Cardiac muscle troponin T (cTnT) is a protein that in humans is encoded by the TNNT2 gene. Cardiac TnT is the tropomyosin-binding subunit of the troponin complex, which is located on the thin filament of striated muscles and regulates muscle contraction in response to alterations in intracellular calcium ion concentration. The TNNT2 gene is located at 1q32 in the human chromosomal genome, encoding the cardiac muscle isoform of troponin T (cTnT). Human cTnT is an ~36-kDa protein consisting of 297 amino acids including the first methionine with an isoelectric point (pI) of 4.88. It is the tropomyosin- binding and thin filament anchoring subunit of the troponin complex in cardiac muscle cells. TNNT2 gene is expressed in vertebrate cardiac muscles and embryonic skeletal muscles. Structure Cardiac TnT is a 35.9 kDa protein composed of 298 amino acids. Cardiac TnT is the largest of the three troponin subunits (cTnT, troponin I (TnI), troponin C (TnC)) on the actin thin filament of cardiac muscle. The structure of TnT is asymmetric; the globular C-terminal domain interacts with tropomyosin (Tm), TnI and TnC, and the N-terminal tether which strongly binds Tm. The N-terminal region of TnT is alternatively spliced, accounting for multiple isoforms observed in cardiac muscle. Function As part of the Troponin complex, the function of cTnT is to regulate muscle contraction. The N-terminal region of TnT that strongly binds actin most likely moves with Tm and actin during strong myosin crossbridge binding and force generation. This region is likely involved in the transduction of cooperativity down the thin filament. The C-terminal region of TnT constitutes part of the globular troponin complex domain, and participates in employing the calcium sensitivity of strong myosin crossbridge binding to the thin filament. Clinical significance Mutations in this gene have been associated with familial hypertrophic cardiomyopathy as well as with restrictive and dilated cardiomyopathy. Transcripts for this gene undergo alternative splicing that results in many tissue-specific isoforms, however, the full-length nature of some of these variants has not yet been determined. Mutations of this gene may be associated with mild or absent hypertrophy and predominant restrictive disease, with a high risk of sudden cardiac death. Advancement to dilated cardiomyopathy may be more rapid in patients with TNNT2 mutations than in those with myosin heavy chain mutations. In patients with active chronic non-inflammatory myopathy and myositis, skeletal muscles are a significant source of cardiac troponin T without any cardiac