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 detected at 11.5 hours post-fertilization (hpf) in dorsal presomitic mesoderm and in the neural keel, extending to the ventral somitic mesoderm during tail budding. At 16-19 hpf, the rostral expression boundary is at somite 10. By the end of somitogenesis, expression decreases in the lateral and ventral mesoderm and becomes restricted to the neural rod. Also expressed in the developing pectoral fins from 34 hpf, with progressive localization to the periphery. Belongs to the Abd-B homeobox family.