Desmin- and Vimentin-containing Filaments and Their Role in the Assembly of the Z Disk in Muscle Cells

Perhaps one of the most striking visual aspects of skeletal- and cardiac-muscle cells is their striated appearance. It has long been suspected that there is present in these cells a framework responsible for holding the constituent myofibrils in place. The presence of structural elements transverse to the long axis of a muscle fiber is suggested by the tendency for the Z disks, M lines, and other sarcomeric units of neighboring myofibrils to be in axial register across the fiber. Numerous ultrastructural observations suggest linkage of cardiac and skeletal sarcomeric units, and in particular the Z disk, transversely to other Z disks and to the plasma membrane (Pease and Baker 1949; Bennett and Porter 1953; Bergman 1958, 1962; Garamvölgyi 1962, 1965; Walker et al. 1968). The molecular nature of this integrating matrix was unknown until recently. Recent studies on the biochemical composition of intermediate filaments, their solubility properties, and cytoplasmic distribution...