**3. Myelin protein gene expression in peripheral nerve after injury**

Investigating the evolution of the main proteins that enter the composition of myelin sheath during and after nerve injury has been a subject of study for many scientists. These proteins are P zero (P0), myelin basic protein (MPZ), and P2. The first two play an important role in maintaining the integrity and compactness of the myelin sheath. P2 is a lipid-binding protein and participates in fatty acid elongation and transport during the myelination process [7]. Myelin associated glycoprotein (MAG) is a transmembrane protein that is found in the periaxonal region and participates in SC-axon contact organization. It seems to be involved in the myelination process after injury [8]. P0 and MBP mRNA in the distal nerve portion after transection were found to be 20% lower than normal levels but have had normal levels after crushing [9, 10]. In the absence of a contact between SCs and the axon, the levels of mRNAs of P0 and MBP remained low, and mRNA of MAG was undetectable, long time after nerve transection, whereas MAG mRNA was undetectable after lesion; in the case of a crush injury, after a sudden and short decrease, the mRNA levels of these proteins were found to increase rapidly afterwards [10, 11].
