Researchers discover small protein essential for formation of skeletal muscle

UT Southwestern Medical Center researchers discovered a small protein named Myomixer essential for the formation of skeletal muscle – findings that could eventually help treat genetic diseases such as muscular dystrophy and other myopathies.

Using a technique that removes genes from cells, scientists showed that both Myomixer and Myomaker – another protein the group previously identified – must be present for muscle cells to fuse together to create muscle fibers, the building blocks of muscles.

Moreover, Myomixer and Myomaker can cause other types of cells to fuse together.

"The most remarkable finding is that if you express both Myomaker and Myomixer together, they can fuse nonmuscle cells. For example, skin cells will fuse to each other or to muscle cells very efficiently in the presence of these two proteins. This ability opens the door for possible therapeutic strategies in which cells that have cargo can be fused with any other cell," said author Dr. Eric Olson, Chairman of Molecular Biology, Co-Director of the UT Southwestern Wellstone Muscular Dystrophy Cooperative Research Center, and Director of the Hamon Center for Regenerative Science and Medicine.

Regenerative Medicine at UTSW:

• The National Institutes of Health awarded UT Southwestern researchers a $7.8 million grant in 2015 to establish the UT Southwestern Wellstone Muscular Dystrophy Cooperative Research Center, one of six coveted Senator Paul D. Wellstone Muscular Dystrophy Centers in the country.
• UT Southwestern's Hamon Center for Regenerative Science and Medicine was made possible by a $10 million endowment gift from the Hamon Charitable Foundation. The Center's goal is to understand the basic mechanisms for tissue and organ formation, and then to use that knowledge to regenerate, repair, and replace tissues damaged by aging and injury.

"For example, if a muscle fiber is missing a gene, then another cell that carries the missing gene could be fused to the defective cell by Myomaker plus Myomixer to provide the missing gene," explained Dr. Olson, who holds the Pogue Distinguished Chair in Research on Cardiac Birth Defects, the Robert A. Welch Distinguished Chair in Science, and the Annie and Willie Nelson Professorship in Stem Cell Research.

Myomixer and Myomaker also have implications for regenerative medicine. Skeletal muscle is the largest tissue in the body, accounting for about 40 percent of human body mass, and is the type of muscle used to move limbs. When skeletal muscle is injured, it repairs itself and the Myomixer/Myomaker combination is fundamental to that muscle repair process.

"The discovery of Myomixer, a micropeptide, provides a key component to our understanding of skeletal muscle formation and regeneration," said Dr. Rhonda Bassel-Duby, Professor of Molecular Biology, Associate Director of the Hamon Center for Regenerative Science and Medicine, and a co-author of the study.