Fig. 4. Diencephalic gene expression is altered in the absence of Fgf8 and Fgf3. Lateral views of embryos bisected along the AP axis and with eyes removed (A-D,E-P), frontal (A'-D') or dorsal (Q-T) views. (A-D) shh expression at 30 hpf. Embryos mounted to show internal surface of the brain. shh is expressed in the ventral midline of the brain, anterior hypothalamus and ZLI in control embryos (A). shh expression is unaffected in embryos injected with Fgf8mo (B), is slightly reduced after injection of Fgf3mo (C), but is reduced throughout the brain, especially in the hypothalamus (arrow) and ZLI, when both Fgf3mo and Fgf8mo are injected (D). (A'-D') As A-D, but frontal views with the ZLI in focus. Arrows indicated the dorsal extent of shh expression. shh expression in the ZLI extends into the dorsal diencephalon in control (A') and Fgf8mo-injected (B') embryos. Dorsal shh expression in the ZLI is severely reduced in embryos injected with either Fgf3mo (C'), or both Fgf8mo and Fgf3mo (D'). (E-H) nk2.1b expression at 30 hpf. nk2.1b is expressed in the subpallial telencephalon, anterior ventral thalamus and hypothalamus in control embryos (E). Expression is unaffected in embryos injected with Fgf8mo (F). Ventral thalamic expression is reduced in embryos injected with Fgf3mo (arrowhead; G), and absent (arrowhead) in embryos injected with both Fgf8mo and Fgf3mo (H). (IL) twhh expression at 30 hpf. twhh is expressed in the anterior ventral thalamus (arrowhead) in control embryos and those injected with either Fgf8mo (J) or Fgf3mo (K), but not in those co-injected with Fgf8mo and Fgf3mo (arrowhead; L). (M-P) pax6.1 expression at 28 hpf. In control embryos pax6.1 is expressed in the telencephalon, posterior ventral thalamus and dorsal thalamus (M). Expression is unaltered following injection with Fgf8mo (N). pax6.1 expression domains are smaller and merged following injection with either Fgf3mo (O), or both Fgf8mo and Fgf3mo (P). (Q-T) pax2.1 expression in developing optic stalks (and isthmic region) at 18 hpf. Two well-separated optic stalks are present in control embryos (Q). A slight reduction in pax2.1 expression is detected in embryos injected with Fgf8mo (R), whereas expression is relatively normal in embryos injected with Fgf3mo (S). The pax2.1 expression domains are fused (arrowhead) in embryos injected with both Fgf8mo and Fgf3mo (T). dt, dorsal thalamus; h, hypothalamus; os, optic stalk; vt, ventral thalamus; zli, zona limitans intrathalamica.

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