Muscular dystrophy dy/dy mice: Abnormal ERG suggests contribution of dystrophin-associated proteins in normal retinal electrophysiology

Purpose: We have shown that Duchenne and Becker X-linked muscular dystrophy patients and analogous mouse models have abnormal electroretinograms. The characteristic findings include reduction in the amplitude of the b-wave and increases in the implicit times of the b-wave and oscillatory potentials. These abnormalities have been related to defects in isoforms of dystrophin in the outer-plexiform layer of retina. In muscle, dystrophin interacts with a cluster of proteins and glycoproteins at the cell membrane. One member of the dystrophin-glycoprotein complex is merosin, which lies on the extracellular side of the muscle cell membrane. The purpose of this study was to investigate potential effects of defective merosin on the ERG phenotype. Methods: Five male C57/BL6J control and 5 dy/dy muscular dystrophy mice were studied by electroretinography (Pillers et al., 19951. Results: Compared to normals, dy/dy mice had a reduction in amplitude of all components of the ERG, giving a dampened appearance. Implicit times of b-wave and oscillatory potentials were normal. Conclusions: These data, together with our previous results, suggest that dystrophin and its associated glycoprotein complex play an important role in retinal electrophysiology and that merosin may have a different effect than dystrophin on the ERG phenotype.