Simple synthetic elements containing homotypic TF motifs can generate complex spatio-temporal activity.

<p>(A) Schematic representation of flow from design of synthetic CRMs, assessment of <i>in vivo</i> activity to tissue-specific modeling. Optimized TFBSs (from ChIP experiments) were separated by spacers, with minimal affinity to known TF binding models, and placed in front of a minimal promoter and <i>lacZ</i> reporter and integrated into the <i>Drosophila</i> genome. (B–F) Homotypic synthetic CRMs containing six TFBSs from the represented sequence logo for each TF, separated by a 6 bp spacer. CRM activity was assessed by double fluorescent <i>in situ</i> hybridization of the <i>lacZ</i> reporter gene driven by synthetic CRM (red) and the corresponding endogenous gene (green). Synthetic CRMs composed from GATA (B–B″) and Doc (C–C″) motifs drive expression in the presumptive amnioserosa (white box). Tin synthetic CRM (D–D″) is expressed in the dorsal mesoderm (arrow), while Twi CRM (E–E″) is expressed in the foregut weakly (white arrowhead), hindgut (white arrows) visceral mesoderm and ectoderm (asterisks). Bin synthetic CRM (F–F″) is active in the foregut (arrowhead), midgut (asterisk) and hindgut (arrow) visceral mesoderm (VM). All embryos are shown laterally with anterior to the left, except for (E) which is a dorsal view.