Interestingly, hedgehog interaction with patched does not always result in the synthesis of Wingless . The anterior-posterior boundary of the wing is drawn by dpp , which is required for differentiation of both compartments, but wingless is not induced in the anterior compartment. It functions instead on the proximal-distal axis. The same holds true for leg development. But contrary to this supposition, development is an orderly, restrained process.
Control systems prevent cells from achieving unrestrained growth.
The Notch pathway of lateral inhibition is just one example from among many. Only through the enforcement of negative regulation can a highly ordered biological system come into being. The negative effects of patched are particularly relevant to the expression of dpp . In the wing disc, dpp is expressed in only a narrow band of cells between the anterior and posterior compartments. Patched not only inhibits wingless, but also dpp .