Fig. 2: Calcium transients are indispensable for MCC apical emergence.

A Representative images of control and 2APB treated skin epithelium of stage 24 embryo. 2APB treatment started at stage 15. MCCs have successfully inserted into the skin epithelium of control embryos. MCCs apical emergence is defective in 2APB treated embryos, with MCCs failing to acquire an apical surface area (arrows). B Quantification of MCC epithelial insertion. Two-sided unpaired student’s t test; ****P <  0.0001; mean ± SEM. n = 39 positions from 24 control embryos and 27 positions from 15 2APB treated embryos. C Representative images of control and 2APB treated stage 24 embryos expressing atub:UtrGFP. D Representative images of MCCs in control and 2APB treated embryos showing anchoring at high-order vertices. E Quantification of the vertex type occupied by MCCs in 3 control and 3 2APB treated embryos. Two-sided χ² test shows no significant statistical differences (ns). F Representative images of control and 2APB treated skin epithelium of stage 24 embryo. 2APB treatment started at stage 19. MCCs in 2APB treated embryos insert the epithelium but fail to fully expand their surface area (white arrowheads). G Quantification of MCC apical surface area. Two-sided unpaired student’s t test; ****p <  0.0001; mean ± SEM. n = 150 MCC from 5 control and 5 2APB treated. H Schematic regarding the role of intracellular Ca²⁺ in the distinct steps of MCCs apical emergence. Scale bars: 20 μm. Source data are provided as a Source data file. Xenopus embryo illustrations, ©Natalya Zahn (2022).