Developing chicken oligodendrocytes express the type IV oligodendrocyte marker T4-O in situ, but not in vitro

Accumulating data suggest that the oligodendrocyte population includes morp hological and biochemical subtypes. We recently reported that a polyclonal antiserum against an unknown antigen, the T4-O molecule, labels a subpopula tion of chicken oligodendrocytes, obviously representing the type IV variet y of Del Rio Hortega. The present study examines the developmental expressi on of the T4-O molecule in situ and in vitro. The results show that T4-O im munoreactive cells first appear at E15 in the ventral funiculus. But, oligo dendrocytes cultured in vitro with or without neurones do not develop a T4- O immunoreactivity. We conclude that oligodendrocytes in the spinal cord of chicken embryos first express the T4-O molecule some time after onset of m yelination, and that the T4-O immunoreactive phenotype does not develop in vitro. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.