Muscular Dystrophy Mystery Solved?

Scientists uncover cause of common form of muscular dystrophy

(RxWiki News) An international team of researchers headed by an investigator from Fred Hutchinson Cancer Research Center have made a critical advance in determining the cause of a common form of muscular dystrophy.

The finding may lead to new therapeutic approaches as well as insights into human evolutionary biology.

Previously, the team of researchers established a model for the cause of facioscapulohumeral dystrophy and now current work indicates the disease may be caused by the ineffective suppression of a gene known as DUX4 which is usually expressed in early development.

DUX4 genes were previously thought to be inactive in humans, belonging to a special class of genes known as retrogenes or "dead genes" that are no longer of use in human biological functioning. However, the researchers at Hutchinson Cancer Research Center discovered DUX4 genes are abundantly expressed in the cells that form sperm and eggs, and thus suggest that the DUX4 genes are necessary in early development.

Normally the DUX4 gene is suppressed in all other bodily cells, but a mutation makes this suppression less effective, resulting in expression in some muscle cells. The expression of DUX4 in some muscle cells is what causes facioscapulohumeral dystrophy, according to the study.

Corresponding author Stephen Tapscott, MD, PhD, a member of the Hutchinson Center's Human Biology Division, compared escaped DUX4 genes to the Old Faithful geyser at Yosemite National Park, which is "usually turned off but occasionally releases a burst of water."

The occasional "bursts" of DUX4 are thought to act as a toxin to muscle cells, leading to muscle cell death and muscular dystrophy.

Muscular dystrophy is a group of nine distinct diseases marked by progressive weakness and degeneration of the muscles that control movement. According to Penn State University College of Medicine, myotonic muscular dystrophy is the most common form of the disease, affecting more than 30,000 people in the United States. Myotonic muscular dystrophy is characterized by generalized weakness first occurring in the face, hands, and feet, and myotonia, the inability of muscles to relax normally after use.

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Review Date: 
January 20, 2011