Age-dependent redistribution and hypersialylation of the central myelin paranodal loop membrane protein Opalin in the mouse brain.

Opalin/Tmem10 is a myelin-associated sialylglycoprotein that is specific to only the mammalian central nervous system. However, little is known about the properties or function of this protein. Here, we analyzed the expression and glycosylation patterns of Opalin in the postnatal mouse brain. Immunolocalization patterns of Opalin were similar to those of myelin basic protein in juvenile and adolescent mice. On the other hand, in the adult mouse brain, decreasing immunoreactivity for Opalin was observed in the hindbrain region especially in the cerebellar white matter compared with the corpus callosum in the forebrain. In addition, Opalin showed increasing molecular size with mouse aging. This age-dependent increase in Opalin molecular weight was mainly owing to hypersialylation of O-glycans. These results indicate that the regional redistribution and the degree of sialylation of Opalin protein are age-dependently regulated in mouse brains.