Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior axis. Controls the segmental transformation of the first to the second thoracic segment (prothorax to mesothorax) and of the labial palps into maxillary palps. In embryo, required for fusion of labial lobes and development of the T1 denticle belt. In adult, expression in the head is necessary for proper development of the labium. In the first thoracic segment of the adult, required for proper development of the sex comb and to suppress improper prothoracic wing development. In embryo, expressed in the labial and anterior prothoracic segments and the extreme posterior of the maxillary segment. In adult, expressed in the maxillary analgen of the eye and antennal imaginal disk and the labial and T1 leg imaginal disks. Belongs to the Antp homeobox family. Deformed subfamily.