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. 2003 Feb 14;100(5):2468–2473. doi: 10.1073/pnas.0434312100

Figure 2.

Figure 2

Morphological abnormalities of Rnf2-KO embryos. (a) A normal day-7.5 embryo (Left) at the late headfold stage; neural folds are visible. Three smaller Rnf2-KO embryos (Right) manifest a characteristic phenotype. (b) Gene expression analysis in pre/early streak stage embryos (E6.2). The Rnf2-HE embryo is at early streak stage; the WT and KO embryos are prestreak. The early anterior visceral endoderm (AVE) marker Cer1 is expressed in all Rnf2 genotypes. Cer1 expression is normally restricted in the KO embryo on the left, whereas it is abnormally localized in the KO on the right. Posterior is to the right; marker line: boundary extraembryonal (up)/embryonal tissue. (c) Histological and gene expression analysis of Rnf2-KO embryos confirms a significant delay in embryonic development. Posterior is to the right (A–D) or to the upper right (E–J); embryonic mesoderm (white arrowhead), embryonic ectoderm (black arrowhead), and allantois (asterisk) are indicated. (A and B) Sagittal sections of embryos at E7.5. Mesoderm has expanded all around the WT egg cylinder (A). am, amnion; ch, chorion. Rnf2-KO embryos show improper epiblast elongation and accumulation of posterior mesoderm (B). amf, posterior amniotic fold. (C–J), Transverse sections of embryos analyzed for Hoxb1 (C, E, G, and I) and Brachyury T (D, F, H, and J) gene expression at E7.5 (C–F) and E8.5 (G–J). Sections G–J are from the same embryo; sections H, G, J, and I are progressively more proximal, with J being at a level passing through the base of the allantois and transecting the proximo-posterior part of the amniotic cavity (the amnion is closed). Hoxb1 expression at E7.5 (C and E) is not yet initiated in the homozygous mutant embryo (E), whereas it is expressed in the posterior epiblast along the primitive streak and in nascent mesoderm in the WT (C; ref. 61). Brachyury T (D and F) is expressed in the mesoderm and ectoderm of the primitive streak in both WT and KO embryos, although it is weaker in the latter. (G–J) In E8.5 Rnf2-KO embryos (G and I) Hoxb1 is expressed in the accumulated posterior mesoderm and in the ectoderm of the primitive streak (G) but not in extraembryonic mesoderm of the allantois (I); Hoxb1 expression does not extend until the anterior end of the primitive streak. A weaker Brachyury T expression is visible in the epiblast and nascent mesoderm of the primitive streak (H) and in extraembryonic mesoderm at the base of the allantois (J) of the Rnf2-KO embryo. Note the posterior accumulation of mesoderm in the KO embryo (G and H). (Bar in J, ±0.1 mm.)