FIG. 4.

Combinatorial mutations reveal functional redundancy in novel regulatory sequences within dppVM. Embryos are stained and presented as in Figure 2. (A) Wild-type dppVM. (B) Lateral view of embryo carrying a mutated dppVM lacking region 1 and the 3′ third of region 5 (region 5c). (C) Dorsal view of embryo carrying an enhancer in which the ATGYTGCA repeats (region 3b) and similar sequences (region 4a) have been altered. (D) Combining the deletion of region 1 with mutations in regions 3b and 4a causes a significant loss of enhancer activity. (E) A mutated enhancer in which all known or predicted binding sites (Ubx + Exd + Bin + TCF) are preserved, but all other sequences are altered such that the wild-type GC content is maintained. (F) A construct similar to the previous, but with the addition of the wild-type ATGYTGCA repeats (3b) and related sequences (4a). Enhancer activity is restored. (G) Two tandem copies of the construct shown in panel E are insufficient for enhancer activity. (H) A construct containing only the most highly conserved sequences from dppVM shows visceral mesoderm activity.