Fig. 6. Grafts of noggin-producing cells cause ectopic OLPs development in the neuroepithelium. Pellets of noggin-overexpressing CHO cells were implanted at E3 between neural tube and somites. Embryos were fixed at E7-7.5 and transverse sections were stained with O4 antibody. (A) Control section showing the normal appearance of O4-positive OLPs in the ventral ventricular zone. (B) Section at the level of the graft in an operated embryo. Note the dorsal enlargement of the O4-positive ventral ventricular zone on the grafted side (bracket), while the contralateral side displays normal development of O4-positive cells. (C,D) Section at the level of graft in another operated embryo. (C) Darkfield/fluorescence view. CHO cells (red) are found dispersed all along the neural tube. (D) Confocal image at higher magnification of the area boxed in C. The O4⁺ ventricular zone is enlarged on the operated side compared with the contralateral side (brackets). Note also the presence of an ectopic neuroepithelial O4-positive cell located dorsal to the normal level of origin of OLPs (asterisks in C and D).