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Muscle Building: A promising new therapy for a tragic childhood condition.

Spinal muscular atrophy, or SMA, is one of the world’s most heartbreaking illnesses.

The condition, caused by the absence of, or a defect in, a gene that codes for critical motor neuron function, affects mostly infants and toddlers. Those with the most severe form of the illness seldom live past age 2. It is the leading genetic cause of infantile death in America.

There is no cure for SMA, but there is hope. Progress in identifying the genetic foundations of the illness has, according to advocacy organizations such as the New York-based Spinal Muscular Atrophy Foundation, “catapulted SMA from a disease that was poorly understood to one on the threshold of treatment.”

Chris Lorson, a professor of veterinary pathobiology at MU, is among those scientists responsible for the foundation’s optimism. Lorson and his research team have identified a promising new “therapeutic target”—boosting skeletal muscle—that has led to enhanced strength, improved motor skills and increased lifespan in mice with SMA.

“We administered a particular protein, follistatin, to SMA mouse models to determine if enhanced muscle mass impacts the symptoms of SMA,” Lorson says. “After treatment, the mice had increased muscle mass, gross motor function improvement and an increase in average life span of 30 percent.”

SMA is caused by the inability of a gene, identified by geneticists as SMN1, to express a protein critical to motor-neuron function. Because SMA patients have been found to have a “backup” gene, SMN2, that expresses a similar protein, most research has focused on boosting SMN2’s role.

Lorson’s study took a different approach. It used follistatin to inhibit the function of yet another protein, myostatin. Because myostatin is known to hinder muscle growth, one might reasonably assume that administering follistatin would produce the opposite effect; i.e., increased muscle mass and strength. And so it did, at least in the mouse model.

If, after further study, follistatin proves itself as useful as researchers hope, it will likely be used in conjunction with traditional SMN protein therapies, Lorson says.

“Because follistatin does not alter the expression level of SMN protein, the most effective treatment would combine strategies that directly address the genetic defect in SMA as well as SMN-independent strategies that enhance skeletal muscle,” he says.

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