Figure 1. Whole-Mount lmmunolocalization Showing That XlHbox 1 Protein Is Expressed in a Circular Band of Cells in the Xenopus Embryo (A) Lower-power photograph of a day 3 embryo viewed from the side. (6) Same embryo, dorsal view, with plane of focus showing nuclear staining in the anterior spinal cord. (C) Same as (B), but with focal plane showing staining in a circular belt of cells through the lateral plate mesoderm. Note that the regions of expression in the CNS and mesoderm have the same A-P borders. Thus, like their Drosophila counterparts, vertebrate homeobox genes subdivide the embryo into A-P fields of expression. Whole-mount staining was performed with an antibody specific for the full-length XlHbox 1 protein (antibody C of Oliver et al., 1988) according to the procedure of Dent et al. (1989).