ABSTRACT Human muscular dystrophies are inherited muscle‐wasting diseases caused by the various kinds of gene mutations. Among them, Duchenne muscular dystrophy (DMD) is a representative type. Before the discovery of the causative dystrophin gene of DMD, the fragile myofiber plasma membrane was thought to be the trigger of myofiber necrosis in DMD. Freeze‐fracture electron microscopy enabled us to observe the hydrophobic interior of the myofiber plasma membrane where the impressive structure called orthogonal array of particles (OAPs) was seen. Although the functional significance of this specific assembly was thought to be important, the precise function of this assembly was unknown at that time. After the OAPs function was found as a water channel aquaporin (AQP)4, the works about the sarcolemmal AQP4 expression were undertaken extensively. At the beginning of such works, altered sarcolemmal AQP4 expression was reported only in the dystrophinopathic muscles, and it was not described in other forms of human muscular dystrophies such as facioscapulohumeral and limb‐girdle muscular dystrophies in the early phase of research. However, the evidence which has been accumulated until now suggested that the reduced expression of sarcolemmal AQP4 was observed in a wide range of neuromuscular diseases such as dystrophinopathies, sarcoglycanopathies, dysferlinopathies, and even in neurogenic muscle atrophy.
Wakayama et al. (Mon,) studied this question.