Fig. 7. Rostrocaudal gradients of Emx2 and COUP-TF1 expression are modified in Fgf8 mutant embryos. Whole-mount in situ hybridization on dissected E11.5 rostral neural tube showing Emx2 (A-A''), COUP-TFI (B-B'') and Bmp4 (C-C'') expression. Lateral views are presented. In C-C'' a box in the lower left corner shows an additional dorsal view. In wild-type embryos, the Emx2-high-expression domain is detected in the caudomedial telencephalon (arrowhead in A). In both Fgf8^Null/Neoand Fgf8^TelKO embryos, the Emx2-high-expression domain is expanded laterally and rostrally (arrowhead in A',A''). In wild-type embryos, the COUP-TF1-high-expression domain is restricted to caudolateral telencephalic regions (arrowhead in B). In Fgf8^Null/Neoembryos, the COUP-TF1-high-expression domain expands rostrally (arrowhead in B') whereas it remains in a caudolateral position in Fgf8^TelKO mutants (arrowhead in B''). Such a differential effect on COUP-TFI expression correlates with the difference in Bmp4 expression in the two Fgf8 mutants. Indeed, in Fgf8^Null/Neo embryos, Bmp4 expression is the same as in wild-type embryos (restricted to dorsal midline tissues; arrowhead in C,C'). By contrast, Bmp4 expression expands in the telencephalic vesicles of Fgf8^TelKO mutant embryos (arrowhead in C''). Os, optic stalk; Tel, telencephalon.