Fig. 8

Fig. 8 Forebrain marker expression in yot/gli2 and syu/shh mutant embryos. (A) The signaling molecule fgf8 is expressed in the telencephalon and in dorsal diencephalic cells adjacent to the developing adenohypophysis (bracket) at 15 h of development. (B, C) In yot/gli2 and syu/shh mutants, fgf8 is expressed normally in cells adjacent to the developing adenohypophysis (arrowheads), suggesting that fgf8 signaling defects do not account for the lack of pituitary development seen in these mutants. (D–F) At 20 h, fgf8 is still expressed adjacent and dorsal to the adenohypophysis in yot/gli2 and syu/shh mutants (arrowheads). (G) The transcription factor isl1 is expressed in adjacent diencephalic cells (arrowheads), as well as in epidermal cells (arrows) that are continuous with and overlap the developing adenohypophysis (bracket) at 15 h of development. (H, I) isl1 is expressed in these same adjacent cells in yot/gli2 and syu/shh mutants (compare arrowheads and arrows). Increased labeling in (H) is due to the presence of additional extraembryonic membrane. (J–L) isl1 is expressed in the diencephalon of both yot/gli2 and syu/shh mutants at 20 h (arrowheads), indicating this diencephalic cell type can differentiate in the absence of Shh signals. Epidermal isl1 expression is largely absent by 20 h in both wildtype and mutant embryos. (M, N) shh is appropriately expressed adjacent to the developing adenohypophysis at 15 h in yot/gli2 mutant embryos (arrowheads), showing that this region of the brain is capable of signaling to adjacent epidermal tissue. In all panels, a black dot shows the position of the optic recess, the anterior border between the telencephalon (te) and diencephalon (di).