Transcription factor that plays a role in larval and adult appendage development. Specifies the identity of ventral appendages (including legs and antennae) and suppresses dorsal appendage development. Involved in patterning the distal-proximal limb axis. May control the adhesive properties of cells during limb morphogenesis. Also has a secondary role in the normal patterning of the wing margin. Expressed in the embryo in limb primordia of the head and thoracic segments. Expressed in regions of the larval leg, wing, antennal and haltere disks that form the distal-most regions of the mature structures (in the leg this corresponds to the tarsus and the distal tibia). Found in the optic center of the developing larval brain.