Fig. 6. Fragilis2-silenced embryos mimic the somite phenotype of the ß-catenin mutants. (A,B,D) Embryos are depicted in a dorsal view; anterior is up. Comparison of wild-type and Fragilis2-silenced embryos at E8.75 (A) and E8.5 (B) demonstrates abnormal development in the posterior region, formation of a large allantois (al), a kinked neural tube and abnormal somite formation (magnified in b' and b''). (C) Comparison of Hematoxylin and Eosin-stained frontal sections of wild-type and Fragilis2-silenced embryos at E8.5. (D) Tissue non-specific alkaline phosphatase (AP) staining to detect primordial germ-cell (PGC) formation at head-fold stage. Embryos are depicted in a posterior view, focusing on the embryonic-extraembryonic border. (E) Whole-mount in situ analysis of wild-type and Fragilis2-silenced embryos with the indicated probes at the 2- to 3-somite stage (upper panels; posterior view, posterior is up) and the 9- to 10-somite stage (lower panel; dorsal view, posterior is down). T and Tbx6 are normally expressed in Fragilis2-silenced embryos at 2-3 somite stage, but expression is slightly reduced at the 9- to 10-somite stage in the tailbud region. In wild-type embryos, PAPC is expressed in two presomitic stripes (s0 and s-1). At the 2- to 3-somite stage, only one presomitic stripe is clearly visible in knock-down mutants, and PAPC expression further diminishes at the 9- to 10-somite stage.