Alpha-actinin and myosin light chains in congenital nemaline myopathy.

The muscle fibers of patients with congenital nemaline myopathy contain nemaline bodies, of which alpha-actinin is a major constituent. In some cases, deficiencies of fast myosin light chains have been reported. We performed 1-dimensional polyacrylamide sodium dodecyl sulfate gradient gel electrophoresis of muscle proteins from 13 patients with congenital nemaline myopathy and 10 controls to examine the alpha-actinin and the distribution of myosin light chains in congenital nemaline myopathy. At 95 kd (corresponding to alpha-actinin), 4 patients and all controls had 1 band, 2 patients did not have any bands, and 7 had bands that were clearly weaker than those of the controls. Because alpha-actinin is present in the nemaline bodies of congenital nemaline myopathy muscle, only the deficiency of this protein must be apparent. No apparent differences in fast myosin light-chain distribution could be documented between patients and controls; no correlation was observed between muscle fiber type and light-chain distribution. The results suggest that alpha-actinin is abnormal in congenital nemaline myopathy.