Fig. 3. MHB abnormalities in En1^cre/+; Otx2^flox/flox embryos. (A-W) In situ hybridisation on E9.5 and E10.5 En1^cre/+ and En1^cre/+; Otx2^flox/flox embryos with Otx2 (A,I,Q), Fgf8 (B,J,R), Gbx2 (C,K,S), Wnt1 (D,L,T), Otx1 (E,M,U), En1 (F,N,V), Otx2-5' (G,O,W) and Pax6 (H,P) probes. (X) Schematic representation summarising MHB abnormalities detected in En1^cre/+; Otx2^flox/flox embryos. The parasagittal section in Q-W is focussed on the ventral midbrain of conditional mutants and approximately corresponds to the area included in the dotted square in J. In conditional mutant embryos, the arrows in A,C-H,I,K-Q,S-W indicate the corresponding position of the ventralmost expression of Fgf8, while the arrows in B,J,R indicate the corresponding position of the ventral and posterior border of the functional Otx2 domain (Otx2). The curved arrows in J,K,N,X indicates the dorsal and anterior rotation of the MHB whose ventral site remains in a fairly normal position; the arrowheads in A,B,E,F,I,J,M,N indicate the posterior border of Pax6; and the arrowheads in Q,U,W indicate the ventral midbrain area lacking functional Otx2 transcripts (Otx2) but still transcribing Otx1 and Otx2 (Otx2-5'). (X) Red, green, orange and yellow correspond to the hindbrain, posterior midbrain, anterior midbrain and forebrain, respectively. MHB, midbrain-hindbrain boundary; Pt, pretectum; Fb, forebrain; Mb, midbrain; Hb, hindbrain.