Fourth gene found for distal muscular dystrophy

MDA grantees Peter Hedera, a neurologist at Vanderbilt University in Nashville, Tenn., and Nigel Laing, a molecular biologist at the University of Western Australia, were part of a team that identified a fourth gene that, when flawed, leads to distal muscular dystrophy (DD). Three other genes have previously been identified for this type of MD.

The new DD gene, called MYH7, carries instructions for a protein known as a myosin heavy chain. It’s needed in heart and skeletal muscle cells, and abnormalities in it have previously been found to cause cardiomyopathy (cardiac muscle disease) and myosin storage myopathy, a muscle disease.

The new link between MYH7 and DD was published online in the American Journal of Human Genetics on Aug. 20.

DD, which weakens the muscles of the forearms, hands, lower legs and feet, can result from flaws in at least seven (four known and at least three unidentified) genes for proteins affecting muscles.

The MYH7 form, which can cause symptoms as early as age 4, is known as Laing early-onset distal MD (or distal myopathy). Nigel Laing and colleagues narrowed the location of the disease-causing gene flaw to chromosome 14 in 1995. People with Laing DD usually don’t have cardiomyopathy.

The precise identification of disease-causing gene flaws (mutations) generally leads to improved diagnostic procedures right away, and to improved treatment in the long run.