Fig. 2. Ventral telencephalic defects in Vax1 mutant brains. Coronal sections from wild-type (A,C,E,G,I,K,M,O) and Vax1 knockout (B,D,F,H,J,L,N,P) E13.5 embryos. The expression of several pallial and subpallial markers has been analyzed by RNA in situ hybridization (C-L,O,P) or by immunohistochemistry (M,N). Nissl analysis of comparable sections from wild-type and mutant telencephalon (A,B) reveals that in the absence of Vax1 the interganglionic sulcus is missing (black arrows). This defect is accompanied by the modification of the expression pattern of Gli1 (C,D), which shows a diffuse labeling pattern in the territory surrounding the mutant interganglionic sulcus. (E,F) In wild-type brains, the homeobox gene Nkx 2.1 is expressed in the proliferative zone of the MGE (E); in Vax1^-/- embryos, its expression is expanded (F). (G,H) Ebf1 is a marker of the mantle zone of the LGE (G). In the mutant brain, its expression is strongly reduced but correctly restricted to this region (H). (I-J) The MGE mantle marker Lhx8 shows a significant reduction in mutants (J) compared with wild types (I). (K-N) The boundary between ventral pallium and subpallium (broken black line) is maintained in the absence of Vax1: expression domains of the pallial markers Ngn2 (K,L) and Pax6 (M,N) are unaltered. (O,P) The subpallial marker Gsh2 does not show a dorsal shift. LGE, lateral ganglionic eminence; MGE, medial ganglionic eminence. Scale bars: 500 µm.