Larval expression of Ct-runt. Stages are marked in the lower left corner of each panel. Anterior is to the left for all panels. All panels are ventral views except for E and J, which are lateral views with ventral down. An asterisk marks the position of the mouth. (A) Ct-runt expression in the brain (arrows). (B,C) Two different focal planes of the same animal showing expression in the brain (B) and ventral nerve cord in anterior segments (long arrows in C). Short arrows point to expression in ventrolateral ectodermal cells. (D) Epi-fluorescence view showing position of medial (long arrows) and lateral-expressing cells (short arrows) within each segment. (E) Arrowhead and arrow mark discrete clusters of Ct-runt-expressing cells visible within a single focal plane in the brain. (F) Arrowheads show nervous system expression extending along the length of the ventral nerve cord. (G) Enlarged view of the posterior body of the larva shown in F. Arrows point to expression in the ectoderm of the PGZ. (H) Expression becomes restricted to a single small cluster in the brain (arrows) and in a small lateral domain of mesoderm (arrowheads). (I) At late Stage 7, Ct-runt is transiently expressed in the foregut (large arrow). There is also expression in the PGZ (short arrows) and the anterior head ectoderm (diagonal arrows). (J) Foregut expression is in the pharynx (large arrow). PGZ expression is ventrally localized (short arrow). Long arrow points to anterior head expression. (K) Expression is restricted to the PGZ at Stage 8 (short arrows). (L) Arrow indicates prominent expression in the hindgut of a late stage larva. tt: telotroch.