Regional potential for oligodendrocyte generation in the rodent embryonic spinal cord following exposure to EGF and FGF-2.

The origin of oligodendrocytes in the developing rodent spinal cord has not been fully established, with some evidence that oligodendrocyte progenitors arise exclusively from the ventral neuroepithelium, other studies suggesting that both halves of the spinal cord have oligodendrogenic potential. One way of exploring this issue is to study more primitive oligodendrocyte precursors. Although specific markers are not available, their presence may be inferred using mitogens such as EGF and FGF-2, which stimulate the proliferation of immature neuroepithelial cells, and subsequently studying their differentiation into lineage restricted cells. We used this approach to assess whether the dorsal embryonic rodent spinal cord has the intrinsic potential for oligodendrocyte formation at E14. We confirm that significant numbers of oligodendrocytes and their immediate (A2B5+) precursors are present only in the ventral spinal cord of the E14 rodent, but following exposure to EGF and FGF-2, significant numbers of oligodendrocytes and A2B5+ precursor cells also develop from isolated E14 dorsal derived cells without interaction from the ventral spinal cord. In addition, bromodeoxyuridine studies demonstrate that isolated dorsal derived cells proliferate and express A2B5 following exposure to EGF and FGF-2. The observation that from E14, the dorsal cord already has latent oligodendrogenic potential provides an alternative mechanism for oligodendrocyte formation to ventro-dorsal migration of oligodendrocyte precursors.