Gold-labelled dystrophin molecule in muscle plasmalemma of mdx control mice as seen by electron microscopy of deep etching replica.

The Duchenne muscular dystrophy product 'dystrophin' has been shown to be located at the inner surface of normal muscle plasma membrane. This study was undertaken to visualize the shape of dystrophin molecules and their topographical distribution at the inner surface of murine skeletal muscle plasma membrane. The immunogold electron microscopy of plastic-embedded quadriceps femoris muscles of six mdx mice and six control mice showed the presence of gold particles along the muscle plasma membrane undercoat of all muscle samples from the control mice without any antibody reaction in the mdx mice muscles. The gold-labelled muscles of six mdx and six control mice were quickly frozen by liquid helium in a rapid-freeze apparatus. High magnification electron microscopy of the quick-freeze, deep-etch, rotary-shadow replicas of the gold-labelled muscles demonstrated the presence of dystrophin molecules associated with gold particles at the cytoplasmic surface of mdx control mice. The dystrophin molecules displayed a variety of shapes, such as rods with a reduction in diameter from one end to the other end and/or with the enlargement of their end(s). These dystrophin molecules were incorporated in the meshwork of muscle plasma membrane-associated cytoskeletons.