Fig. 4. Reduction of rostral diencephalon and expansion of caudal diencephalon in Fez^-/-Fezl^-/- embryos at E9.5. Expression of Emx2 (A,B), Pax6 (C,D), Fgf8 (E,F), Wnt3a (G,H) and En2 (I,J) in control (A,C,E,G,I) and Fez^-/-Fezl^-/- embryos (B,D,F,H,J) was analyzed by whole-mount in situ hybridization. Lateral views of anterior neuroectoderm, with anterior to the left. Expression of Emx2 (A) and Pax6 in the dorsal telencephalon (between arrowheads, C) was reduced, but the Pax6 expression in the diencephalon (marked by dots) was maintained in Fez^-/-Fezl^-/- embryos. Fgf8 expression in the commissural plate and mid-hindbrain boundary was maintained, but that in the dorsal prethalamus was absent (arrowheads E,F) in Fez^-/-Fezl^-/- embryos. The expression domain of Wnt3a was caudal to the ZLI in control embryos (G) and was expanded rostrally in Fez^-/-Fezl^-/- embryos (arrow in H). Expression of En2, which marks the midbrain, was not affected in Fez^-/-Fezl^-/- embryos (I,J). cp, commissural plate; mhb, mid-hindbrain boundary; pth, prethalamus.