Caption: Abnormal connections between leg muscle fibers (red) and nerves (green) in Pompe disease.
Credit: Darin J. Falk, A. Gary Todd, Robin Yoon, and Barry J. Byrne, University of Florida, Gainesville
Mistletoe? Holly? Not exactly. This seemingly festive image is a micrograph of nerve cells (green) and nerve-muscle junctions (red) in a mouse model of Pompe disease. Such images are helping researchers learn more about this rare form of muscular dystrophy, providing valuable clues in the ongoing search for better treatments and cures.
People with Pompe disease lack an enzyme that cells depend on to break down a stored sugar, known as glycogen, into smaller glucose molecules that can be readily used for energy. Without enough of this enzyme, called acid alpha-glucosidase (GAA), glycogen can accumulate destructively in the liver, heart, and skeletal muscles, making it increasingly difficult to walk, eat, and even breathe.
Darin Falk, an NIH-funded neuroscientist at the University of Florida, suspected there was more to the muscle weakness seen in Pompe disease than muscles alone. Using a variety of techniques, including the keen microscopy skills recognized by the Federation of American Societies for Experimental Biology’s 2014 BioArt contest, Falk has been busy exploring this hunch.
When Falk used a confocal microscope to examine muscle tissue from the legs and diaphragms of mice with Pompe disease, he saw the nerve-muscle, or neuromuscular, junctions looked strikingly different than those in normal mice. They were more fragmented and showed expansion of the area where nerves contact the muscle (the motor endplate). And, within the nerve cells themselves, Falk detected unusually low levels of certain key proteins that are essential for transmitting the signals that tell muscles to move .
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