Sarcomere visualized via Troponin I, slow skeletal muscle

Movie. Timelapse movie of sarcomeres in beating cells. Time-lapse movie of live hiPSC-derived cardiomyocytes expressing mEGFP-tagged troponin I. Cells were continuously imaged on a spinning-disk confocal microscope with a 100ms exposure time. Inset shows detail of sarcomeres in myofibrils. Scale bars, 5 µm and 10 µm for inset and larger field respectively. Movie plays in real time.
 
Observations

• Troponin I, slow skeletal muscle labels the thin filament of sarcomeres (actin-based), the contractile apparatus in muscle cells, and regulates myosin-based contraction. Sarcomeres align end-to-end to form myofibrils, striated filaments that generate force when sarcomeres contract.
• Troponin I is absent from Z-disks, which results in a striated appearance along a myofibril. The spacing of this striation shortens as the cardiomyocytes beat. Sometimes buckling of the myofibril can be seen during beating.