May negatively regulate Notch-induced cell proliferation in the eye-head primordium. Required for development of the supraesophageal ganglion and ocelli. May act in leg and wing primordia to negatively regulate body-wall specifying genes and thereby promote appendage formation. Plays a role in tracheal development. Interacts with elB. Highly expressed in the adult head. Expressed from stage 4 in the embryonic termini and at stage 5/6 in the ectodermal stripes. Expressed in the invaginating tracheal pits at stage 11, and ubiquitously throughout the embryo from stage 13. Expressed in the highly proliferative region of the eye-head primordium. Expressed in the distal regions of leg and wing imaginal discs. Expressed predominantly in embryo and pupae. Belongs to the Elbow/Noc family.