What if a method of determining the severity of muscular dystrophy lies within a familiar summertime insect?
Scientists at Stanford University School of Medicine have recently created a mouse model of the disease in which degenerating muscle gives off visible light- using the same protein that allows fireflies‘ tails to glow. This precise technique causes luminescence to occur in direct proportion to the amount of damage the muscle has sustained. So, not only will a damaged muscle “glow,” but the more damaged the tissue is, the more it will glow.
Here’s how it works: Under normal conditions, a rare class of stem cells, called “satellite cells,” sit quietly next to muscle fibers. But under abnormal conditions, such as muscular injury or degeneration, these satellite cells divide and integrate themselves into the damaged tissue, repairing the muscle. The Stanford team, under Thomas Rando, created an experimental mouse strain in which an inserted gene for luciferase, or firefly-glow-protein, is activated only by satellite cells.
Once a luciferase gene is “turned on” in a mouse’s satellite cell, it remains “on” for the rest of the mouse’s life and is passed on to its progeny as well. Luminescence is shown by giving the mice a compound that gives off light in the presence of luciferase.
“In these luminescent mice, we could pick up the disease’s pathological changes well before they could be seen otherwise,” says Rando. “The readout was so sensitive we could observe those changes within a two-week period. Not only that, but we got our measurements instantaneously, without killing the mice.”
Although this technique is not yet applicable to humans, it holds promises for quicker, cheaper, and more accurate assessments of muscular dystrophy drugs.