Cure for muscular dystrophy closer than ever

February 27, 11:46 AMScience News ExaminerMeg Marquardt

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Fifteen years ago, researchers made a major breakthrough in muscular dystrophy (MD): after much investigation, they isolated dystrophin, a protein which is severely limited or absent in MD patients, and which is responsible for muscle formation and function.  While many thought this would lead directly to a cure for MD, it was not to be the case.  There were still missing pieces in the puzzle.

MD is a genetic disorder that causes muscle tissue to be replaced by incorrect types of tissue (such as boney or fatty).  This of course leads to loss of muscle function and can even lead to premature death (this is especially true in children who have a severe form of MD).  And while replacing the mutated dystrophin-producing genes with healthy genes promoted muscle growth, the muscle tissue was not fully functioning and eventually failed.

Over a decade after the identification of dystrophin, researchers at University of Missouri have found an essential genetic key to understanding MD.  It has long been known that muscles need helper proteins and other biochemical agents in order to function properly.  One of the helpers is nNOS, which produces nitric oxide, a molecule important to high-impact movement like exercise.  "When you exercise, not only does the muscle contract, but the blood vessels are constricted," said Dongsheng Duan, associate professor of molecular microbiology and immunology at MU. "nNOS is important because it produces nitric oxide that relaxes the blood vessels, helping to maintain the muscle with a healthy blood supply. If no blood reaches the muscle cells, they will eventually die.  In [MD] patients, this means the disease will progress as the muscle cells are replaced by the fibrous, bony or fatty tissue” [EurekAlert]

The hunt has been on for the genetic components of nNOS, but for the past fifteen years, but researchers “have not been able to determine how to produce nNOS in a dystrophic muscle, or a muscle lacking dystrophin.” [EurekAlert]  But Duan’s group has not only identified what is producing nNOS, they have also created new dystrophin genes that have shown promising results.  Mice engineered to develop MD that express the new genes have both better functioning muscles as well as a better response to exercise including little muscle fatigue or muscle damage.

With over 250,000 people suffering from MD in the US, this study is extremely important.  “We have finally found the genetic material that can fully restore all the functions required for correcting a dystrophic muscle and turning it into a normal muscle," said Duan. [EurekAlert]