"No pain, no gain." So say those working out to build up their muscles, and on a cellular level it is a pretty accurate description of how muscle mass increases. Exercise causes tears in muscle membrane and the healing process produces an increased amount of healthy muscle. Implicit in this scenario is the notion that muscle repair is an efficient and ongoing process in healthy individuals. However, the repair process is not well understood. New University of Iowa research into two types of muscular dystrophy now has opened the door on a muscle repair process and identified a protein that plays a critical role.

The protein, called dysferlin, is mutated in two distinct muscular dystrophies known as Miyoshi Myopathy and limb-girdle muscular dystrophy type 2b. The UI study suggests that in these diseases, the characteristic, progressive muscle degeneration is due to a faulty muscle-repair mechanism rather than an inherent weakness in the muscle's structural integrity. The research findings, which appear in the May 8 issue of Nature, reveal a totally new cellular cause of muscular dystrophy and may lead to many discoveries about normal muscle function and to therapies for muscle disorders.

The research team led by Kevin Campbell, Ph.D., the Roy J. Carver Chair of Physiology and Biophysics and interim head of the department, UI professor of neurology, and a Howard Hughes Medical Institute (HHMI) Investigator, studied the molecular consequences of losing dysferlin and discovered that without dysferlin muscles were unable to heal themselves.

The UI team genetically engineered mice to lack the dysferlin gene. Just like humans with Miyoshi Myopathy and limb-girdle muscular dystrophy type 2b, the mice developed a muscular dystrophy, which gets progressively worse with age. However, treadmill tests revealed that the muscles of mice that lack dysferlin were not much more susceptible to damage than the muscles of normal mice. This contrasts with most mu
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Contact: Jennifer Brown
jennifer-l-brown@uiowa.edu
319-335-9917
University of Iowa
7-May-2003

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