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Figure 2. Ion pump genes expressed in Xenopus. A variety of known ion channel and pump genes are also expressed during early Xenopus embryogenesis. Clones with specific expression patterns are shown here at representative stages. A: Sense probe controls show no signal. B: A probe for the maternal gene Xombi shows that whole-mount in situ hybridization can detect vegetal mRNA localization when it is present (arrow). C: Sectioning perpendicular to the animalegetal axis of a four-cell embryo stained in whole-mount in situ hybridization with a probe for the Ac45 V-ATPase subunit EST and embedded in JB4 shows (arrowheads) nuclear mRNA in the center of cells, as well as cytoplasmic mRNA. D,E: The neural β3 subunit of the Na+/K+ ATPase is detected at st. 11 in cells around the ventral margin of the blastopore (arrows). F: At st. 32, it is detected in the neural tube and in the posterior gut (arrows). G: Maternal mRNA encoding a subunit of the H+ pump (V-ATPase) is present throughout the animal hemispheres of the four-cell embryo (arrows). H: It is later expressed throughout the neural tube and head of the tail bud stage embryo (arrows). I: mRNA for the H+/K+-ATPase (ion exchanger) is present in a more laterally restricted region of the two-cell embryo (arrow). J: mRNA for the 16-kDa proteolipid component of the H+ synthase is expressed in bilateral stripes of deep tissue ventral to the neural tube, demonstrating that signal along the length of the neural tube and in the head is not obligatory or artifactual at tail bud stages. Red arrows indicate expression; white arrows indicate regions of no detectable expression. G is a photograph of the internal surface of two blastomeres of a four-cell embryo manually separated after in situ hybridization. I is a view of the internal surface of one blastomere of a two-cell embryo. |
