Expression of CheSox5, CheSox13, CheSox15, CheSox14 , and CheSox2 in non-fertilised eggs and two-day planulae. (A-E) In non-fertilised eggs (animal pole on the top indicated by a white star), CheSox5 (A), CheSox14 (D) and CheSox2 (E) are homogeneously expressed throughout the egg cytoplasm. Restricted expression around the nucleus at the animal pole was obtained for CheSox13 (B), while no transcripts were detected for CheSox15 (C). (F-J) Expression in 2-day planula (oral pole on the top). CheSox5 (F), CheSox14 (I) and CheSox2 (J) are expressed in endodermal cells concentrated in the oral half of the larva. CheSox13 transcripts (G) are present in basi-epithelial ectodermal cells, essentially in the oral half of the planula. CheSox15 (H) is expressed at two different sites: in ectodermal cells at the aboral pole, and in ectodermal and endodermal cells of the oral half of the larva. (K, L, M, O, P) Higher magnification views of the areas boxed in black in F to J reveal the presence of a round non-stained capsule within the cytoplasm of positive cells, for each of the five Sox genes (black arrows), indicating that these cells correspond to maturating nematoblasts. (N) Higher magnification view of the area boxed in white in H. This area is rich in cells whose cytoplasm is densely filled with granules, some of these cells being stained with the CheSox15 riboprobe (white arrow) while others are deprived of any signal (grey arrow). The boundary between the ectodermal (ect) and endodermal (end) layers is indicated by a dotted line in K, L, N, O, P. Scale bars: A-J, 50 μm; K-P, 10 μm.