Slow myosin heavy chain isozyme in nemaline myopathy.

Muscle biopsies from two sporadic cases of congenital nemaline myopathy were examined for myosin heavy chain composition. Electrophoresis of congenital nemaline myopathy (CNM) muscle myosin in SDS-5% polyacrylamide gels gave rise to a single heavy chain band, with a migration rate and antigenic properties identical to that of the adult slow form, as demonstrated by Western blot techniques and by using specific antibody. Immunofluorescent studies indicate that CNM muscle fibers, including the most severely atrophic fibers, are homogeneous with respect to myosin heavy chain composition.