Fig. 4. Analysis of Fgf8, Wnt1, En1 and Pax2 expression in the MHB of Lmx1b^-/- embryos. (A-D) Whole-mount in situ hybridization showing the absence of Fgf8 expression in the MHB at the 4-somite stage (B, arrow) and in the isthmus at E9.5 (D, arrow) in the Lmx1b^-/- embryo. Note that Fgf8 expression in other areas of the mutant embryo (B, arrowhead) was normal as compared with that in the wild-type embryo (A, arrowhead). (E-H) Lmx1b deletion resulted in reduced Wnt1 expression in the MHB at the 3-somite stage (F, arrow) and the loss of Wnt1 expression in the isthmus at E9.5 (H, arrow) as compared with that in the wild-type brain (E,G). Note that Wnt1 expression in the roof plate was maintained in the mutant brain at E9.5 (H). (I-L) Lmx1b deletion caused a marked reduction in En1 expression in the MHB at the 3-somite stage (J, arrow) and the loss of En1 expression at E9.5 (L, arrow), as compared with that in the control (I,K). (M-P) Lateral view of embryos showing similar changes in Pax2 expression (arrows) to those found for En1 (I-K).