Fig. 5. Gli2 can only partially rescue the Ptc mutant phenotype at E10.5. Ptc+/ (A,D), Ptc+/;Gli2zfd/zfd(B,E) and Ptc/;Gli2zfd/zfd(C,F) embryos. Ptc/;Gli2zfd/zfd embryos survive beyond E10.5, whereas Ptc/ embryos die by E9.5. At E10.5, even though the spinal cords are closed, Ptc/;Gli2zfd/zfd embryos show exencephaly (indicated by a white arrow). (D-F) X-gal staining of Ptc-lacZ. The expression of Ptc-lacZ is reduced in Ptc+/;Gli2zfd/zfd embryos (E, indicated by an arrow), when compared with Ptc+/ embryos (D). In Ptc/;Gli2zfd/zfd embryos at E10.5, Ptc-lacZ expression is upregulated in the brain.