The PRX gene provides instructions for making a protein called periaxin. Periaxin is required for the maintenance of myelin, the protective substance that covers nerves and promotes the efficient transmission of nerve impulses. The exact function of periaxin is unclear, but research suggests that it helps stabilize myelin.
The PRX gene produces two forms of periaxin, called long (L) and short (S) because they differ in size. Research studies show that the short form (S-periaxin) is distributed throughout the cytoplasm, the fluid inside cells. The long form (L-periaxin) is concentrated initially in the nucleus, then relocates to the cell membrane during the formation of myelin. L- and S-periaxin probably have slightly different functions, based on their different cell locations.
Researchers have identified at least 10 PRX gene mutations that cause a form of Charcot-Marie-Tooth disease known as type 4F (sometimes called Dejerine-Sottas syndrome). These mutations result in an abnormally short L-periaxin protein that cannot maintain the myelin structure. Disrupted myelin structure can lead to the loss of myelin (demyelination) and impaired transmission of nerve impulses. As a result, peripheral nerves are less able to activate muscles used for movement or relay information from sensory cells back to the brain. These peripheral nerve abnormalities cause the signs and symptoms of type 4F Charcot-Marie-Tooth disease.