Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior axis. First expressed at the 1- to 2-somite stages posterior to rhombomere 5 (r5) of the developing hindbrain. By the 3- to 4-somite stages, the anterior expression limit is at the r4/r5 boundary. At 5- to 10-somite stages, expressed at high levels in r5 and r6. From the 20- to 30-somite stages, expressed weakly in r4. Belongs to the Antp homeobox family.