Fig. 5. Onset of double mutant defects. (A-D,M-P) Otx2, (E-H) Emx2, (I-L,Q-V) Pax2 and Gbx2 (W,X) expression at the three- (A,B,E,F,I,J,M,N,Q,R) and four- (C,D,G,H,K,L,O,P,S-X) somite stages. (A-L,U,W) Wild-type embryos and (M-T,V,X) Emx2^-/-Otx2^+/- embryos. (A,C,E,G,I,K,M,O,Q,S,W,X) Lateral views; (B,D,F,H,J,L,N,P,R,T) dorsal views; and (U,V) frontal views. Arrows denote the posterior limit and arrowheads the anterior limit of expressions. In S,T, arrows and double arrows indicate the posterior limits of expression in the most medial (future ventral) and lateral (future dorsal) points, respectively; the double arrows coincide with preotic sulcus. Broken lines in U,V indicate the anterior end of the neural plate. In W,X, arrows indicate the anterior limit of the expression, single arrowheads preotic sulcus and double arrowheads otic sulcus. Scale bars: 150 µm.