Fig. 5. Loss of a T-box binding site in homology region-c (HR-c) results in ectopic expression in the diencephalon. (A,B) Whole-mount salmon-gal staining of transgenic embryos at 9.5 dpc expressing either (A) wild-type (Rc9) or (B) mutated T-box (Rc14) constructs. The arrows in A and B point to the rostral limit of salmon-gal staining detected at the level of prosomeres 3 and 5, respectively. (C-D) Transverse sections through the rostral diencephalon of transgenic embryos expressing either (C) wild-type Rc9, or (D) mutated T-box (Rc14), double-stained for lacZ reporter activity (salmon-gal) and Shh mRNA (BM-purple). The blue arrowhead points to the stripe of lateral expression of endogenous Shh mRNA adjacent to the ventral midline in this region of the diencephalon (di). The salmon-colored arrowhead in D points to the ectopic reporter activity in the ventral midline of the diencephalon. The asterisk marks the floor plate of the hindbrain (hb).