Fig. 1. Morphogenetic defects in Nap1^khlo mutant embryos. (A,B) Mox1 expression marks the somites and presomitic mesoderm of wild-type E8.5 embryos (A) and reveals the small somites of E8.5 Nap1^khlo embryos (B). (C-F) Brachyury (T) expression marks the primitive streak and notochord in E8.5 wild-type (C,E) and Nap1^khlo (D,F) embryos. In the mutant, the primitive streak (arrow) was distended and the allantois failed to fuse with the chorion (asterisk). The notochord (arrowhead) appeared normal in Nap1^khlo mutants. (G,H) The pancardiac marker Nkx2.5 was expressed in a single heart in wild-type embryos (G) and in the two lateral heart domains in Nap1^khlo mutant embryos (H). Anterior is to the left in all panels.