Fig. 8.

The second intron of deltaD contains a conserved cluster of T-box sites required for T-box-dependent mesodermal expression. (A) The second intron from fish dld orthologs (there is an unsequenced gap in the Medaka intron). Grey rectangles represent T-box binding motifs, diamonds indicate putative Tcf/Lef sites and grey ovals represent putative Suppressor of Hairless-binding sites. (B) An alignment of the second intron of fish dld orthologs reveals two particularly well-conserved Spt/Ntl-binding motifs (sites c and d). (C-F) A construct containing 1.2 kb upstream and 1.3 kb downstream sequences relative to the dld transcription start site, including the known neural regulatory element (HII) (Hans and Campos-Ortega, 2002) and the T-box site cluster (C,D) drives robust mCherry expression in the non-axial margin during gastrulation (E) and in the tail bud and somites during segmentation (F). (G-I) When two well-conserved T-box sites (c,d) and a T-box consensus sequence (e) are mutated (G), mCherry expression is greatly reduced (H,I). The percentages of embryos with robust, faint or no mCherry expression is given in Table 1.