Fig. 6. Region-specific deletion of Lmx1b in the MHB by Wnt1-Cre conditional knockout and its effect on gene expression. (A,B) Whole-mount in situ hybridization showing inactivation of Lmx1b in the MHB at the 6-somite stage (B, arrow) by the Wnt1-Cre recombination method. (C-J) Expression (arrows) of Fgf8 (D), Wnt1 (F), Pax2 (H) and En1 (J) was lost in the isthmus of Lmx1b^w CKO embryos at E9.5. Normal expression (arrows) patterns of each gene in the control (C,E,G,I) are shown for comparison. (K,L) Decreased expression of En2 in the MHB of the Wnt1 Lmx1b^w CKO embryo at E9.5 (arrow, L) as compared with that in the control (arrow, K). (M,N) The expression of Gbx2 of the Lmx1b^w CKO embryos was lost in the isthmus (N, arrow) but normal in the otic vesicle (N, arrowhead) as compared with the control embryo (M). (O,P) Otx2 expression and the rostral-caudal distance of the midbrain (double-arrowed line) were normal in the conditional knockout embryo (P) as compared with the control embryo (O).