The Johns Hopkins scientists who first discovered that knocking out a particular muscle gene results in "mighty mice" now report that it also softens the effects of a genetic mutation that causes muscular dystrophy.
The findings, scheduled for the December issue of the Annals of Neurology and currently online, build support for the idea that blocking the activity of that gene, known as myostatin, may one day help treat humans with degenerative muscle diseases.
Working with mice carrying the genetic mutation that causes Duchenne muscular dystrophy in humans, the scientists discovered that mice without the gene for myostatin had less physical damage to their muscles and were stronger than other mice with the Duchenne mutation.
"'Knocking out' the myostatin gene isn't possible for treating patients, but blocking the myostatin protein might be," says senior investigator Se-Jin Lee, M.D., Ph.D., professor of molecular biology and genetics at Johns Hopkins School of Medicine. "However, myostatin still needs to be studied in people to see if it has the same role in our muscles as it has in mice."
The researchers caution that, even if myostatin does limit muscle growth in people, blocking it would not cure muscular dystrophy or any other degenerative muscle condition because the underlying cause of disease would be unchanged.
"However, increasing muscle mass and strength by blocking myostatin could conceivably delay progression or improve quality of life," notes first author Kathryn Wagner, M.D., Ph.D., assistant professor of neurology at Hopkins.
The Hopkins team bred mice without the myostatin gene with mice carrying the genetic mutation that causes Duchenne muscular dystrophy in humans. Muscular dystrophy mice completely lacking myostatin were more muscular and stronger than those with myostatin at 3, 6 and 9 months of age, the researchers report. Perhaps most importantly, their muscle tissue appeared to be healthier.
Duchenne muscular dystrophy is the most common muscular dystrophy and the most common inherited lethal disease of childhood, affecting 1 in 3,500 live male births. (The genetic mutation that causes it is found on the X chromosome, and so is "covered up" in girls, who have two X chromosomes.) There's no good treatment at this time, and few patients survive into adulthood.
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