Fig. 2. Gli1 expression in somites requires Gli2 or Gli3. Gli1 expression was investigated in E9.5 wild-type (A,G,M), Gli3^–/– (B,H,N), Gli2^–/– (C,I,O), Gli2^+/–Gli3^–/– (D,J,P), Gli2^–/–Gli3^+/– (E,K,Q) and Gli2^–/–Gli3^–/– (F,L,R) embryos using whole-mount in situ hybridisation. Transverse sections were performed at the level indicated by double black arrows. Black arrows indicate domains of Gli1 expression that are unchanged or upregulated. Black arrowheads indicate loss of Gli1 expression.