Emory Report
November 16, 2009
Volume 62, Number 11


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November 16, 2009
Investigating muscle repair, scientists follow their noses

By Quinn Eastman

When muscle cells need repair, they use odor-detecting tools found in the nose to start the process, Emory researchers have discovered.

The results were published in the November issue of Developmental Cell.

Found on the surfaces of neurons inside the nose, odorant receptors are molecules that bind and respond to substances wafting through the air. Researchers have shown that one particular odorant receptor gene, MOR23, is turned on in muscle cells undergoing repair.

“Normally MOR23 is not turned on when the tissue is at rest, so we wouldn’t have picked it up without looking specifically at muscle injury,” says pharmacologist Grace Pavlath. “There is no way we would have guessed this.”

Interfering with MOR23 inhibits muscle cells’ ability to migrate, stick to each other and form long fibers, Pavlath and graduate student Christine Griffin showed. In addition, MOR23 is the first molecule found to influence the process of myofiber branching, a form of degeneration seen in muscular dystrophies and aging.

The finding could lead to new ways to treat muscular dystrophies and muscle wasting diseases. It also raises intriguing questions about what odorant receptors are doing in muscle tissue and possibly other tissues as well.

“There is a tremendous variation in humans as far as what odors individuals can recognize,” Pavlath says. “Could this be linked somehow to differences in the ability to repair muscle?”

MOR23 responds to lyral, a fragrance ingredient in many cosmetics that smells like lily-of-the-valley. Although Griffin could show that muscle cells migrate towards lyral, this doesn’t mean muscles in the body use the same chemical or “ligand.”

The human genome contains around 400 genes encoding odorant receptors, and mice have more than 900. It is not clear what the MOR23 equivalent is in humans, or whether the odorant receptors that respond to lyral in humans are also involved in muscle repair.

Pavlath says she wants to identify the molecule the body uses to direct muscle repair through MOR23. Apparently, when muscle cells are injured, the molecule leaks out or is released.