Chaoptin, prominin, eyes shut and crumbs form a genetic network
controlling the apical compartment of Drosophila photoreceptor cells.
The results suggested that each of the Wnt genes (Wnt - 2b, Wnt - 8c, Wnt - 3a) were responsible for turning on two forms of FGF, each of which
controls both limb initiation and a bud or bulge known as the
apical ectodermal ridge (AER), which acts as the «organizer» of limb development.