Fig. 7. Forebrain phenotype in knock-in mutants; loss of commissural region of pretectum. (A,B) Parasagittal sections of 12.5 dpc wild-type (A) and knock-in embryos (B) stained with Hematoxylin and Eosin. 1, ventral thalamus; 2, dorsal thalamus; 3, anterior pretectum; and 4, posterior pretectum. The area of low cell density indicated as 4 in A is not apparent in the knock-in mutant (B). (C-R) Analyses with forebrain markers in wild type (C,E,G,I,K,M,O,Q) and in knock-in mutants (D,F,H,J,L,N,P,R). Endogenous Emx2 (C,D), Emx1 (E,F), Wnt7b (G, H), Tcf4 (I, J), Gbx2 (K,L), Pax6 (M-P), Lim1 (Q,R) expression in whole-mount (C-J,M,N,Q,R) and in midsagittal (K,L,O,P) views at 9.5 dpc (G,H), 10.5 dpc (C-F,I,J,M,N,Q,R) and 12.5 dpc (K,L,O,P). (S,T) Midsagittal views of anti-GAP43 staining of 12.5 dpc wild-type and knock-in embryos, respectively. Arrows in G-J,M,N indicate the caudal limits of the expressions, arrowheads in G,H indicate the anterior end of the midbrain, arrowheads in O,R indicate expression in the posterior pretectum and in the tegmentum, respectively. Asterisks in S indicate the anti-GAP43-positive posterior commissure. Scale bars: 250 µm.