SEATTLE – An international research team co-led by a scientist at Fred Hutchinson Cancer Research Center has identified two genetic factors behind the third most common form of muscular dystrophy. The findings, published online in Nature Genetics, represent the latest in the team's series of groundbreaking discoveries begun in 2010 regarding the genetic causes of facioscapulohumeral muscular dystrophy, or FSHD.
The team, co-led by Stephen Tapscott, M.D., Ph.D., a member of the Hutchinson Center's Human Biology Division, discovered that a rare variant of FSHD, called type 2, which accounts for about 5 percent of cases, is caused by two genetic mutations that together cause the production of muscle-damaging toxins responsible for causing symptoms of this progressive muscle disease.
Specifically, the researchers found that a combination of genetic variants on chromosomes 4 (called DUX4) and 18 (called SMCHD1) can cause type 2 FSHD. The DUX4 variant was first described by the research team in 2010 as a mechanism behind the more common, type 1, version of the disease.
"Many diseases caused by a single gene mutation have been identified during the last several decades, but it has been more difficult to identify the genetic basis of diseases that are caused by the intersection of multiple genetic flaws," Tapscott said. "Recent advances in DNA sequencing made this study possible and it is likely that other diseases caused by the inheritance of multiple genetic variants will be identified in the coming years."Understanding the genetic mechanisms of type 2 FSHD could lead to new biomarker-based tests for diagnosing the disease and could lead to the development of future treatments, Tapscott said.
FSHD affects about half a million people worldwide. Symptoms usually first appear around age 20 and are characterized by a progressive, gradual loss of muscle strength, particularly in the upper body.