Decapentaplegic (Dpp)
In Drosophila, decapentaplegic (dpp) guides dorsal/ventral polarity. Dpp plays a role in the definition of boundaries between segmental compartments as they appear. It works in collaboration with hedgehog and wingless in defining positions of future limbs, such as wings, legs and antenna. Dpp is also responsible for structuring mesoderm. It acts downstream of Hh and en in the final stages of appendage development to define boundaries between appendage compartments and ensures the anterior/posterior polarity is correct.Hedgehog controls the secretion of dpp, which traverses wingless expressing cells. All three proteins are required to assign cells involved in the formation of imaginal discs that later develop into appendages.
Engrailed (en)
In Drosophila, the engrailed gene aids in directing development by encoding a DNA binding protein that contains a homeodomain. Hedgehog allows communication between en expressing cells in the anterior compartment of each parasegment (embryonic segments) and its adjacent compartment (expressing wingless). En activates transcription of hedgehog leading to signals affecting the induction of wingless. It has a suppressive effect on proteins made in the posterior compartments including wg, dpp, ptc and Ci.
Wingless (wg)
Wingless is a segment polarity gene that controls different cell fates in the anterior and posterior compartments of segments. Wg is secreted from cells in posterior compartments of parasegments, a process dependent upon hedgehog. Failure to secrete wg results in absence of functional posterior parasegmental compartments and thus altered activity underneath the outer cell membrane.Other Targets:
Patched (Ptc) - the patched gene encodes the patched protein, a repressor in the Hh signalling pathway.Hedgehog (Hh)
