We have investigated the expression, using immunohistochemical and Western blot methods, of some
cytoskeletal proteins including
desmin,
vimentin, actin,
alpha-actinin, and
ubiquitin in hereditary
myopathy of the diaphragmatic muscles in Holstein-Friesian cattle (the histochemical and electron microscopical aspects have been previously reported). Immunohistochemically, the expression of
desmin was observed strongly in the subsarcolemmal regions, but was lacking or faint in the area corresponding to the core-like structures.
Vimentin showed almost the same localization as
desmin, but no activity could be observed in the core-like structures. In addition, the core-like structures showed strong immunoreactivity for actin and
ubiquitin, but no immunoreactivity for
alpha-actinin.
F-actin stained with
phalloidin-tetramethyl-
rhodamine was strongly positive in irregular spots that corresponded to the core-like structures, but was negative for
desmin-positive regions. Western blot analysis of the diseased muscles revealed a significant increase in the amount of
desmin and
vimentin immunoreactivities and similar amounts of actin and
alpha-actinin compared with the control muscles. Two-dimensional electrophoresis revealed no
isoforms of
desmin, suggesting the absence of abnormal phosphorylated forms of
desmin. Since the co-localization of
desmin and
vimentin and the absence of phosphorylated
desmin suggest that the overexpression of
desmin may be reflected in the reactive change or regenerating process, the present
myopathy should be regarded as an entity separate from
desmin-storage myopathy or
desmin-related
myopathies. We also discuss the possibility that the present
myopathy could be considered as
myofibrillar myopathy, a recently proposed nosological entity.