Researchers at the University of Minnesota Medical School have discovered the gene responsible for a type of ataxia, an incurable degenerative brain disease affecting movement and coordination.

This is the first neurodegenerative disease shown to be caused by mutations in the protein beta-III spectrin which plays an important role in the maintaining the health of nerve cells.
The scientific discovery has historical implications as well -- the gene was identified in an 11-generation family descended from the grandparents of President Abraham Lincoln, with the President having a 25 percent risk of inheriting the mutation.

Understanding the effects of this abnormal protein, which provides internal structure to cells, will clarify how nerve cells die and may provide insight into other diseases, including amyotrophic lateral sclerosis ( Lou Gehrig's disease ) and Duchenne muscular dystrophy.

The research is published in the Nature Genetics.

Ataxia is a hereditary disease that causes loss of coordination resulting in difficulty with everyday tasks such as walking, speech, and writing. About 1 in 17,000 people have a genetic form of ataxia.

Spinocerebellar ataxia type 5 ( SCA5 ) is a dominant gene disorder; if a parent has the disease, each of their children has a 50 percent chance of inheriting the mutation and developing ataxia sometime during their lifetime. The onset of SCA5 usually occurs between the ages of 30 and 50, but can appear earlier or later in life, with reported ages of onset ranging from 4 to more than 70 years of age.

Now that researchers have identified the specific mutation that causes SCA5, testing of patients at risk of developing this disease is possible before any symptoms appear. The availability of predictive testing allows people with a family history of the disease to determine whether they will develop the disease and whether their children are at risk of inheriting the mutation. In addition, the prognoses of the different types of ataxias vary greatly, so identifying the specific type of ataxia provides patients with a more accurate picture of what the future holds.

Laura Ranum, senior investigator added: " Finding the SCA5 mutation in Lincoln's family makes it possible to test Lincoln's DNA – if it becomes available – to unequivocally determine if he carried the mutation and had or would have developed the disease." Biographical texts of Lincoln include descriptions of his uncoordinated and uneven gait, suggesting the possibility that he showed early features of the disease.

Source: University of Minnesota, 2006


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