Figure 1: mab21-l3 expression in Xenopus embryonic epidermis.

(a) Whole-mount in situ hybridization combined with double immunostaining indicates that mab21-l3 is strongly expressed in α-ionocytes and weakly expressed in MCCs at stage 31. Left panels are lateral views. Anterior is to the left and dorsal is upwards. Right panels are magnified images of the epidermis. mab21-l3 mRNA-expressing cells detected with in situ hybridization are dark blue. MCCs and α-ionocytes were identified by staining with anti-acetylated α-tubulin (red) and anti-ae1 (green) antibodies, respectively. Yellow arrowheads show MCCs weakly expressing mab21-l3. Black arrowheads show α-ionocytes strongly expressing mab21-l3. Essentially the same results were obtained in 19 embryos from five independent experiments. Scale bars, 500 μm (left panels) and 50 μm (right panels). (b) mab21-l3 is initially expressed in the inner cell layer, but later expressed in the outer cell layer, of Xenopus embryonic epidermis. The left panels show vertical sections of embryos processed for whole-mount in situ hybridization against mab21-l3. The right diagram shows the current model for MCC and ionocyte specification. In all panels, apical is at the top. Scale bars, 40 μm. Essentially the same results were obtained in two to five embryos of each stage from one to three independent experiments.