55 DEVELOPMENTAL CHANGES OF THE MYELIN/OLIGODENDROCYTE GLYCOPROTEIN (MOG): A BIOCHEMICAL AND IMMUNOCYTOCHEMICAL STUDY

Abstract

The myelin/oligodendrocyte glycoprotein (MOG) is exposed at the surface of myelin and oligodendrocyte processes. Using an immunofluorescent technique and antibodies to different oligodendrocyte and myelin components, we followed the expression of these markers in cryostat sections of rat optic nerves. Galactocerebroside and proteolipid protein were already present in newborn optic nerves. At 5 days postnatally, the myelin-associated glycoprotein was present in a few oligodendrocytes whereas MOG appeared later. By gel electrophoresis and immunoblotting, two closely migrating bands with apparent Mr of 26 and 28 kDa were identified. Treatment with N-glycanase or trifluoromethane sulfonic acid showed that carbohydrates represent ca 10% of MOG Mr and that carbohydrates were mainly linked by N-bonds. The concentration of both MOG components increased coordinately in mouse CNS during the most active phase of myelin deposition and, with a delay of 2-3 days, followed the increase of myelin and myelin basic protein. These results suggest that MOG is not involved in the early phase of myelin formation, but could play a role in terminating and maintaining the compact myelin sheath in the CNS.