Common Cause of Lou Gehrig's Disease Found

Aug. 22, 2011 -- Researchers from Northwestern University are reporting a major breakthrough in understanding of the cause of amyotrophic lateral sclerosis (ALS), the fatal disease also known as Lou Gehrig’s disease.

They say their discovery proves that different forms of ALS actually have a common cause and that this could lead to better strategies to treat the disease.

Their study was reported online in the journal Nature.

In ALS, nerve cells in the brain and spinal cord that control movement stop functioning. The condition leads to paralysis, and patients eventually cannot breathe or swallow on their own.

The disease afflicts about 350,000 people a year worldwide, and about half of patients die within three years of diagnosis.

ALS One Disease, Research Suggests

Northwestern professor of neurology Teepu Siddique, MD, and his research team have been searching for the cause and underlying mechanism of ALS for more than two decades.

He tells WebMD that a critical mutation in a protein involved in the recycling of damaged nerve cells was first identified in a family followed since 1985. Nineteen of the family members over five generations were afflicted with the condition.

Only about one in 10 ALS patients have the inherited form of the disease. Because no cause had been identified in people without a family history, researchers have not been certain that different forms of ALS were actually the same disease.

Siddique and colleagues found that in people with and without inherited ALS, the disease results from the inability of a protein system to repair the nerve cells that tell the muscles what to do.

Their research centered on the protein ubiquilin2, which is involved in recycling damaged and misformed proteins in key nerve cells.

In people with ALS, ubiquilin2 does not do this effectively, leading to an accumulation of the damaged proteins and ubiquilin2 in critical nerve cells in the spinal cord and brain.

When viewed through a microscope, the protein accumulations look like twisted balls of yarn, which is a hallmark characteristic of ALS.

‘Protein Degradation Pathway’ Key

The findings add to the evidence that a defect in a process known as the protein degradation pathway contributes to ALS and possibly other degenerative disorders, such as Parkinson’s disease and even Alzheimer’s, the researchers conclude.

“Abnormality in protein degradation has been suspected, but there was little direct evidence before this study,” study co-author Han-Xiang Deng, MD, notes in a written statement.

Raymond Roos, MD, the Marjorie and Robert Straus Professor of Neurological Science at the University of Chicago Medical Center, says the discovery appears to represent an important step forward in the understanding of ALS.

He adds that it remains unclear why ubiquilin2 does not function properly in some patients without a family history of ALS.