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 15 hours post-fertilization (hpf) in the presumptive proctodeum. At 22 hpf, expressed in the most distal part of the hindgut, the future rectum and the cloacal region; cloacal expression is still detectable until 64 hpf. First detected in the dorsal pre-somitic mesoderm and neural keel at 17 hpf. At 22-26 hpf, expression is restricted to the posterior tip of the trunk, begins to weaken and is undetectable by 40-56 hpf. Belongs to the Abd-B homeobox family.