Fig. 4. Caudal gradients of gene expression are shifted rostrally in the dorsal telencephalon of E13.5 and E14.5 Fgf8neo/neo embryos. In situ hybridization on sagittal sections of wild-type (A,C,E) and Fgf8neo/neo embryos (B,D,F) with the indicated probes. The graded expression of COUP-TFI and Fgfr3 (black arrowheads) expands into the rostral neocortex. Pax6 expression appears normal in Fgf8neo/neo embryos (compare C with D). Note that the expression of these three genes outside of the neocortex is not affected in Fgf8neo/neo embryos except in the midbrain, which is dramatically reduced in size. M, midbrain; Ncx, neocortex; OB, olfactory bulb.