Fig. 3. Similar changes in Fgf8 and Wnt3a expression by BMP inhibition or loss of EMX2. (A-I) E10.5 forebrains viewed dorsally, anterior towards the top, processed for whole-mount in situ hybridization. EGFP alone (A,D,G) or EGFP and Nog together (B,E,H) were electroporated into the telencephalic vesicle at E9.5. EGFP fluorescence indicates the position of the electroporated site (insets). Brains electroporated with EGFP alone show wild-type expression patterns of Fgf8, Wnt3a and Msx2 (a reporter of BMP activity). Co-electroporation of Nog results in inhibition of BMP activity, reflected in decreased Msx2 expression (arrow in H), increased and ectopic Fgf8 expression in the cortical primordium (B), and lowered expression of Wnt3a in the cortical hem (arrow in E). The forebrains of Emx2 homozygote mutant mice are not identical to Nog-electroporated brains, but, like the latter, show expanded Fgf8 expression (C, arrow) and reduced expression of Wnt3a in the hem (F, arrow). A slight decrease in Msx2 expression is most evident in the cortical hem (I, arrow). The latter region is buried in a dense mass of Msx2 expression in control forebrains (G). Scale bar: 0.4 mm.