Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior axis. At the 10-somite stage, expressed strongly in the paraxial mesoderm with an anterior expression limit at somite 6. At the 20-somite stage, expressed in the developing CNS with an anterior expression limit adjacent to the somite 2/somite 3 boundary. Belongs to the Antp homeobox family.