Fig. 5

Loss of Gli repressors in the absence of Hh signaling is not sufficient to activate the Hh pathway. Wild-type control zebrafish embryos (A,C,E,G) and wild-type embryos injected with a cocktail of gli2a, gli2b and gli3 morpholinos (B,D,F,H) were treated with cyclopamine from 50% epiboly to 24 hpf, and stained for the expression of ptc1 (A,B), gli1 (C,D), olig2 (E,F) and eng2 (G,H). (A-D) Embryos treated with cyclopamine, gli2a^MO, gli2b^MO and gli3^MO show a slight upregulation of ptc1 expression (arrowheads in B) and substantial upregulation of gli1 expression (D). Note that gli1 is expressed at a low level in the absence of Hh signaling (arrowhead in C). (E,F) Compared with control embryos (E), embryos treated with cyclopamine, gli2a^MO, gli2b^MO and gli3^MO show a small patch of olig2 expression in the brain (arrowhead in F), but display no olig2 expression in the neural tube similar to controls. (G,H) Embryos treated with cyclopamine, gli2a^MO, gli2b^MO and gli3^MO show no eng2 expression in somites similar to controls. Note that expression of eng2 in the midbrain-hindbrain boundary (arrowheads) does not require Hh signaling. Lateral views. Scale bar: 100 μm.