Local control of oligodendrocyte development in isolated dorsal mouse spinal cord

The earliest oligodendrocyte precursors have been proposed to arise in the ventral ventricular zone of the embryonic thoraco-lumbar spinal cord and su bsequently migrate to populate dorsal spinal cord. Using the expression of O4 immunoreactivity to define cells of the oligodendrocyte lineage, the dev elopment of oligodendrocytes in different regions of the mouse spinal cord was assayed. Consistent with earlier studies in other species, isolated exp lants of Ell ventral but not dorsal mouse spinal cord developed oligodendro cytes after 7 days in vitro. In contrast, in cultures derived from E13 embr yos O4(+) oligodendrocytes developed in both ventral and dorsal cultures af ter 5 days in vitro. These data ave consistent with a ventral to dorsal mig ration of committed oligodendrocyte progenitors occurring between Ell and E 13. Although isolated early embryonic dorsal spinal cord does not give vise to oligodendrocytes in short term cultures, in long term cultures O4(+) ce lls develop in a subset of dorsal explants. After 10 days in vitro approxim ately 25% of both cervical and thoraco-lumbar Ell derived dorsal explants c ontained significant numbers of O4(+) cells. The molecular requirements for the dorsally-devived oligodendrocytes was similar to that in ventral cord. The appearance of O4(+) cells was dependent on sonic hedgehog and enhanced by neuregulin. These data suggest that early embryonic dorsal mouse spinal cord has an independent potential to generate oligodendrocytes under appro priate conditions. Whether this potential is realized during normal spinal cord development is currently unknown. (C) 2000 Wiley-Liss, Inc.