Figure 9.

FgfR signaling regulates Notch and proneural gene expression in cortical neurogenesis. NICD staining of intracellular puncta was reduced in Emx1;TKO embryos (A, B), suggesting that Notch production and/or cleavage is impaired. Insets (A, B) are high-magnification images of the boxed regions. In situ hybridization for Notch1 demonstrated decreased expression in the cortical VZ of Emx1;TKO embryos at E13.5 (C–F). E, F, High-power images of the boxed regions in C, D. Analysis of Notch downstream targets showed decreased Hes1 (G, H), increased Ngn2 (I, J), and increased Dll1 (K, L) mRNA production as early as E11.5 in the cortical VZ (arrowheads) during the period of increased early neurogenesis in Emx1;TKOs. (M, N). Scale bars: A, B, E, F, 125 μm; C, D, G, H, 2 mm; I–L, 1 mm.