The TNNT3 gene encodes the fast skeletal muscle isoform of troponin T, a key protein subunit of the troponin complex responsible for regulating skeletal muscle contraction in a calcium-dependent manner. This gene produces a protein that anchors the troponin complex to tropomyosin on the thin filaments of sarcomeres, playing a crucial role in the conformational changes that permit actin-myosin cross-bridge formation during muscle contraction. Tissue-specific expression is largely restricted to fast-twitch skeletal muscles, where alternative splicing generates multiple developmentally regulated isoforms. Clinically, dominant pathogenic mutations in TNNT3 are associated with distal arthrogryposis multiplex congenita type 2B (DA2B), also known as Sheldon-Hall syndrome, characterized by congenital joint contractures, while rare recessive variants have been linked to congenital myopathies featuring nemaline rods and fiber atrophy.