Fig. 8. BMP4 effect on E6 neuroepithelial explants. Ventral neuroepithelial explants were dissected from E6 embryos, i.e. just after oligodendrocyte induction has occurred. They were grown for 2 days in the absence (A) or presence (B) of 0.6 nM BMP4. (A) Control explant. E6 ventral neuroepithelial explants generate numerous O4-positive cells. (B) Upon BMP4 treatment, explants generate reduced numbers of O4-positive cells. (C) Quantification of the number of O4-positive cells developing in ventral neuroepithelial explants. Bars represent the mean±s.e.m. of at least 17 separate explants. At this stage, BMP4 treatment does not totally block O4-positive cell production.