Even in culture, oligodendrocytes myelinate solely axons.
Cerebral hemispheres from mouse embryos at 15 days of gestation were dissociated and maintained in culture for several weeks in a medium which permitted homochronic and homotypic oligodendrocytes and neurons to interact in the presence of other central nervous system cells. After 13-14 days in culture a few oligodendrocytes changed from highly branched, "sun-like," nonmyelinating cells to sparcely branched myelinating cells. The number of fibers myelinated per oligodendrocyte ranged from 1 to 10, similar to that described previously in vivo in the corpus callosum. When an oligodendrocyte began to myelinate, it immediately myelinated a maximum number of fibers, suggesting that the number of axons to be myelinated by the oligodendrocyte was predetermined. When only one fiber was in the vicinity of a myelinating oligodendrocyte, whorls of myelin-like figures were seen at the tip of oligodendrocyte processes that had not reached an axon. Myelinated fibers were unambiguously identified as axons both by immunostaining and by electron microscopy. Myelin was not observed around astrocyte processes or around dendrites. The exclusive myelination of axons suggests the existence of a specific axonal recognition signal which attracts oligodendrocyte processes.
Lubetzki
C
C
Laboratoire de Neurobiologie Cellulaire Moléculaire et Clinique, Institut National de la Santé et da la Recherche Médicale, Unité-134 and -289, Hôpital de la Salpêtrière, Université Pierre et Marie Curie, Paris, France.
Demerens
C
C
Anglade
P
P
Villarroya
H
H
Frankfurter
A
A
Lee
V M
VM
Zalc
B
B
D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D009186:Myelin Sheath / Q000378:metabolism* / Q000648:ultrastructure; D009836:Oligodendroglia / Q000166:cytology / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology / Q000196:embryology / Q000378:metabolism*