Dorsal spinal cord inhibits oligodendrocyte development.

Oligodendrocytes are the myelinating cells of the mammalian central nervous system. In the mouse spinal cord, oligodendrocytes are generated from strictly restricted regions of the ventral ventricular zone. To investigate how they originate from these specific regions, we used an explant culture system of the E12 mouse cervical spinal cord and hindbrain. In this culture system O4(+) cells were first detected along the ventral midline of the explant and were subsequently expanded to the dorsal region similar to in vivo. When we cultured the ventral and dorsal spinal cords separately, a robust increase in the number of O4(+) cells was observed in the ventral fragment. The number of both progenitor cells and mature cells also increased in the ventral fragment. This phenomenon suggests the presence of inhibitory factor for oligodendrocyte development from dorsal spinal cord. BMP4, a strong candidate for this factor that is secreted from the dorsal spinal cord, did not affect oligodendrocyte development. Previous studies demonstrated that signals from the notochord and ventral spinal cord, such as sonic hedgehog and neuregulin, promote the ventral region-specific development of oligodendrocytes. Our present study demonstrates that the dorsal spinal cord negatively regulates oligodendrocyte development.