(A) Sarcomeres are the smallest contractile units in muscle, consisting of myosin-based thick filaments and actin-based thin filaments decorated with the regulatory proteins troponin (Tn) and tropomyosin. (B) Magnification of the Tn complex, consisting of TnC, TnT, and TnI, and tropomyosin on the actin-based thin filament. The images are modified from Servier Medical ART, licensed under a Creative Commons Attribution 3.0 generic license (58). (C) Schematic representation of the amino acid sequence of fsTnC; N = N-terminus; C = C-terminus. Both patient variants are indicated [F1:P1, c.100G>T, p.(Asp34Tyr), D34Y; F2:P1, c.237G>C, p.(Met79Ile), M79I]. (D) Alignment of the fsTnC amino acid sequence in various species. The mutated residues are outlined in red.