Fig. 3. Defects in telencephalon formation and regionalization of the diencephalon in Fez^-/-Fezl^-/- embryos. Expression of Emx2 (A-D), Pax6 (E-H), Dlx1 (I-L), Shh (M-P), Tcf4 (Q-T) and Lhx5 (U-X) in control (A,E,I,M,Q,U), Fez^-/-Fezl^+/- (B,F,J,N,R,V), Fez^+/-Fezl^-/- (C,G,K,O,S,W) and Fez^-/-Fezl^-/- embryos (D,H,L,P,T,X) at E10.5. (A-T) Whole-mount in situ hybridization and lateral views of anterior neuroectoderm, with anterior to the left. (U-X) Coronary sections of the diencephalon. Emx2 expression in the dorsal telencephalon was reduced in Fez^-/-Fezl^-/- embryos. Pax6 expression was downregulated in the thalamus at this stage (marked by dots, E,F,G) in control, Fez^-/-Fezl^+/- and Fez^+/-Fezl^-/- embryos, but not in Fez^-/-Fezl^-/- embryos (arrow, H). The expression domain of Pax6 in the dorsal telencephalon was reduced but not significantly affected in the diencephalon except for the thalamus (region between arrowheads) in Fez^-/-Fezl^-/- embryos. Dlx1 expression was detected in the ganglionic eminence (arrow, I,L) but not in the prethalamus (arrowhead, I,L) in Fez^-/-Fezl^-/- embryos. Shh expression was detected in the AEP, but not in the ZLI in Fez^-/-Fezl^-/- embryos (arrow, P), compared with controls (M-O). The domain expressing Tcf4 at a high level (thalamus and pretectum region, marked by dots) was expanded in Fez^-/-Fezl^-/- embryos (T), compared with controls (Q-S). Lhx5 expression was abolished in the prethalamus of Fez^-/-Fezl^-/- embryos (X). ht, hypothalamus; pth, prethalamus; th, thalamus.