Fig. 2. Defects in prethalamus and thalamus development and rostral expansion of the pretectum in Fez^-/-Fezl^-/- embryos at E12.5. A-T) Expression of Dlx1 (marker for prethalamus and ganglionic eminence, A-D), Gbx2 (thalamus, E-H), Lhx1 (posterior pretectum and ZLI, I-L), Ebf1 (anterior pretectum, M-P) and Sox14 (rostral domain of thalamus, Q-T) in control, Fez^-/-Fezl^+/-, Fez^+/-Fezl^-/- and Fez^-/-Fezl^-/- embryos was analyzed by in situ hybridization. Sagittal sections with anterior to the left. Dlx1 expression was not detected in the prethalamus but was maintained in the hypothalamus and ganglionic eminence in Fez^-/-Fezl^-/- embryos (D). Gbx2 expression was strongly reduced and detected in patches (arrows in H) in Fez^-/-Fezl^-/- embryos. Lhx1 expression was absent in the ZLI, but was not significantly affected in the posterior pretectum of Fez^-/-Fezl^-/- embryos (I-L). The expression domain of Ebf1 was expanded rostrally in Fez^-/-Fezl^-/- embryos (P), compared with that in the wild-type, Fez^-/-Fezl^+/- and Fez^+/-Fezl^-/- littermates (M-O). The expression of Sox14 was abolished in Fez^-/-Fezl^-/- embryos (T). apt, anterior pretectum; GE, ganglionic eminence; ht, hypothalamus; ppt, posterior pretectum; pth, prethalamus; th, thalamus.