Fig. 6. Gli1 cannot restore Shh responsiveness in Gli2^–/–Gli3^–/– PSM. PSM from wild-type and Gli2^–/–Gli3^–/– embryos was cultured with Shh-N in the presence (+) or absence (–) of Gli1 adenovirus for 24 hours. Induction of Shh target genes was assessed by RT-PCR. Infection with Gli1 adenovirus increased the expression of Ptch and Hhip but not other Shh target genes in wild-type PSM. In Gli2^–/–Gli3^–/– PSM infection with Gli1 adenovirus does not restore responsiveness of any Shh targets nor increase the expression of Ptch and Hhip (n=3).