Figure 2.

(a) Schematic illustrating the range of thin filament lengths found in nebulin-deficient muscle fibers. Immunoelectron microscopy [14] showed that thin filament lengths in wildtype tibialis cranialis muscle are a constant 1.2 μm, but in nebulin-deficient muscle are on average ~0.8 μm and range from ~0.4 to 1.2 μm. (b) The force-sarcomere length relation of murine wt muscle fibers has a characteristic force plateau followed by a descending limb. The force-sarcomere length relation of nebulin-deficient fibers is shifted leftward compared to wt fibers, and the force plateau is absent. (c) Similarly, the force-sarcomere length relation of nebulin-deficient human muscle fibers (dissected from biopsies obtained from patients with nemaline myopathy) is shifted to the left, and the force plateau is absent as well [16].