Figure 1.

Overview of the layout of actin, tropomyosin, titin, and nebulin filaments in Z lines from vertebrate striated muscles. Titin: The N-terminal region spans the Z line, and, therefore, titin filaments from opposite sarcomeres fully overlap within the Z lines (12). Within the Z line, titin filaments connect to α-actinin Z filaments at multiple sites, which then cross-link the titin and thin filaments (12–15). Nebulin:Nebulin filaments appear to insert about 30 nm away from the center of the Z line (10). Triangles on the left indicate the location of the six identified mutations (Figs. 2 and 3). On the right, arrows indicate the location of the epitopes to which antibodies were raised for immunofluorescence studies (Fig. 4).