THE EXPRESSION OF FERRITIN SUBUNITS AND IRON IN OLIGODENDROCYTES IN NEONATAL PORCINE BRAINS

Myelination is an essential component of normal development in the bra in. Thus, the factors which influence the onset of myelination need to be identified and monitored during development to insure adequate mye lination, These factors may also play a role in remyelination attempts which occur as a result of demyelinating diseases, One factor known t o be involved in myelination is iron, In this study, the cellular depo sition of iron and the intracellular iron storage protein ferritin are examined in the brains of 1-month-old piglets, Ferritin consists of 2 subunits (H and L chains) which occur in different ratios in differen t organs. The subunits are functionally distinct so their pattern of-e xpression at the cellular level reveals information about the iron req uirement of the cell and utilization versus storage, The H subunit of ferritin is expressed in abundance in oligodendrocytes within white-ma tter tracts whereas the L subunit in this region is found only in endo thelial cells of blood vessels. H-ferritin-positive cells occur in cle arly defined patches which are scattered throughout the white-matter t racts, The cellular distribution of iron is identical to that of H fer ritin, H-ferritin-positive cells are identified as oligodendrocytes on the basis of immunofluorescent colocalization with CNPase, Also, some of the H-ferritin-positive cells are positive for myelin basic protei n, However, the distribution of CNPase-positive cells is more even in the white matter than the patches of H-ferritin/iron-positive cells, T he relationship between H-ferritin- and CNPase-positive cells indicate s that the former are oligodendrocytes, but also reveals a subset of o ligodendrocytes in the white matter, The results of this study provide insight into how the intracellular iron is managed in oligodendrocyte s. The factors which initiate iron and ferritin expression in a select population of oligodendrocytes, and the relationship of this select p opulation to myelinogenesis and myelin maintenance, have yet to be ide ntified.