Fig. 6. Excess Hh signaling and ventralization of the neural tube in Sufu^-/- mutants. Cross-sections of the thoracic region stained with Hematoxylin and Eosin show the morphology of a normal neural tube of wild type (A) and the open neural tube of Sufu^-/- mutants (B) at 9.5 dpc. Immunohistochemistry with markers of neural progenitor cells (anti-PTCH, anti-Foxa2, anti-Nkx2.2 and anti-Pax6) in wild-type (C,E,G,I) and Sufu^-/- (D,F,H,J) 9.5 dpc embryos. Ptch1 (a Hh target gene product), Foxa2 and Nkx2.2 were expressed in the floor plate of wild-type embryos (C,E,G), with Foxa2 expression being restricted to the ventral midline. In Sufu^-/- embryos (D,F,H), expression of ventral markers expanded to dorsal regions of the neural tube. Pax6 was expressed in lateral regions of the ventricular zone of the wild type (I), but its expression was repressed in Sufu^-/- mutants (J). Cross-sections are of the thoracic region. Scale bars: 50 µm.