Figure 3.
Sox2βgeo mutant embryos lack epiblast. (A–H) Histological and marker analysis of 6.0-dpc embryos from Sox2βgeo intercrosses. (A,C,E,G) Normal embryos. (B,D,F,H) Mutant embryos. Sections were stained with haemotoxylin and eosin (H & E) in A and B. RNA in situ hybridization was performed for H19 (extraembryonic marker; C,D), Oct4 (epiblast marker; E,F), and Evx1 (VE marker; G,H). 35S-UTP-labeled probes were used for H19 and Oct4, and sections were counterstained with methyl green. A DIG-labeled probe was used for Evx1. The arrows shown in the main panel and inset of G refer to the same region. Evx1 staining in the wild-type embryo is distal to the embryonic/extraembryonic border as expected (G) and appears more punctate because the cells are flatter than those in the mutant embryo (H). Sox2βgeo null embryos form disorganized extraembryonic tissues, but do not form epiblast. Bars: A,B, 50 μm; C–F, 65 μm; G (inset), 75 μm; G,H, 30 μm.