Fig. 3. Analysis of potential cross-repressive interactions in the early telencephalon. (A-H) Immunohistochemical analysis of Nkx2.1, Gsh2 and Pax6 expression on coronal sections in Pax6^–/– (Sey/Sey), Nkx2.1^–/– and Gsh2^–/– mutant mice, respectively. Arrows mark the ventral or dorsal limit of expression of each protein. (A,B) At 22 somites, when expression of Pax6 and Nkx2.1 form a distinct border, Nkx2.1 expression does not expand dorsally in Sey/Sey mutants. (C,D) At this same stage, Pax6 expression also does not expand ventrally in Nkx2.1^–/– mutants. (E,F) Between 26 and 30 somites, in Nkx2.1^–/– mutants, Gsh2 expression in the lateral domain does not expand ventrally into the presumptive MGE region. (G,H) Conversely, in Gsh2^–/– mutants at 31-32 somites, Nkx2.1 expression remains restricted ventrally. Scale bars: 50 µm (A-H).