The large family encoding POU transcription factors has been described in several species. In particular, class III POU genes regulate critical steps of vertebrate and invertebrate neurogenesis. A novel amphioxus class III POU gene, AmphiBrn1/2/4, has been isolated and its spatio-temporal expression has been reported. AmphiBrn1/2/4 is first expressed in the dorsal epiblast, then throughout the neural plate except for a gap at level of the anterior region of the cerebral vesicle. Transcripts are also detected in the primordium of gill slits, pharynx and left Hatschek's diverticulum.