Researchers at the University of California, San Diego School of Medicine have identified the mechanism by which a rare, inherited neurodegenerative disease causes often crippling muscle weakness in men, in addition to reduced fertility. The study, published August 10, 2014 in the journal Nature Neuroscience, shows that a gene mutation long recognized as a key to the development of Kennedy's disease impairs the body's ability to degrade, remove, and recycle clumps of "trash" proteins that may otherwise build up on neurons, progressively impairing their ability to control muscle contraction. This mechanism, called autophagy, is akin to a garbage disposal system and is the only way for the body to purge itself of non-working, misshapen trash proteins. "We've known since the mid-1990s that Alzheimer's disease, Parkinson's disease, and Huntington's disease are caused by the accumulation of misfolded proteins that should have been degraded, but cannot be turned over," said senior author Albert La Spada, M.D., Ph.D., and professor of pediatrics, cellular and molecular medicine, and neurosciences. "The value of this study is that it identifies a target for halting the progression of protein build-up, not just in this rare disease, but in many other diseases that are associated with impaired autophagy pathway function." Of the 400 to 500 men in the U.S. with Kennedy's disease (see image), the slow but progressive loss of motor function results in about 15 to 20 percent of those with the disease becoming wheel-chair bound during later stages of the disease. Kennedy's disease, also known as spinal and bulbar muscular atrophy, is a recessive X-linked disease men inherit from their mothers. Women don't get the disease because they have two copies of the X chromosome.
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