and it interacts with other troponin subunits to modulate the contractile apparatus.

Expression and structure information indicate that TNNC2 is primarily expressed in fast-twitch skeletal muscle, with varying levels in other skeletal muscles. The gene can produce multiple isoforms through alternative splicing, and the encoded protein contains domains typical of EF-hand calcium-binding proteins that mediate its calcium responsiveness. In humans, TNNC2 is part of a small troponin C gene family; a related gene, TNNC1, encodes a cardiac and slow skeletal troponin C isoform.

Clinical significance for TNNC2 is based on rare reports linking variants in the gene to inherited muscle disorders. Such associations are uncommon, and the genotype-phenotype relationships are not yet fully established. Research continues to clarify the role of TNNC2 in skeletal muscle physiology and disease.

Overall, TNNC2 provides the fast skeletal troponin C component that enables rapid, calcium-dependent regulation of contraction in fast-twitch muscle fibers.