TNNT3 encodes fast skeletal muscle troponin T, the tropomyosin-binding subunit of the troponin complex that regulates calcium-dependent contraction of fast-twitch skeletal muscle fibers 1. TNNT3 is a single-copy gene located on chromosome 11.5 containing 19 exons with developmentally regulated alternative splicing 2. The protein functions as a central regulator of actin thin filament dynamics, conferring calcium-sensitivity to striated muscle actomyosin ATPase activity and enabling contraction through tropomyosin binding and troponin complex assembly 1. Pathogenic variants in TNNT3 cause distinct neuromuscular phenotypes depending on inheritance pattern. Dominant missense mutations cause Sheldon-Hall syndrome, a congenital contracture disorder affecting distal joints 3, and have been implicated in familial dilated cardiomyopathy through impaired troponin-tropomyosin binding 4. Recessive TNNT3 variants, including splice-affecting intronic mutations, associate with congenital myopathy presenting with hypotonia, proximal weakness, and myofibrillar disorganization with nemaline bodies 5. Alternative splicing of TNNT3 is dynamically regulated by metabolic factors; saturated fatty acids and ceramides modulate TNNT3 isoform expression through protein phosphatase 2A activation 6. These findings establish TNNT3 as critical for skeletal muscle development, contraction, and cardiac function, with disease relevance spanning congenital myopathies and cardiomyopathies.