Expression of CheSox1, CheSox3, CheSox10 and CheSox12 in non-fertilised eggs and two-day planulae. (A-D) In non-fertilised eggs (animal pole on the top indicated by a white star), CheSox1 transcripts (A) are detected around the nucleus at the animal pole whereas CheSox3 (B), CheSox10 (C), CheSox12 (D) transcripts are homogeneously distributed throughout the egg cytoplasm. (E-H) Gene expression in two-day planula larvae. The stained cells are endodermal and their aspect is similar for CheSox1 (E), CheSox3 (F) and CheSox12 (H). In contrast, CheSox10 (G) is expressed in ectodermal basi-epithelial cells distributed throughout the oral-aboral axis but particularly concentrated at both poles. All planulae have the same orientation, with oral pole (= posterior pole) on the top. (I-L) Higher magnification views corresponding to the boxed areas in E to H. Stained cells in I, J and L have the typical aspect of interstitial cells. CheSox10 is expressed in small cells forming a dense basi-epithelial population (black arrowheads). The boundary between ectoderm (ect) and endoderm (end) is indicated by a dotted line in I, J, L. This boundary cannot be placed in K because the optical plane is more superficial (ectoderm throughout the picture). (K') Higher magnification picture corresponding of the boxed area in K, showing two neighbouring stained cells, with typical neuronal morphology. Scale bars: A-H, 50 μm; I-L, 10 μm; K', 2 μm.