FIG. 1.

Synthetic versions of well-studied developmental enhancers fail to recapitulate their activity in vivo. All panels show imaginal discs from larvae carrying lacZ reporter transgenes. Reporter gene expression is visualized by X-gal staining. (A) Proneural expression pattern in the developing wing driven by a Notch-regulated enhancer of the E(spl)m4 gene, which contains binding sites for Achaete/Scute [A] and Su(H) [S]. (B) A synthetic version of the E(spl)m4 enhancer, containing multimerized high-affinity A and S binding sites, does not produce an E(spl)m4-like pattern. (C) Cone cell–specific expression pattern driven by the sparkling (spa) enhancer of the dPax2 gene, which contains binding sites for Lozenge [L], Su(H) [S], and Pointed-P2 [P]. (D) A synthetic enhancer containing high-affinity L, P, and S binding sites does not recapitulate dPax2 expression. (E) A disc-specific enhancer of the dpp gene (dppD), containing binding sites for Engrailed [E] and Ci [C], drives expression in Hedgehog-responding cells of the developing wing. (F) A synthetic version of dppD, containing only the E and C sites in their native spacing, fails to drive gene expression in vivo.