In vitro differentiation of trout oligodendrocytes: evidence for an A2B5-positive origin

The molecular differentiation of oligodendrocytes derived from larval trout brain was studied in dissociated cell cultures using a range of cell type and stage specific antibodies. By double-labeling immunostaining using A2B5 antibodies in conjunction with antibodies against the myelin glycoproteins IP1 and IP2 evidence was obtained that oligodendrocytes of trout in vitro originate from A2B5+ precursor cells, which in terms of morphology closely resemble 0-2A progenitors of the mammalian CNS. Most surprisingly these cells did not differentiate in vitro beyond the level of IP2 expression, which signifies the initial step of oligodendroglial development in vivo. Hence it appears that in trout oligodendrocytes the initiation of the developmental program is intrinsically regulated, whereas further maturation of the cells requires appropriate environmental stimulation.