Fig. 3. Tc-ASH exhibits a proneural expression pattern while Tc-ase expression is restricted to neural precursors. (A-D) Ventral views of 20-hour Tribolium embryos. (A,B) Tc-ASH in situ hybridization (blue) and Engrailed protein (brown). (C,D) Tc-ase in situ hybridization (blue) and Engrailed protein (brown). (A) Tc-ASH is expressed in cell clusters in developmentally younger segments at the posterior (arrow); in developmentally older anterior segments Tc-ASH expression has resolved to single cells, the CNS neural precursors (arrowhead). In each segment Tc-ASH is expressed in a transverse stripe posterior to the engrailed stripe (asterisk). (B) High magnification view of two segments that shows Tc-ASH expression in proneural clusters (arrow) and single neural precursors (arrowhead). (C) Tc-ase is expressed in neural precursors (arrowhead) but not in ectodermal cell clusters. Tc-ase staining is not detected outside of the neuroectoderm (asterisk). (D) High magnification view of two segments showing Tc-ase expression. Note the position of Tc-ase-expressing neural precursors in D is identical to that of the large Tc-ASH expressing cells in B. Scale bars: 100 µm (A,C); 25 µm (B,D). Images in A and C are photomontages. Anterior, left.