TUESDAY, July 29 (HealthDay News) -- A protein dysfunction could help drive amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, according to a study by researchers at Brandeis University and Harvard Medical School.

ALS is a fatal neurodegenerative disease caused by the death of motor neurons in the brain and spinal cord that control muscle movement. In this study, researchers focused on the rare, familial form of ALS (fALS) as a way of better understanding the sporadic form of ALS, which accounts for 90 percent of all cases. Clinical symptoms are identical in both forms of the disease.

About 15 years ago, scientists found that mutations in the gene that makes the protein superoxide dismutase caused familial ALS, but just how these mutations cause ALS has remained a mystery.

In this new study, researchers found that fALS is caused by two properties of superoxide dismutase that create toxic levels of the protein in motor neurons.

"We discovered that increased protein unfolding and the propensity of the proteins to aggregate (clump together) are the major factors in the familial form of ALS," Brandeis chemist Jeff Agar said in a university news release.

"The protein superoxide dismutase, normally a useful antioxidant, goes from Dr. Jekyll to Mr. Hyde when it clumps up," Agar said.

The study was published this week in the journal PLoS Biology.

The next phase of this research is to develop drugs that prevent superoxide dismutase from clumping together.

More information

The Muscular Dystrophy Association has more about ALS.