Synergicistic effects of HH and FGF signaling on otp1 expression in the PO cluster. Anterior is left and dorsal is up in all panels. Eyes have been removed in A. All embryos are 28 hpf and have been double stained with otp1 riboprobe and anti-acetylated α-tubulin (TU) antibody. Compared with the wild-type PO (A), the anterior otp1 cluster is expanded and reduced, respectively, in ace (B) and syu (C), but its normal size is rescued in double ace; syu mutant embryos (D). cf, cephalic flexure; dt, dorsal thalamus; h, hypothalamus; po, preoptic area; pt, posterior tuberculum; sot, supraoptic tract; t, telencephalon; tac, tract of the anterior commissure; tpoc, tract of the postoptic commissure; vt, ventral thalamus.