Hox proteins and segment-polarity proteins control appendage location

Integration of Hox and segmentation-protein inputs by a cis-acting regulatory element. (a) Left: A cis-acting regulatory element of the Dll gene governs the repression of D//expressioninthe abdomen by a set of transcription factors. (a) Right: Dll expression (red) extends to the thorax but not into the abdomen in a wild-type embryo. (b-f) Mutations in the respective binding sites shown derepress Dll expression in various patterns in the abdomen. Binding sites are: Slp, Sloppy-paired; Hox1 and Hox2, Ultrabithorax and Abdominal-A; Exd, Extradenticle; En, Engrailed; Hth, Homothorax.

[Data from B. Gebelein, D. J. McKay, and R. S. Mann, “Direct Integration of Hox and Segmentation Gene Inputs During Drosophila Development,” Nature 431, 2004, 653-659.