Fig. 2. Morphology and gene expression in differentiating pluripotent cells in vitro and in vivo. (A) EBM⁷ and (B) EBM⁹ viewed using Hoffmann interference contrast microscopy. (C) 7 µm section of an EBM⁹ aggregate stained with haemotoxylin and viewed using Hoffmann interference contrast microscopy. Size bars: 210 µm. (D) Northern blot analysis of 20 µg RNA isolated from EB^4-8 and EBM^4-8 probed for Oct4 and mGAP. (E) Whole-mount in situ hybridisation analysis of an EBM⁷ aggregate seeded and cultured for a further 24 hours and probed with a digoxigenin-labelled antisense probe to Oct4. Size bar: 210 µm. (F,G) 10 µm transverse section of a 7.75 d.p.c. mouse embryo probed with a radiolabelled antisense probe to Oct4 viewed in brightfield (F) and darkfield (G) illumination. A concentration of silver grains can be seen over the neural ectoderm (black arrow). Mesoderm (outlined arrow).