Prion protein, previously implicated in "mad cow disease", is also critical for maintaining the myelin sheath that surrounds the axons of peripheral nerves, reports a study published online this week in Nature Neuroscience. This suggests a novel role in normal brain function for the mysterious prion protein.
Adriano Aguzzi and colleagues studied mice which were deficient in the prion protein. These mice are known to be resistant to prion infections. However, they also show a number of abnormalities, including a late-onset degeneration of the peripheral neurons and the myelin that surrounds them. To determine how the prion protein contributes to the maintenance of peripheral myelin, the researchers compared the effects of prion deficiency in the neurons themselves to prion deficiency in the surrounding Schwann cells which make the myelin sheath. Surprisingly, they found that only loss of neuronal prion protein resulted in loss of the myelin sheath and degeneration of peripheral axons. Eliminating prion protein in the Schwann cells had no effect.
Demyelinated neurons lead to serious health problems, and the discovery of a new player in the process of myelin maintenance presents the possibility for novel avenues of treatment.