Fig. 5. Myoferlin null mice have a decreased body mass and muscle mass, and the muscle fibers of myoferlin null animals are decreased in area and size. Individual muscles were dissected, weighed and preserved for histology. (A) Body mass was significantly less in myoferlin null mice than in littermate control mice. (B) Individual muscle mass was also reduced in myoferlin null mice compared with in littermate controls. (C) Representative cross-sections of myoferlin null and wild-type quadriceps muscle. Scale bar: 50 µm. Multiple images of cross-sections through the belly of the quadriceps were used to quantify fiber size, revealing that the average area of myoferlin null fibers is reduced. (D) The mean wild-type fiber size was 2301 µm² whereas the myoferlin null mean was 1740 µm². (E) The distribution of fiber sizes was also examined and showed that myoferlin null muscle is composed of smaller fibers, and specifically lacks the largest fibers. 1740 wildtype and 2240 myoferlin null fibers were measured from 21 images of each genotype.