Muscular Dystrophy

There are several forms of muscular dystrophy, which comprise a group of inherited diseases characterized by muscle fiber degeneration and weakness. The most common of these is Duchenne muscular dystrophy (DMD). The gene responsible for DMD is located on the X chromosome, and is called dystrophin. The dystrophin gene encodes a membrane protein important to the cytoskeleton of striated muscle cells. On the cytoplasmic side the dystrophin proteins are attached to actin filaments (part of the cytoskeleton) and on the membrane side they are attached to DAPs (dystrophin associated proteins) which are part of the plasma membrane and which attach to components of the extracellular matrix, especially the protein laminin. The actin-dystrophin-DAP-extracellular matrix complex forms a functional pathway linking the extracellular matrix with the cytoskeleton which provides structural support for the plasma membrane under repetitive contraction and relaxation of the muscle fiber.  In DMD there is a virtual absence of dystrophin protein. Patients show dramatic abnormalities in both skeletal and cardiac muscle tissue. The disease begins in childhood with muscle weakness that progresses until respiratory or cardiac function ceases.

Other muscular dystrophies:

Becker Muscular Dystrophy - the dystrophin protein is present but is abnormal or greatly reduced in amount.

Congenital Muscular Dystrophy  (CMD)is a deficiency in one of the subunits of the laminin molecule.

In Severe Childhood Autosomal Recessive Muscular Dystrophy (SCARMD) results from the absence of one of the subunits of the DAP complex.

Promising treatments:

Gene therapy - One avenue lies in finding a way to get human muscle cells to make a similar protein, utrophin, which is present in embryonic tissue. This process has been done successfully in mice.

Cell transplantation - The transplantation of myoblasts, undifferentiated muscle cells, from close relatives might provide the source for new normal muscle cell production.