Fig. 1

 Isolation, mapping, and functional characterization of cdx1a. (A) Predicted peptide alignment of Cdx1 proteins from zebrafish, X. tropicalis, chicken, and human. The sequence of the homeodomain is underlined in red. (B) Genetic and radiation hybrid map positions of cdx1a showing syntenic relationships with human chromosome (Hsa) 5q31–33. (C) Expression of cdx1a (purple) by whole mount in situ hybridization from 50% epiboly (early gastrula) to 48 h post-fertilization (hpf). Embryos in the top panels are oriented with their dorsal side to the right; all others are shown with anterior to the left. Embryos at the 3- and 10-somite stages have been flatmounted and are shown in dorsal views. Transcripts for scl at the 3-somite stage are stained red. Arrowhead indicates expression of cdx1a in the intestinal bulb at 48 hpf (shown in dorsal view). (D) Expression of cdx1a in a control-injected wild-type, cdx1a morphant, cdx4 mutant, and an embryo doubly deficient for cdx1a and cdx4. Arrows indicate the anterior boundary of the cdx1a expression domain in the paraxial mesoderm. (E) Morpholino-mediated knockdown of cdx1a. Images of live embryos injected with cdx1a morpholinos (cdx1a^mo;cdx4^+/− and cdx1a^mo;cdx4^−/−) or mis-match control morpholinos (wild type and cdx4^−/−) at 24 hpf. Embryos are shown in lateral views with anterior to the right. Abbreviations: lat., lateral view; veg., vegetal view; tb, tailbud.