Scientists supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) have found that mouse odorant receptor 23 (MOR23), a protein involved in odor recognition, also affects the ability of muscle cells to grow, migrate, change and fuse to form muscle fibers. Grace Pavlath, Ph.D., and her colleagues at the Emory University School of Medicine in Atlanta discovered that when muscle cells began to come together to form fibers, the gene for MOR23 becomes more active, producing the receptor protein. Their study has been reported in the journal Developmental Cell.

Odorant receptors, which bind chemicals in the air to activate the sense of smell, have recently been found to be involved in processes outside the nose, including migration of nerve and sperm cells and the growth of prostate cancer cells. To understand more about the role of MOR23 in muscle cell development, the Emory researchers altered mouse muscle cells to produce only about half of the normal amount of cellular MOR23. They found that muscle cell migration was reduced to roughly 50 percent of that observed in unaltered cells. Moreover, the altered cells failed to fuse normally with other muscle cells to form fibers, eliminating a critical step in the process of muscle growth and repair.

The investigators also used mice to study MOR23 activity following muscle injury. They discovered that MOR23 production increased fourfold during muscle regeneration. In addition, the researchers genetically altered mouse muscle tissue to decrease and increase MOR23 after injury. Decreasing MOR23 resulted in more, but smaller muscle fibers in a process called myofiber branching, which is associated with the muscular dystrophies. Increasing MOR23 generated fewer, but larger fibers.

The study results point to a necessary role for MOR23 in muscle growth and repair. Such emerging information about the influence of molecular factors could eventually help uncover new targets for therapies. Muscle injury is common, and muscle loss associated with aging and diseases like the muscular dystrophies can be devastating.

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the U.S. Department of Health and Human Services' National Institutes of Health (NIH), is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.

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Griffin C, Kafadar K, Pavlath G. MOR23 promotes muscle regeneration and regulates cell adhesion and migration. Developmental Cell. 2009 Nov;17(5):649-61.