Scientists identify a new kind of genetic problem in muscular...( A newly identified genetic problem unde...)

A newly identified genetic problem underlies a common neuromuscular disorder called facioscapulohumeral muscular dystrophy (FSHD), scientists say. In a new study, they show that deletion of repetitive DNA sequences in people with this disorder allows nearby genes to go into overdrive. The finding solves a decade-old riddle about the cause of this disorder and may ultimately lead to the first effective treatments.

The study found that abnormally short strings of repeated DNA sequences on chromosome 4 interfere with the function of a protein complex that controls nearby genes. This leads to over-activity of several genes that may play a role in the disorder. This type of genetic problem has never before been identified in a human disease. The study was funded in part by the National Institute of Neurological Disorders and Stroke (NINDS) and appears in the August 9, 2002, issue of Cell.*

Scientists first linked the short strings of DNA in this region to FSHD in 1992. People with FSHD typically have fewer than 11 copies of this nucleic acid sequence, called D4Z4, due to a deletion of part of the chromosome. In contrast, people without the disorder usually carry between 11 and 150 copies of the sequence. People with a very small number of copies (three or fewer) have severe disease symptoms that begin in childhood, while those with several more copies typically have milder symptoms that begin in the teens or early adulthood. However, until now, researchers have been unable to determine exactly how the number of DNA sequences influences the disease.

FSHD is the third most common inherited neuromuscular disorder, affecting one in every 20,000 people (only Duchenne muscular dystrophy and myotonic dystrophy are more common). People with FSHD have progressive muscle degeneration that primarily affects the face, shoulder blades, and upper arms, although other muscles also deteriorate. Despite intensive efforts, researchers have been unable t
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Contact: Natalie Frazin or Paul Girolami
301-496-5751
NIH/National Institute of Neurological Disorders and Stroke
8-Aug-2002

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