Naturally occurring genetic change in humans that dramatically increases muscle size and strength

A research team funded by MDA has discovered a naturally occurring genetic change (mutation) in humans that dramatically increases muscle size and strength.

The mutation is in the gene for a protein called “myostatin” that normally acts to slow muscle growth. When this gene is inactivated, restraints on muscle growth are lifted.

The researchers, led by Markus Scheulke of Charite University Medical Center in Berlin, identified a mutation in both copies of the myostatin gene in a 4-year old child who had been noted to have unusually well-developed musculature from the time of birth. At 4, the child was reportedly able to hold two 3-kilogram (6.5-pound) weights in his outstretched arms. His mother, a former professional athlete, was found to have a single copy of the same mutation.

Natural defects in the myostatin gene have been identified previously in animals, including the prized Belgian Blue cattle that appear to be “double muscled” and are very lean. Also, mice engineered to lack the myostatin gene develop unsually large muscles and have been dubbed “mighty mice.” This is the first report of a similar mutation and effect in humans.

Researchers have long wondered if blocking myostatin might represent a useful approach to treating muscular dystrophy.

MDA-funded researcher Kathryn Wagner of Johns Hopkins University has shown that the loss of the myostatin gene leads to much milder disease in mice that are destined to have a disease like Duchenne muscular dystrophy.

Also MDA grantee Tejvir Khurana of the University of Pennsylvania in Philadelphia demonstrated that the effects of muscular dystrophy in mice can be reduced by administering antibodies (proteins produced by the immune system) that block myostatin.

The current finding that loss of myostatin in humans leads to extra muscle growth lends credence to the possibility that artificially blocking myostatin may help counteract muscle weakness in degenerative muscle disease. This report appears in the June 24 issue of the New England Journal of Medicine.

MDA is currently funding Kathryn Wagner’s group to further explore the potential for developing a muscular dystrophy therapy based on blocking myostatin.

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