Free radicals are highly reactive chemicals that are a byproduct of normal energy metabolism. If produced in excess or insufficiently controlled, these chemicals damage critical components of nerve cells. Because nerve cells, and especially motor neurons, require so much energy to carry out their electrical and metabolic activities, they are especially vulnerable to free radical damage. Molecular genetics is contributing greatly to our understanding of ALS, and has reinforced the suspicions about a role for free radicals in the disease process. Although only about ten percent of people with ALS inherit the disease, studying those familial cases is helping scientists to understand ALS because genetics can identify the first step in the disease,a mutant gene,in these cases.
SOD normally acts to safely remove free radicals.
However, it appears that the mutation may lead to ALS not because the enzyme fails to do its job, but because it creates excess free radicals. This surprising result is an excellent illustration of the power of genetics to focus attention and generate new hypotheses. Inherited ALS is clinically similar to the more common forms of the disease, and scientists are actively investigating the extent to which the underlying mechanisms of inherited and sporadic ALS are also alike. Meanwhile, geneticists are searching for other mutations that can cause this disease and provide additional clues. The discovery of SOD mutations led to another crucial advance in ALS research.