Fig. 3

Ct-soxB is expressed in regions overlapping Ct-soxB1 expression. a–p Ct-soxB transcripts were detected in stage 3–6 animals using WMISH. The scale bar in (a) is 40 µm; all other images are to the same scale unless otherwise noted. Arrows in (a–c) indicate expression in the anterior neuroectoderm. Arrows in (e) and (f) point to pygidial expression. Arrowheads in (m) and (p) point to Ct-soxB ⁺ cells in the VNC. White arrowheads in (m)–(o) point to ventrolateral rows of Ct-soxB ⁺ cells in the ectoderm. Arrows in (n) and (o) indicate lateral ectodermal patches of Ct-soxB1 expression. Black arrowhead in (o) denotes a circumferential ring of cells posterior to the prototroch. In each panel, the stage of the animal is indicated in the lower left, and the view is indicated in the lower right (lat lateral, vlat ventrolateral, vent ventral, ant anterior). In all lateral and ventrolateral views, anterior is to the left and ventral down; in all ventral views, anterior is to the left; and in all anterior views, ventral is down. Panels (h) and (l) are cropped images of the episphere from a ventral view. An asterisk marks the position of the mouth, and the prototroch (pt) and telotroch (tt) are labeled with dashes. In (h) and (l), the prototroch is denoted using dashes. ST3epi, stage 3 epiboly; STBPclg, stage 3 blastopore closing