Fig. 2. Zebrafish gli mutations block Hh signaling. (A) Wild-type expression of the Hh target gene nk2.2 is unaffected by injection of lacZ mRNA. (B,C) nk2.2 expression is regionally absent in dtr and yot/gli2 mutant embryos (arrows). (D) Injection of shh mRNA leads to an expansion of nk2.2 throughout the CNS in wild-type embryos (arrowheads). (E,F) Over expression of shh does not activate nk2.2 expression in defective regions of dtr and yot/gli2 mutants (arrows), but nk2.2 expression is expanded in unaffected regions (arrowheads). All panels show lateral views of 20-somite (19 hour) embryos, anterior to the left, eyes removed. di; diencephalon; HB, hindbrain; MB, midbrain; MDB, mid-diencephalon boundary; MHB, midbrain-hindbrain boundary; te, telencephalon.